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COC ORAL EXAM PREPARATION (PART – 12): STERN TUBE

1245Image Credit: www.libramar.net

Stern Tube:

The stern tube is a hollow tube-like structure at the stern or rear part of the ship. A ship needs the propeller to drive it forward in water. The propeller, located outside the ship, needs to be connected to the engine inside the ship’s engine room. The propeller shaft is used for connecting the ship’s engine and the propeller. The stern tube is a narrow hole in the hull structure at the rear end (aft peak) of the ship, through which the propeller shaft passes and connects the engine and propeller.

Stern tube bearings serve two main functions:
1. To properly connect the propeller to the ship
2. To keep water from leaking into the stern tube (and lubricant from leaking out)

There are three types of stern tube bearing arrangements that are used to accomplish these goals:
1. Stuffing boxes, which uses packing material to seal the area
2. Lip seals, which are connected to the tail shaft to prevent lubricant or water from passing through the shaft
3. Radial face seals, which are supported with specially fitted springs around the shaft, aft bulkheads and near the back end of the stern tube

Stresses in tail shafts:

1. 
Due to the considerable weight of the propeller, the tail shaft is subject to a bending stress.
2. There is a torsional stress due to the propeller resistance and the engine turning moment, and
3. Compressive stress due to the propeller thrust.

Stern Bearing Wear-down Measurement:

1. Use Poker Gauge or Wear down Gauge or Vernier Caliper.
2. Remove Rope Guard.
3. Take out Check Plug and Drain Plug.
4. Turn Tailshaft until ‘0’ marks on periphery of aft chrome steel liner flange and mating marks on Simplex seal and Sterntube are in line.
5. Measure at measuring plug (top) and drain plug (bottom) through 180°at same radial position as previous docking.
6. Compare with previous readings.

Stern Bearing Wear Measurement:

1. Measured at same radial position at every dry dock.
2. Look for reference mark left usually on propeller boss when measured during last docking.
3. The same mark should be used again, so that reading can be taken at same radial position.
4. Sometimes measurement had been taken when No. 1 Unit was at TDC, and important thing is that it should be at same radial position as last docking.
5. Measuring at top telltale hole or check plug is enough and bottom check plug is only used for counter check.
6. As a CE, witness the measuring procedure when vessel is on dock

Examining a tail shaft and stern tube:
1. Before the periodic inspection the bearing weardown should be measured.
2. After shaft removed given thorough examination.
3. On water lubricated shafts the integrity of the fit of the bronze liner should be checked by tapping with a hammer along its length listening for hollow noise indicating a separation.
4. Measure wear of shaft.
5. Examine key way for cracks especially the nut thread area.
6. Replace rubber rings.

How to check Stern tube wear down? (Lignum Vitae, water cooled stern tube)

1. Measurement can be taken by Wedge Gauge or Feeler.
2. If Wedge Gauge is used, the side of the Wedge contacting the bearing is chalked and inserted into the clearance space between top of the screw shaft and bearing.
3. Gauge is pressed home and withdrawn.
4. Clearance is measured on the Wedge at the point where the chalk marking is scrapped-of by bearing.

For Oil Lubricated bearing, 

1. 2 mm clearance.
2. When the ship is on Dry Dock, release system oil and remove plug on the end of the stern tube, and insert Poker Gauge to measure the distance from the datum to the top of the shaft.
3. The difference between new reading and original measurement is bearing wear down value.

All types of Stern Bearing:

1. Fit a Dial Gauge on the Rope Guard or Sterntube Nut so that the Gauge spindle is vertical and touching the Propeller Boss.
2. A hydraulic jack is placed on the Stern Frame Skeg at same point over a Keel Block so that the Skeg is supported.
3. A wood shoe is placed between the jack and the Propeller Boss.
4. The jack is then used to lift the Propeller until the Screw Shaft contact the upper parts of its Stern Bearing.
5. The lift recorded in Dial Gauge gives the bearing clearance.

Skeg: An arm extending to the rear of the Keel to support Rudder and protect Propeller.

Tail end shaft taper: ¾” to 1″ per foot length.

Stern tube bearing length:

  • Aft bearing 4 D Forward Bearing 1 – 2 D (Water-cooled)
  • Aft bearing 1.5 – 3 D Forward Bearing 0.6 – 1.25 D (Oil cooled)

How you check Stern tube Sealing in Dry dock?
–  LO header tank is topped-up and checked for leakage for 24 hours.

What action to be taken when SW leaks into Sterntube oil system?
–  Higher up the Stern tube oil tank level to counteract SW force.

Stern tube Leakage Test:

  1. Remove screw plug and fill up the stern tube oil (normally using main engine system oil). Oil pressure must amount to only 0.2 – 0.3 Kg/cm² more than SW pressure.
  2. Preheated to 60 – 70°C when viscose oil is used or low temperature prevails
  3. Remain in this condition for several hours (says overnight) and turn engine by Turning Gear to change the shaft position 3 – 4 times.
  4. Check oil leakage from Drain Plug and if it is all right, fit back Drain Plug and fill oil from venting and Filling Plug and close.
  5. Forward Seal is fitted.

Constant Air flow type Stern Tube: 

New Bitmap Image

Fig: Constant Air flow type Stern Tube (Source: KOBELCO Air Seal, Japan)

  • . A constant  quantity  of  air  supplied  from  the  air source, which then passes through the #2/3 seal chamber and is then spouted into sea. The air pressure is always maintained about 0.01 Mpa (0.1 bar)  greater  than  the  seawater  pressure  so  to slightly exceed the tightening force of the #1 and #2 sealing rings.
  • The air pressure is added to stern tube oil tank, which is installed at 3m (0.03 Mpa) above a shaft center.   The stern tube oil pressure becomes “air pressure in the #2/3 chamber + 0.03 Mpa and it also follows the draft change.
  • Any  draft  change  can  be  automatically  detected and both the air pressure in the #2/3 chamber and the stern tube oil pressure follow the draft change instantly. Accordingly all pressure differences on the aft sealing rings are always negligible.
  • Leaking oil and seawater can be drained from the #2/3 chamber.
  • In order to drain any leaking liquid smoothly, a small quantity of air is always blown through a flow controller on the drain tank.

There are two advantages of the constant air flow system:

  1. One is that seawater rarely comes into the #2/3 chamber because the air pressure is always greater than seawater pressure.
  2. The life of sealing rings, especially the #1 and #2 rings, increases because of the small pressure difference maintained.

COC ORAL EXAM PREPARATION (PART- 11): PROPULSION MACHINERY

Marine-propulsion-systemImage Credit: Wikipedia.org

FUEL INJECTION TIMING

Checking of fuel injection pump timing:

  1. Turn 1 piston to TDC at the beginning of firing stroke.
  2. Turn backward to a point, a little earlier than fuel injection point.
  3. Shut fuel supply to engine, remove No. 1 fuel pump delivery valve assembly and put a bent pipe.
  4. Open fuel supply and when fuel lever is put to running position, oil will flow out at bent pipe.
  5. Turn engine towards TDC in its running direction slowly until fuel cease to flow.
  6. Check the marks on flywheel whether timing position is correct or not.

 Slight difference can be adjusted by:

For large engine:

    •  Timing can be altered by shifting the camshaft to the position relative to crankshaft, after removing the idler gear between crankshaft and camshaft.
    • Timing can be altered by individual fuel pump cam for adjustable cam type engine.

 

For small engine:

  • Adding or reducing shims on pump base.
  • Turning the plunger up & down adjustment screw on pump roller guide.
  • Shifting the coupling flanges between pump and drive side of the engine.

Crankshaft:

  1. Device for converting reciprocating motion of piston, driven by expansion of gases, to rotating motion.
  2. Power produced by engine is taken off the crankshaft by transmission.

Stresses in Crankshaft:

  1. Bending of crank pin, causes tensile, compressive and shear stresses. (Due to gas load)
  2. Twisting moment of journal, causes shear stress.
  3. Compressive stresses set up in journals and pins. ( Due to shrink-fit)
  4. Tensile stresses set up in webs. ( Due to shrink-fit)
  5. Torsional stresses due to power transmission fluctuate widely. ( In heavy sea)
  6. Shock loading on crank pin. ( Sudden fluctuation of engine speed )

Types of crankshaft:

  • Solid forged
  • Semi-built
  • Fully-built
  • Welded crankshaft.

In large marine engine which type is used and why?

Usually, Semi-built is used because:

  • Only one shrink-fit between web and journal as less chance of slippage.
  • Can get grain flow in way of web and pin.
  • Webs are smaller as there is no shrink-fit.
  • Can be repaired section by section when damage occurred.

Welded Crankshaft:

  • Die-forged crankthrow, consisting of thin webs and crankpin in one piece, having half a main journal on each side.
  • Welds are placed and welded at the middle of all main journals, to make complete crankshaft.
  • High technology Narrow gap welding process applied.

Fully-built Crankshaft manufacturing:

  1. Raw material melted in Cupola Furnace.
  2. Refined to remove impurities, by decarburising, controlling carbon amount and soaking time.
  3. Degassed in Vacuum Furnace, to remove H and N.
  4. Molten metal is then poured into prepared mould.
  5. Removed from mould, after slow cooling, and casting is rough-machined.
  6. Normalised to improve grain structure, and tempered to remove stresses.
  7. Rough-machined to final dimensions.
  8. Cold roll the crank pin fillets, to increase bending and corrosion fatigue
  9. Finish machining.
  10. Shrink-fitting process [Shrinkage allowance: 1/570 to 1/660 of journal diameter.]
  11. Set upon a large lathe, and journals checked for throw, and throw errors machined out.

When to take Crankshaft Deflection:

  1. At initial installation and after 1000 running hours.
  2. At subsequent annual intervals if normal, ( 6000-8000 hrs. )
  3. At the time of main bearing overhaul or removal for survey.
  4. At foundation chock repair or renewal.
  5. Damage on bearing bracketholding down boltchock.
  6. When major structure has been disturbed, such as: after fire breakoutpropeller bending or impounding with something, ship grounding, before and after docking.

Causes of misalignment:

  1. Wear of main bearing lower shell.
  2. Wear and ovality of main journal pin.
  3. Main bearing damage.
  4. Main bearing pocket cracked.
  5. Bedplate deformed, transverse girder damaged.
  6. Foundation bolts loose or fractured.
  7. Foundation chocks broken, cracked or fretted.
  8. Slacked or broken tie bolts.
  9. Distortion of supporting ship’s structure.
  10. Defective structure due to corrosion.
  11. Defective propeller shaft bearing
  12. Lifting of flywheel side.
  13. Hull deformation due to: Improper loaded condition of vessel, grounding and fire.

Results of misalignment:

  1. Bending of crankshaft.
  2. Fatigue failure owing to cyclic stresses.
  3. Undue vibration within the engine.
  4. Damage to main bearing.

Why you measure crankshaft deflection?

  1. To ascertain whether or not, the axis of crankshaft journals deviates from theoretical shaft axis.
  2. Measuring is by a dial gauge, inserted between crank webs, and altered distances can be read, when turning the crankshaft.

How to know the amount?

  1. Difference between the values at TDC and BDC indicates the amount of crankshaft deflection, during one revolution.
  2. Interpretation of crankshaft deflections gives an indication of high and low bearings.

What will happen if a bearing is high or low?

  1. When a bearing between 2 cranks is higher than those on either side of it, both sets of crankwebs will tends to open out, when the cranks are on BDC, and close in when on TDC.
  2. Vice versa, if there is a low bearing between 2 cranks.

Requirements when taking crankshaft deflection:

  1. Hull deflection not excessive.
  2. Bed plate not distorted or bearing pockets not worn.

 Foundation Chock:

Purpose:

  1. To avoid misalignment on tank top surface.
  2. To carry out adjustments on individual chock.
  3. To correct any distortion.
  4. To absorb collision load by end chocks.
  5. To absorb side load, due to unbalanced reciprocating forces, by side chocks.

Advantages of Chockfast System: (Eposy Chock)

  1. Reliable and permanent alignment of machinery foundation.
  2. Resist degradation by fuel, LO and eliminate chock area corrosion.
  3. Give uniform and precise mounting.
  4. Non-fretting permanently.
  5. Reduce noise level.
  6. Can be used on all sizes and types of engines.
  7. Maintain C/S deflection, machinery alignment and even Hull fouling.
  8. Installation time is measured in hours, not in days.
  9. Withstand temperature up to 80°
  10. Give chock thickness up to 44 mm.

Chain Drive System:   

  1. Used for camshaft driving, on any length between shaft centres with very small friction loss.
  2. Fuel Pumps and Exhaust Valves are operated by Camshaft, driven from Crankshaft, by a roller chain [main] running over each sprocket wheel, being bolted to both shafts.
  3. Chain should wrap around at least 120°on both sprockets.
  4. Upward-running-side chain passes over an intermediate wheel, on which Tensioning Device is fitted.
  5. On another intermediate wheel’s shaft, there is another chain wheel and chain [smaller], to drive Start Air DistributorGovernor and Lubricators.
  6. Chain is lubricated by oil sprayer jets, with continuous stream of oil onto the chain.
  7. A roller chain consisting of side plates, bushing and rollers, and pin joints, which mesh with tooted sprockets.
  8. Shock-absorbing rubber clad guide bars, are provided to support the long chain, and to prevent transverse vibration.
  9. Renew cam chain after 15 years life.
  10. Factor of safety of chain: Never less than 25.

Slack chain: 

Symptoms:

  1. Excessive chain vibration and noise.
  2. Power loss in all units, indicated [by Power Card].
  3. Late injection, low Pmax, [by Draw Card].
  4. Late closing of Exhaust Valve, [by Light Spring Diagram].
  5. High exhaust temperature and smoke.

Effects:

  1. Impose heavy mechanical load, resulting fatigue failure.
  2. Damage to chain system and engine frame.
  3. Retardation of Fuel Pump and Exhaust Valve timings, resulting:
  4. Reduced Scavenge Efficiency, due to late closing of Exht: V/v.
  5. High exhaust temperature and smoke, due to after burning.
  6. Low Pmax, due to late injection.
  7. Reduced engine power.

Chain Casing Inspection: 

  1. Before 4000 running hrs and after lengthy voyage, chain tension is checked at mid span of slack side, in transverse direction.
  •    Limited transverse movement is ½ to one link pitch on slack side.
  •    Excessive tension may cause chain breakage.
  •    Excessive slackness may cause vibration and eventual failure.
  1. Elongation [chain wear] is checked between 3000–5000 running hours.
  •  Total length of 10 links drawn tight and measured, and chain-stretch calculated          in % by comparing with original length of 10 links.
  • Maximum elongation: ≯2%.  Over 2%, the whole chain must be renewed.
  • Due attention given when elongation reaches 1.5%
  • Stretching is the results of pin and bushing surface wearing out.
  • Chain length is measured in terms of number of links.
  1. Nozzle sprayersLO pipes and oil flow and direction, checked.
  2. Loose bolts and pipe connections, checked.
  3. Every link checked for blemish, and bright marks due to misalignment of wheels.
  4. Sprocket teeth and wheel bearings checked for wear.
  5. Rubber clad guide barsrollers and side plates, checked for crack or damage.

How to adjust chain tension: 

  1. Tensioning device [chain tightener] is used, and adjusting is limited to removing a maximum 2 chain links.
  2. Limited transverse movement is ½ to one link pitch on slack side.
  3. When tightening, engine is to be turned ahead, that the slackness of chain is on tightening side.

Advantages of Chain Drive over Gear Train: 

  1. Unaffected by foreign particles as gear trains.
  2. Class requires only a few links [6 links] for spares. The whole set required for gear train.
  3. Even if the chain breaks, engine can still be operated after repair.
  4. Accuracy of camshaft drive is very high, because chain tightener can adjust and compensate for inevitable mechanical wear. Gear train is non-adjustable.
  5. Enable camshaft position to be placed higher, thus shorten the hydraulic connections of fuel pumps and exhaust valves, and minimise timing error. 

Camshaft Timing Adjustment (By Pin Gauge):

  • As the chain stretches and re-tensioned camshaft is gradually retarded.
  • Thus camshaft must be repositioned relative to crankshaft to correct the timings of Fuel Pumps and Exhaust Valves.
  1. Engine must be in Ahead position.
  2. Bring cylinder no: 1 to TDC, and ‘0’ on flywheel.
  3. Check that cylinder no: 1 crank throw is in TDC; (with D-1 pin gauge)
  4. Check that camshaft position deviates from original marking; (with D-2 pin gauge) 

      If camshaft deviates:

  1. Connect high-pressure hydraulic pump oil connections to flanges next to chain drive, and pressurised until oil seep along the camshaft.
  2. Turn the whole camshaft using tackle until D-2 pin gauge mark is in line with original marking. Fixed markings are on roller guide housing [after removing cover] and on camshaft.
  3. D-3 pin gauge is for Lubricator Unit.

Methods of reversing:

  1. Direct reversal of engine: Propeller turns in opposite direction.
  2. CPP: Blade angle changes, as engine rotates in same direction.
  3. Diesel electric system: Engine and electric generator run in constant direction, supplying power to reversible electric motor.
  4. Reverse gears and clutches: Propeller turns in opposite direction.

Reversing Interlocks:

  1. Safety cut-out devices for JCW, Piston CW, and
  2. Reversing direction interlock.
  3. Hydraulic blocking device and mechanical blocking device for start air handle.
  4. Reversing Servomotor.
  5. Telegraph
  6. Turning Gear.
  7. Overspeed Trip.

Advantages of single cam and double cam:

  1. Single cam on camshaft is suitable for reversing of 2/S, large bore engine. But not suitable for 4/S engine, because reversing of 4/S engine requires turning of Inlet Valve cam, Exhaust Valve cam, Fuel cam and arrangement for Starting air Distributor, with their correct timings.
  2. Double cam on camshaft, is moved axially by means of servo system or manual system, so that all cams get their correct timings, in 4/S engine. (Used also for 2/S).

Lost motion:

Angular period between TDC points for Ahead and Astern running will be the “lost motion” required for Astern running.

  1. When reversing 2/S, exhaust ported engine, both Fuel Injection timing and Air  Starting timing must be changed.
  2. Retiming is carried out by altering camshaft position radially, relative to crankshaft. This is called “lost motion” of camshaft.

Why ‘lost motion’ necessary on some engine?

  1. Some 2/S, large bore, exhaust ported engines are Direct Reversing.
  2. Both Fuel Injection timing and Air Starting timing must be changed.
  3. Camshaft has single cam
  4. Retiming is carried out by altering camshaft position radially, (not axially), relative to crankshaft, by means of servo system.

Why ‘lost motion’ not necessary on some engine?

  1. Some 2/S and 4/S engines are Direct Reversing.
  2. Inlet Valve cam, Exhaust Valve cam, Fuel cam and arrangement for Starting air Distributor, with their correct timings, must be changed.
  3. Camshaft has double cam
  4. Retiming is carried out by altering camshaft position axially, from Ahead cams to Astern cams, by means of servo and manual systems.

Lost Motion Camshaft:

  1. When reversing 2/S Exhaust Ported Engine, both Fuel Injection and Air Starting timings must be changed.
  2. Lost Motion Clutch cam design can be used to alter reversing direction.
  3. Camshaft position is altered radially relative to crankshaft.
  4. Same cam is used for ahead and astern running.
  5. Reversing Servomotor, operated by Engine Reversing Controls, is fitted to camshaft drive mechanism to do this.
  6. Camshaft will lose motion or be retarded, through required angle (about 98°) by oil operated Lost Motion Clutch, causing the Reversing Servomotor to rotate the camshaft.
  7. Fuel Pump cam and Air Start cam will now operate the Engine in reversed direction.
  8. Lost motion is carried out while the Engine is at rest.
  9. For Uniflow Scavenge Engine, the second Servomotor is fitted to Exhaust Valve drive.

4 Stroke Engine Reversing Systems: 

  1. By means of camshaft, shifting axially. (Direct Reversing)
  2. By CPP.
  3. By gearing and clutch.

Tacho Generator:

  • AC or DC generator that provides an output voltage proportional to rotational speed, to remote rpm counter (tachometer).
  • It may be used to measure speed, or as part of automatic control system, to regulate speed.
  • In Sulzer RTA, also used for overspeed trip, using output current.
  • Fitted on ME intermediate shaft, for remote rpm counter.
  • Fitted on housing of Reversing Servomotor, and driven by gear wheel on Cam Shaft for overspeed cut-out.

V-Type Connecting Rod:

1)  Side by side   2)  Articulated    3)  Fork and Blade.

 Cross-head bearing is prone to failure, because of:

  1. High sudden load: Full effect of combustion, directly to the bearing.
  2. High bearing pressure: Bearing is placed high and the whole assembly reciprocates full length of stroke. So, limited bearing area results in high specific load.
  3. Distortion: Bending moment and deflection are maximum at centre, where pin is often bored to carry piston rod.
  4. Poor lubrication: Due to following factors:
  • Slow oscillating movement: Connecting rod swings through 25~30°, hence it is difficult to build up full fluid film.
  • Reciprocating movement: Vertical movement of pin and bearing disturbs oil supply. It is difficult to get smooth, uninterrupted oil flow.

5.  Two-stroke engine: No load reversal takes place, which does not help the oil flow into loaded part of bearing.

Different approaches adopted to overcome cross-head bearing problems:

  1. Conjugate deflection: Bearing deflection follows that of crosshead pin. Natural deflections of pin and bearing remain in line, resulting in lower specific load.
  2. Crosshead mounted LO pump: Attached high-pressure pump, operated by connecting rod movement, press oil into bearing gap when bearing load is lowest.
  3. Large diameter stiff crosshead pin: Reduced Length/Diameter ratio, but pin deflection is minimum for uniform distribution of oil films over the whole bearing
  4. Continuous full length bearing face under pin:
  • Low specific load on bearing.
  • Load is transmitted directly downwards.
  1. Large diameter pin and smaller “Connecting rod : Crank throw” ratio: Obtained higher sliding velocity of the bearing, with better LO oil film, to carry high loads.
  2. Hardened crosshead pin with high degree of surface finish: Surface finish is preferably better than  0.1 µm.
  3. Eccentric bored bearing: One of the finest designs for crosshead, which gives the same effect of load reversal. (GMT engine)
  4. Thin shell bearing: Bearing is renewable and pin is detachable. Produces high load carrying capacity, and better resistance against fatigue failure. Thin shell gives true circular shape, which improves lubrication characteristics.

Thrust block:

  • To prevent axial movement of crankshaft, resulting from propeller thrust.

Measurement of Axial clearance of thrust pads:

  1. Thrust block is cleaned by draining oil. And lift the top cover
  2. Place screw jack between casing and the back of the coupling, and push the thrust shaft aft until the collar is hard up on the
  3. Check alignment of shaft and take feeler gauge reading of open pads by using long feeler. It is inserted at one corner and ease diagonally across to the other.
  4. Repeat this operation, moving the shaft
  5. Difference between two readings is total axial clearance.
  6. Axial clearance is 1 ~ 2 mm. (0.5 ~ 1.0 mm for new engine and for engine in service, it must not exceed 2.0 mm.) 

Alternative method:

  • Bear the thrust collar on foremost thrust bearing segment, by pressing the crankshaft
  • Set dial gauge (zero position) to flywheel.
  • Bear the thrust collar on aftmost thrust bearing segment, by pressing the crankshaft
  • Check clearance by reading the indication of dial gauge.

Radial clearance of journal bearing:

  1. Remove end cover with oil seal.
  2. Radial clearance measured, by taking lead reading, or roughly by means of feeler gauge.
  3. Radial Clearance is 0.5 ~ 0.8 mm for 440 mm dia.shaft.

Advantages of Tilting Pad Bearing:

  1. Have ability to absorb, change in direction of load, more readily.
  2. Have greater flexibility to absorb shaft deflection or misalignment.
  3. Tilting of pads, allow oil to form wedge shaped film, between faces of collar and pads.
  4. Wedge shaped oil film prevents metallic friction and enables the thrust pads to carry loads.

Disadvantages:

  • Each pad in a set must be exactly the same thickness, and even a ‘thou’ difference might result in a single pad carrying the entire load, thus increasing the risks of failure.

