Guideline for electrical plant on board
With all types of electrical equipment cleanliness is essential for good operation. Electrical connections must be sound and any signs of sparking should be investigated. Parts subject to wear must be examined and replaced when necessary. The danger from a.c. equipment in terms of electric shocks is far greater than for similar d.c. voltages. Also a.c, equipment often operates at very high voltages. Care must therefore be taken to ensure isolation of equipment before any inspections or maintenance is undertaken.
The accumulation of dirt on electrical equipment will result in insulation breakdown and leakage currents, possibly even an earth fault. Moisture or oil deposits will likewise affect insulation resistance. Regular insulation resistance measurement and the compiling of records will indicate the equipment requiring attention. Ventilation passages or ducts may become blocked, with resultant lack of cooling and overheating. Oil deposits from a direct-coupled diesel engine driving an open generator (usually d.c.) can damage windings and should therefore be removed if found. Totally enclosed machines should be periodically opened for inspection and cleaning since carbon dust will remain inside the machine and deposit on the surfaces.
Brushgear should be inspected to ensure adequate brush pressure and the springs adjusted if necessary. New brushes should be ‘bedded in’ to the commutator or slipring shape with fine glass paper. Sparking at the commutator will indicate poor commutation. This may require polishing of a roughened commutator surface. The mica insulation between commutator segments may require undercutting if it protrudes, or simply cleaning if deposits have built up.
Control equipment, such as starters, will require attention to contacts which may be worn or pitted as a result of arcing. Contactors usually have a moving or wiping action as they come together. This helps clean the surfaces to provide good electrical contact, and also the arc produced during closing and opening is not at the finally closed position. The contactor contact surfaces of frequently used equipment should therefore be subject to regular inspections.
Safety precautions
Work on electrical systems and equipment is considered a specialised work and must be undertaken only by qualified personnel from the ship’s staff or shore contractors. Work on electrical equipment in an area where an explosive atmosphere may be present requires special precautions and permission of the Master. He shall ensure that qualified persons are doing the work, in compliance with regulations in force and with adequate safety precautions in place. The Master shall ensure that personnel are supervised and all measures are taken to avoid any accidents or injuries from such work. Reference is to be made to the relevant sections of the Safety and Environmental Procedures.
Work Performance
Whenever work is to be carried out on electrical equipment, or on equipment powered by electricity, in a gas dangerous zone, the electrical supply of the equipment has to be isolated. Warning signs must be posted adequately. The use of portable electrical equipment or wandering leads is prohibited unless the zone is gas free for hot work and a hot work permit is issued. Intrinsically safe equipment shall be used within their maker’s parameters and company regulations only.
Cold Work on Electrical Equipment
Work shall not be carried out on any apparatus or wiring, nor shall any flammable – proof or explosion-proof enclosures be opened, nor the special safety characteristics provided in connection with standard apparatus be impaired, until all voltage has been cut-off from the apparatus or wiring concerned. The voltage shall not be restored until work has been completed and safety measures have been fully re-instated.
Hot Work on Electrical Equipment
A Hot Work Permit (SAF04) must be issued as per company regulations. Work is permitted provided that the area has first been made safe and certified gas free and no hazardous situation exists – such safe situation should be maintained in that condition as long as the work is in progress. No such work shall be left unattended or without supervision. All regulatory and company safety precautions shall be taken.
High Voltage Systems (Defined here as Voltages exceeding 1000 volts)
All maintenance and testing of high voltage equipment must only be carried out by qualified staff, strictly in accordance with the Company Safety Regulations and the Permit to Work documentation must be completed prior to commencement of any maintenance.
Work by Contractors
The Master shall ensure that whenever contractors are employed, they must be qualified professionally for the work. Arrangements must be such that their understanding of and compliance with all safe working practices are ensured and that they are fully qualified to do the work effectively and they are supervised and controlled by an officer. Checks must be made regularly to ensure that work is being done professionally, that time is not wasted and that correct spares and materials are used when required.
Verification
It is of vital importance for the safe execution of the work on electrical equipment and fittings comply with all regulations and recommendations in force. The materials used shall conform to the regulations and certification provided where applicable.
Circuit Breakers
Main Circuit Breakers are to be clearly labelled to ensure that engine room staff do not inadvertently trip or try to close an incorrect circuit breaker.
Documentation
The planning for electrical work in a gas dangerous zone including safety precautions taken, shall be recorded in the log book and by use of the company Hot Work procedures, checklist and certification.
Source : http://www.machineryspaces.com/electrical-equipment-maintenance.html
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