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Engine Room Watchkeeping

Q) Explain the arrangements required for ensuring safe engineering watch when carrying dangerous cargo.

Ans:- Routine Work during watchkeeping:

  1. Soot Blowing – Soot deposits are un-burnt carbon particulates which accumulate on the gas side of the boiler. Unnecessary buildup of soot deposits impedes heat transfer and causes exhaust pipe uptake fires. Soot blowing a boiler is done once every 12 hours using pressured steam or air. Soot blowers are operated manually or driven by an electric or pneumatic motor.
  2. Pumping Out bilges through OWS – Water and oil leaking from the pump glands and other machinery are collected in the engine room bilge. The content of the bilges are passed to the OWS to separate the oil and to ensure that the water being pumped out does not content more than 15 ppm of oil. Each operation must be recorded and completed operation must be signed by the Engineer in charge and Chief Engineer.
  3. Turbocharger Blower washing – Depending on the maker’s instruction, the blower side of the turbocharger may be water washed daily to remove the deposits accumulated during operation.
  4. Transfer of Oil from Bunker Tank to Settling Tank – Fuel is transferred from the Bunker tanks to the settling tank and water and impurities are allowed to settle. This oil is then purified using purifier before transferring it to the Service tank. All line valves must be correctly opened /closed for a smooth operation.
  5. Draining of Air bottles – This is a very important routine operation. Water in the compressed air causes corrosion in the air bottles and the pneumatic control systems.
  6. De-sludging of Purifier – Usually the purifier will run in auto-mode. If they are run in manual mode, then de-sludging operation must be carried out manually once in a watch to remove the sludge deposits accumulated in the bowl.
  7. Boiler Blow down – Boiler is blown down atleast once in a day to get rid of the suspended and dissolved solids. This is done by using the upper scum valve and bottom blow-down valve.
  8. Boiler water tests – Boiler water is tested for alkalinity, chlorides and dissolved solids once in a day by following correct procedures. Treatment chemicals are added according to the test results.
  9. Other routine jobs include – draining of lube oil sumps off water, LO analysis, incineration, cleaning or changing of filters, etc.
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Diesel Engines

Q) Write short notes on: Why pre-heating of main engine is carried out?

Ans:- Pre-heating of main engine:-

  • Diesel engines are self-ignition engines i.e. fuel is injected into hot compressed air and is ignited. To obtain this, the air inside the engine should be hot which is achieved by pre-heating the engine. Pre-heating heats all parts of the engine which in turn heats the air in the cylinder.
  • Pre-heating the engine also reduces cold corrosion and there are lesser thermal stresses during starting.
  • Also, when engine is warm, the clearances are correct, thus lubrication is made easier and there is less chance of undue wear of moving parts.
  • Pre-heating is usually done using steam or electrical heaters. Hot water is kept in circulation to engine thus keeping all parts in warm condition.
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Crank Case

Q) Write short notes on: Protection / Precautions against Crank Case Explosion.

Ans:- Protection against Crankcase explosions:

  1. Crankcase doors of sufficient strength are provided so that they do not get displaced by crankcase explosion. They must be fastened sufficiently.
  2. One or more crankcase explosion relief doors are fitted, depending on engine size. Crankcase explosion relief valves are fitted with flame arrestors.
  3. Crankcase oil mist detectors (OMD) and monitoring equipment are provided. They give an alarm and also indicate the unit where the mist level is high. Low level of mist is generally an alarm only. But high level of mist gives an alarm / initiates slowdown of the main engine. The OMD must be checked to see it is functional.
  4. High bearing temperature alarms are provided.
  5. Warning notices are provided on crankcase doors indicating doors not to be opened immediately if overheating is suspected.
Crankcase Relief Door & Valve
Crankcase Relief Door & Valve

The figure alongside shows a Crankcase explosion relief door & valve. It consists of:-

  1. A woven wire gauze assembly that does not allow flame to travel out of the crankcase.
  2. A relief valve usually made of aluminum.
  3. A spring against a retaining plate and
  4. A discharge hood so designed that products of explosion are discharged in such a way that it does not cause harm to the engine room personnel.
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Q) Write short notes on: Use of indicator card on board.

Ans:- Use of indicator card on board:

  • Power Card is the measurement of the variation of pressures in a cycle.
  • Irregularities in the shape of the diagram will show operational faults. Maximum or peak pressure may be measured to scale between the atmospheric line and the highest point on the diagram.
  • Compression diagram is taken in a similar manner to the power card but with the fuel shut off from the cylinder.
  • The height of this curve shows maximum compression pressure. If compression and expansion lines coincide, it shows that the indicator is correctly synchronized with the engine.
  • Reduction in height of this diagram show slow compression, which may be due to worn cylinder liner, faulty piston rings, insufficient scavenge air or leaky exhaust valve, any of the which will cause poor combustion.
  • Draw card or out of phase diagram is taken in a similar manner to the power card, with fuel pump engaged but with the indicator drum 90″C out of phase piston stroke. This illustrates more clearly the pressure changes during fuel combustion. Fuel timing or injector faults may be detected from its shape.
  • Light or Weak spring diagram is again similar to the power card and in phase with the engine, but taken with a light compression spring fitted to the indicator showing pressure changes during exhaust and scavenge to an enlarged scale.
  • It can be used to detect faults and scavenge to an enlarged scale. It can be used to detect operations.
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Deck Machinery

Purpose of Deck Mooring Winch and Windlass Winch used on board ship:

Deck Mooring Winch:-

Deck Mooring Winch
Deck Mooring Winch
  • Mooring winch is a mechanical device used for securing a ship to the berth. An equipment with various barrels used for pulling ropes or cables, mooring winches play an important role in berthing the ship ashore.
  • The barrels, also known as winch drums, are used for hauling in or letting out the wires or ropes, which will help in fastening the ship to the berth.
  • Mooring winches assembly comes in various arrangements with different number of barrels, depending on the requirement of the ship.
  • The main parts of mooring winch includes a winch barrel or a drum, a warp end and a driving motor. Modern mooring winches comprises of elaborate designs with various gear assemblies, which can be electric, pneumatic or hydraulic driven.