Plumber block renewal:  (during heavy weather)

Practically it should be done in calm weather, but following ways can reduce overheating of plumber block bearing.

  1. By applying maximum lubrication.
  2. By applying maximum cooling after opening out the cooling coil out into bilge.
  3. By reducing to suitable speed.
  4. Then the ship proceeds to the sheltered sea and renew the plumber block bearing.

Removal of plumber block bearing.

  1. Take immobilisation permit.
  2. Mark the relative positions between each bearing halves and between the lower bearing halve and the
  3. Remove the upper bearing halve.
  4. Lift the shaft at the place close to bearing by jackscrew.
  5. Remove the lower bearing halve with chocks from the stool.
  6. Sent both bearing halves for repair.

Refitting Procedure:

  1. After repairing, place back the lower halve with chocks on the stool. But foundation bolts should not be placed.
  2. Remove the shaft-lifting device.
  3. Boxed back upper half.
  4. Remove all coupling bolts of intermediate shaft flange close to the bearing.
  5. Alignment checked by gap and sag method.
  6. After ensuring that the alignment is satisfactory, tightened foundation bolts.
  7. Refit and tighten the coupling flange bolts.

Allowances:

Gap method  Equal to or less than  0.10 mm per meter for  1 to 2 pieces of shafts.

  • ≤  0.15 mm / m  for  3 to 4 pieces of shafts.
  • ≤  0.2 mm/m  for > 5 pieces.

Checked with a feeler gauge between the two coupling flange faces, at least at four places to check whether the bearing is in line with shaft or not.

 Sag method:

  • ≤  0.10 mm for 1 to 4 pieces of shafts.
  • ≤  0.15 mm for more than  4 pieces shafts.

Place a straight edge over the two flanges, at least four places around, to check whether the bearing is in line with shaft or not , or out of the shafting vertically and horizontally.

CPP:

Two main types:  Hub Servo and External Servo.

Hub Servo Type:

  1. Pitch altering mechanism, enclosed in propeller hub is most popular type, and used for higher power above 1000-Bhp.
  2. Propeller mechanism consists of 4 main parts:
  • Propeller hub incorporating servomotorcrank pin ring for turning blades, and necessary seals.
  • Oil distribution box (transfer box), mounted at forward end of tailshaft.
  • Control system; either pneumatic or
  • Hydraulic system; motor or shaft driven pumps, cooler, filter, and tank. etc.

Functioning Principle:

Movements of piston effect blade pitch:

  1. Servomotor in propeller hub consists of a piston rod with piston, which moves axially fore and aft when pressure oil is led to either side of piston.
  2. Piston rod is equipped with 4 or 5 “ears”, depending on number of propeller blades.
  3. Each ‘ear’ has a transverse slot in which a shoe slides.
  4. Eccentric crank pin fits into the hole of sliding shoe.
  5. Crank pin ring is supported on a bearing, which is built-in into hub body.
  6. When piston rod moves axially by pressure oilcrank pin ring rotates in circular motion, transmitted via pistonpiston rodslotsliding shoe, and crank pin.
  7. Propeller blades, which are bolted to crank pin rings, turn.

Failure Arrangements:

  1. Hydraulic system failure:  
  • Safety springs, fitted in main servo, push the servo piston forward, to allow propeller pitch to full ahead position, in the event of hydraulic system failure. The springs are powerful enough to overcome friction, but RPM of 70% maximum should not be exceeded.
  1. Telemotor system failure:
  • Hand-operated control valve is used, in the event of telemotor failure.
  1. Main hub servo failure: 
  • If main servo fails, the system has either Emergency Servo or Mechanical Link.

CPP Bridge Control:

  1. CPP in large vessels are usually fitted with Combinator Control on the Bridge.
  2. A single lever controlling both propeller pitch and engine speed, either through pneumatic or electronic means.
  3. In either case, closed loop circuits are employed, so that feedback of propeller position and engine speed, balance off the control signal.
  4. In electronic control system, ME load is kept at desired value, by automatically changing the propeller pitch, irrespective of variation in external conditions; e.g. change in resistance in propulsion caused by wind and sea.
  5. Main panel receives, converts and transmits signals, and a potentiometer for adjusting ME load, and an instrument showing fuel pump setting, is provided.
  6. Control panel on Bridge contains instrumentation corresponding to that of Main panel.

Pilgrim Nut: 

  1. Pilgrim nut is a threaded hydraulic jack, screwed onto tailshaft, provided with hydraulic oil connection, steel jacking ring and nitrile rubber tyre.
  2. It gives predetermined frictional grip between tailshaft and propeller boss.
  3. Spherical graphite cast iron tapered sleeve is bedded onto shaft cone, before mounting the boss, to achieve better fit.
  4. When combined with Pilgrim Nut pushing up, it ensures a good frictional grip.
  5. No key is required; friction is sufficient to prevent slip.

Propeller mounting procedure:

  1. Tapered sleeve is bedded onto shaft conepropeller boss is mounted, and pilgrim nut is run-down the shaft threads.
  2. Steel jacking ring on landing face of the nut, is loaded with hydraulic pump to predetermined pressure, and this forces the propeller hard on its cone.
  3. Pressure is released on jacking ring and air release plug
  4. Nut is hardened-up with spanner, and locked in normal way.

Propeller removing procedure:

  1. Pilgrim nut is taken-off the end of the shaft, reversed so that jacking ring is facing outward, and screw back the nut onto shaft, leaving some clearance between it and propeller boss.
  2. Studs are screwed into aft face of the boss and a “strong back” plate is fitted over the studs.
  3. Stud nuts are fitted so that the plate contacts with jacking ring.
  4. When hydraulic pressure is applied to jacking ring, propeller is pulled-off the conical end of the shaft.

Shaft Generator:

Shaft Generators are fitted on diesel engine propulsion ships, especially those sailing for long period at a constant ship speed.

Lloyd’s Requirements:

  1. Lloyd’s register would regard a shaft generator as a service main generator, if ME is intended to operate at constant speed. (CPP).
  2. If ME does not operate at constant speed, shaft generator would be disregarded as a service main generator, and at least 2 other independent generators would be required.

Running condition:

  1. Full generator capacity is available at within 60~100% of normal speed.
  2. More suitable for shaft with CPP, [constant shaft speed and variable blade pitch].

Advantages of shaft generator:

  1. Saving in fuel cost is main advantage.
  2. Saving in LO consumption, repair and maintenance cost due to reduced main generators’ running hours.
  3. Reduction in noise, space and weight, capital saving by reduction of numbers and ratings of main generators.

Disadvantages:

  1. Reduction in ship speed.
  2. Problems can arise to maintain electrical supply, during emergency manoeuvring astern.
  3. Increase in capital cost.

ME driven Generator:

  1. Fuel consumption is saved.
  2. Lower running and maintenance cost.
  3. Lower noise level in ER.
  4. Simple and most compact installation.

Varying speed of ME, driving a fixed pitch propeller, can be converted by variable gear ratio, to provide constant Generator speed.

COC ORAL EXAM PREPARATION (PART-10): SHIP CONSTRUCTION

Ship_size_(side_view)Image Credit: wikipedia.org

Definitions and Ship’s Dimensions

Hull:
The structural body of a ship including shell plating, framing, decks and bulkheads.
 Afterbody :
That portion of a ship’s hull abaft midships.
 Forebody:
That portion of a ship’s hull forward midships.
 Bow :
The forward of the ship
 Stern :
The after end of the ship
Port :
The left side of the ship when looking forward
Starboard :
The right side of the ship when looking forward
Amidships:
point midway between the after and forward perpendiculars

Length Overall (L.O.A.):
Length of the vessel taken over all extremities.
Ship Construction- Ship Dimensions
Base line:
A horizontal line drawn at the top of the keel plate. All vertical moulded dimensions are measured relative to this line
Moulded beam:
Measured at the midship section is the maximum moulded breadth of the ship
Moulded Draft/ Draught:
The distance from the bottom of the keel to the waterline. The load draft is the maximum draft to which a vessel may be loaded
Moulded Depth:
Measured from the base line to the heel of the upper deck beam at the ship’s side amidships.
 Sheer:
Curvature of decks in the longitudinal direction. Measured as the height of deck at side at any point above the height of deck at side amidships
Camber / Round of Beam:
Curvature of decks in the transverse direction. Measured as the height of deck above the height of deck at side
Rise of floor / Deadrise:
The rise of the bottom shell plating line above the base line. This rise is measured at the line of moulded beam
Half siding of keel:
The horizontal flat portion of the bottom shell measured to port or starboard of the ship’s longitudinal centre line. This is useful dimension to know when dry-docking.
Tumble home:
The inward curvature of the side shell above the summer load line.
Freeboard:
The vertical distance measured  from the waterline to the top of the deck plating at the side of the deck amidships. Normally exposed to weather and sea.
Flare:
The outward curvature of the side shell above the waterline. It promotes dryness and is therefore associated with the fore end of ship
Extreme Beam:
The maximum  beam  taken over all extremities.
Extreme Draft:
Taken  from the lowest point of keel to the summer load line. Draft  marks  represent extreme drafts.
Extreme  Depth:
Depth of vessel  at  ship’s side  from  upper deck  to  lowest point  of keel.
Half  Breadth: 
Since  a  ship’s  hull  is  symmetrical about  the  longitudinal centre line, often  only the half beam  or half breadth at any section  is given.
SCANTLING
The dimensions of the structural items of a ship, e.g. frames, girders, plating , etc.

strong>INTERCOSTAL
Composed of separate parts, non-continuous
CENTER OF FLOATATION
It is the center of the waterplane area and is the axis about which a ship changes trim.

CENTER OF BUOYANCY
It is the center of the underwater volume of the ship where the force of buoyancy acts.

CENTER OF GRAVITY
It is the point at which the whole weight of the object may be regarded as acting. If  the object is suspended from this point, it will remain balanced and not tilt.

TONNAGE MEASUREMENT

  • This is often referred to when the size of the vessel is discussed, and the gross tonnage is quoted from Lloyd’s register.
  • Tonnage is a measure of the enclosed internal volume of the vessel, 100 cubic feet representing one ton
  • Its normally divided into categories as follow:
  1. DISPLACEMENT TONNAGE
  • A ship’s displacement is the sum of the ship’s actual weight (lightweight) and it’s contents (deadweight).
  • The metric unit of measurement is 1 tonne (= 1000 Kg).
  • The displacement represents the amount of water displaced by the ship expressed in tonnes.
  • The weight of water displaced therefore equals the weight of the ship

TONNE PER CENTIMETRE (TPC)
It is the mass required to increase the mean draught by 1 centimetre.

LOAD DISPLACEMENT
The weight of the ship and its content, measured in tonne. The value will vary according to the ship’s draught.

DEADWEIGHT SCALE
It is a scale diagram indicating the deadweight of the ship at various draughts.

FORM COEFFICIENT
It is devised to show the relationship between the form of  the ship and the dimension of the ship.

2. Lightweight Tonnage (LWT)

  • The lightweight is the weight of the ship as built (hull, machinery) including boiler water, lubricating oil and the cooling water system.
  • Lightweight like displacement is expressed in units of tones.
  • It assumes importance in a commercial sense only when considering the value of the vessel which is to be broken up for scrape.

3. Deadweight tonnage (DWT)

  • Deadweight is the weight of the cargo which a ship carries plus weights of fuel, stores, water ballast, fresh water, crew and passengers and baggage.
  • It is the difference between the loaded ship displacement and the lightweight.

4. Gross Tonnage (GT)

  • Measurement of total internal volume of a vessel and includes all under deck tonnage and all enclosed spaces above tonnage deck.
  • 100 cubic feet of space being considered as 1 ton

5. Nett Tonnage (NT)

  • Ship measurement derived from gross tonnage by deducting spaces allowed for crew and propelling power.
  • 100 cubic feet of space being reckoned as 1 ton

LOAD LINE

The marking on the ship side that relate to the loading condition of the ship termed as the load line mark.

Load line mark

  • consists of a ring 300 mm in outside diameter and 25 mm thick which is
  • intersected by a horizontal line 450 mm in length and 25 mm thick, the upper edge of which passes
  • through the centre of the ring. The centre of the ring is placed amidships and at a distance equal to the assigned summer freeboard measured vertically below the upper edge of the deck line.

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Margin Plate: 

  1. The outboard strake of the inner bottom.
  2. Knuckle down to the shell by means of Margin Plate at angle of 45°to tank top, meeting the shell almost at right angle.
  3. It can form a bilge space.

Keel plate:  

Keel is a horizontal plating of increased thickness, which runs along the centre line, for complete length of bottom shell plating.

Types of keel:   (1) Bar keel  (2) Flat plate keel  (3) Duct keel.

 Bar keel:  

  • The first type, used from wood to iron ship building.
  • Do not provide sufficient strength for larger ship.
  • No direct connection between the keel and floor.

Flat plate keel: 

  • A keel of welded ship. The centre girder is attached to the keel and inner bottom plating by continuous welds.
  • Keel plate width is about 1 to 2 meter
  • It must be full thickness, for 3/5 of length amidship and then thickness may reduce towards the ends of ship.

Duct keel:  

  1. An internal passage of watertight construction, running same distance along the length of ship, often from fore peak to forward machinery space bulkhead.
  2. It is to carry pipeworks, and entrance is at forward machinery space bulkhead through a watertight manhole.

Bulkhead

Class A bulkhead

  • Constructed to prevent passage of flame for 1 hour standard fire test at 927°C
  • It must be insulated so that the unexposed sides will not rise more than 139°C above the original temperature within the time, as follows:

Class A- 60 ,  1 hour:       Class A- 30 ,  30 minutes.

Class B bulkhead:

  • Constructed to prevent passage of flame for ½ hour standard fire test
  • It must be insulated so that the unexposed sides will not rise more than 139°C above the original temperature within the time, as follows.

Class B- 15 ,  15 minutes:       Class B- 0 ,  0 minute.

Class C bulkhead:   

  • They are constructed of non-combustible material.

 Standard fire test:     

  • The exposure of a material specimen in a test furnace, to a particular temperature for a certain period of time.

Collision Bulkhead:

  • Foremost major watertight bulkhead, which extends from bottom to main deck (upper deck).
  • It is at a distance of L/20  from forward perpendicular.

Corrugated bulkhead:   

  • Used on transverse bulkhead, thus improves transverse strength.

Non-watertight bulkhead:   

  • Any bulkhead, which does not form, part of a tank or part of a watertight subdivision of a ship, may be non-watertight.

Wash bulkhead: 

  • perforated bulkhead fitted into a cargo tank or deep tank, to reduce sloshing or movement of liquid through the tank.

After peak bulkhead:

  • Provided to enclose the stern tube in watertight compartment.
  • Aft peak bulkhead needs only to extend to first deck above load water line.
  • Plating must be doubled to resist vibration around stern tube.

Minimum required bulkhead:

  1. One collision bulkhead.
  2. An after peak bulkhead.
  3. One bulkhead at each end of machinery space.
  4. Total no: of bulkheads depends upon the ship and position of machinery space

Functions of bulkhead:

  1. To increase transverse strength of ship, particularly against racking
  2. To divide the ship into watertight compartments.
  3. To give protection against fire.
  4. To prevent undue distortion of side shell.
  5. To restrict volume of water, which may enter the ship, if shell plating is damaged.

Construction of bulkhead:

  • Collision bulkhead must extend from bottom to upper deck.
  • Aft peak bulkhead needs only extend to first deck above load water line.
  • All others must extend to uppermost continuous deck.
  • Plating usually fitted vertically, and thickness gradually increases from the top downward.
  • Stiffeners are fitted at 750mm apart, but collision bulkhead and deep tanks have 600mm spacing.

Why Collision Bulkhead kept at L/20 of the ship?

  • In the events of collision and grounding, standard of subdivision has to give good chance, that the ship remains afloat under such emergencies.
  • Longitudinal Bulkheads are avoided, as far as possible, as they might cause dangerous angles of heel, in the event of flooding of large compartment through damage.
  • Transverse Bulkheads are reliable in this case, and Classification Society requires a watertight Collision Bulkhead within reasonable distance from forward.
  • If the ship is supposed to have wave trough amidships, there will be excess weight amidships and excess buoyancy at the ends, hence the ship will be (Assuming wave length = length of ship)
  • If the ship is supposed to have wave crest amidships, there will be excess weight at the ends, and excess buoyancy amidships; hence the ship will be
  • By “Trochoidal Theory”, wave height from trough to crest is 1/20 of the wave length, therefore maximum shearing force usually occurs at about L/20 of ship from each end.
  • For this reason, Collision Bulkhead is located at L/20 of the ship, so that it is not so far forward, as to be damaged on impact. Neither should it be too far aft, so that the compartment flooded forward causes excessive trim by bow.

Panting:

  • As wave passes along the ship, they cause water pressure fluctuation, which tends to create in and out movement of the shell plating, especially at forward end.
  • This in and out movement is called panting.
  • Resisting structures against panting are beams, brackets, stringer plates, etc.

Racking:

  • When a ship rolls, there is a tendency for the ship to distort transversely.
  • This is known as racking.
  • Resisting structures are beam knee, tank side bracket, and especially transverse

Slamming or Pounding:

  • When ship is heaving and pitching, the fore end emerges from water and re-enter with a slamming effect.
  • It is called pounding.
  • Resisting structure: extra stiffening at the fore end.

Hogging:

  • When buoyancy amidships exceeds the weight due to loading, or when the wave crest is amidships, the ship will hog.

Sagging:

  • When the weight amidships exceeds the buoyancy, or when the wave trough is amidships the ship will sag.

Function of port hole:
1) For light    2) For ventilation    3) For escape for emergency.

Transverse stresses:

  • Transverse section of a ship is subjected to transverse stresses, i.e. static pressure due to surrounding water, as well as internal loading due to weight of structure, cargo, etc.
  • Structures or parts, that resist transverse stresses:
  • Transverse bulkhead
  • Floors in double bottom
  • Brackets between deck beams and side frame
  • Brackets between side frame and tank top plating
  • Margin plates
  • Pillars in holds and tween deck.

Local stresses:

Causes:

  • Heavy concentrated loads like engineboiler.
  • Deck cargo such as timber.
  • Hull vibration.
  • Ship, resting on blocks in dry dock.

Dynamic forces:

  • Caused by the motion of the ship itself
  • A ship among waves has three linear motions:
  1. Vertical movement: heaving 
  2. Horizontal transverse movement: swaying
  3. Fore and aft movement: surging And
  • three rotational motions:
  1. Rolling about longitudinal axis
  2. Pitching about transverse axis
  3. Yawing about vertical axis.
  • A ship among waves has three linear motions:
    1. Vertical movement: heaving
    2. Horizontal transverse movement: swaying
    3. Fore and aft movement: surging  AND 
  • three rotational motions:
    1. Rolling about longitudinal axis
    2. Pitching about transverse axis
    3. Yawing about vertical axis.

The difference between Timber Load Line and Load Line:

  • When ship is carrying timber, the deck cargo gives additional buoyancy and a greater degree of protection against the sea.
  • The ship has smaller freeboard than normal (type-B) vessel.

Bulbous Bow:

  • It is a bulb shaped underwater bow.
  • Reduce wave making resistance, and pitching motion of the ship
  • Increase buoyancy forward, and hence reduce pitching of the ship
  • Outer plating of bulbous bow is thicker than normal shell plating, to resist high water pressure and possible damage cause by anchor and cables.
  • Due to reduction in wave making resistance, it can reduce SFOC under full speed and loaded condition.

Bow Thruster:

  • Lateral Bow Thrusters are particularly useful, for manoeuvring in confined water at low speed.
  • For large vessel, used at channel crossing, and docking.
  • For research vessels and drilling platform, etc. very accurate positioning
  • Bow Thruster consists of: (As a Rule)
  • controllable pitch or reversible impeller, in athwartship watertight tunnels.
  • Bridge controlled and driven by
  • Thrust provided is a low thrust, about 16 tons.
  • Greatest thrust is obtained, when ship speed is zero.
  • Less effective, when ship gets underway.
  • Athwartship tunnels appreciably increases hull resistance.
  • Close the tunnels at either end, when not in use, by butterfly valve or hydraulic valve.

Cofferdam:

  • narrow void space between two bulkheads or floors that prevents leakage between the adjoining compartments.
  • In tankers, between cargo tanks: In ER, between DB LO tank (sump tank) and adjacent tanks. Maximum width =  760 mm.

Double Bottom:

  • The double bottom consists of outer shell and inner skin, 1m and 1.5 m above the keel and internally supported by

Double Bottom Tank:

  • Double bottom space is subdivided longitudinally and transversely, into large tank, by means of watertight structures. Its functions are:
  1. Protection of shell in the events of damage to bottom shell.
  2. Tank top being continuous increases the longitudinal strength.
  3. To act as platform for cargo and machinery.
  4. Can be used for storage of fuelfresh waterballast, and for correcting list, trim and draught.
  5. Diminish oil pollution, in the event of collision.

Wing Tank:

Purpose:

  • To carry water ballast or liquid cargo.
  • Protection of shell in the events of damage to side shell.
  • To locate oil cargo tank
  • To correct list of the ship.

Deep Tank:

  • When ship is underway in light condition, it is necessary to carry certain amount of water ballast.
  • If DB tanks alone are used for this purpose, the ship might be unduly “stiff”.
  • So it becomes a practice to arrange one of the lower holds, so that it can be filled with water when necessary.
  • This permits a large amount of ballast to be carried without unduly lowering the centre of Gravity of the ship.
  • Such a hold is called a Deep Tank.
  • This tank is usually designed to carry dry cargo, and in some cases may carry vegetable oil or oil fuel as cargo.
  • If the tank extends full breadth of the ship, a middle line bulkhead, called Wash Plate must be fitted to reduce free surface effect.
  • Strength of Deep Tank structure is greater than that required for dry cargo hold bulkhead.

Freeboard:

  • Vertical distance from water load line, up to the main deck [freeboard deck], measured at the shipside amidships.
  • Main deck is the highest deck that is water sealed. Water falling on upper decks may run down companion ways, but it cannot go any further down into the ship than the main deck.
  • Freeboard has considerable influence on seaworthiness of the ship. The greater the freeboard, the larger is the above water volume of the ship and this provides reserved buoyancy, assisting the ship to remain afloat in the event of damage.

Reserved buoyancy:

  • Watertight volume of a ship above the water line is called the reserved buoyancy.
  • It can be defined as the buoyancy, a ship can call upon, to meet losses of buoyancy in case of damage to main hull. [Water plane area, multiplied by freeboard.]

 Purpose:

  • To meet loss of buoyancy, in case of hull damage.
  • To provide sufficiency of freeboard, to make the vessel seaworthy.

Marking of freeboard:

Marking of minimum allowable freeboard, in conjunction with an overall seaworthiness evaluation, is to ascertain that the vessel:

  1. is structurally adequate for its intended voyages,
  2. has adequate stability for its intended voyages,
  3. has a hull that is essentially watertight from keel to freeboard deck, and watertight above these decks,
  4. has a working platform that is high enough from water surface, to allow safe movement on exposed deck, in the heavy seas,
  5. has enough reserved buoyancy above the water line, so that vessel will not be in danger of foundering and plunging when in heavy seas.

Hatchways: 

These constructions must be in accordance with standards, such as heights of coamings, covers, and fittings exposed. They have standard of strength and protection.

Machinery Casing:  

Machinery space openings on exposed portion of freeboard deck (superstructure deck), must be provided with Steel Casing, with any opening fitted with Steel Doors. Fiddley Opening is to have permanently attached Steel Covers.

Tonnage:  

  • Tonnage is a measure of cubic capacity, where one ton represents  100 ft³ or  2.83 m³. It is a measure of the ship’s internal capacity.

Gross Tonnage:

  • Gross tonnage is the total of the Underdeck tonnage & the tonnage of the following spaces:
  1. Any Tweendeck space , between second and upper deck.
  2. Any excess of hatchways over ½ % of vessel’s Gross Tonnage.
  3. Any permanently closed-in spaces, on or above the upper deck.
  4. Any engine light and air space on or above upper deck, at shipowner’s option and with Surveyor’s approval.
  5. Certain closed-in spaces, on or above the upper deck are not included in gross tonnage, and these are known as Exempted Spaces.

