Electrical Relay Maintenance on Ships

A relay is an important electro-mechanical safety devices in ship’s electrical circuit and is normally open the faulty circuit from the main supply when any kind of electrical fault occurs. A relay is fitted in the Main and Emergency switchboards of the ship as a protective device. Relay has to be kept operational and healthy at all times, else at the time of fault if the relay does not operate properly, the whole system may suffer loss of power or damage. The most common application of relays is for overload and short circuit protection. A ship engineer or electrical officer has to make sure that the relay is efficiently in operation and the maintenance is carried out on the same as per schedule.

If during inspection, the relay is found out to be defective it must be replaced immediately with a spare one. A simple electromagnetic relay will get activated when the magnetic effect of the iron core is sufficiently increased by the excess or high current in the coil, which will attract the iron armature held against the spring force to trip the circuit.

A brief maintenance procedure for relay is given as follows.

1. Checks to be carried out on relay contacts for damage due to arcing.
2. Polish the contact with emery paper to remove rust and deposits.
3. Check the closing linkage for free movement.
4. Check the continuity of the contacts with multimeter.
5. There are arc chutes provided to quench the arcing. Check for burnout of the same.
6. Check the tension of the spring.
7. Open circuit and short circuit tests to be performed on the coil by multimeter.
8. Check the continuity of the trip circuit by multimeter.
9. Check tightness of the supply terminals.