(Adapted from:D.T. Hall:Practical Marine Electrical Knowledge)
From the surveyor’s point of view steering gear system can be envisaged as consisting of three parts: Power unit Steering control Indications and alarms
On many ships one of the steering gear motors will be supplied via the emergency switchboard as recommended by the SOLAS requirements for certain vessel types, e.g. passenger ships and ferries.
Rudder control from the bridge position may be via a hydraulic tele-motor or via an electric controller or both. Main and alternative electric supplies, including any changeover facilities for the electric control from the steering wheel and for the auto pilot, must be tested
The steering gear and its control must be functionally tested for its response. This is generally specified to be that the rudder must be swung from 32° port to 32° starboard in 28 seconds. Note, a fully loaded response can only be obtained when the ship is loaded and under way at sea. Steering gear status indications must be operating correctly in the steering flat, main control room and on the bridge.
The rudder position indicators on the bridge may be checked during the functional testing of the steering gear. The bridge indication should be compared with the direct mechanical indicator on the rudder stock in the steering flat.
Motor overcurrent alarms can be initiated by simulating the action of the overcurrent relay. Remember that a steering gear motor does not have overcurrent trip protection; the only main circuit protection being from the back- up fuses which are essential for short-circuit protection. Hydraulic fluid low level alarms, if fitted, must be checked for correct initiation by the oil level sensors.
Essentially, the surveyor will expect to prove that the navigation light indicator operates correctly and gives the appropriate alarms. A broken wire or lamp can be simulated by pulling the appropriate fuse. The power supply for the navigation lights must be duplicated (usually the alternative supply is obtained from the emergency switchboard) and the changeover facilities must be checked.
Although the actual light fittings for navigation are part of the Safety Equipment Survey, the electrical survey will naturally include a check on the supply cables to the lights.
If a ship is classified for Unattended Machinery Space (UMS) operation, the electrical survey will be extended to include all the alarms, fire detection, controls and fail-safe features of such an installation. All alarms associated with the main engine, auxiliary machines, lubrication and cooling are to be tested for correct operation.
Testing of the electrical circuits from the various sensors is relatively straightforward. This can be achieved by operating the sensor switch by hand or by simulating the switch action under the expected alarm condition. To prove that the overall sensor (pressurestat, flow switch, level switch, temperature switch, etc.) is functioning correctly is obviously more involved. Often, specialist contractors may be called upon to service and calibrate the sensors and alarm annunciators.
Particular attention will be paid to the main engine and auxiliary generators in respect of their alarms for lubrication and cooling. Initiation and action of automatic shut-down features will be tested. Essential drives for lubrication, cooling and fuel supply are duplicated and arranged so that one pump can be selected on a duty/standby basis. Loss of pressure at the duty pump should automatically start up the standby unit.
Automatic start-up of the emergency generator must be demonstrated. The initiation of the undervoltage or under- frequency relay can usually be accomplished by pulling the fuses in the detection unit. The emergency generator should then run up to speed and supply voltage to the emergency switchboard.
UMS requirements demand that a standby main generator starts automatically on loss of the duty generator. The standby generator is to start and close onto the dead bus-bars within 45 seconds. This is followed by automatic sequential re- starting of essential auxiliaries for lubrication, cooling, fuel and steering. The correct functioning of the system will be tested. The duplicate bilge level alarms together with automatic bilge pumping must be proven to the surveyor's satisfaction.
The main and standby electric power supplies to the overall alarm monitoring system must be inspected and tested. The standby power arrangement usually includes battery back-up. It will be necessary to inspect the general condition of the battery and its trickle- charger.
Tests are made on the UMS alarm system to verify: that alarms displayed on the main console in the engine control room are relayed to the smaller group alarm panel on the bridge; that the duty engineer call system is operating in the accommodation areas, i.e. in the cabin of the selected duty engineer and in the duty mess and lounges; that the selected duty engineer is allowed 2-3 minutes to respond to a machinery alarm. If the engineer has not reached the control room and accepted the alarm within this time, a dead man alarm should be sounded generally in the alleyway adjacent to the engineers' accommodation.
A complete inspection and test of the fire detection apparatus must be performed. All smoke, heat and flame sensors must function correctly to initiate the appropriate audible and visual alarms on the bridge, in the main control room and in the accommodation. Hand operated fire-alarm switches of the break-glass type must also be examined and tested to be in proper working order.
Main engine controls must function correctly and will be tested from the bridge position, local position (engine control room) and at the emergency position alongside the engine. The operational features of the electrical equipment for main engine control and indication will be best demonstrated during a full engine test during an engine survey. Such electrical equipment and connections associated with engine control will be examined as usual for wear and tear, insulation level, cleanliness, loose connections and overheating.