Exempted spaces:

  • Dry cargo space.
  • Space fitted with machinery or condensers.
  • Wheelhouse, chartroom and radio room.
  • Galley and bakery.
  • Washing and sanitary spaces in crew accommodation.
  • Light and air spaces.
  • Water ballast tanks not appropriated for any other use.

 Net or Registered Tonnage:

  • It is obtained by making “deductions” from the Gross Tonnage.
  • Principal “Deducted Space”, which already have been included in Gross Tonnage are:
  1. Master’s and crew accommodation.
  2. Chain lockers and space for working anchor and steering gear.
  3. Propelling Power Allowance.
  4. Ballast tank, capacity ≯ 90%.
  • Port and Harbour dues are assessed on Net Tonnage.

Where Tonnage value is used?

  1. To determine port and canal dues.
  2. To determine Safety Equipment.
  3. To measure the size of fleet.

Propelling Power Allowance:

The largest “Deduction” and is determined according to certain criteria, as follow:

  1. If machinery space tonnage is between 13% and 20% of gross tonnage, PPA is 32% of gross tonnage.
  2. If machinery space tonnage is less than 13% of gross tonnage, PPA is the amount expressed as a proportion of 32% of gross tonnage.
  3. If machinery space tonnage is more than 20% of gross tonnage, PPA is 1.75 times the machinery space tonnage.
  4. There is a maximum deduction for propelling power of 55% of gross tonnage, remaining after all other deductions have been made.

Tonnage Deck:  The tonnage deck is the second deck, except in single deck ships.

Water tightness of steel hatch cover:

Rubber jointing is used, and the hatch being pulled down by cleats and cross joint wedges.  Cleats are placed about  2 m apart with minimum of two cleats per panel. Cross joint wedges should be 1.5 m apart.

Hose test and chalk test:

  1. To check the water tightness of hatch covers and watertight doors :
      • By using water jet pressure of 2 kg/cm² and a distance of  5 m, and jet diameter  ½”.
      • If hose test cannot carried out, chalk test can be done.

2. Cover or door seals, painted with chalk powder, and close the cover or door tightly.
3.  Open the cover or door, and check whether the chalk painted is cut off or not.

COC ORAL EXAM PREPARATION (PART – 9): REFRIGERATION & AIR CONDITIONER

header_refrigeration

Image Credit: almaco.cc

Refrigeration:

 What is a Refrigerant?

  • Refrigerants are used as working substances in a Refrigeration systems.
  • Fluids suitable for refrigeration purposes can be classified into primary and secondary refrigerants.
  • Primary refrigerants are those fluids, which are used directly as working fluids, for example in vapour compression and vapour absorption refrigeration systems.
  • These fluids provide refrigeration by undergoing a phase change process in the evaporator.
  • Secondary refrigerants are those liquids, which are used for transporting thermal energy from one location to other. Secondary refrigerants are also known under the name brines or antifreezes

 

Desirable properties of a refrigerant

  1. Low boiling point (otherwise operation at high vacua becomes a necessity)
  2. Low condensing pressure (to avoid heavy machine plant scantling and reduce the leakage risk)
  3. High specific enthalpy of vaporisation ( to reduce the quatity of refrigerants in circulation and lower machine speeds, sizes etc.)
  4. Low specific volume in vapour state (reduces size and increases efficiency)
  5. High critical temperature (temperature above which vapour cannot be condensed by isothermal compression)
  6. Non corrosive and non solvent (pure and mixed)
  7. Stable under working conditions
  8. Non flammable and non explosive
  9. No action with oil ( the fact that most refrigerants are miscible may be advantageous e.e. the removal of oil films, lowering pour points etc, provided separators are fitted
  10. Easy leak detect
  11. Non toxic
  12. cheap, easily stored and obtained

Refrigeration Working cycle:

The refrigeration cycle is shown in the Figure and can be broken down into the following stages:

234

Fig: Vapor Compression Refrigeration working cycle

Cycle 1-2: 

Low-pressure liquid refrigerant in the evaporator absorbs heat from its surroundings, usually air, water or some other process liquid. During this process it changes its state from a liquid to a gas, and at the evaporator exit is slightly superheated.

Cycle 2-3: 

The superheated vapour enters the compressor where its pressure is raised. The temperature will also increase, because a proportion of the energy put into the compression process is transferred to the refrigerant

Cycle 3-4: 

The high pressure superheated gas passes from the compressor into the condenser. The initial part of the cooling process (3-3a) de-superheats the gas before it is then turned back into liquid (3a-3b). The cooling for this process is usually achieved by using air or water. A further reduction in temperature happens in the pipe work and liquid receiver (3b – 4), so that the refrigerant liquid is sub-cooled as it enters the expansion device

Cycle 4-1:

The high-pressure sub-cooled liquid passes through the expansion device, which both reduces its pressure and controls the flow into the evaporator

Thermostatic Expansion Valve (TEV)

The thermostatic expansion valve performs following functions:
1) Reduce the pressure of the refrigerant: The first and the foremost function of the thermostatic expansion valve is to reduce the pressure of the refrigerant from the condenser pressure to the evaporator pressure. In the condenser the refrigerant is at very high pressure. The thermostatic expansion valve has an orifice due to which the pressure of the refrigerant passing through it drops down suddenly to the level of the evaporator pressure. Due this the temperature of the refrigerant also drops down suddenly and it produces cooling effect inside the evaporator.
2) Keep the evaporator active: The thermostatic expansion valve allows the flow of the refrigerant as per the cooling load inside it. At higher load the flow of the refrigerant is increased and at the lower loads the flow is reduced. It won’t happen that the load on the evaporator is high and the flow of the refrigerant is low thereby reducing the capacity of the evaporator. The thermostatic expansion valve allows the evaporator to run as per the requirements and there won’t be any wastage of the capacity of the evaporator. The TEV constantly modulates the flow to maintain the superheat for which it has been adjusted.
3) Allow the flow of the refrigerant as per the requirements: This is another important function of the thermostatic expansion valve. It allows the flow of the refrigerant to the evaporator as per the load on it. This prevents the flooding of the liquid refrigerant to the compressor and efficient working of the evaporator and the compressor and the whole refrigeration plant.

TEV construction:

  1. Small quantity of Vapour Refrigerant is sealed in a bulb or phial, and attached to Compressor suction pipe, just coming out from Evaporator.
  2. Other end is connected by Capillary Tube to the chamber above Flexible Bellow in valve body.
  3. The space below the Bellow is in communication with Evaporator outlet pressure (this is called Equalising Line)
  4. If no further action is taken, pressure above and below the Bellow will be equalised and hence no superheat is obtained.
  5. This is overcome by providing adjustable Bias Spring under the Bellow, and Bias Spring pressure is proportional to required superheat.

 Operation:

  1. Refrigerant Liquid from Condenser enters into TEV via Dryer, it expands to Evaporation Pressure, and some flash gas is formed.
  2. Flash Gas amount varies between 25 – 35%, depending on refrigerant typeplant capacity and ambient temperature.
  3. Mixture of this expanded gases and some part of liquid, passed into Evaporator, where complete Evaporation takes place.
  4. Evaporator outlet pressure plus Spring pressure tends to close the valve, and is opposed by the pressure above the Bellow, trying to open it.
  5. This pressure above the Bellow is in relation to temperature in Compressor suction pipe.
  6. Equilibrium condition is reached, when Superheat is correct at phial attachment point.
  7. Starved condition in Evaporator will result greater Superheat, so expansion of Vapour Refrigerant in phial will tend to open the valve further, to increase the flow.
  8. Flooded condition in Evaporator will result lower Superheat, so contraction of Vapour Refrigerant in phial will tend to close the valve further, so decrease the flow.
  9. Superheat Temperature adjusted at: 3 – 6°C, by Bias Spring pressure.

 Why Equalising Connection is fitted

  1. In some plant having large Evaporator or Multi-circuit Evaporator, excessive pressure drop across Evaporator occurs, and always tend to starve the Evaporator and increase the Superheat.
  2. To counteract this, if pressure drop across Evaporator, exceeds 3 bar, an Equalising Connection must be provided at TEV.
  3. A direct connection between underside of Bellow and suction piping of Compressor, preferably between phial and Compressor.

Safety devices on Refrigeration Plant:

  1. LP cut-out switch: Set at a pressure corresponding to 5°C below the lowest expected evaporating gauge reading.
  2. HP cut-out switch: Set at a pressure corresponding to 5°C above the highest expected condensing gauge reading.
  3. Lub Oil LP cut-out: Oil pressure usually set at   2 bar  above crankcase pressure.
  4. Condenser cooling water LP cut-out.
  5. Liquid shock valve on Compressor cylinder head.
  6. Bursting disc on cylinder head, between inlet and discharge manifold.
  7. Bursting disc on Condenser, [if fitted].
  8. Relief valve on Condenser.
  9. Master solenoid valve: To prevent liquid being entered into Compressor, when the plant is standstill, especially in Large Plant.

Refer plant survey:

  1. General examination of machinery and testing under working condition.
  2. The log examined, to ascertain successful operation during voyages.
  3. Compressor and prime mover to be open-up and examined.
  4. Primary system to be leak-tested to their w. p. and brine cooling coils are to be hydraulically tested to 3  kg/cm².
  5. Survey is done at 1 year from the date of installation, and special periodical surveys are to be carried out at 5 years intervals. ( 1+ 5 )

CFC: Chlorofluorocarbon

  • Due to damaging effects on OZONE layer and causing Global Warming, most CFCs are now replaced by HFCs,
  • HFC 134a has Ozone Depletion Potential, ODP ‘0’ and Global Warming Potential, GWP ‘0.28’.
  • Banned from 19 May 2005

 Defrosting: 

A method of removal of frost, built-up on Evaporator coils. Defrosting should be done before snow thickness exceeds ¼”.

 Reasons for defrosting:

  1. Affecting heat transfer properties.
  2. Affecting air flow and circulation.
  3. Liquid back to Compressor. 

Defrosting Systems:

  1. Water wash defrosting
  2. Hot gas defrosting
  3. Electric defrosting
  4. Manual shut down defrosting
  5. Warm brine defrosting

Various methods to defrost Brine System: 

  1. Hot brine thawing: Best and fastest method, used powerful brine heater with separate thawing system. Watertight trays under the pipes, collected the dripping water.
  2. Hot air from atmosphere: It is important that isolating doors in air trunks are perfectly tight, so as to prevent hot air going into cargo spaces.
  3. By shutting off brine : Allow the snows to be melted by the heat of the air in circulation. Very slow operation and tends to throw back great deal of moisture into cargo space.

 

  • Direct expansion grid system:   Hot gas defrosting.
  • Battery cooling system:    Water spray, electrical or steam heater.
  • Brine cooling:    Hot brine thawing.

Cargo Fridge Defrosting:

  1. In Battery System, hot brine passing brine heater is used.
  2. Steam is released to brine heater and brine flow is restricted by brine inlet valve, until brine temperature has risen above 0°
  3. Brine temperature of 43°C is suitable for defrosting.

Why Cold Room is defrosted and how many methods of defrosting?

  • Coil Room is required to defrost to gain more Heat Transfer Efficiency.
  • Methods of Defrosting are: ( i)  Plant stopped and manual watering    (ii)  Hot gas circulating   (iii)  Electric Heater.

Faults in Shipboard Refrigeration Systems

  1. Undercharging of Refrigeration System

 Indication:

  • Compressor is running hot and performance of the compressor falls off due to high superheat temperature at the suction side of compressor.
  • Suction and discharge pressure of the compressor is low.
  • Large vapor bubbles in the liquid sight glass.
  • Low gauge readings in the condenser.
  • Ammeter reading for the compressor motor is lower than normal.
  • Rise in room temperature which is to be cooled.
  • Compressor is running for extended period of time.

Causes:

  • Leakage of refrigerant at the shaft seal, flange couplings, valve gland etc.
  • Expansion valve may be blocked at the strainer.
  • Partial blockage of refrigerant at the filter or drier or evaporator may cause undercharging.

Action:

  • Identify and rectify the leakage of refrigerant from the system.
  • Clean the filter and drier.
  • Charge the system with fresh refrigerant as required.

2.  Overcharge of Refrigeration System

Indication:
•           The liquid level in the condenser is too high (high condenser gauge reading). This will reduce the available condensing surface, with corresponding increase in the saturation temperature and pressure.
•           High pressure switch of the refrigerant compressor activates and stops the compressor.
•           The suction and the discharge pressures are high.
Causes:
•           It may be due to the reason that excessive refrigerant has been charged in the system.
•           Air in the system may also cause over charging indication.
•           It may also be due to the formation office on the regulator.
Action:
•           Remove the refrigerant from the system. This is done by connecting a cylinder to the liquid line charging valve, starting the compressor, and then operating the charging valve.
•           Purge the air from the system and maintain effective cooling.
•           Remove ice from the regulator by using any of the defrosting methods.

3.  Moisture in the System
This normally comes with the ingress of air in the system. Moisture may freeze at the expansion valve, giving some of the indication of under charging. It will contribute to the corrosion in the system. It may cause lubrication problems and breakdown of the lubricating oil in the refrigerant compressor.

Action:
–  Renew silica gel in case of minor moisture.
–  collect refrigenant and remove all air and moisture by vacuum pump if the amount is huge.

4.  Air in the System
Indication:
•  This may cause the refrigeration compressor to overheat, with a high discharge pressure and normal condensing temperature.
•  There are possibilities of small air bubbles in the liquid sight glass of the condenser.
•  Condensing pressure of the refrigerant in the condenser may be high.
•  If there is excessive air, it may reduce the cooling capacity of the system, making the compressor to run for the extended period of time.
•  It may cause the gauge pointer of the condenser to jump indefinitely.

Causes:
•  During charging, air may enter in to the system.
•  If Freon-12 is used air may leaks in to the suction line because the working pressure of the Freon-12 refrigerant is less than the atmospheric pressure.
Action:
•  Air in the system can be removed by collecting the system gas in the condenser, leaving the condenser cooling water on and venting out the air from the top of the condenser because air will not be condensed in the condenser but remains on top of the condenser above the liquid refrigerant.
•  Connect the collecting cylinder to the purging line of the condenser, open the valve, and collect air in the cylinder.
•  After purging the air from the system don’t forget to shut the purging valve.
•  Check the level of the refrigerant in the system. If required, charge the system with fresh refrigerant.
•  Restart the compressor with all safety precautions.

5.  Oil in the Refrigeration System
Indication:
•  Temperature is not dropping in the cold rooms as normal, due to fact that oil act as insulation in the evaporator.
•  It may cause excessive frost on the suction line.
•  Refrigerant compressor runs for the extended period of time.
•  Lubricating oil level in the compressor will drop.
•  Refrigerant level will fall if oil has caused blockage.

Causes:
•  This may happen if the oil separator is not working properly.
•  Oil may carry over from the compressor and may not come back to the compressor due to blockage in the system.
•  Defective piston rings or worn out liner of the compressor may cause the oil to carry over along with the refrigerant.
•  Compressor may take high capacity current during starting.

Action:
•  Check the oil separator for proper functioning.
•  Check the drier for proper cleaning and if its require cleaning clean it
•  Evaporator coil should be drained to remove any trace of oil.
•  If there is oil in the cooling coils, increase the condenser and evaporator temperature differentials and remove excess frost on the suction pipe.
•  Heat pipes with blow torch.

6.  Flooding of Refrigerant in the System
This is seen as liquid getting back to the suction of the refrigerant compressor. It may be due to a faulty or incorrectly adjusted expansion valve and also due to solenoid valve leakage. It may also result from overcharging of the refrigeration system. Flooding may lead to an iced up evaporator.

7.  Evaporator Coil Icing:
Icing of the evaporation coils which may happen due to:
1. Cause:Too low temperature setting
Action: Increase the coil temperature by adjusting TEV or it’s sensor.
2. Cause: The coil capacity is less
ActionInstall large capacity evaporator coils
3. Cause: Defrost is not operational
Action: Check if the defrost system is functioning at regular intervals.

8.  Compressor Start and Stops Frequently:
If while maintaining the correct temperature of the ship’s provision room or reefer cargo, the reefer compressor is frequently cutting-in and out, then such problem needs to be sorted out immediately. The most normal causes for such operation are:
1. Cause: Wrong Setting of Cutouts: It may be because the high pressure (HP) cutout is set too high or LP cutout is set too low
Action: Check and change the setting to advisable limit
2. Cause: Differential Setting Span is Small: The low pressure (LP) cut out is provided with starting and stopping pressure setting. If the setting span is too small, it will lead to frequent cut-in and cut-out of the compressor
Action: Change the setting and increase the span between starting and stopping compressor pressures.
3. Cause: Defective Valves: If the compressor discharge valve is leaky or the line solenoid valve is not closing properly, this will lead to variation in sensor pressure and result in frequent cut-in and cut-out of compressor
Action: Replace all the defective valves
4. Cause: Clogged Suction Filters: Compressor is provided with a filter in the suction line. If that is clogged, it will lead to frequent LP cut out
Action: clean the filter.

 9.  Compressor Starts But Stops immediately
When the compressor in the reefer circuit starts and suddenly stops, it can be because of the following reasons:
1. Cause: Low pressure cut out gets activated
Action: Ensure that all the suction line valves are in open condition, the refrigeration is properly charged and the low pressure cut out is not defective.
2. Cause: Defective oil pressure cut out
Action: Check for proper functioning of oil pressure cutout and replace the defective cutout.
3. Cause: Defrosting timer is getting activated frequently
Action: If the defrost timer is getting activated frequently, leading to cutout of compressor, check and repair defrost timer.
4. Cause: The lube oil level is below required level
Action: This can be because of leakage of lube oil from seal or carry over of oil. Rectify the leakage and refill the oil level.
5. Cause: Foaming of oil leading to reduced oil pressure
Action: Ensure no foaming takes place, renew the oil if required.
6. Cause: Motor overload cutouts are activating
Action: Ensure that electrical motor trips are working properly.

10.  Excessive icing up at Compressor suction:

Causes:

  1. Abnormal operation of TEV.
  2. Overcharge of the system.
  3. Moisture in the system owing to dirty Dryer.
  4. Defective Suction valve:

    Indication:

  1. Continuous running of Compressor.
  2. Insufficient cooling effects.
  3. Noisy operation.
  4. High suction pressure.

11.   Defective Discharge valve:

    Indication:

  1. Continuous running of Compressor.
  2. Insufficient cooling effects.
  3. Noisy operation.
  4. High suction pressure during running.
  5. Low discharge pressure during running.
  6. Suction pressure rises faster after Compressor is shut-down.
  7. Warm cylinder head.

12.  Choked Expansion valve:

Causes:  

Due to dirt and freeze-up of water present in system.

  Effects:    

  1. Starved Evaporator
  2. High superheat temperature.
  3. Rapid Condenser pressure rise can cause stopping of Compressor,

 Remedy

  1. Clean Expansion valve and filter
  2. Renew Dehydrator.

Secondary Refrigerant:

  • Calcium Chloride Brine ( 3 ½ lb. of Ca Cl₂  +   1 gal. of water ) with density of 1.25 is widely Sodium Dichromate or lime added to maintain
  • pH values of 8.0 – 8.5.
  • Sodium Chloride Brine.

Why LP Cut-off fitted?

Fitted as safety control and it protect against:    (a) Extreme compression ratio.   (b) Freezing up of Evaporator.  (c)  Entrance of air and water vapor resulting from LP side leakage.

Fridge compressor sump oil filling:

  1. Stop condition:  (i) Tight shut both inlet and outlet valves of compressor.  (ii) Open filling plug and fill to required level. (iii) Air purge to be done when plant resume.
  2. During running:   (i)  Make vacuum pressure in crankcase and suck oil itself.                                       (ii)  Ensure oil pipe immersed in oil to prevent air ingress.

What is made of fridge filter dryer?     

Ans:     (i)  Activated Alumina   (Aluminium Oxide)    (ii)  Silica Gel    (Thorzone)

Safety Devices fitted on Fridge Compressor:

  1. Safety Head or Unloader.
  2. Bursting Disc in Compressor.
  3. LP and HP Gauges and Cut-out.
  4. LO Low Pressure Cut-out.
  5. Condenser cooling water Low Pressure Cut-out

Charging of Refrigeration Plant:

There are two methods for charging reefer plants:

  1. Liquid charging and
  2. Gas charging.
    Now a day’s gas charging is preferred over liquid charging because it is more safe and simple.

Gas Charging of Refrigeration Plant:
For gas charging, a special T piece valve block with mounted pressure gauge is provided to combine three connectors inter-connecting:
-Vacuum pump
-Charging Cylinder
-Charging Point

Following steps are to be taken for charging gas into the reefer plant:
New Bitmap Image
1. Connect gas bottle or charging cylinder, vacuum pump and charging point in the reefer system to the valve block.
2. The discharge of the vacuum pump is to be connected in the empty recovery bottle
3. First open the valve between vacuum pump and charging bottle located in the valve block without opening the main valve of the charging cylinder. This will remove all the air inside the pipe. Once vacuum is reached, close the valve of charge cylinder in the valve block
4. Now open the valve of the charging point pipe in the valve block and run the vacuum pump until the vacuum is reached. This will remove the trapped air from this pipe. Then shut the valve in the valve block
5. Now keep the system idle for 5 minutes to check there is no pressure drop. This will ensure there are no leakages in the system
6. Now open charging bottle pipe valve and the charging point pipe valve located in the valve block. This will set the line for charging. Ensure that the vacuum pump valve is shut7. Now open the main valves in the charging cylinder and charging point of the reefer system
8. Do not overfill the system. Make sure the receiver has 5 % space for expansion
Ensure that no refrigerant is leaked out in the environment as these effects the ozone layer in the atmosphere.
Gas bottle is kept on weighing scale for measuring the amount of charged supplied to the system.

Air Conditioning:

Relative Humidity:

Ratio of amount of water vapour in given volume of air, to maximum amount of water vapour that can be present before precipitation occurs.

Control of temperature:

Comfortable temperature range is about 22°C and RH about 60%, (usually 40 ~ 70%).

 All zone temperature:   

  1. Controlled by Compressor suction pressure, via solenoid valve as step controlling.

Thermostat, placed at some accommodation space actuates the Master Solenoid

Valve of the plant, which will stop the Compressor, when pre-set temperature

is reached.

  1. Capacity Unloader of Compressor units, does last step controlling, as required.

Particular zone temperature:

  1. Controlled by flap valve fitted in each zone loop.
  2. Local cabin temperature can be adjusted by volume control at delivery point of air duct controller.

Ozone Depletion: 

  1. Ozone gas layer is a region of the atmosphere, 12 – 30 miles above Earth’s surface.
  2. This layer moderates the climate, and protects life on Earth from ultraviolet rediation
  3. Release of industrial waste and other process breakdown ozone layer and so disturb natural balance.
  4. Chlorofluorocarbons, CFCs, at ground level, rise and broken down by sunlight, whereupon chlorine reacts with and destroys ozone molecules.
  5. Single chlorine atom may destroy 10 – 100,0000 ozone molecules.

Ozone Depletion Substance (ODS):

CFC 11     1.0                Halon1211     3.0     (Used in portable extinguishers)

CFC 12     1.0                Halon1301     10.0   ( Used in fixed installation)

CFC 115   0.6                HCFC 22        0.05

CFCs: Chlorofluorocarbon Refrigerant:

Chlorofluorocarbon Refrigerants includes:  

CFC11,  CFC12,  CFC22,  CFC 115,

CFC500,  CFC502,  CFC 503 and  CFC 504.  (8 Types)

Difference between Air Cond. and Fridge:

  • Air Cond. controls Humidity, Temperature and Flow Rate of fresh air.
  • Fridge cools down the provisions.

