CoC Oral Exam Preparation (Part- 3) – Electrical
image credit: www.rchelectrical.co.uk
Electrical equipment inspected and tested, during complete engine survey, at 4 years interval.
Such a survey is prescribed, under the rules and regulations for the classification of ship.
Following survey items generally apply to all ships:
1. Generators and governors.
2. Circuit breakers
3. Switchboard and fittings (main and emergency switchboard, distributor switchboard).
5. Insulation resistance
6. Motors and Starters
7. Emergency power equipment
8. Parts of steering gear
9. Navigation light indicator
For UMS operation:
1. Alarms associated with ME, AE, lubricating and cooling, tested for correct operation.
2. Electrical circuits from various sensors such as pressurestat, flow switch, level switch, temperature switch, tested.
3. Action of auto-shut down for ME and AE, auto-starting up of stand-by units, tested.
4. Auto-starting of emergency generator, demonstrated.
5. UMS requirements demand that a stand-by main generator should be automatically started on loss of duty generator within 45 sec.
6. Bilge level alarm together with automatic bilge pumping, proved to correct action.
7. Main and stand-by electric power supply to overall alarms and monitoring system inspected and tested.
8. Complete inspection and test of fire detection and alarm system.
9. ME control will function correctly and tested from bridge position, main control room and emergency position alongside the engine.
For Tankers / Gas Carrier:
– Electrical equipment in hazardous area is surveyed every year, during each Docking Survey and Annual Survey.
Required conditions for Surveyor:
- Main and emergency generators are cleaned.
- Show stable operation when run in parallel with other generator.
- Generator windings on stator and rotor must be free of dust, rust, oil and moisture.
- Visual check made for any obvious deterioration, abrasion, and cracking of insulation around winding coils in stator.
- The insulation test to earth and between stator phase windings is done while the machine is still hot after running on load.
- Air gap between stator and rotor checked to ensure that pedestal bearings are in good condition.
1. Thorough cleaning internally and externally at switchboard, when all generators are stopped and their prime movers locked off.
2. Main bus bar and their connections checked for tightness.
3. Bus bar supports, checked for damage due to insulation material.
4. Overheating signs at connection junctions, due to loose joint.
5. Internal wiring securely fixed.
6. Cable entries at switchboard bottom, sealed with non-flammable material.
7. Earth bar, securely bonded to both frame and to the ship’s hull.
8. Hinged panel door bonded with an earth strap to main switchboard frame.
9. Insulation resistance of each terminal measured.
10. Voltmeters, Watt meters and Ammeters calibrated and tested.
11. All trips tested [Safety devices].
12. Synchronising test [load sharing] demonstrated.
13. Earth lamps checked.
14. Automatic circuit breaker (ACB) and Automatic voltage regulator (AVR) tested.
Emergency Power and Associated Equipment Survey:
1. Emergency generator started manually and automatically.
2. Electrical supplies from emergency switchboard, checked for their proper voltage, ampere and frequency.
3. Correct functioning of emergency lighting, fire pump, and other electrical equipment.
4. Electrical interlocking arrangement between main and emergency switchboard checked.
5. Emergency battery installation and its charging rectifier checked.
6. Keep battery environment dry and well ventilated, battery tops cleaned, electrolyte at proper level and have correct value of specific gravity by checking with hydrometer.
7. Battery charging equipment checked for dirt, overheating, loose connection and correct functioning of indicator instruments.
8. Battery locker ventilation arrangements should be checked.
Insulation Resistance Survey:
1. Survey will require a list, which shows the results of recent insulation tests on all 440V and 220V main circuits.
2. The list should also indicate the test date, weather condition, hot or humid etc. together with any comment relevant to the test conditions such as machine is hot or cold.
Navigation light indicator survey:
1. Surveyor will ensure that Navigation light indicator operates correctly and has appropriate alarm.
2. Broken wire or lamp can be simulated by pulling appropriate fuse.
3. Power source for navigation lights must be duplicated [usually alternate power supply being used from Emergency Switchboard].
4. Changeover facility for power source, to be checked.
5. Although the actual light fitting for Navigation is part of Safety Equipment Survey, the Electrical Survey will naturally include a check on the supply cables to the Navigation lights.