Air Reducing Valve:

  1. Fitted on compressed Air Bottle outlet.
  2. Reduced compressed air is used for control of Reversing Mechanism in unidirectional gear drive engines, ship whistleautomatic controls and air motors.
  3. High-pressure air enters under the valve.
  4. The spring, acting on the valve spindle, opens the valve and the air passes to the reduced pressure
  5. Compression given to the spring controls the amount of opening of the valve.
  6. If the opening increases, the higher pressure obtained on other side, acts to close down the valve to normal lift, and hence correct reduced pressure maintained.
  7. Relief Valve is fitted on low-pressure side to prevent excessive pressure rise on reduced air system.

Where fitted Dehumidifier and its function.

  1. Fitted at discharge side of Reducing Valve on control air line.
  2. Main function is to prevent oil and condensate water passes through control air line.

Psychrometric chart

This chart is used for finding the relative humidity of air which has been measured using a ‘wet and dry bulb’ thermometer. This is a pair of thermometers, one of which has its bulb wrapped in a damp cloth. The drier the air,the greater the evaporation of water off the cloth and therefore the lower the reading on the ‘wet bulb’ thermometer.

124

Dew point:
When a mixture of dry air and water vapour has a saturation temperature corresponding to the partial pressure of the water vapour it is said to be saturated. Any further reduction of temperature (at constant pressure) will result in some vapour condensing. This temperature is called the dew point, air at dew point contains all the moisture it can hold at that temperature, as the amount of water vapour varies in air then the partial pressure varies, so the dew point varies.

COC ORAL EXAM PREPARATION (PART – 8): AIR COMPRESSOR

Air Compressor

H-274
Image Credit: leelloyds.com

Effects of leaking valves in Air Compressor:

First Stage Suction:

  • Reduce air delivery
  • Reduce 2nd stage suction pressure
  • Unload the compressor
  • Increase running time.

First Stage Delivery:

  1. Reduce air delivery
  2. Increase discharge temperature
  3. Less air drawn in, due to high-pressure air leaking back into cylinder.

 

Second Stage Suction:

  1. Reduce air delivery
  2. High temperature & pressure in 2nd stage suction line
  3. Increase running time

Second Stage Delivery:

  1. Reduce air delivery
  2. Increase suction pressure in 2nd stage
  3. Increase delivery pressure from 1st stage.
  4. Back pressure from air bottle.

How to check Air Compressor Efficiency?

  1. Regular overhauling of valves done or not.
  2. Check Air Bottle filling time.
  3. Compare test results and records.

How to check Air Compressor capacity is sufficient?

  • Total no. of Air Compressors must be sufficient to fill the empty Air Bottle to maximum pressure within 1 hour.
  • Must be sufficient to start at least 12 times for Reversible Engine, and at least 6 times for Non-Reversible Engine.

Bursting Disc:

  1. Fitted on the shell of Intercooler at waterside.
  2. Relieves pressure if the tubes burst.
  3. Rolled Copper Alloy and relief pressure is set while the disc is at softest condition.
  4. Material tends to harden due to time and surrounding temperature, and set pressure also increased.
  5. Bursting Disc needed to be annealed, to regain correct relief pressure.

Compound Valves, why used in Air Compressor?

  1. Give large area of opening and small amount of valve lift.
  2. Improve Volumetric Efficiency, as valve open and close in minimum time.
  3. Reduce bumping clearance.
  4. Reduce wear and tear.

LP Relief Valve opening:

Causes:

  1. HP suction valve
  2. Intercooler choked.
  3. Relief valve, jammed by foreign particles, in open position.

HP Relief Valve opening:

Causes:

  1. HP discharge valve, in closed position.
  2. After cooler choked.
  3. Relief valve, jammed by foreign particles, or spring sticking in open position.

(Relief Valves opening pressure are set at  ≯ 10% above stage pressure.)

Why Intercooler is fitted?

  1. Reduce air temperature and volume, and increase air density for next stage.
  2. Increase Compressor Capacity and Volumetric Efficiency.
  3. Better lubrication for cylinder and rings.
  4. Water and excess oil can be drained out, preventing fouling of Intercooler and pipes, Air Bottle corrosion, and starting airline explosion.
  5. Work done is saved.
  6. Metal stresses reduced, due to control of temperature.

Volumetric Efficiency:

VE  = (Volume of Air drawn into Cylinder) / (Stroke Volume of LP Piston)

and

VE = (Volume of Air discharged as ‘free air’) / (Stroke Volume of LP Piston)

Why Multistage Air Compressor is built?

  1. To obtain near to ideal isothermal compression, compressor is to be constructed of multistage with inter-stage cooling.
  2. Inter-stage cooling reduces air temperature and volume after 1st stage compression, thus increase mass of air for 2nd
  3. Workdone is saved and air compressor efficiency increased.

Other advantages are:

  1. Easy to get high final air pressure.
  2. Easy to control air temperature.
  3. Easy to maintain correct lubrication.
  4. Better compressor balancing.
  5. Reduction in size.
  6. reduction in clearance volume loss.

Capacity of air compressor:

  1. Capacity is checked upon how much filling time is lowered.
  2. Compressor should have enough filling capacity so that sufficient stopping time should be provided between fillings.
  • 12 consecutive starts in reversible engine  and
  • 6 consecutive starts in non-reversible engine.

What is Free Air Delivery, FAD?

  1. Capacity of Air Compressor is stated in terms of [ m³/ hr ].
  2. Volume of air actually discharged in 1 hour, that would occupy if expanded down to atmospheric pressure and cooled to atmospheric temperature.

Safety devices on Main Air Compressor:

  1. Bursting Disc on Intercooler: (At water side)
  2. Bursting Disc and Fusible Plug (121°C) on Aftercooler
  3. Relief valves on LP and HP stages. (Set to lift at 10% rise above normal stage pressure.)
  4. Automatic Moisture Drain Valve.
  5. Cooling water supply failure alarm.
  6. Low LO pressure alarm.
  7. Relief valve on crankcase LO pump.
  8. Delivery air HT cut out and alarm on Aftercooler outlet. (Max. 93°C)
  •   LP discharge pressure 4 bars and HP discharge pressure 30 bar
  • Intercooler inlet air 130°C and intercooler outlet air 35°C
  • Aftercooler inlet air 130°C and Aftercooler outlet air 35°C:

Intercooler is single pass type:  Aftercooler, double pass U-tube type:}

Uses of Compressed Air: 

  • Engine Starting 20 to 25 bar
  • Boiler Soot Blowing 20 to 25 bar
  • General Service (Whistle, Pneumatic Tools, Lifeboat , service air for cleaning and Pilot ladder) 7 to 10 bar
  • Instrumentation and Control 5 bar

Air Filter: 

  1. Material: Felt, Metal gauze or Nylon strands
  2. Removes contaminants from air. Dirt and dust act as abrasives and increase wear.
  3. Contaminant deposits on valves can become hot and source of ignition.

Hazard of Dirty Filter: 

  1. Very dirty filter or muffling a filter results in large pressure drop.
  2. Air has to be compressed over higher range.
  3. In extreme case, discharge air temperature may exceed flash point, or auto-ignition temperature resulting in an
  4. As a safety against explosion, air temperature is limited to 93° Fusible Plug (121°C) or a High Temperature cut out (93°C) is provided on Compressor.

Pressure Test on Air Compressor:

  • Cylinders, cylinder cover, Inter & After coolers are hydraulically tested to:

Air Side:  1.5 x max. Working Pressure.
Water Side: 4 bar or 1.5 x max. WP (whichever is greater)

Air receiver:

  • Total capacity of air receivers must be sufficient to give at least 12 starts for reversible engine, and at least 6 starts for non-reversible engine, without refilling the receivers.
  • There must be two identical main air receivers and one emergency bottle for every vessel.

 Mountings of Air receiver:  

  1. Fusible plug: 
  • composition – Bismuth 50%, Tin 30%, Lead 20%,
  • Melting point: 220΄F (104.4΄C).    Fitted at the reservoir’s bottom or on reservoir at ship side, when relief valve (safety valve) is not directly fitted on the reservoir.
  1. Atmospheric relief valve: provided for back-up of fusible plug. In case of ER fire when CO₂ flooding is required, this valve is opened before evacuating ER.
  2. Spring loaded safety valve: setting pressure: 32 bar (for 30 bar working pressure), with ≯ 10% rise in accumulation of pressure. May be fitted directly or with extension.
  3. Compensation ring: when a hole is cut or machined in pressure vessel, higher stresses will subject to the material around the hole, and to reduce this, compensation rings are fitted. It is a flange on which a valve or fitting is usually mounted.
  4. Manual Drain valve or Automatic Drain valve.
  5. Pressure gauges.
  6. Access doors.
  7. Main starting air valve, auxiliary starting air valve, filling valve, service air or whistle air valve.

Internal surface coating:

Graphite suspension in water, Linseed oil, Copal vanish or Epoxy coating having basic properties of anti-corrosive, anti-toxic or anti-oxidation.

Safety devices on Main Air Bottle:

  1. Fusible plug.
  2. Pressure Relief Valve
  3. Atmospheric Relief Valve.
  4. Low Air Pressure alarm.
  5. Automatic or remote control Moisture Drain Valve.

COC ORAL EXAM PREPARATION (PART-7) – MARITIME SECURITY

isps1
Image Credit: www.msecurity.ru

When do the security measures come into force ?

– 1st July, 2004.

SOLAS amendments adopted in December 2002 :

Chapter V:
– Automated Identifications Systems(AIS)

Chapter XI-1:
-Ship identification number
-Continuous Synopsis Record (CSR)

Chapter XI-2:
-Measures to enhance maritime security
-International Ship and Port Facility Security (ISPS) Code (Parts A & B)

Automatic identification systems (AIS)

– The requirement became effective for all ships by 31 December 2004.
– In 2000, IMO adopted a new requirement (as part of a revised new chapter V) for all ships to carry automatic identification systems (AIS) capable of providing information about the ship to other ships and to coastal authorities automatically.
– AIS to be fitted aboard all ships≥300 gross tonnage engaged on international voyages,
– cargo ships≥ 500 gross tonnage not engaged on international voyages
– all passenger ships irrespective of size.

The regulation requires that AIS shall:
1. Provide information – including the ship’s identity, type, position, course, speed, navigational status and other safety-related information – automatically to appropriately equipped shore stations, other ships and aircraft;
2. Receive automatically such information from similarly fitted ships; monitor and track ship
3. Exchange data with shore-based facilities.

Ship Identification Number

In December 2002, the Diplomatic Conference on Maritime Security adopted a number of measures aimed at enhancing security of ships and port facilities. This included a modification to SOLAS Regulation XI-1/3 to require ships’ identification numbers to be permanently marked in a visible place either on the ship’s hull or superstructure. Passenger ships should carry the marking on a horizontal surface visible from the air. Ships should also be marked with their ID numbers internally.

  • The IMO ship identification number is made of the three letters “IMO” followed by the seven-digit number assigned to all ships by IHS Fairplay (formerly known as Lloyd’s Register-Fairplay) when constructed.
  • The IMO number is never reassigned to another vessel and is shown on the ship’s certificates.
  • This number is assigned to the total portion of the hull enclosing the machinery space and is the determining factor should additional sections be added.
  • The number should Permanently marked and visible on:

* stern or side of hull or superstructure
* horizontal surface for passenger vessels

  • Contrasting color with the alphabet size not less than 200 mm; width proportionate to height and raised lettering or by cutting it into or center punching (or other equivalent)
  • This is a unique seven digit number that is assigned to propelled, sea-going merchant ships of 100 GT and above upon keel laying with the exception of the following:

– Vessels solely engaged in fishing
– Ships without mechanical means of propulsion
– Pleasure yachts
– Ships engaged on special service (e.g. lightships, SAR vessels)
– Hopper barges
– Hydrofoils, air cushion vehicles
– Floating docks and structures classified in a similar manner
– Ships of war and troopships
– Wooden ships

Continuous Synopsis Record (CSR)

  • To be issued by the Administration to each ship under its flag
  • In case of changes, Administration to issue amended record
  • To be kept on board and available for inspection at all times
  • Basic diary of ship or historical record of ship – Issued by Administration, but must be maintained and updated onboard and left onboard with change of ownership or registry.
  • Information should be included in CSR:

* name of flag state
* date of registry
* ship’s ID number
* name of owners
* name of registered demise charterers
* name of shipping company
* name of classification society(ies)
* name of authorities or associations issuing certifications

Ship Security Alert System

  • Required to be provided on all ships constructed on or after 1 July 2004 and ships constructed before 1 July 2004 :

– Oil & chemical tankers, gas & bulk carriers, and cargo HS craft, of equal or more than 500 GT; Passenger ships including HS passenger craft; not later than the 1st survey of radio installation after 1 July 2004

–  other cargo ships of equal or more than 500 GT and mobile offshore drilling units; not later than the 1st survey of radio installation after 1 July 2006

  • Shall initiate & transmit alert to a competent authority designated by administration
  • Shall identify ship, its location and indicate that ship’s security is under threat
  • Shall not send the alert to any other ship nor raise alarm on board
  • Shall continue the alert until deactivated or reset
  • Have activation possible from bridge & at least one other location
  • Performance standard; not necessarily requires new
    equipment installation (eg. Piracy alarm)
  • It’s a security silent ship-to-shore alert
    * activated from bridge and at least one other location
    * not heard by other ships
    * include name and location of ship
  • Protected from inadvertent initiation
  • Administration or coastal state notification requirements

ISPS Code:

The Code provides for considerable flexibility to allow for required security measures to be adjusted to meet the assessed risks facing particular ships or port facilities.

It has two Parts:

  • Part A containing mandatory provisions covering the appointment of security officers for shipping companies, individual ships and port facilities. It also includes security matters to be covered in security plans to be prepared in respect of ships and port facilities; and
  • Part B containing guidance and recommendations on preparing ship and port facility security plans.

Maritime Security (MarSec) Levels:

The ISPS Code contains three security levels. The security level will be set by the Contracting Government (CG).

The three levels are:

  • Security Level 1, normal; the level at which ships and port facilities normally operate.

–  This will mean that minimum protective security measures shall be maintained at all times.

  • Security Level 2, heightened; the level applying for as long as there is a heightened risk of a security incident.

–  This means the level for which appropriate additional protective security measures shall be maintained for a period of time as a result of heightened risk of a security incident.

  • Security Level 3, exceptional; the level applying for the period of time when there is a probable or imminent risk of a security incident.

–  This means the level for which further specific protective security measures shall be maintained for a limited period of time when a security incident is probable or imminent, although it may not be possible to identify the specific target.

COC ORAL EXAM PREPARATION (PART-6) – BOILER OPERATION & BW TREATMENT

Boiler :

Boiler Automatic Burning System:

1. With correct water level, steam pressure transmitter initiates cut-in at about 1.0 bar below working pressure.
2. Steam pressure transmitter initiates Master Relay to allow ‘Air On’ signal to force draught fan.
3. Air feedback signal confirms ‘Air On’ and allows 30-sec. delay for purge period.
4. Then Master Relay allows Electrode to strike ‘Arc’.
5. Arc striking feedback signal confirms through electrode relay and allows 3-sec. delay.
6. Then Master Relay allows burner solenoid valve for ‘Fuel On’ operation.
7. Fuel On feedback signal allows 5-sec. delay to proceed.
8. As soon as receiving Fuel On feedback signal, Master Relay checks ‘Photocell’, which is electrically balanced when light scatter continuously on it.
9. Result is OK and cycle is completed.
10. If not, fuel is shut-off, Alarm rings and cycle is repeated.
11. Steam pressure transmitter initiates cut out automatically at about 1/15 bar above W.P.

Accumulation Pressure Test:

1. Required for new boiler or new safety valve.
2. Tested under full firing condition.
3. Feed Check valve and Main Stop valve shut.
4. Test is to be continued as long as water in the boiler permits, but 7 minutes for Water tube Boiler and 15 minutes for Cylindrical Boiler.
5. With Safety Valve opening, Boiler pressure must not accumulate to exceed 10% of Working Pressure.

Difference Between Safety Valve and Relief Valve:

1. Safety valve fully open at set pressure. Start open at set pressure. But relief valve fully open at 15 – 20% above set pressure.
2. Safety valve close at set pressure. But the relief valve close below set pressure.
3. Safety valve relieve excess mass. But the relief valve relieve excess pressure.
4. Safety valve can open manually but relief valve cannot open manually.
5.  Safety valve set to open 3 % above WP  but the relief valve set to open 10 % above WP.

Waste Heat Recovery System

  • The use of exhaust gas from main engine to generate steam is means of heat energy recovery and improved plant efficiency.
  • In ME ≯ 40 % of fuel consumed is converted into useful work, and 30 – 34 % of remaining energy contain in Exhaust Gas.

Waste Heat Recovery System is employed as:

1. Composite boiler system.
2. Two separate boiler system ( One oil fire and one ordinary coil type exhaust gas boiler)
3. Tubular type heat exchanger system ( One oil fire and one tubular economizer)
4. Separate steam receiver system ( Two duel pressure boiler and one economizer)
5. Advanced waste heat system (Exhaust gas economizer with 3 separate sections).

Why boiler water test carried out?

  1. To know boiler water condition.
  2. To control chemical treatment and blow down.
  3. To prevent scale formation, corrosion and impurities.
  4. To prevent damage to steam operated equipment and condensate line.
  5. To maintain alkaline condition.
  6. To improve boiler efficiency.

Boiler Water Test:

1. Chloride Test.
2. Excess Phosphate Test.
3. Total Dissolved Solid Test (Conductivity Test).
4. pH value Test.
5. Hydrazine Test.
6. Alkalinity Test: ‘P’ Alkalinity (Phenolphthalein) and ‘M’ Alkalinity (Methyl-orange) and Total Alkalinity

Proper Sample:

1. Sample line is usually located in steam drum, just above the tubes and as far as possible from chemical feed line.
2. Sample water is taken at water surface, since highest concentration is at this point.
3. Sample water is cooled down to about 25°C.
4. Flush out sample stream for 5 minutes before taking.
5. Test apparatus should be cleaned with sample water.
6. Sample water is tested as soon as possible after drawing.

Alkalinity Tests:

1. ‘P’ Alkalinity finds presence of Hydroxyl, Phosphate and half of Carbonates, excluding Bicarbonates.
2. ‘T’ Alkalinity gives total quantity of all Alkaline Dissolved Salts in boiler water.
3. ‘M’ Alkalinity finds presence of remaining Carbonates and Bicarbonates.
4. Total Alkalinity is < 2 x ‘P’ Alkalinity. 5. Desired value is 150 – 300 ppm for ‘P’ Alkalinity. Increase of Alkalinity Level: Causes: 1. Alkalinity treatment has been done recently. 2. Using of Alkaline rich makeup feed water. 3. Incorrect strength of reagent used. Effect: Caustic Embrittlement. Decrease of Alkaline Level: Causes: 1. Feed water is contaminated with acid. 2. Direct water loss from boiler. 3. Incorrect strength of reagent used. Effect: Corrosion. Chloride Test: 1. Gives quickest indication of any salt-water leakage into boiler. 2. Must be carried out daily. 3. Chlorides of Calcium, Magnesium and Sodium are extremely soluble. 4. Chloride level is proportional to TDS level in boiler water. 5. Rate of blow-down is governed by chloride level. 6. Chloride Level should be 0 – 300 ppm, and blow-down if > 300 ppm.

Increase of Chloride Level:
Causes:
1. SW leaking into system.
2. Incorrect strength of reagent used. (Silver Nitrite and Potassium Chromate).
3. Due to treatment chemical and hardness salt reaction.

Effects:
1. Increase in TDS level causes Foaming/Priming.
2. Drop in Alkalinity causes Corrosion.

Phosphate Test:

1. Presence of Phosphate in sample means no hardness salts.
2. Na₃PO₄ added to boiler water, precipitate all scale forming hardness salts of Calcium and Magnesium.
3. With Phosphate Test done, no need to do Hardness Test.
4. Phosphate ppm of 20 – 40 is satisfactory, and blow-down if > 40 ppm.

pH value Test:

1. Once Alkalinity Test is done, no need to check pH value, since Alkalinity and pH value are proportional.
2. Litmus Strip is used for quick reference however.
3. pH value maintained at 10.5 – 11.5.

Condensate pH:

1. Condensate pH is measured at Condenser outlet.
2. By theory, it should not be acidic, i.e. (9.5 – 11.5) but practically it is always less than 9.5.
3. (8.3 – 8.6) is satisfactory.
4. If < 8.3, increase dosage by 25% Condensate Corrosion Inhibitor. 5. If > 8.6, decrease dosage by 25% Condensate Corrosion Inhibitor.

Hydrazine Test: (for Dissolved Oxygen)

1. Hydrazine ppm maintained at 0.1 – 0.2 ppm.
2. If < 0.1 ppm, increase dosage by 25% hydrazine. 3. If > 0.2 ppm, decrease dosage by 25% hydrazine.

Types of Boiler Gauge Glass:

1. Fitted directly.
2. Fitted to a large bored bent pipe.
3. Mounted on a hollow column.
4. Fitted to a column with its centre part solid.

 

Boiler Corrosion:

(1) Electro-chemical Corrosion:

  1. Hydrogen ions (H⁺) are generated by acid concentration under hard dense deposits and can penetrate grain boundaries of tube metal,
  2. Hydrogen attack can occur very rapidly, causing the tubes cracked, failed and ruptured.
  3. General wastage occurs when pH value is < 6.5.
  4. Pitting (Air Bubble pitting and Scab pitting) occur when pH value is between 6–10 in the presence of dissolved Oxygen.

(2) Caustic Cracking corrosion:

  1. Inter-crystalline cracking occurs when excess concentration of Caustic Soda (NaOH) in boiler water, comes in contact with steel, under stresses and high temperature.
  2. Metal becomes brittle and weak.
  3. Damage occurs to riveted seams, tube ends and bolted flanges.
  4. 4. Prevented by dosing Sodium Sulphate (Na₂SO₄) to give protective layer.

5. Ratio of Na₂SO₄ to NaOH should be maintained 2 : 5.

(3) Corrosion by Oil:

1. Animal or vegetable oil decomposed to fatty acid and causes corrosion. 2. Causes are over lubrication of machinery, leakage of heating coils & inefficient filtering of feed water. 3. Prevented by Liquid Coagulant Treatment, which coagulates oil droplets & suspended solids and settle them at low points, and they can be blown-down.

(4) Corrosion by Galvanic Action:

1. With dissimilar metals in a saline solution, galvanic action results and more anodic metal corrodes. 2. Corrosion occurs when feed water is contaminated with salt-water. 3. Prevented by carrying out Chloride Test daily. 4. Chloride Level should be 0 – 300 ppm, and blow-down if > 300 ppm.

CO₂:
1. Reacts with H₂O to form Carbonic Acid (H₂CO₃) which reduces pH value (Alkalinity) of feed water and accelerates general type of corrosion.
2. Groovings along the pipe’s bottom, bends & threaded section.

NH₃:
1. Attacks Copper based Alloy, in the presence of O₂.

COC ORAL EXAM PREPARATION (PART- 5) – BOILER

Exhaust Gas Boilers:

  • About 30% – 34% of Fuel Energy input to engine are discharged to Exhaust Gas, as Thermal Energy.
  • This thermal energy is converted into useful work in Exhaust Gas Boiler.

Cochran Exhaust Gas Boiler:
1. A double-pass, vertical type, in which Exhaust gases from ME pass through 2 banks of tube.
2. Served as an efficient silencer, when the boiler is in use.
3. A separate Silencer, always fitted along with exhaust gas boiler, to be used when the boiler is generating more steam than required.
4. All or part of exhaust gases can be directed to the Silencer and atmosphere, without going through the boiler.
5. Working Pressure is around 7 bars.

Composite Boiler (Composite type Cochran boiler):

1. If Exhaust Gases and Oil fire can be used at the same time, it is termed Composite Boiler.
2. In double-pass, composite type Cochran Boiler, it provides a separate tube nest for exhaust gas passage, situated immediately above the return tube nest from Oil-fired Furnace.
3. Exhaust gases from Oil-fired Furnace and ME; pass through the tubes, which are surrounded by boiler water.
4. Separate Uptakes provided for Exhaust Gases and Oil-fired Smoke.
5. Heavy Changeover Valves are fitted, to divert the gases straight to the funnel, when desired.

Alternative Boiler: (Alternative type Cochran boiler)

1. If Exhaust Gases and Oil fire can be used only one at a time, it is termed Alternative Boiler.
2. Double-pass, Alternative Cochran Boiler, can be oil fired and heated by exhaust gases alternatively.
3. Since both systems use the same Combustion Chamber, one system required being blank, while the other is in operation.
4. Only one Uptake required.

Economiser as Exhaust Gas Boiler:

1. In this system, a separate Exhaust Gas Economiser EGE is connected to an Oil-fired Auxiliary Boiler (or an Accumulator) by means of piping and a set of Circulating Pumps.
2. Heat absorbed from exhaust gas in EGE is transmitted by working fluid, to Auxiliary Boiler or Accumulator, from which steam is drawn for use.
3. Economiser unit cannot deliver steam, directly to steam range.
4. Straight gas lead from ME Exhaust Manifold, pass through EGE under the Funnel, and this arrangement permits the Auxiliary Boiler or Accumulator, to be placed in any convenient position in ER.
5. Inlets and outlets of piping coils are connected to External Headers [Distributing and Collecting], that are simply inserted in Exhaust Trunk way.
6. Water from Auxiliary Boiler or Accumulator is fed by Circulating Pump through
a Non-Return Valve into Distributing Chest or header and from it, water passes into Coils.
7. Water and steam from outlets of these Coils pass into Collecting Header, and then to the steam space of Auxiliary Boiler or Accumulator.
8. EGE Safety Valve is adjusted at slightly higher pressure than Safety Valves of Auxiliary Boiler; in order to ensure that Economiser operates in flooded condition at all times.

EGE out of order:

1. Isolate the EGE.
2. Wash down the economiser tubes and completely dried.
3. Drain all water content.
4. Start the auxiliary boiler.
5. Maintain low steam consumption.
6. Proceed to next port with suitable speed.
7. Write down damage report.

Exhaust Gas Boiler Safety Valve setting:

1. EGE safety valves to be set under full load steaming condition, if Surveyor delegates the responsibility to CE.
2. Setting pressure ≯ 3% above max: working pressure.
3. In doing so, EGE steam pressure control is done as follows:

EGE steam pressure controls:

1) Steam control: By providing Dumping Valve in by-pass system, to Condenser.
Excess steam can be discharged into Condenser.
2) Water control: By shutting the inlet valve to boiler coils.
3) Exhaust gas control: By controlling the Exhaust Gas Damper.

Boiler Safety Devices as for UMS status:

1. Flame failure: (Photocell shut down combustion system and gives alarm.)
2. Low and high water level: (Level is maintained by feed pump, controlled by float
operated on/off switch.)
3. Low and high Steam pressure: (If steam demand drops, high steam pressure will
shut down burner and/or ME speed reduced. Low steam pressure
alarm, will be given if there is fault in combustion condition)
4. Fuel temperature: (Deviation from set temperature range, cause burner to be shut
off and alarms given for both low and high temperature.)
5. Fuel pressure: (Low fuel pressure cause automatic controller to shut down
burner and alarms given.)
6. Smoke density: (Emitted smoke through uptake, being monitored and if deviate
from normal limit, shut down the system and alarm given.)
7. Air / fuel ratio: (Air register damper controller keeps correct ratio, and shut down
the system and alarm given on deviation.)
8. Draught fan failure: (Air supply fan failure operate audible and visual alarms.)
9. Very low water level: (Burner stopped and alarms given.)
10. Very high water level: (Burner stopped or ME slow down and alarms given to
avoid foaming and carry over.)
11. High flue gas temperature: (Burner stopped and alarms given.)

Safety Devices on Boiler:

1. Flame failure alarm
2. Low water level alarm.
3. Very low water level alarm and cut-off.
4. High water level alarm
5. Low steam pressure alarm
6. Low oil temperature alarm and cut-off
7. High oil temperature alarm and cut-off
8. Low oil pressure alarm and cut-off.
9. Force Draught Fan failure alarm and cut-off.
10. Power failure alarm.
11. Safety Valves.
12. Gauge Glass.
13. Easing Gear.

Mountings on Boiler:
1. Safety Valves
2. Easing Gear.
3. Gauge Glass.
4. Pressure Gauge.
5. Feed Check Valve.
6. Flame Eye.

Open-up Procedure:

1. Stop firing and cool down.
2. All steam valves tight shut.
3. Blow down until empty. [ Ship-side Cock opened first, then gradually open Blow-down Valve. When loud noise dies down and blow-down pipe becomes cold, boiler is about empty. Blow-down Valve shut and then shut Ship-side Cock.]
4. Easing Gear lifted.
5. Open Air Vent Cock, Salinometer Cock and Drain Cock of water Gauge Glass, to let air enter. Ensure no vacuum and only atmospheric pressure inside, before knocking in the manholes.
6. Slacken dog-holding nut of Top Manhole door, break the joint, from the place safe from blast as a safeguard against scalding, and then nut removed and door taken out.
7. When knocking in the Bottom Manhole door, use crowbar and stand back when breaking the joint, as there may be hot water left.
8. Mud holes and all other doors open-up for cleaning, both smoke side and waterside.
9. Allow the boiler to be ventilated before entry.

Boiler Internal Inspection: [For Survey]
1. After normal open-up procedure, allow the boiler to ventilate.
2. Initial internal inspection is done before cleaning, for general condition and
any special deposited area.
3. Plugged Blow-down hole to prevent choking.
4. Cover Manhole door’s landing surface to prevent damage.
5. Final internal inspection done after thorough cleaning:
a) Check level gauge connections for blockage.
b) Check securing system of internal pipes and fitting.
c) Hammer-test furnace, fire and stay tubes.
d) Check firebrick, casing, baffles and welding seams.
e) Tubes checked for leak, crack, distortion and bulging
f) Check fireside is clean, without soot.
g) Cleaning and inspection of Manhole doors, joint landing surfaces.
h) Use new joints.

Refitting Procedure:
After Internal Survey:
1. Remove plug at blow-down pipe.
2. Box back all manholes and mud doors with new joints, and refit all mountings.
3. Open Air Vent Cock, and boiler filled-up with water up to ¼ of Gauge Glass level. ( If hydraulic test is required, fill-up completely.)
4. Normal flash-up procedure follows.
5. Pressure setting of Safety Valves, under steaming condition, with Surveyor’s presence.

Safety Valves:
Function:

1. Must open fully at definite pressure, without preliminary simmering.
2. Must be still opening until pressure in boiler has dropped to a certain definite value, not more than 4% under set value.
3. Must close tight without chattering.
4. Must close tightly without leaking.

Setting of Safety Valves:

1. Take Standard Pressure Gauge for accuracy.
2. Fill up water up to ¼ of Gauge Glass level, and shut Main Stop Valve, Feed Check Valve.
3. Without Compression Rings, Hoods and Easing Gears, reassembled the Safety Valves with spring compression less than previous setting.
4. Raise boiler pressure to desired blow-off pressure.
5. Screw-down Spring Compression Nuts of any lifting valves, until all are quiet.
6. Adjust each valve in turn:
a) Slacken Compression Nut until valve lifts.
b) Screw-down Compression Nut sufficiently enough, so that when valve spindle is lightly tapped, valve returns to its seat and remain seated.
c) Measure gap between Compression Nut and spring casing.
d) Make a Compression Ring equal to this gap, and insert under Compression Nut.
e) Gag the Spindle of this Safety Valve, to prevent opening, while remaining valve is being set.
7. Remaining valve is again set and insert Compression Ring.
8. Remove gag and retest both valves to lift and close together.
9. Caps and Cotter Pins padlocked.
10. When the Surveyor satisfied the setting pressure, Easing Gear should be tested.
11. All Safety Valves set to lift at ≯ 3% above approved working pressure (design pressure).

Accumulation of Pressure:

1. Pressure is liable to rise after Safety Valves have lifted, caused by increased spring load due to increased compression.
2. This rise in pressure is known as “Accumulation of Pressure”. {OR}
3. Pressure rise in excess of Working Pressure is termed, “Accumulation of Pressure”.
4. Accumulation of pressure test is carried out to see whether this safety valve is suitable or not for this boiler. Pressure rise after safety valves have lifted, must not exceed 10% of working pressure.
5. Tested when safety valves are new or boiler is new or safety valves and boiler are new ones.

Safety Valve on EGE and Economiser:

1. Slightly higher set pressure than drum Safety Valves.
2. It is to ensure operation under flooded condition at all times.

Hydraulic Testing of Boiler:

Necessary condition:
1. Boiler internal inspection is not satisfactory.
2. Surveyor demanded.
3. After structural repairs of boiler.

Requirement:
1. Surveyor must be present.
2. Gag the Safety Valves.
3. Close all opening.
4. Blanks inserted at Main Steam Stop Valve and Gauge Glass.
5. Measuring tape placed around boiler to check bulging.
6. Deflection gauge placed in the furnace.
7. Remove lagging to check leak points.

Procedure:
1. Open vent cock, fill boiler with warm water completely, until water overflows from vent cock, and close the vent cock.
2. Attach force pump and test pressure gauge.
3. Apply water pressure, 1.25 times of approved working pressure, for not more than 10 minutes.
4. If satisfied, Surveyor will stamp on bottom front plate near the furnace.

Chemical Treatment:

Two ways of treating the water for boiler use:

1. External Feed Water treatments.
2. Internal Boiler Water treatment.

External Feed Water Treatment:
Purpose:
1. To reduce TDS in feed water.
2. To arrest Suspended Solid Particles.
3. To reduce Dissolved Gases.
4. To prevent feed water system corrosion, by maintaining correct pH value of feed water.

Treatments:
1. To reduce TDS, the best way is to use evaporated feed water.
2. To arrest Suspended Solids, use feed line filters.
3. To reduce Dissolved Gases, inject Hydrazine and maintain Hot Well temperature between 60~70°C to promote O₂ deaeration through hot well vent.
4. To prevent feed water system corrosion, use Salinometers on feed line or Evaporator outlet. Maintain pH value by dosing Hydrazine or Amine.

Internal Boiler Water Treatment:
Advantages:
1. Precipitate Calcium and Magnesium salts, into non-adherent, harmless sludge.
2. Prevent these salts, from baking on boiler heating surfaces.
3. Sludge is blown-down from boiler.
4. Treatments also remove Dissolved Oxygen, Dissolved Gases, and CO₂, to avoid their corrosive actions.

Treatments for Moderately Rated Auxiliary Boiler:
[Medium and Low Pressure Boilers]
(1) Phosphate Treatment:
1. AGK 100 or Adjunct B is used.
2. Combat scale-forming salts to form non-adherent sludge.
3. Give Alkalinity to reduce corrosion.
4. Form Iron Phosphate Film on internal surfaces, as protection against corrosion.

(2) Caustic Soda Treatment: [NaOH]
1. Maintain correct pH value and required Alkalinity.
2. Precipitate scale-forming Permanent Hardness Salts. [Chlorides and Sulphates of Calcium and Magnesium: They are in Acid nature. ]
3. Remove Temporary Hardness Salts. [Bicarbonates of Calcium and Magnesium: They are slightly in Alkaline nature.]
4. Excess concentration of NaOH may cause Caustic Cracking of metal.

(3) Soda Ash Treatment: [Na₂CO₃]
1. Precipitate scale-forming Permanent Hardness Salts, (Non-Alkaline Hardness Salts) as Calcium Carbonate, CaCO₃.
2. Produce NaOH, to give required Alkalinity.

(4) Dissolved Oxygen Treatment:
1. Two chemicals, Hydrazine N₂H₄, and Sodium Sulphite Na₂SO₃ are used to remove dissolve O₂.
(5) Liquid Coagulant Treatment:
1. High molecular weight, colourless solution, likes Sodium Aluminate or Starch is used.
2. Coagulate oil droplets and Suspended Solids, and settle them at low points.
3. They can be Blown-down.

(6) Blow-Down Treatment:
1. Integral part of water treatment program, as it removes solids, which are results of chemical conversion of salts and impurities in water.
2. Surface Blow-down or Scumming is quick removal of solids, without wasting feed water.
3. Bottom Blow-down is vital, when solids become dense, heavy and remain at boiler bottom, despite circulation.
4. Daily short blows of top and bottom are necessary.

Boiler Laying up Procedure:
(Boiler may be laid up wet or dry.)

Wet Method:
1. When laid up in warm climate, boiler is filled with water until it comes out from air vent.
2. Then the boiler is sealed off.

Dry Method:
1. Boiler is emptied and cleaned thoroughly on both fire and waterside.
2. Corroded parts, wire brushed and coated with anti-corrosive paint.
3. Shallow metal trays filled with quicklime should be placed in both water and fire space.
4. Then boiler is closed up airtight.

Proper Maintenance of Boiler:

Water Side:

  • Daily boiler water test.
  • Boiler water treatment.

Gas Side:

  • Regular cleaning.

Combustion System:

  • Fuel pressure, temperature and viscosity correct values maintained.
  • Burner maintenance.
  • Air register, Air damper and forced draught fan.

Caustic Cracking or Embrittlement of metal:

1. Caused by excess concentration of Sodium Hydroxide, NaOH [Caustic Soda] in boiler water, and the material under stresses.
2. Ratio of Na₂SO₄ to NaOH should be maintained 2 : 5.
3. Caustic Soda is used for boiler water treatment, to maintain correct pH value and required alkalinity, so excess concentration should be avoided.
4. Excess concentration of NaOH may be from Overdosed Chemical and Leakage.
5. Damage occurs to riveted seams, tube ends and bolted flanges.

To prevent Caustic Embrittlement:

1. Sodium Sulphate, Na₂SO₄ should be dosed, to give protective layer.
2. Ratio of Na₂SO₄ : NaOH should be maintained at 2 : 5

Turn Down Ratio of Burner:

1. The ratio of maximum to minimum oil throughput of the burner.
2. In case of pressure jet burner, this can be stated in terms of square root of the ratio of maximum to minimum oil supply pressure.
3. Large Turn Down Ratio of up to (20: 1) is available with blast jet burner, without having resort to unduly high pressure.

Foaming:

Formation of thick layer of steam bubbles, on top of water surface inside boiler.
Priming: Rapid carry-over of large amount of water, in steam as it leaves the boiler.
Carry-over: Carry-over of small amount of water, in steam as it leaves the boiler.

Causes:
1. Higher water level than normal
2. High amount of TDS, total dissolved solids
3. High amount of suspended solids
4. Contamination by oil and other organic substances
5. Forcing the boiler

Effects:
1. Water hammer
2. Contamination and scaling
3. Fluctuation of working water level

COC ORAL EXAM PREPARATION (PART- 4) – LUB OIL & FUEL OIL

Lubricating Oil

Viscosity:
1. A measure of internal resistance to flow.
2. Viscosity of an oil changes with temperature, falling when temperature rises and vice versa.
3. For crankcase oil, viscosity is between 130 – 240 Sec. Redwood No. 1 at 60°C.
4. For cylinder oil, viscosity is 12.5 – 22 Cst.

Viscosity Index, VI:
1. The rate of change of viscosity of an oil, in relation to change of temperature.
2. Oil of low VI has greater change of viscosity with change in temperature,
than the oil of high VI.
3. For crankcase oil, VI is between 75 – 85; For cylinder oil, VI is 85.
4. Highest VI of mineral oils is about 115 and with special additives, this may be raised to about 160.
5. Hydraulic oils, used in remote control hydraulic circuits must have very high VI; otherwise erratic response to the controls can be troublesome. (Telemotor hydraulic system oil has VI of 110.)

Pour Point:

  • Lowest temperature at which an oil will barely flow.
  • Pour point indicates that oil is suitable for cold weather or not.
  • or crankcase oil, Pour Point is, – 18°C.

TAN and TBN:
1. TAN is the ability of an oil, to react with basic reagent, which indicates the acidity
expressed as TAN.
2. TBN is the ability of an oil, to react with acidic reagent, which gives an Alkali figure, the TBN.
3. Expressed in milligrams of KOH required to neutralise one gram of sample oil, for both TAN and TBN.
4. For crosshead type engine crankcase oil: TBN is 8 mg KOH/gm of oil.
5. For Trunk type engine using HO, crankcase oil: TBN is 30 mg KOH/gm of oil.

Detergency/Dispersancy:
1. Deposits occur in engine crankcase or ring zone, due to semi-solid precipitation from LO.
2. High temperature effect accelerates the rate of such deposition.
3. To reduce formation of such deposits, oil is treated with Detergent/Dispersant Additives, for keeping the system clean and trouble-free.
4. When using conventional mineral oils, these deposits block exhaust passage and prevent free movement of piston rings.
5. Addition of Detergent Additive prevents deposition of such deposits and washes them away with LO.
6. By addition of Dispersant Additive, tiny particles are carried in colloidal suspension, and dispersed evenly throughout the bulk of oil.
7. Detergent/Dispersant Additives are complex chemical compounds, such as metallic based Sulphonates, Phosphonates, Phenates and Salicylates.

Function of Lubricant:

1. Reduce friction.
2. Remove heat.
3. Flush away contaminants.
4. Protect corrosion.
5. Dampen noise.
6. In some case, act as sealant.

Types of Lubrication:

1. Hydrodynamic lubrication.
2. Boundary lubrication.
3. Hydrostatic lubrication.
4. Elasto hydrodynamic lubrication.

Hydrodynamic lubrication: 
1. Moving surfaces are completely separated by continuous unbroken film.
2. Lubricant, because of its viscosity, is drawn between the surfaces and builds up a film, by the action of moving parts.
3. Thickness of film: 0.025 – 0.10 mm.
4. Essential requirement is formation of oil wedge between the surfaces.
5. Lubrication for Journal Bearing, Bottom End Bearing, Tilting Pad Thrust Bearing.

Boundary lubrication.
1. It exists when full fluid film lubrication is not possible.
2. High friction between surfaces, and a degree of metal to metal contact occurs.
3. Lubricant oil film decreases, until asperities of mating surfaces touch.

Hydrostatic lubrication:
1. A form of Hydrodynamic lubrication, but instead of being self-generated, it is supplied from external source of oil under pressure, from a pump.
2. Lubrication for Crosshead Bearings, with attached pump.

Elasto-hydrodynamic lubrication:
1. Applied to line contact or nominal point between rolling or sliding surfaces, as in ball bearings, roller bearings and gear trains.
2. Thin film lubrication limits metal to metal contact.
3. Elastic deformation of metals occurs, and there is high-pressure effect on the lubricant.

Contaminants in LO:

(1) Water:
1. Owing to condensation of water vapour in crankcase.
2. Leakage from cooling water system for cylinder or piston.
3. Combined with oil in the form of emulsion.
4. Combined with sulphurous products of combustion to form Sulphuric Acid, in trunk engine.

(2) Fuel Dilution:
1. Presence of fuel oil in crankcase oil is indicated by reduction in viscosity and flash point.
2. Result from poor atomisation of fuel injectors.

(3) Oxidation Products:
1. Mineral oils react with oxygen in air and form oil-soluble organic acid, lacquers, resin and sludge, depending upon temperature and degree of contact with air.
2. Accelerated by contact with copper and iron, which act as catalyst.

(4) Fuel Combustion Products:
1. Mainly acids and incompletely burnt fuel form sludge and deposits.
2. Inorganic acids from combustion of high-sulphur residual fuel.

(5) Foreign Mineral Matters:
1. Rust and scales from storage tanks and pipes, etc.
2. Dust from surrounding atmosphere.
3. Wear debris from lubricated surface [not entirely hydrodynamic], and from corrosion of cylinder liner.

(6) Biological contamination:
1. Associated with ‘wet oil’ caused by leakage from cooling system.
2. It causes formation of organic acids, sludge and additive depletion, corrosion of shaft and bearings.
3. If happened, complete oil change may be necessary, thorough sterilisation and cleaning out of cooling system, and leakage to be stopped.
4. Addition of biocides to both oil and water, helps.

Symptoms of LO Contamination:

1. Increased Sump sounding (severe SW contamination).
2. Change in pressure and colour (Emulsification of oil, with water and residues of treated cylinder oil from diaphragm or scrapper box leakage).
3. Change in pressure (Reduction in viscosity and flash point, due to fuel oils.)
4. Frequent choking of filters due to sludge formation and Additive depletion, due to biological contamination.
5. Darkened oil colour and yellowish colour film on surface, pungent smell & sludge formation, due to microbial degradation.
6. Particles of rust and scales, mostly ferrous, trapped in magnetic filter (Corrosion of shaft and bearings, due to water, fuel combustion products.)
7. Wear debris, and welding spatter trapped at magnetic filter (Contamination of foreign mineral matters.

How to remove contaminants:
1. Filtering – removed large oil insoluble matter.
2. Gravity separation – heavy matters, sludge and water.
3. Adding special additives – reduce acids, sludge, finer oil insoluble matter.
4. Centrifuging – Sludge, foreign matter and water.
5. Water washing – only for straight mineral oil or oil without additives, can remove acids.

Water washing:
1. It can be carried out on straight mineral oil but not for detergent / dispersant type oil
2. The purpose is to remove acids, salts and other impurities from the oil.
3. Water should be injected before purification at a rate of 3% to 5% of oil flow.
4. Oil temperature should be around 75˙C and water temperature about 5˙C higher than oil temperature.

Batch purification:
1. If oil is contaminated with strong acids, high insoluble contents or water, batch purification of the entire charge oil should be done.
2. In port, the entire charge oil is pumped by purifier or circulating pump into Renovating Tank, fitted with steam heating coils.
3. Allowed to settle for at least 24 hours at about 60˙C.
4. Water and sludge must be periodically drained out.
5. Then oil is passed through the purifier at its optimum throughput and pumped back to Sump Tank.
6. During the time when the sump tank is empty, its interior should be cleaned and examined.
7. This should be done at least once a year.

Throughput of a purifier: The best purification result is obtained if oil is kept inside the bowl as long as possible, i.e. throughput should be as low as possible and also more frequent desludging once every hour.

If LO is contaminated with SW:

1. When sump oil is contaminated with SW, find sources of leakage [may be from LO cooler during ME stoppage] and rectified.
2. In port or while ME is stopped, transfer contaminated oil through purifier or transfer pump into Renovating Tank, settled for at least 24 hours at about 60°C, and water and sludge drained out periodically.
3. Oil passed through purifier at 78°C with optimum efficiency, and pump back to Renovating Tank.
4. When Sump Tank is empty, interior cleaned and examined.
5. Purified oil sent to Laboratory and tested.
6. During this time, new oil should be used.
7. Oil should be reused, if Lab results recommended that it is fit for further use.
[Straight mineral oil: 3% water washed. Additive oil: 1% water washed.]

L.O. for Crankcase Viscosity 130 – 240 Sec. Redwood No. 1 at 60’C.
VI 75 – 85 Pour pt. – 18’C Closed flash pt.220’C
TBN (trunk type) 30 mgKOH/gm of oil
TBN ( X-Head Type ) 8 mgKOH/gm of oil.

Water in LO
Effects:
1. Can form Acids.
2. Can cause corrosion on m/c parts.
3. Microbial degradation. [Reduce centrifuging efficiency; promote local pitting and corrosion].
4. Reduce load carrying capacity.
5. Reduce L.O. properties, and TBN of oil.
6. Form sludge due to emulsification.
Remedies:
1. Proper purification with minimum throughput.
2. Batch purification if heavy contamination.

Maximum Allowable % of water in LO
1. For crosshead engine, < 0.2% is satisfactory. 2. If water content exceed 0.5 ~ 1.0%, immediate action should be taken. If > 1%, engine can be damaged.
3. For trunk type engine, < 0.1% is satisfactory. If > 0.5%, immediate action should be taken and
it is maximum permissible content.

LO tests onboard:

Tests carried out on used diesel crankcase oil:
1. Viscosity {changes caused by dilution with fuel oil}.
2. Closed flash point {changes caused by dilution with fuel oil}.
3. Insoluble
4. Water content
5. Acidity.

(1) Viscosity determination:
–  Viscosity and closed flash point will fall by fuel oil contamination.
–  Changes in these values are a measure of dilution, and up to 8% contamination can be tolerated.
Three Tubes Rolling Ball Viscometer:
1. Assume that system oil is SAE 30.
2. One tube filled with minimum safe viscosity, SAE 20.
3. One tube filled with maximum safe viscosity, SAE 40.
4. Last tube filled with test sample.
5. All tubes placed in warm water, until at same temperature.
6. All tubes placed on tilted board and inverted, so that internal hollow balls rise to surface, with different time taken.
7. If time taken for test sample is between upper and lower limit oils, this sample oil is fit for further use.

(2) Insoluble Content:
» Insoluble are soot, dust, metallic particles, asphaltene, oxidation products, and products of deterioration.
Blotter Test:
1. Single drop of sample oil is released from a given height onto a sheet of Special Filter Paper.
2. The result is compared with Standard Test Paper, of similar oil with known varying insoluble content.
3. Test oil should be below the upper limit:
Upper limits of insoluble are: 1.00% to 1.5% for Straight Mineral Oil,
5% for Detergent/Dispersant type Oil.
(3) Water and other contaminants by:

Crackle Test:
1. Pour a known amount of sample oil into a test tube.
2. Hold the test tube over small spirit lamp, shaking it while doing so.
3. If there is no crackling, the oil is dry.
A slight crackle indicates a trace of water.

(4) Acidity Determination:

1. Tested by extracting the acids from sample oil, by means of shaking with known amount of distilled water, in a test tube.
2. Acidic extract is placed on a watch glass, with Indicator Solution of known strength.
3. The mixture is drawn into a glass tube, and compared with Colour Standards, each representing a known pH value. Sample can be determined quite accurately.

Microbial Degradation:

  • If free water is present in crankcase, micro-organisms may grow, at oil water interface, by consuming hydrocarbons in oil.
  • Infestation at early stage may not be harmful but in case of severe infestation, corrosion within machinery parts may arise.
  • Complete oil change is necessary.

Indication:

1) Darkened oil colour and yellowish colour film on surface.
2) Pungent smell
3) Sludge formation.

Poor quality fuel:

High pour point.: Needs extra heating for storage tank.
High density: Causes purification difficulties.
High viscosity: Pumping difficulties and more heat required getting suitable injection
viscosity at injector.
Low cetane number. Late injection and after burning. It is considered as poor fuel, if C  37 .
Abrasive group: (ash, silica, nickel, catfines): Cause wear on cylinder liner, piston rings, ring
grooves and fuel injection equipment.
Corrosion group: (Sulphur, Vanadium, Sodium): Low temperature corrosion due to sulphur.
Acid dew point is 120 – 160°C
High temperature corrosion due to Vanadium, Sodium and Sulphur
at 460 – 570°C
Corrosion or vapour locking at fuel injection equipment, due to water.
Fouling group: (catfines, CCR): Slow burning due to Asphaltine, combustion space fouling
and T/C fouling due to CCR.

Flash Point:
1. Lowest temperature at which an oil will give off sufficient flammable vapour, to produce a flash when a small flame is brought to the surface of the oil.
2. Minimum flash point for on-board use is 60°C.
3. Fuel storage temperature must be kept at least 14°C lower than its flash point.
4. Average closed flash points: Petrol – 20°C: Paraffin 40°C: Diesel Oil 65°C:
LO 220°C: 70 cst Fuel Oil 71°C: Heavy Oil 100°C:

Pour Point:
1. Lowest temperature at which the oil barely flow.
2. It is just above the lowest temperature at which liquid flows under its own weight.
3. It must be low, otherwise fuel tends to solidify and due to poor heat transfer property, fuel cannot be returned to its original state by heating.
4. Fuel storage temperature must be kept at least 10°C higher than its pour point.
5. At least 40 – 50°C higher than its pour point, for cold weather condition.

Homogenizer:
1. It is a device to create stable oil and water emulsion, which can be bunt in boilers and diesel engines.
2. This emulsion can burn more efficiently and reduce solid emission in exhaust gas.
3. It can reduce catfines into finely ground particles, which do not harm.

Bunkering Operation

How to order bunker:

1. Take essential data from master, such as distance to go with average speed, river passage, pilotage, port stay, etc. To check ROB.
2. Estimate HO and DO consumption based on weather, wind and current condition, running hours of AEs auxiliary boiler and ME.
3. Estimate the 3 days reserve, considering unpumpable quantity, bunker allowance or bunker margin.
4. Calculate the capacity to receive, bunker amount, type of bunker, HO, DO or LO.
5. Bunker should be allowed 85% of tank capacity.
6. Arrange not to mix with remaining onboard fuel.

Total required bunker from port to port = {Distance to go with average speed + River
Passage + Pilotage + Port Stay + 3 Days Reserve }

Bunker to be ordered: = { Total required – ROB }

CE’s Responsibility during Bunkering:
CE is overall in charge of bunkering.

Responsibilities are:

1. Fire prevention
2. Oil pollution prevention
3. Calculation
4. Recording and informing.

Discuss at Bunkering Meeting about: Quantity / Bunkering Sequence / Distribution Plan.
Make preparations for both Deck and Engine Department, in accordance with pre-bunkering checklist.
Prepare all necessary papers as per local regulations.

Fire Prevention:

1. Prohibit naked light and smoking around bunker area.
2. Place portable fire extinguisher at bunker point.
3. Bunker oil flash point ≮ 65°C, as a rule.
4. Ensure no oil leakage.

Pollution Prevention:

1. Clear overflow tank and top up settling and service tank.
2. Clean System filters, sight glass, and pressure gauge in good order.
3. Ensure bunker system valves in good order, and the correct valves have been opened.
4. Take all soundings of fuel tanks, and calculate the amount to be put into each tank.
( 85% of tank capacity is maximum. )
5. Explain bunkering sequence to all engineers.
6. Check security of hose coupling, and one responsible engineer to be stand-by at bunker station to watch break or spill at hose connection.
7. Agree the pumping rate or pressure with pump man or barge master, remembering that a burst hose can cause pollution. Discuss slow down operation and emergency stop procedure.
8. Make good communication between bunker point, barge or shore supply, and tank control station.
9. Leakage or overflow of oil to deck strictly prevented. Saw dust, OSD, and rags, ready at bunker point.
10. Duty officer to be informed, the amount to be bunkered and expected time of the work.
11. Plugged all deck scuppers.
12. Maintain the upright position as possible as.

 

For Calculations:

1. Take all soundings of fuel tanks, before and after bunkering.
2. Take fore and aft draughts, before and after bunkering.
3. Take soundings of barge or to check flow meter reading, before and after bunkering.
4. Record the oil temperature.
5. Calculate corrected sp.gr. at measuring point temperature, SGc.
6. By multiplying SGc with total volume, obtained from sounding table, total amount of bunker in tons will be obtained.

Bunker Barge Arrival:

1. Record exact time of barge arrival and departure.
2. Check local supplier’s paperwork, to ensure that specification and quantity ordered is correct.
3. Check for correct specification, and compatibility tested, by using a test kit.
4. Check water content of bunker is at acceptable level.
5. Ensure that onboard fuel handling equipment is adequate and serviceable at all times.

Bunkering:

1. Start bunkering at slow rate, and then raise the pumping rate.
2. Always check and witness the flow meters, tank gauges and tank dips, before and after delivery, to ensure that the right quantity has in fact been supplied.
3. Random checks to ensure correct specification of oil being supplied during bunkering.
4. Take a continuous drip sample. Compatibility test of bunker carried out.
5. Always insist on being given a sealed sample of bunkers delivered, which should be witnessed and signed by both parties.
6. When 80% of total capacity reaches, pumping rate slow down and final topping up done.

After Bunkering:

1. Record the time and read flow meter on bunker boat or on shore.
2. All filling valves kept open, until final air blowing is completed.
3. Remain hose connections until correct quantity of oil has been received after calculation.
4. Then close bunker main valve, system valves and individual tank valves.
5. Take final soundings and bunker temperature from both ship and barge to calculate actual amount.
6. When calculating the bunker received, the ship’s trim and temperature of the oil must be taken into account.
7. Both party signed on sample bottles and sent to laboratory. The statutory sample to be kept in sample store and retain it for 12month.
8. Inform duty officer, starting and stopping time, amount of bunker received and tank soundings, for stability calculation and custom claiming purposes.
9. Make entries into ORB, Sulphur record book and Logbook.
10. BDN to be collected from supplier and file it properly to retain it for 3 years.
10. Prepare Bunker Report and sent to HO.

FO Overflow while Bunkering: [Action taken by CE.]

1. Stop pumping of fuel immediately.
2. Report to Master and contact Port Authority or persons concerned, about oil pollution incident.
3. Detail description of actions taken immediately by crew, using equipment from Oil Spill Locker to reduce and control the oil flow.
4. Arrange point of contact onboard, for co-ordinating shipboard action with local authorities, in combating pollution.
5. Make entry into ORB, date, time, place and amount of overflow.

Bad fuel:

1. Bunker should be received in empty tank and made segregated.
2. During bunkering, compatibility test should be done.
3. Sealed sample sent to laboratory for analysis.
4. Maintain storage temperature well above pour point. (About 40’/50’C under coldest climate condition.)
5. Settling tank temperature maintained about 14’C below flash point to improve gravitational separation. Regular drain out of water and impurities.
6. Fuel transfer lines steam traced, and transfer pump suction filter cleaned.
7. If necessary, dose chemicals, e.g. Gamma Break- Unitor, into storage tanks ( DB tanks) by using dosage pump for chemical.
8. Regular cleaning of coarse filters.
9. Two purifiers run in parallel, to get enough fuel for engine, with optimum throughput and correct heating temperature (98’C). Gravity disc, carefully chosen. If necessary, double stage centrifuging will be done with purification and clarification in series.
10. Maintain correct service tank temperature. Dose some chemicals, to improve combustion efficiency. (Duel Purpose Plus, Unitor)
11. Maintain correct oil temperature, to get suitable viscosity at injectors,
( 10 ~ 18 Cst.). Fuel outlet from heater, controlled by Viscotherm Unit.
12. Steam tracer lines correctly heated, up to injector.
13. Maintain correct working temperature of engine, to prevent hot and cold corrosion due to Vanadium and Sulphur attacks.
14. Check engine performance by taking indicator diagram.
15. If damage occurred due to bad fuel, prepare for insurance claim.

Compatibility:
1. Ability of two fuel to be blended together without precipitation of sediments, such as asphaltine and sludge, etc.
2. Due to asphaltine and sludge, it can cause choking of filters, overloading of purifier and immobilisation of vessel in severe case.

Remedies: For Incompatibility:
1. Keep fuels in empty tank and segregated.
2. Always carry out compatibility test when bunkering.
3. Incorporate homogenisation system to completely mix incompatible fuel components prior to injectors.

Compatibility Test:
1. Pour 40 ml of sample into test tube. (20 ml for each fuel)
2. Add reagent of white spirit up to 80 ml. (ē 40 ml white sprit)
3. Then the mixture is mixed well.
4. One drop of mixture is deposited on chromatographic paper and allowed to dry at room temperature.
5. Then test drop is compared with five standard spots.
Spot 1 ~ 2 indicate compatible fuel.
Spot 3 ~ 5 indicate incompatible fuel.

Requirements for the use of high viscosity fuel:

1. Bunker tank-heating systems capable of maintaining fuel temperature about
40-50’C higher than Pour Point under the coldest climate condition.
2. Exposed bunker transfer pipes insulated and trace heated.
3. Treatment plant capable of purifying/clarifying high density fuels.
4. Engine preheaters designed to achieve recommended injection viscosity.
5. Trace heated and pressurised engine fuel system, allowing manoeuvring on residual fuel.
6. Main and auxiliary engine designed to burn high viscosity fuel oil.

Effects of Bad Fuel Oil:

1. Too much sludge formation in DB tank.
2. Frequent fuel line filter blockage.
3. Upsetting purifier.
4. Premature wears of fuel pump.
5. Carbon trumpet formation and leaky FV.
6. Excessive wears and cold corrosion of cylinder liner.
7. Excessive carbon deposits in piston rings.
8. Hot corrosion attack on Exhaust valve.
9. Choked turbine nozzle rings and broken blades.
10. Excessive carbon deposits on EGE.

Bunker Specifications:
Includes: Name of vessel, Port of bunker, Date of delivery, Product name, Temperature of product, Sulphur Content,
Quality:
1. SG at 15°C
2. Viscosity at 50°C
3. Sulphur content % by weight
4. CCR % by weight
5. Flash Point [closed] °C
6. Pour Point °C
7. Water content % by volume
8. Sludge / Sediment % by weight
9. Cetane No.
10. Vanadium in ppm.

Bunkering:
1. Slow rate and record.
2. Take soundings.
3. Random check
4. Continuous drip sample.
5. Compatibility test
6. Slow down when 80% is reached.
7. Remain v/vs opened until after air blow.
8. Remain hose connection until after calculation.
9. Take sealed sample
10. Close all valves.

Viscotherm Unit:
A device to adjust the viscosity of oil to get desired value, which is essential for correct atomisation and combustion of engine.

Operation:
1. Constant quantity of oil is taken from the flow and fed into capillary tube by means of motor operated gear pump through reduction gear.
2. Oil flows through capillary tube under laminar condition and pressure drop across the tube is measured by DP cell and its signal is directly proportional to oil viscosity. A transducer is incorporated with DP cell.
3. Signal given by DP cell is compared with a set value and any deviation can cause
drive signal to adjust pneumatic control steam inlet valve to oil heater.
4. Normally the required injection viscosity is 10 ~ 18 Centistrokes and required value is set at transducer.

VIT:

1. Load-dependent start of fuel injection control system.
2. VIT mechanism automatically change the fuel injection timing, according to load,
to get maximum combustion pressure (Pmax) at engine load between 85% ~ 100%.
3. Reduction in SFOC is about 2.0 gm / bhp / hr at 85% engine load.
4. VIT fuel pump incorporates variable injection timing with optimised fuel economy,
at part load.
5. Expansion Ratio is increased.
Maximum Pressure
Expansion Ratio =
Pressure at the start of Exhaust Blow-down

6. Required fuel viscosity at engine inlet is 10 ~ 20 Cst.

In other words:
1. If an engine running at prolong period at reduced load, lower air temperature after compression, will cause increase in ignition delay of injected fuel, subsequently causing knocks and poor combustion.
2. This problem can be reduced by adoption of VIT system, to advance the start of injection, then allowing the same Pmax, at part load.

Operation of VIT: [ Valve control type: Sulzer RTA ]

1. Fuel Quality Setting [FQS] lever is used for manual adjustment of VIT mechanism to alter valves timing, according to ignition quality of fuel used. [If poorer quality fuel is used at same valve timing, Pmax will drop, and with better ignition quality fuel, Pmax will rise.]
2. VIT mechanism is linked to Governor Load Setting Shaft and built-in cam system, which is positioned by FQS lever.
3. This mechanism controls the timings of Suction Valve closure (beginning of delivery) and Spill Valve opening (end of delivery) through linkages simultaneously.
4. Hence, fuel injection timing, Pmax, and fuel delivery to injectors, are controlled load-dependently.

Thermal Cracking:

1. Atoms within hydrocarbon molecule are excited by heating, thus lighter fraction of molecule breaks-off and condensed.
2. Remaining portions of original molecule then unite to form more heavier molecule.
3. Thermal cracking produces Asphaltene, which has heavy hydrocarbon molecules,
causing slow burning in fuel combustion.

COC ORAL EXAM PREPARATION (PART- 2) – SURVEY & CERTIFICATION

images (1)

Image Credit: Marinelink

Survey:

Authorised independent examination, investigation, and inspection, measuring or testing of ship structure, machinery and equipment, done and supervised by Surveyors appointed by regulatory or commercial organisations.

Classification Societies:
They are third party independent bodies e.g. ABS (American Bureau of Shipping), BV (Bureau Veritas), LR (Lloyd’s Register), ClassNK (Nippon Kaiji Kyokai), DNV (Det Norske Veritas), GL (Germanischer Lloyd).

Their functions:
1. To ensure that ship is soundly constructed and the standard of construction is maintained.
2. Carried out Statutory Survey on behalf of the Administration regarding the ship safety and prevention of pollution of marine environment.

Classed ship:

  •  A ship, which is built in standard and maintained under rules and regulations of Classification
  • For a ship to be entitled to a class, Classification Society issues a Classification Certificate after carrying out Classification Surveys.
  • Classification Certificate confirms that the ship has both structural and mechanical fitness for their intended services.

Maintaining the class:
To maintain a ship in the class:
–  The owner must carry out regular surveys of hull, machinery and equipment.
–  Carry out repairs necessary from time to time, under the supervision of Class Surveyors.

Statutory Survey:
–  Carried out by Administration regarding the safety of the ship, sea worthiness and pollution, in accordance with national and international rules.
–  Issued a certificate, this is essential to the ship’s ability to trade.
–  If Statutory Survey is not certified, the ship can be detained.

Statutory Surveys are:

  • International tonnage survey
  • International load line survey 5 years interval
  • Cargo ship safety construction survey 5 years –
  • Cargo ship safety equipment survey 2 years –
  • Cargo ship safety radio survey 1 year –
  • Marpol IOPP & IAPP survey 5 years –

Classification Survey:

  • Carried out by Classification Surveyor, to ensure that the ship has both structural and mechanical fitness, for intended voyage, in accordance with the class requirements.
  • A classification survey is a visual examination that normally consists of:
    –  an overall examination of the items identified in the Rules for survey;
    –  detailed checks of selected parts, on a sampling basis;
    –  witnessing tests, measurements and trials where applicable.

Difference bet: Statutory Survey and Classification Survey:

  •  Statutory surveys are not assessing or measuring something for a client.
  • Statutory survey will inspect something against a set standard or law.
  • On completion of this survey, the ship is issued with a certificate, which is essential to the ship’s ability to trade.
  • Class cannot go to the ship unless requested by the owner, or unless the ship is detained by the Port State Control.

Why Classification Societies sometimes issue the Statutory Certificate?

  • Sometimes Administration delegates the authority, to the Classification Society to inspect and issue Certificates, on their behalf, regarding statutory requirements.

Port State Control:

1. Port State Inspection is a particular form of Statutory Survey.
2. Intention of Survey is to check that, ships flying the Flags of States comply with the Requirements of the Conventions.
3. When these ships are in Ports of States, Port State Authority has control over the ships in port, and has rights to inspect the followings, in order to avoid Substandard Ships:
– Safety Equipment.
– IOPP & IAPP Certificate.
– Oil Record Book.
– Sewage Treatment Plant.
– MARPOL Equipment.

For PSC purposes, Port Authorities will apply in general, the following Instruments.
ILL 66, SOLAS 74, MARPOL 73/78, STCW 78, COLARG 72 and ILO 76.

4. A Surveyor representing the Authority of the Government carries out the Port State Inspection.

Preparation for Port State Control Inspection: [As a CE]

  •  IOPP, IAPP, IEE Certificates for MARPOL
  • Load Line Certificate
  • SOLAS Certificates
  • STCW Certificates, kept ready.
  • Safety Equipment prepared for testing and inspection.
  • MARPOL Equipment prepared for testing and inspection, such as:
    – OWS operation and alarm test.
    – Incinerator tested and kept ready for demonstration, and alarm test.
    – Sewage Treatment Plant, in good order, and dose chemicals.
    – Tank top near OWS and Bilge Pumping Station kept clean.
    – Bilge overboard discharge valve, tightly closed and kept under lock and key.
    – Update and attach ORB, with photocopies of MARPOL Certificates, original Oil Disposal Receipts, and Dirty Oil and Sludge Piping Diagram.

Flag State control:

1. Flag State or Administration has responsibilities that the ships built to their flag, comply with the Requirements of the Conventions, in construction and upkeep afterwards.
2. Government body carried out Surveys and issued Certificates relating to safety of the ship, sea worthiness and pollution.
3. Flag State Control is limited to ensure that valid Certificates are onboard:

  1. Passenger ship safety certificate Validity 1 year.
  2. Cargo ship safety construction certificate 5 years
  3. Cargo ship safety equipment certificate 2 years
  4. Cargo ship safety radio certificate 1 year
  5. International load line certificate 5 years
  6. MARPOL IOPP & IAPP certificate 5 years
  7. International sewage pollution prevention certificate (ISPP)  5 year.

Preparation for Entering a Stringent Port:

  • In Port State Control system, inspections are done at the port, in order to avoid Substandard Ships.
  • For PSC purposes, Port Authorities will apply in general the following Instruments.

1. International Convention of Load Line. ILL 66
2. International Convention for Safety of Life at Sea. SOLAS 1974.
3. International Convention for the Prevention of Pollution from Ships.
MARPOL 1973/78
4. International Convention on Standard of Training,
Certification and Watch Keeping for Seafarers. STCW 1978.
5. Convention or the International Regulation for Prevention of Collision at Sea.
COLARG 72
6. Merchant Shipping (minimum standard) Convention. ILO 1976

Before entering the port, prepare the following in general:

1. Certificates and Documents prepared.
2. ORB properly entered and updated.
3. Sludge formation should be compared with 1% of voyage fuel consumption.
4. Receipt for sludge and waste oil disposal to shore facility, attached to ORB.
5. ORBs retained for 3 years after date of last entry should be onboard.
6. IOPP Certificate has validity.
7. OWS alarm tested, discharge valve closed, spare filter onboard, tank top near OWS cleaned.
8. ODM tested for 15ppm alarm, and automatic stopping device.
9. USCG Notice posted especially near OWS and bilge pumping station.
10. Boiler not to emit black smoke.
11. Incinerator prepared for demonstration:

  • Waste oil tank, drained-off water and heated up to 80 – 90˙C.
  • Photocell, pilot burner and waste oil burner of incinerator removed and cleaned.
  • Flame failure, high flue gases temperature, and force draught fan failure alarms tested.
  • Line filter for waste oil line, cleaned.
  • Incinerated ash collected to show to Surveyor, or if disposed to shore facility, receipt attached to ORB.

12. Fire extinguishers and fire detection system, CO₂ alarms system, tested.
13. Check Sewage plant.

Periodical Survey: Mainly consists of Annual Survey and Special Survey.

Annual Survey (machinery):

  • General Inspection of conditions of the whole machinery and equipment.
  • At each Annual Survey between Special Surveys, main and auxiliary machinery are generally examined, and placed in satisfactory running condition.
  • If necessary, some of the machinery or parts are to be opened-up for the surveyor to examine.
  • Survey items include steering arrangement, windlass, weather decks, watertight bulkheads, doors, fire equipment, hatch ways, etc: (hull survey items).

Special Surveys (machinery):

  • Thorough Inspection of the whole machinery and equipment
  • Including open-up inspection of machinery and equipment, their performance tests and inspection of electrical installation.
  • Main and auxiliary machinery are subjected to Special Survey, at intervals similar to those for special surveys of the hull, i.e. every 4 years, in order that both may be recorded approximately at the same time at each Special Survey.

1. All openings to sea, including sanitary and all overboard discharges together with cocks and valves to be examined internally and externally.
2. Fastenings to the shell plating are to be renewed, if surveyor recommends.
3. Pumps and pumping systems including valves, cocks, pipes and strainers are to be examined.
4. Shafts, except propeller shaft, bearings and line shafts to be examined.
5. Foundations of main and auxiliary machinery to be examined.
6. Cylinders, cylinder heads, valves and gears, fuel pumps, scavenging pumps, superchargers, pistons, crossheads, connecting rods, crankshaft, clutch, reversing gears, air compressors, intercoolers, and such other items covered by CMS system.

CMS/ CSM:

  • A Special Survey carried out on a planned schedule, within a circle of 5 years, at the request of the owner, and upon approval of the proposed arrangement
  • Approximately 20% of the surveyable machinery items shall be examined each year.
  • Completion of circle implies that all essential machinery parts have been examined within a previous 5 years.

Items covered by CMS:

1. Main propulsion machinery, steam turbine.
2. Power transmission and main shafting.
3. Auxiliary engine.
4. Air compressors, air receiver and blowers.
5. CW, FO, LO, feed water, condensate, bilge, ballast and fire pumps, etc:
6. Condenser and feed water heaters, coolers, oil heaters, and evaporators.
7. Fuel tanks (more than 1 m³), cargo oil pumping installation.
8. Deck machinery.
9. Steering gear including operational test and checking of relief valve setting.
10. Reduction gears; to check the gear teeth, pinions, etc.
11. Other items of machinery and equipment, which the Society considers to be covered by CMS.

Items not covered by CSM:

1. Propeller and shaft.
2. Sea valves below load water line.
3. Boiler, EGE.
4. Cargo handling gears
5. Measurement of crank shaft deflections for ME.
6. Measurement of clearance at the aft end of stern tube.
7. Items of machinery and equipment which are not required open-up inspection at Periodical Surveys, e.g. foundation bolts, refer installation, electrical installation, incinerators, etc.
8. Performance tests, pressure tests required at Periodical Surveys.
9. Machinery and equipment of small capacity or low frequency operation, e.g. emergency air compressor, hand pump for bilge, FO tanks less than 1 m3
10. Machinery and equipment of special type or newly developed type.
11. Other items which the society considers not to be included in CMS system.

Planned Maintenance:

Planned maintenance should be flexible, and following items should be considered.
1. Weather Condition.
2. Length of voyage, trade.
3. Maintenance of Safety Equipment, and Emergency Team Training.
4. Optimum conditions for Statutory and Classification Surveys.
5. Dry Docking.
6. Manufacturer’s advises.
7. Breakdown maintenance.
8. Replacing of spares.
9. Controlling and recording of maintenance up-to-date.

Planned Maintenance should include:

1. Short term maintenance, weekly, fortnightly, and monthly.
2. Long term maintenance, 3 monthly, 6 monthly, yearly.
3. Operational maintenance, to be carried out if necessary.

Construction of a Planed Maintenance Schedule:

1. Plan must be flexible, so that changes, orders, or cargoes do not upset it unduly.
2. Adaptable to various weather conditions.
3. Length of voyage, routes and trades, that vessel is involved must be considered.
4. Maintenance of Safety Equipment and Emergency Team Training should be integrated with overall maintenance plan.
5. Appropriate equipment is brought-up to optimum condition for Statutory and Class Surveys, such as ‘Safety Equipment’, ‘Load Line’, and ‘Lifting Apparatus’.
6. Dry-docking and repair period should be integrated with the plan.
7. Manufacturer’s advises, to be complied with, and all Manufacturer’s Maintenance Logs to be completed.
8. Plan should include availability of appropriate equipment, for breakdown maintenance, due to unforeseen circumstances.
9. Provisions made for spare part replacements for wear and tear maintenance.
10. Plan must be carefully thought-out, well controlled, and efficient recording system must be kept up-to-date.

Classification Surveys:

– Annual Survey of hull and machinery.
– Special Survey of hull and machinery: the first special survey becomes due 4 years after the date of built. Special Survey can be extended up to 5 years if not completed at one time. [S/S 4+1 year.]
– Continuous Survey or running survey of hull and machinery.

Automation Survey :

Carried-out at 1 year from the date of installations and periodical Special Surveys are to be carried out at 4 years intervals. ( 1 + 4 )

At 1 year from the date of installation, during this Survey:
1. General examination of automatic and control system.
2. Examination of ship service generator in operation and control system.
3. Random checking of function indicators, alarms and control actuators.
4. Examination of machinery records to ensure that the performance of the control system are in good order through the period since last survey.
5. Machinery space fire detection and bilge alarms.

At interval of 4 years, during this Special Survey:
1. All requirements of Annual Survey are done.
2. Examination of control actuator,
3. Insulation resistance of all electrical equipment and circuits.
4. Control system of UMS for proper operation.
5. Automatic alarms and safety systems.

Tail shaft Survey:

  • Tail shaft with water lubricated bearing, to be drawn and surveyed, every 3 years for single screw, and every 4 years for twin screw.
  • Tail shaft with oil lubricated bearings, to be drawn and surveyed once every 4 years.
  • It is a survey done by Surveyor at the request of owner or his agent, due to damage of hull, machinery or equipment, which can effect the seaworthiness, or class of ship.
  • All necessary repairs to be carried out to Surveyor’s satisfaction.

Tail shaft Survey includes:

1. Complete withdrawal of tail shaft.
2. Propeller nut and tail shaft threaded end to be checked.
3. Cone, key and keyway to be checked, and forward part of the taper to be checked for crack with approved crack detecting method.
4. Tail shaft bearing wear, to be checked.
5. Stern bush and bearings, to be checked.
6. Shaft sealing arrangement, including oil system, to be checked.

Boiler Survey:

The Class Surveyor shall survey every boiler of working pressure 3.5 bar and heating surface area 4.65 m² and above.

Survey interval:
DNV & LLOYDS: Every 2-years interval until 8 years old, and every 1-year interval after 8 years old.
GL: Every 2½ years interval until 10 years old and every 1-year interval after 10 years old.

Annual Boiler Survey includes:

1. Hydraulic testing ( 1.25 x approved working pressure for not more than 10 minutes ).
2. Pressure testing of main steam piping at 15% in excess of approved working pressure for not more than 10 minutes.
3. Internal inspection, hammer test to furnace, stays bolts, fire and stay tubes, brickwork, baffles and casing.
4. Inspection of alarm and control system, fuel system, feed system, all steam piping and lagging arrangement, foundation and chocking system.
5. Checking of pressure gauge and water level gauges.
6. Testing of safety valves to blow off at the pressure not greater than 3% above w.p.
7. After 10 years old or at any time, if surveyor demands, drill test near the water line should be done to determine actual thickness of boiler shell. If found necessary, lower working pressure may be reassigned

At 4 years interval :
In addition to above Annual inspection procedure, all valves on boiler required to open-up and inspected, every 4 years at the time of Annual Survey, or at the next regular dry docking period thereafter.

Preparation for survey:

1. Clean water and fire sides.
2. Gags or clamps must be prepared for safety valves.
3. Boiler must be filled with water at a temperature not more than 38˙C for fire tube boiler and not more than 82˙C for water tube boiler.
4. Drip pan placed under all burners.
5. Tank top and bilges cleaned.
6. Pump for pressure test to be kept ready.
7. Blanks must be installed at steam valves and water level gauge.

Damage Survey:

1. It has to do with causalities and accidents, repairs, causes and remedies.
2. Damage to hull, machinery and equipment, which effects seaworthiness or classification, is to be submitted by owner and representative, for examination by Surveyor.
3. All repairs to be carried out to surveyor’s satisfaction.

When damage occurs:

If the vessel is classed, and the port has facilities of Classification Society, and Underwriter Surveyors and repairs firm:
1. Invite Classification Surveyor
2. Invite Underwriter Surveyor (appointed by Insurers)
3. Both Surveyors to survey the damage
4. Repairs to be carried out as per Class Requirements.
5. Quotation of repairer and repair cost to be submitted to Underwriter Surveyor to negotiate any reduction that may appears necessary.
6. Both Surveyors to survey the repairs when completed.
7. Repair bills must be endorsed by the Underwriter Surveyor so as to claim insurance.
8. Underwriter Surveyor does not accept bills for transportation.
9. Class Surveyor must confirm class of machinery (Interim Certificate of Class)
10. Log Abstracts and damage reports must be submitted to the Class Surveyor and owner.

If the vessel is classed, but the port is very small, and duly appointed Surveyor may not be available:
1. Call the next best surveyor.
2. If no surveyor is available, Damage Survey may be carried out by two Chief Engineers of same Flag (Port of Registry), but should not be from same company, to avoid biased report.

Actions taken by C/E when ME breakdown, fire / explosion occurred:

1. Find out extent of damage or breakdown.
2. Find out whether the damage can be repaired or not by ship crew.
3. Consider that vessel can resume the voyage or not.
4. Inform present situation to HO and take instruction.
5. Record exact times and position of ship.
6. Take pictures of damage for evidence.
7. After temporary or proper repair, resume voyage under suitable speed.
8. Prepare detail damage report and submit to head office.

CE damage report form:

1. Date, time, approximate ship position, voyage no.
2. Where damage occurs.
3. Causes and extent of damage.
4. HO confirmation and approval for major repair.
5. Actions taken.
6. Repaired condition, detail statement of clearances, measurements, etc.
7. Used and required spares to be ordered.
8. Training and instructions to prevent reoccurrence.
9. Take photos before and after repairs.

Insurance:

Ship owners insured their ships against unforeseen damage or loss such as:

  • Actual Total Loss.
  • Constructive Total Loss (the cost of repair being greater than the value).
  • Presumed Total Loss.
  • Partial Loss.
  • Third party Liabilities (collision, injury to crew)

The rate of Insurance:
It depends on size, age and engine, and a vessel with valid Certificates of Classification is likely to attract more favourable rate than a vessel without.

Insurance claim purpose:
Following items are necessary:

1. C/E damage report
2. Log abstracts.
3. Damage report form for insurance claim.
4. Class Surveyor recommendation.
5. Repair bills endorsed by Underwriter Surveyor.

Protecting and Indemnity Association:

  • This is a P&I Club or Mutual Insurance Club or Small Damage Club.
  • An association formed by Ship Owners, having certain risks to insure.
  • That certain risks are not covered by the Insurance Policy.
  • A Mutual Insurance Company, belonging to ship owners, which insures the damages relative to the ship, which are not covered by Insurance Policy.

Protecting:

1. Loss of life and personal injury.
2. Hospital, medical and funeral expanses arising from injury claim.
3. Sickness and repatriation.
4. Cargo damage due to improper navigation.
5. Oil pollution.
6. Collision damage, etc.

Indemnity:
1. Claim in respect of wrong delivery of cargo.
2. Ship’s liability to cargo, after collision, not covered by policy.
3. Fine or penalty imposed as a result of custom law, health regulations, and immigration law including smuggling.

Interim Certificate of Class:

  • Class Surveyor will issue the Certificate, when repairs have been completed to the Surveyor’s satisfaction.
  • This Certificate enables the vessel to remain in class, until the next full survey due.
  • Validity is until next survey due.

Certificate of Seaworthiness:

  • To enable to proceed to the next port, the Surveyor other than Class Surveyor issues it.
  • If the Classification Surveyor does not carry out the survey, the requisite certificate that is issued will be one of seaworthiness.
  • This Certificate enables the vessel to proceed to her next port, where a further survey by the Classification Surveyor will be conducted, so that Interim Certificate of Class can be issued.

Seaworthiness:
1. The fitness of the vessel in all respects for carrying cargo and crew in safe condition.
2. Important items concerned are stability, strength, freeboard, machinery and design, and they must be entirely satisfactory.

Franchise Clauses:

  • These state certain portion of insured value, for which Insurers are not liable to pay.
  • There are two kinds of franchises:
    [These state the percentage of the claim, which the Assured must bear.]

Deductible:

1. If amount of loss does not exceed the franchise amount the Insurers (Underwriters) are not liable to pay at all.
2. But if the amount of loss exceeds the franchise amount Insurers are liable to pay that portion which exceeds the franchise amount.
[Only claims in excess of certain percentages are paid, i.e. the Assured pays the first so much
percentage of any claim.]

Non-Deductible:

1. If amount of loss does not exceed the franchise amount the Insurers (Underwriters) are not liable to pay at all.
2. But if the amount of loss exceeds the franchise amount Insurers are liable to pay the whole amount.
[The Underwriter pays the whole claim if it exceeds the stipulated percentage.]

 

Load Line Survey:
1. Carried out as first Survey when a new ship is completed.
2. During this survey freeboard arrangement and conditions of assignment, are made in accordance with International Regulations and Documentation.
3. After thorough inspection, Load Line Certificate is issued, and its validity is 5 years, subjected to Annual Survey.
4. Load Line Renewal Survey held at 5 years interval from the date of build, and whenever a periodical Special Survey is made.
5. Validity of Load Line Certificate extends to the end of next Special Survey.
6. During this survey, all freeboard items to be examined, and load line markings to be verified. [With trammel gauge]
7. On satisfactory completion of the Survey, an International Load Line Certificate, valid for 5 years is issued.
8. Load Line Annual Inspection carried out within 3 months ± anniversary date of the Certificate.
9. Main purpose of Load Line Survey is, to examine that the ship construction complies with Requirements of Convention.
Requirements can be grouped into 4 categories:
1. Structural Strength.
2. Watertight Integrity.
3. Stability.
4. Crew Quarter Protection.

Conditions of Freeboard Assignment: Why it is important?

1. Efficient means of protection must be provided for all openings to hull and superstructure, for protection of crew in heavy weather, and for rapid freeing of water from weather deck.
2. Condition of Assignment must be maintained, at all times in satisfactory condition.
3. Annual Inspection to be made by assigning authorities, to ensure that they have been maintained in satisfactory condition for continued validity of Load Line Certificate.

Preparation for Load Line / Annual Survey:

Ship Officers/Engineers should ensure, the following items are in efficient condition, prior to the Classification Society Surveyor’s arrival on board.

1. Load line marks, verified with existing Load line Certificate.
2. Coamings and closing appliances of exposed hatchways, hatchways within superstructures, to be examined.
3. Holding-down clips/bolts are in good order; packing and seats are watertight.
4. Watertight steel hatch covers are to be hose-tested (pressure not less than 2 kg/cm² from a distance of 1.5m with ½ ” bore jet) for water-tightness.
5. Spring-loaded battening-down wedges between covers, and holding down cleats, to be in good working condition.
6. Exposed engine casing and their openings, fiddley openings, ER skylights and their closing appliances, to be checked and tested. ER skylight to be able to close from remote position.
7. Test Ventilators, check all flap levers are free, and locking pins are in place and secured by chain to ventilation casing.
8. Check air pipes and their closing means, flame traps for fuel oil tank’s air pipes, are in order.
9. Watertight doors and closing arrangements to be checked.
10. Scuppers and their discharge pipe and valves below the freeboard deck, checked for corrosion/wastage.
11. Gangways and cargo ports below freeboard or superstructure deck, to be checked.
12. General condition of hull, as far as could be seen.

Load Line Certificate:

  • A Certificate issued to a ship, if she is built and maintained thereafter, according to the requirements of International Convention on Load Line (1966)
  • Issued by the Administration or Classification Society.
  • Validity is 5-years and subjected to Annual Survey.

FO DB Tank Survey:

Transferring, cleaning and gas freeing must be done.

Testing of atmosphere:

˗ Toxicity
˗ O₂ content with Oxygen Analyser
˗ Explosive Gases with Explosimeter
˗ Gas free certificate from Chemist.

Survey:

1. Heating coil leak test: [1.5 times working pressure.]
2. Condition and testing of level alarm
3. Condition of sounding pipe, striker plate and flame trap
4. High temp. alarm sensor
5. Internal inspection by surveyor.

Sounding pipe requirements:

1. Used to determine the dept of liquid in a tank.
2. Should be as straight as possible.
3. If it is not possible, pipe curvature should allow easy passage of sounding rod or chain.
4. Normally, bore of pipe must be not less than 32mm.
5. Striking pad of adequate size and thickness placed under the pipe.

IOPP Certificate:

Issued after Survey is carried out by Administration, in accordance with International Convention for Oil Pollution Prevention. Validity is 5 years.

Checking procedure for IOPP Certificate, When CE sign-on:

1. Check the validity of certificate.
2. Check the ORB up to date recording.
3. Visual inspection of plants in good order.
4. Check 15-ppm alarm and automatic stopping device.
5. Check spare filter element, at least one no.
6. Waste oil tank and capacity.
7. Compare fuel consumption and sludge formation.
8. Incinerator capacity and workability.

IOPP Survey preparations:

1. Validity of the IOPP Certificate checked.
2. Proper entry of ORB and, sludge disposal receipts to shore facilities attached to ORB.
3. Calculate the sludge formation, and compared with 1% of voyage fuel consumption.
4. Incinerating time, incinerated waste oil amount, remainder of waste oil in waste oil tank should be reasonable.
5. Incinerator kept ready for demonstration, such as heating of waste oil tank, alarms, control and functional test, done prior to survey.
6. OWS in good order, its piping free from oil leaks, overboard valve from OWS locked in closed position. If possible, one section of discharge pipe removed and free from oil residues.
7. ODM checked for 15-ppm alarm and automatic stopping.
8. High level alarms of sludge tank, waste oil tank and bilge holding tank checked.
9. Spare filter for OWS must be onboard.
10. USCG Notice posted near OWS and bilge pumping out station

Survey by CE:

Requirements:

  • CE must have first class competency certificate or equivalent.
  • At least 3 years service as CE on owner’s vessels.
  • Should be at sea or in port with no Class Surveyor.
  • Generally cannot survey on Safety Equipment, pressure vessels, and main engine except in unit overhaul.
  • Can survey auxiliary machinery such as, AE, pumps, and Air Compressors.
  • DNV allows half of all items covered by CMS, of which there are more than one, may be surveyed by CE.

Confirmatory Survey:

1. When any machinery and equipment, allowed to be surveyed by CE, were opened-up and examined by CE at sea, Confirmatory Survey of these items must be done by the Class Surveyor at next port of call, or the first port of opportunity.
2. During this survey, show the followings to Class Surveyor:
a) Relevant entries in log book.
b) Two copies of statement, signed by CE.
c) Description of items surveyed by CE.
d) Spare parts replaced.
e) All photos for evidence.
3. If the surveyor does not satisfied, he has right to open up the item for inspection. If he satisfy, he will issue Interim Certificate of Class.

AE survey by CE:

Safe operation of propulsion must not be effected, when CE surveys AE.
1. All cylinder covers, valve gears, pistons, piston rings, liners, top and bottom end bearings, all upper half of main bearings, gudgeon pins are to be opened up.
2. To withdraw at least two bottom half bearings for inspection.
3. Checking of all crank pin bearings, journals and gudgeon pins.
4. Cylinder liner gauging and recording.
5. L.O. cooler to be opened up for inspection.
6. Defective attached pumps such as LO pump, FW pump, etc. to be opened up.
7. Testing of all safety devices, alarm and trip.
8. Crankshaft deflection taken and recorded after reassembled.

Confirmatory survey by Class Surveyor:
» He has rights to open up at least two main bearings and two bottom end bearings, and crankshaft deflections to be taken and checked with CE records.
» Run the engine and load-tested. All safety devices tested for alarms and trip for generator and switchboard, and are to be witnessed by the surveyor. (DNV).

Generator load test:

1. After priming the AE, start and run under no load, low speed condition for about 3 to 5 min.
2. Then stop and checked externally for overheating. If no overheating, crankcase doors to be opened and checked temperature of bearings and running gears.
3. If satisfactory, restart the engine at full speed, no load condition for about 30 min., then stopped and recheck again.
4. If satisfactory, restart and load-shared with running generator engine. Load sharing should be gradually increased in small steps, taking about 6 to 10 hours to reach at full load condition. While running in full load, another generator to be run in stand-by for possible emergency use. Synchronising or load sharing steps: 25%, 50%, 75%, and 100% within 6 to 10 hrs.
5. All necessary items checked, during load increasing steps.
6. Then peak pressure indicator and other performance data, taken for each cylinder and compare with test results.
7. Load test should be done, until preferential trip initiates.

A/E Damage Insurance Claim:

Items necessary to submit to Superintendent Engineer are:
» CE damage report.
» Log abstracts.
» Damage report form for insurance claim.
» Class surveyor recommendation.
» Repair bills endorsed by Underwriter Surveyor.

If A/E damage occurred at sea:

1. Date, time, position, voyage no., where the damage occurred, extent of damage, causes of damage, are reported to Head Office in detail.
2. Take HO confirmation and approval for major repair.
3. Take required damage photos.
4. When at nearest port, repair condition, photos before and after repair are submitted to Surveyor for Confirmatory Survey.
5. If Surveyor does not satisfy, he has right to open-up for inspection.
6. If Surveyor is satisfied, he will issue Interim Certificate of Class, and give recommendation.

If A/E damage occurred in Port:

1. Invite Class and Underwriter Surveyors through Master or Agent to make surveys.
2. Negotiate with shipyard repair firm, about cost and prices.
3. After completion of shipyard repair firm’s work, Surveyor will inspect the AE, and issue Interim Certificate of Class, and Underwriter Surveyor will inspect and give repair cost and certified endorsement.
4. Repaired condition with photos, and used spares, reported to HO and required spares ordered.

Surveys, requested by owners, charterers, underwriters and authorities:
1. Damage Survey
2. On and Off Hire Survey
3. Lay-up Survey
4. IMCO Survey (Inter-governmental Maritime Consultative Organisation.)
5. Pre-loading Survey
6. Draught Survey
7. Ullage Survey
8. Conditional Survey: [the ships over 15 years of age may be subjected to survey, annually, so as to ensure their seaworthiness, only upon request by owners and underwriters.]

On and Off Hire Survey:
1. The most time-consuming survey and must be done in daylight, with the hatches fully open, empty and clean.
2. Two Surveyors will have to carry out this Survey.
3. One representing the owner, may be the Master, and the other representing the Charterers.

The areas of Survey include:
1. Portside Bulwark/rails and Deck. [Bulwark is the part of ship’s side, above Upper Deck.]
2. Starboard side Bulwark/rails and Deck.
3. Deck houses and cargo gears.
4. Hatch coamings and hatches.
5. Shipsides, Tank tops, Bulkheads fore and aft.
6. Bunker Survey.

In Water Survey:

1. Due to increasing in size of oil tankers and bulk carriers and consequently, small numbers and size of docks incapable of docking these vessels, In Water Survey is permitted by Class.
2. This survey includes visual examination of hull, rudder, propeller, sea inlets and measuring the wearing of rudder bearings and cleaning of hull by suitable methods.

Limitation:
1. Not periodical special survey.
2. For less than 10 years old of vessels.
3. Must have Class notation to suit for in water survey.
4. Hull painted with high resistance paint and fitted with impressed current system for hull protection.
5. Class must approve Diver Firms.
6. Ship draught not more than 10 meters.

Requirements:
1. Hand held closed circuit TV camera that can be controlled remotely from surface monitoring system.
2. Communication between Diver Party and Surveyor.
3. Water is clean and clear.
4. Carried out in daylight.

Docking Survey:

1. The ship must be examined in dry dock preferably at 1-year intervals, but new Class Regulations allowed intervals of up to 2 years.
2. The vessel is to be placed in dry dock or upon a slip way and the keel, stern frame post, rudder and outside plating, propeller, exposed part of stern bearing assembly, rudder pintle and gudgeon securing arrangements, sea chest, strainers and other fastenings are to be cleaned and examined.
3. The stern bearing clearance and rudder bearing clearance are to be ascertained.

Underwater [Bottom] Survey on Dry Dock:

1. Shell plating washed and brushed down, checked for distortion, bulging, roughness and corrosion.
2. Welding seams inspected for cracks.
3. Zinc anodes checked for replacement.
4. Shipside valves and cocks removed, overhauled and refitted.
5. Shell box or Sea Chest wire brushed and applied anti-fouling paint.
6. Remove drain plug of rudder to determine the present of water.
7. Measure wear down of rudder and jumping clearance.
8. Bearing metal of gudgeon pin of rudder checked and clearance
must not exceed 6 mm.
9. Pintle nuts with locking device checked.
10. Propeller carefully examined especially near the tip on the driving face and fore side for cavitation. Damaged propeller blades repaired.
11. Wear down of tail shaft measured. For oil lubricated: 2 x original clearance.
For water lubricated: maximum 10 mm.
12. Stern tube checked for tightness.
13. For CPP, checked for good working order.
14. Anchor and chain cable, lay up and measured.

Dry Docking:

Required Plans and Arrangements for Docking:
1. Docking plan.
2. General arrangement plan.
3. Capacity plan.
4. Shell expansion plan.
5. Shell painting area plan.
6. Mid ship section plan.
7. Longitudinal section plan.
8. Anode plan.
9. Shafting and propeller arrangement.
10. Rudder, to check.

Docking plan:

▭ Provides the positions of frame spacing, watertight bulkheads, docking plugs, etc.
▭ Determine the positioning of keel blocks, bilge blocks, bilge shore, breast shore
when the ship is on dock.

Preparation for Dry Docking: [As a CE.]

1. Take all information from HO and dockyard.
2. Sent Docking Plan to Dockyard.
3. Prepare dockyard and ship staff repair lists and survey items.
4. Prepare necessary spares and store, drawings, Manuals, Certificates, special tools and measuring equipment.
5. 2/E should be instructed to perform the followings:

a) Label all sea valves, all shipside valves and cocks. Mark the positions of items to be repaired, with tags or colour code.
b) Keep Emergency Fire Pump, Emergency Generator, Air Compressors, Emergency Air Bottle, and portable Fire Extinguishers in good order.
c) Lock Fixed Fire Fighting Installation, as per shipyard rules.
d) Shut down Boiler, OWS, Sewage Plant if dockyard does not allow.
e) Lock overboard discharge valve in closed position.
f) Fill up Settling and Service Tanks.
g) Press up Air Bottles and Emergency Air Bottle, and shut the valves tightly.
h) ME crankshaft deflections to be taken and recorded.
i) Hose down tank tops, and empty Bilge Holding Tank, Sludge Tank, Waste Oil Tank.
j) Prepare for receiving of Shore Power Supply, International Shore Connection, cooling arrangement for Air Conditioning and Provision Plants.
k) Provide fire watch in ER at all times, and follow Dockyard Fire and Safety Regulations.
l) Adjust required trim and draught, with deck officer.
m) Take soundings of DB tanks and cofferdam.

During Docking:
1. Discuss with the superintendent and dockyard repair manager about repair jobs.
2. Assist Surveyor and record the survey items.
3. Witness all alignment works and clearance measurements.
4. Take and record propeller shaft wear down, rudder wear down and jumping clearance.
5. Check oil tightness of stern tube.
6. Check all completed underwater jobs, done by dockyard.
7. Check all sea valves, shipside valves and cocks, after overhauling.
8. Check all repaired jobs done by ship staff, and used spares and store.
9. Make daily records.

Undocking:
1. Check all repair and underwater jobs in accordance with repair list.
2. Check all measurement data are correct and completed.
3. Make price negotiation.
4. When sea water level covers the sea chest, each sea valve should be opened and checked for any leakage.
5. Purge air from cooling seawater pumps, run the pumps and check pressure.
6. Test run the ship generators, until satisfactory, and cut out shore supply, cut in ship generator, disconnect the shore connection, restart seawater pump, record the time and read watt meter.
7. All sea valves, shipside valves, repaired pipes, repaired jobs must be finally checked, before leaving the dock.
8. Prepared for ME.
9. All DB tank soundings checked.

After Leaving the Dock.
1. Checked ME crankshaft deflection and compare with former record.
2. Prepare for Docking Report.

Cargo ship Safety Construction Certificate:

  • Issued after survey to every cargo ship of 500 GRT and over, by the government of Flag State.
  • Validity is 5 years, subjected to survey at specified intervals.
  • During survey, following items must be in accordance with the requirements of SOLAS 1974 Convention.

1. Ship structure, including structural fire protection.
2. External examination of ship’s bottom.
3. Electrical installation.
4. Steering gear.
5. Pressure vessels and fitting.
6. Main and auxiliary machinery.

Cargo ship Safety Equipment Certificate:

  • Issued after survey to every cargo ship of 500 GRT and above, by the government of flag state.
  • Validity is 2 years and annual inspection of ± 3 months.
  • Safety Equipment Survey, consists of inspection and demonstration:

1. Fire fighting appliance, FFA
2. Life saving appliance, LSA
3. Navigation equipment
4. Vessel documentation
5. Alarm system.

Concerning items for CE:

1. All portable and semi-portable fire extinguishers
2. Fixed installation of fire fighting
3. Fixed fire detection and alarm system
4. Fire man’s outfit
5. Emergency fire pump, main fire pump
6. Emergency stop switches, remote quick closing valves, skylight, watertight doors
7. Emergency generator and lighting system
8. Escape ways in ER.
9. Steering gear and communication system
10. Life boat engines and launching system.
11. All the items required by SOLAS must be prepared.

Some government administrators publish checklist for survey. This is an essential tool for preparing for a survey, so that one surveyor should be able to complete the survey in ½ day.

Safety Equipment Survey:

  • Government body carried out at every 2-year interval, and annual inspection of its validity.
  • At every port, where the ship called on, Government body concerned has a right to inspect Safety Equipment, IOPP Certificate, Sewage treatment plant, Marpol equipment, and ORB for Port State Control measures.

1. To inspect Fire hoses, Nozzles and container box.
2. Fireman’s outfits: Breathing apparatus.
3. All portable extinguishers.
4. Emergency and Main fire pumps.
5. Emergency generator.
6. Fixed installation [gas level, cleared lines and nozzles, operating mechanism and alarm system].
7. Audible Fire alarms, Fire detection system, Abandon ship warning, and Ship Siren and Muster list.
8. Stop switches outside ER, for fans, fuel pumps, fuel tank valves, Skylight doors, Watertight doors, Fire dampers.
9. Inert gas system of cargo ships, 500 tons Gross Tonnage and above.
10. Life raft Certificate.
11. Life buoys, Smoke floats, Buoyancy lines.
12. Lifeboat internally and externally.
13. Condition of Buoyancy tanks inside lifeboat.
14. Illuminating power sources, for launching of Lifeboat and Rafts
15. Latest Nautical Publications.
16. To run Lifeboat Engine, ahead and astern in water.
17. To swing out all lifeboats at least 50% lowered into the water.
18. To lower Davit span ropes and Boarding ladders.
19. To lay out and survey all lifeboat equipment.
20. To survey Life jackets.
21. To check Navigation lighting.
22. To check pilot ladder with lighting.
23. To inspect fall release mechanism [free fall or float free].

Certificates onboard:

1. Certificate of Registry
2. International Tonnage Certificate
3. International Load Line Certificate
4. International Load Line Exemption Certificate
5. Certificates for Master, Officers and Ratings
6. Derating or Derating Exemption Certificate
7. International Oil Pollution Prevention Certificate
8. International Sewage Pollution Prevention Certificate
9. International Safety Management Certificate, SMC
10. International Medical Certificate
11. Passenger Ship Safety Certificate
12. Cargo Ship Safety Construction Certificate, SAFCON
13. Cargo Ship Safety Equipment Certificate, SEC
14. Cargo Ship Safety Radio Certificate
15. Exemption Certificates for SAFCON, SEC and Radio Certificate
16. Certificate of Classification
17. Certificate of Insurance or other financial security
in respect of civil liability for oil pollution damage.

18. International Pollution Prevention Certificate
for the Carriage of Noxious Liquid Substances in Bulk. [NLS Certificate]
19. Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk
(Chemical Tanker)
20. Certificate of Fitness for the Carriage of Liquefied Gases in Bulk
(Gas Carrier)

SOLAS Certificates:

  1. Passenger Ship Safety Certificate
  2. Cargo Ship Safety Construction Certificate
  3. Cargo Ship Safety Equipment Certificate
  4. Cargo Ship Safety Radio Certificate
  5. Cargo Ship Safety Certificate 1
  6. Exemption Certificate
  7. Document of Compliance with the special Requirements for Ships carrying Dangerous Goods
  8. Minimum Safe Manning Document
  9. Document of Authorization for the Carriage of Grain
  10. International Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk
  11. International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk
  12. International Certificate of Fitness for the Carriage of INF Cargo
  13. Safety Management Certificate (ISM)
  14. Document of Compliance (ISM)
  15. High Speed Craft Safety Certificate
  16. International Ship Security Certificate

MARPOL Certificates:

MARPOL Annex I:
1. International Oil Pollution Prevention Certificate (IOPP Certificate)
2. Statement of Compliance with CAS (as a supplement to ship’s IOPP Certificate)

MARPOL Annex II:
1. International Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk
2. Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk
3. International Pollution Prevention Certificate for the Carriage of Noxious Liquid Substances in Bulk (NLS Certificate)
4. Certificate of Fitness for Offshore Support Vessels

MARPOL Annex IV:
1. International Sewage Pollution Prevention Certificate
2. Result of calculation of moderate rate of discharge in accordance with MEPC.157(55)

MARPOL Annex V:
1. Garbage Management Plan
2. Garbage Record Book

MARPOL Annex VI:
1. International Air Pollution Prevention Certificate
2. Engine International Air Pollution Prevention Certificate
incl. Technical File and Record Book of Engine Parameters if applicable.
3. International Energy Efficiency Certificate

Oil Record Book: Part I

  • Operations involving oil and oily mixtures recorded in ORB.
  • Dates, geographical position, quantity, tank identification, and duration of operation entered.
  • Port State Authority may take copies of entries, and if so requested, the master is required to state that it is a true copy.
  • ORB retained onboard for 3 years after date of last entry.

To be recorded:

1. Ballasting and cleaning of fuel oil tanks. (Code a.)
2. Discharge of dirty ballast or cleaning water from oil fuel tanks. ( b.)
3. Disposal of oil residues (sludge). ( c.)
4. Non-automatic discharge overboard or disposal otherwise, of bilge water accumulated in machinery spaces ( d.)
5. Automatic discharge overboard or disposal otherwise, of bilge water accumulated in machinery spaces ( e.) (e.g. transfer of bilge water to slop tank) (identify tank)
6. Conditions of ODM and Control System. ( f.)
7. Accidental or other exceptional discharge of oil. ( g.)
8. Bunkering of fuel or bulk of LO. (h.)
9. Additional operational procedures and general remarks. ( i.)

Oil Record Book: Part II

To be recorded:

1. Loading and unloading of oil cargo.
2. Internal transfer of oil cargo during voyage.
3. Cleaning of cargo tanks.
4. Crude Oil Washing (COW System only)
5. Ballasting of cargo tanks.
6. Ballasting of Segregated Clean Ballast Tanks (CBT Tankers only)
7. Discharge of dirty ballast.
8. Discharge of clean ballast contained in cargo tanks.
9. Discharge of ballast from Segregated CBTs. (CBT Tankers only)
10. Discharge of water from Slop Tanks into the sea.
11. Condition of ODM and Control System.
12. Accidental or other exceptional discharge of oil.
13. Additional operational procedures and general remarks.
14. Loading of ballast water. (Tankers engaged in specific trades)
15. Re-allocation of ballast water within the ship. (do)
16. Ballast water discharged to reception facilities. (do)

Shipboard Oil Pollution Emergency Plan: SOPEP.

Every oil tanker of 150GRT and above, and every ship of 400GRT and above, shall carry onboard a Shipboard Oil Pollution Emergency Plan.

The plan shall consist at least of:

1. Procedures to be followed by Master, or other person having charged of the ship, to report an oil pollution incident.
2. List of authorities or persons to be contacted, in the event of oil pollution incident.
3. Detailed description of actions to be taken immediately by persons onboard, to reduce or control the discharge of oil.
4. Procedures and point of contact onboard, for co-ordinating shipboard action with local authorities in combating the pollution.

Procedures, when accidental oil overflow occurs:

1. Notify Harbour/Terminal Authority immediately through the Master.
2. Actions immediately taken by persons onboard to stop, reduce or control the oil discharge.
3. Co-ordinate shipboard actions with local Authorities.
4. Inform owner, agent, P&I Club, Flag State Authorities, and vessels in vicinity.
5. Invite P&I (Protection and indemnity) correspondents.
6. Record in ORB, time & place of occurrence, approximate amount & type of oil, circumstances of discharge or escape.

Sludge Tank requirements:

1. Capacity must be minimum 1% of used HFO for 30 days (or)
½ % of used DO for 30 days.
2. Sufficient manholes to reach all parts of tank.
3. Adequate heating arrangement.
4. No direct connection between sludge tank discharge piping and overboard discharge piping.
5. Fitted with designated pump, having suitable capacity and discharge head.
6. Fitted with standard discharge connection.
7. Fitted with high level alarm.

Sludge Tank Capacity and Requirements:

For ship, which does not carry ballast water in oil fuel tank, minimum sludge tank capacity should be calculated as:

V = KCD m³

Where K = 0.01 for ship, where HO is purified for ME ( i.e. 1% )
K = 0.005 for ships using DO or HO, which does not require
purification before use ( i.e. ½ % )
C = Daily fuel oil consumption.
D = Maximum period of voyage between ports ( in days).
In absence of precise data, a figure of 30 days should be used.
Note: Sludge Tank Capacity (min) = 0.01 or 1% of used HFO for 30 days. [or]
0.005 or ½ % of used DO for 30 days.
Requirements:
1. Manhole
2. Heating coil
3. No direct connection to overboard.
4. Sludge pump.
5. International Discharge Connection.
6. High level alarm.
Biological Sewage Treatment Plant:

1. The unit is divided into 3 compartments: Aeration Chamber, Settling Chamber and Chlorinator.
2. Sewage enters Aeration Tank through soil inlet, and retained for about 24 hours and thoroughly mixed and aerated by aerators located at the bottom of the tank.
3. Aerobic bacteria and micro-organisms breakdown the organic waste and produce new bacteria cell.
4. Air, which provides oxygen for bacteria and micro-organisms, is supplied by Rotary Blowers to aerators.
5. The mixture is replaced by incoming sewage into Settling Tank, after passing through coarse screen.
6. All solids are precipitated in Settling Tank as Activated Sludge, which are then returned to Aeration Tank by airlift, and mixed with incoming raw sewage.
7. Clean liquid is displaced into Chlorinator, where remaining bacteria are killed.
8. Discharge of harmless effluent from Collecting Tank is controlled by Float Switch connected to Discharge Pump.

Important Equipment:

1. Two Rotary Blowers
2. Two Discharge Pumps.
3. Safety Valve at Aeration Blower.
4. High water level activating switch.
5. Low water level activating switch.
6. High water level alarm.

Biochemical Oxygen Demand, BOD:

  • Amount of Oxygen taken up by Bacteria Incubation Process, in PPM.

Coliform Count:

1. Coliform is the name given to bacteria group, found in intestine.
2. Not normally harmful, but can cause Dysentery, Typhoid, and Gastro-enteritis.
3. Coliform Count checks effectiveness of disinfection.
4. Carried-out on effluent sample and incubating it for 24 – 48 hours at 35°C.
5. Coliform Bacteria count: 200/100 mlt. [Maximum].

Welding:

Welding on Cast Iron:

Oxy-acetylene Welding:

1. Flame adjusted with slightly excess acetylene, to get a temperature of
1200°C, [Melting point of CI].
2. Welding rod: pure CI with high silicon content.
3. Part to be welded is preheated to 600 ~ 700°C, to avoid excessive stresses.
4. During welding, gas bubbles are developed in molten weld pool. By striking the pool in circular motion with welding rod, these bubbles can be removed.
5. It is necessary to use welding flux.

Arc Welding:

1. Electrode: pure nickel (or) nickel iron.
2. Weld metal, deposited in short thin beads with small electrode and low amperage, to avoid local heat built up and expansion, around weld point.
3. Casting is allowed to cool, between each run.

Welding on Aluminium:

Gas Welding:

1. Used for thickness of plate up to 3/16″.
2. Slightly excess acetylene is used, due to lower melting point, 660°C.
3. Welding rod: Pure aluminium.
4. Necessary to use flux, to dissolve oxide.
5. Avoid inhalation of smoke, produced during welding.

Arc Welding:

1. Thickness of plate ¼ ” or more.
2. Electrode: 95% Aluminium, 5% Silicon: with 20°of vertical.
3. Keep arc as short as possible, low amperage and movement is in straight line.
4. Welding speed is 3 times faster than mild steel.
5. Thick plate should be preheated for smooth weld.
6. Traces of flux, removed with hot water after gas or arc welding, otherwise flux corrosion will occur.

Inert gas welding:

1. Welds are superior in strength and pressure tightness.
2. No flux is required, so no risk of corrosion.
3. Very high speed is possible with welding machine.
4. Gas metallic arc welding GMAW or MIG is easier to use, particularly where position welding is needed, vertical, horizontal or overhead.
5. For plate thickness of ¼ ” MIG is more economical and practical.

CE’s Instruction, regarding Welding Equipment handling:

1. Leather gloves, Safety shoes, helmet, and clean clothing [not oily Boiler Suit] to be worn.
2. Remove combustible material from vicinity.
3. Wear Safety Goggle when chipping and grinding.
4. One bucket of water and portable fire extinguisher kept near-by.
5. Cable connections, tight and well insulated.
6. To avoid Welding in confined spaces.
7. Never use oxygen and acetylene without attached pressure regulator.
8. Open oxygen cylinder valve slowly, and acetylene cylinder valve not more than 1½ turns.
9. Never attempt to mix any other with oxygen cylinder, and transfer or mix acetylene from one bottle to another.
10. Never use acetylene at a pressure higher than 15 psi [1kg/cm²].

Welding Distortion:
Depends upon:

1. Cooling rate.
2. Size of work.
3. Heat conductivity.
4. Melting point.
5. Welding speed.
6. Type of electrode.

Oxy-Acetylene Welding

  • Never use Oxygen and Acetylene without pressure reducing regulators attached to cylinders.
  • Open Oxygen cylinder valve slowly and fully.
  • Open Acetylene cylinder valve not more than 1 turns.
  • Use Acetylene at a pressure not higher than 15 psi (1 kg/cm²).
  • Pressure ranges of 20 – 39 psi for Oxygen and 1 – 12 psi for Acetylene should be used depending on tip size, torch type and thickness of work.

Electric Arc Welding

  •  Electrode diameter 1/16″ Ampere controlled bet: 50 – 100 Amp.
    Voltage 30 Volts
    Thickness of plate up to 3/16″
  • Electrode diameter 1/8″ Ampere controlled bet: 125 – 175 Amp.
    Voltage 28 Volts
    Thickness of plate above 1/2″

Electron Beam Welding:

1. A welding process directing high energy electron beam on workpiece (anode),
in a high vacuum chamber.
2. Applied to rare metal, and no electrode, no welding rod and no gases required.
3. This process can weld deeply in one pass, without overlapping.
4. Potential difference between cathode and anode is 15 kV.
Speed of electron flow, 140,000 miles/sec.

Testing of material:

1. Non- Destructive Test
2. Destructive Test.
Non- Destructive Tests:

Carried-out on components and not on test pieces:

1. Visual Probe
2. Electrical eddy current
3. Liquid penetrant
4. Magnetic particles
5. Ultra-sonic
6. Radiographic inspection

Destructive Tests:

Carried-out only on specimen, which are subjected to damage during testing.

1. Harness test
2. Impact test
3. Tensile test
4. Bend test
5. Creep test
6. Proof test

Arctic D steel:

» If part of ship’s structure is liable to particularly low temperature, a special type of steel known as Arctic D is used, as normal grade of steel is not suitable.
» Has higher tensile strength than normal mild steel.
» Has higher impact strength.
» Most important quality is its ability to absorb Impact value of 40 Joules at – 55°C,
in Charpy Impact test using standard specimen.

ISM Code:

IMO has adopted International Safety Management Code on 4th Nov 1993 for safe operation of ships and pollution prevention, in accordance with SOLAS, MARPOL and STCW.

Objectives:

1. To cover safety and pollution
2. To provide a framework for achievement of Total Quality System ISO 9002,
and ISM Code.

Purpose:
Safe management and operation of ship, and Prevention of marine pollution:

Mainly to ensure:
1. Safety at sea
2. Prevention of human injury or loss of life
3. Avoidance of damage to marine environment and property
Implementation:
Every shipping company should develop, implement and maintain Safety Management System SMS.

SMS includes following requirements:

1. Safety and Environmental Protection policy.
2. Instruction and procedure for safe operation of ship, and protection of environment, in compliance with International and Flag State Legislation.
3. Lines of communication between Shore-based and Shipboard personnel.
4. Procedures for reporting Accidents and Non-Conformities.
5. Procedures for preparedness and response, to emergency situations.
6. Procedures for Internal Audits and management reviews.

Documentation:

Quality/safety system should include following levels:
1. Quality/Safety Policy Manuals.
2. Quality/Safety Procedures Manuals.
3. Instruction Manuals.

Mandatory key dates:
1/7/98 applied to all passenger ships, bulk carriers, oil tankers, chemical and gas carriers. 1/7/2002 applied to all other cargo ships.

Certification:
Flag State Administration or Government or authorised body, issue Certificates
valid for 5-years, after thorough Audit.

Safety Management Certificate SMC:

  • Issued to the ships, audited 2 ½ years after an Initial Audit, [within ± 6 months] and subjected to a Renewal Audit, before 5-years period has elapsed, but not later than 3 months before expiry date.
  • It verifies that the company and its shipboard management operate in accordance with approved Safety Management System, SMS.

Interim SMC:
For ships that are taken-up into shipping company anew, and it is valid for 6 months.

Document of Compliance DOC:

» Issued to onshore organisation, which is audited annually after an Initial Audit, and subjected to a Renewal Audit, before 5-years period has elapsed, but not later than 3 months before expiry date.

Interim DOC:
For a new company, valid for 12 months, or for an existing company if new ship-type enters the company’s fleet, valid for 6 months.

General Checklist for Audit:

1. Certificates and documents including ORB, Logbooks.
2. Safety in general.
3. Testing and drills.
4. Navigation equipment.
5. LSA.
6. FFA.
7. Radio installation including GMDSS.
8. Load Line.
9. Machinery in ER.
10. Electrical equipment.
11. Mooring equipment.
12. Cargo gears.
13. Hull construction.
14. Marine pollution.
15. Accommodation.

Main Drills in ISM:

1. Lifeboat Drill
2. Fire Drill
3. Abandon Ship Drill
4. Man Overboard Dill
5. Enclosed Space Rescue Drill
6. Oil Spill Response Drill
7. Emergency Steering Gear Drill

SMC:
Issued by;
 Administration
 Organization recognized by Administration.

DOC:
Issued by;
 Administration
 Organization recognized by Administration
 Another contracting government recognized by Administration.

CE hand over / take over:

1. Discuss with outgoing CE about machinery condition and standing order from HO.
2. To read, hand over note / maintenance record.
3. Check logbook at least for last 3-months, CMS quarterly list, Survey items, previous voyage report ORB up-to-date filling, garbage book, sludge formation compared with 1% of voyage fuel consumption, sludge remaining onboard, all certificates, documents, and validity such as IOPP, ISPP etc:
4. Take all FO, LO tank soundings, calculate ROB, based on API gravity method, and check with log entry. Ensure fuel consumption is enough for next port or next bunker port.
5. Check all running machinery, MARPOL equipment, OWS, incinerator, sewage plant, FFA, emergency generator, quick closing arrangement and lifeboat engine.
6. Check standard spares and store, special tools and measuring equipment.
7. If everything is OK, sign the hand over note.

CE’s Routine Works:

i. Every morning: Round check of operating machinery and engine room,
Discuss with 2/E, about ER repair and maintenance jobs.
Discuss with master, about ship situation and company instruction.
ii. At noon: To check ER logbook, FO, LO, DO consumption and ROB,
Performance and running hours of machinery.
Prepare Noon Report.
iii. Once a month: Fuel and LO onboard.
Store and spare inventory.
Maintenance report and breakdown report.

iv. Every voyage: Voyage Report.

CE reports: includes confidential report, voyage report, LO and FO consumption report, maintenance report, repair list, store and spare report and vouchers.

Joining a vessel, which is not commissioned. (New ship delivery)

1. Check Specifications and Class Requirements thoroughly.
2. Inspect the works of shipyard staff for final acceptance. Unsatisfactory works should be informed to company representatives and dockyard manager.
3. All alignment and clearance measurement works, witnessed by CE.
4. Before closing the tank manholes, make final inspection.
5. Before undocking, all underwater jobs must be completed and checked by CE.
6. Check the list of spares to be supplied, and inform if necessary items are missing.
7. Received spares properly stored and recorded.
8. Make familiar with all the layout of machinery, piping, cooling arrangement, etc.
9. Check fire fighting system, and location of remote stops and shut-off devices.
10. When other engineers arrived, CE must explain the layout and operations of machinery.
11. All initial records, ideal conditions, shop test records, trial test records must be kept for the whole life of ship.