Windlass Winch:-

Windlass Winch
Windlass Winch
  • A windlass is a machine used on ships that is used to let-out and heave-up equipment such as a ship’s anchor or a fishing trawl. On some ships, it may be located in a specific room called the windlass room.
  • An anchor windlass is a machine that restrains and manipulates the anchor chain on a boat, allowing the anchor to be raised and lowered by means of chain cable. A notched wheel engages the links of the chain or the rope.
  • A trawl windlass is a similar machine that restrains or manipulates the trawl on a commercial fishing vessel. The trawl is a sort of big fishing net that is wound on the windlass. The fishermen either let-out the trawl or heave-up the trawl during fishing operations. A brake is provided for additional control. The windlass is usually powered by an electric or hydraulic motor operating via a gear train.
  • Technically speaking, the term “windlass” refers only to horizontal winches. Vertical designs are correctly called capstans. Horizontal windlasses make use of an integral gearbox and motor assembly, all typically located above-deck, with a horizontal shaft through the unit and wheels for chain and/or rope on either side. Vertical capstans use a vertical shaft, with the motor and gearbox situated below the winch unit (usually below decks).

Q) List the routine maintenances carried out on board.

Ans:- Efficient planning and adequate usage of equipments is the key to productive maintenance.

Types of Maintenance Procedures:-

  1. Preventive or Scheduled Maintenance System: – It is famously known as the PMS or Planned Maintenance System. In this type of system the maintenance is carried out as per the running hours like 4000 hrs, 8000 hrs etc., or by the calendar intervals like 6 monthly, yearly etc. of the machinery. The maintenance is carried out irrespective of the condition of the machinery. The parts have to be replaced if it is written in the schedule, even if they can be still used.
  2. Corrective or Breakdown Maintenance: – In this system the maintenance is carried out when the machinery breaks down. This is the reason it is known as the breakdown maintenance. This is not a suitable and good method as situations may occur wherein the machinery is required in emergency. The only advantage of this system is that the working of machinery parts is used to its full life or until it breaks. This system might get costly as during breakdown several other parts may also get damaged.
  3. Condition Maintenance system: – In this system the machinery parts are checked regularly. With the help of sensors etc. the condition of the machinery is accessed regularly and the maintenance is done accordingly. This system requires experience and knowledge as wrong interpretation may damage the machinery and lead to costly repairs which may not be acceptable by the company.
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Oil Monitoring

Q) With reference to oil monitoring of bilge and tanker ballast discharges: Describe with aid of a sketch, the general arrangements of an oil monitoring system.

Ans:- Oil content monitoring – Working principles & procedure for ship service systems:-

  • In the past, an inspection glass, fitted in the overboard discharge pipe of the oil/water separator permitted sighting of the flow. The discharge was illuminated by a light bulb fitted on the outside of the glass port opposite the viewer. The separator was shut down if there was any evidence of oil carry over, but problems with observation occurred due to poor light and accumulation of oily deposits on the inside of the glasses.
  • Present-day monitors are based on the same principle. However, whilst the eye can register anything from an emulsion to globules of oil a light-sensitive photo-cell detector cannot. Makers may therefore use a sampling and mixing pump to draw a representative sample with a general opaqueness more easily registered by the simple photo-cell monitor. Flow through the sampling chamber is made rapid to reduce deposit on glass lenses. They are easily removed for cleaning.
  • Bilge or ballast water passing through a sample chamber can be monitored by a strong light shining directly through it and on to a photo-cell (Figure 1). Light reaching the cell decreases with increasing oil content of the water. The effect of this light on the photo-cell compared with that of direct light on the reference cell to the left of the bulb, can be registered on a meter calibrated to show oil content.
  • Another approach is to register light scattered by oil particles dispersed in the water by the sampling pumps (Figure 2), Light reflected or scattered by any oil particles in the flow, illuminates the scattered light window. This light when compared with the source light increases to a maximum and then decreases with increasing oil content of the flow.
  • Fibre optic tubes are used in the device shown to convey light from the source and from the scattered light window to the photo-cell. The motor-driven rotating disc with its slot, lets each light shine alternately on the photo-cell and also, by means of switches at the periphery, causes the signals to be passed independently to a comparator device, These two methods briefly described, could be used together to improve accuracy, but they will not distinguish between oil and other particles in the flow.
  • Methods of checking for oil by chemical test would give better results but take too long in a situation where excess amounts require immediate shut down of the oily water separator.
Monitor for oily water using direct light
Monitor for oily water using direct light (Figure-1)
Monitor based on scattered light (courtesy Sofrance) (Figure-2)

Tanker ballast:-

  • Sampling and monitoring equipment fitted in the pump room of a tanker can be made safe by using fibre optics to transmit light to and from the sampling chamber (Figure 3). The light source and photo-cell can be situated in the cargo control room together with the control, recording and alarm console. The sampling pump can be fitted in the pump room to keep the sampling pipe short and so minimize time delay.
  • For safety the drive motor is fitted in the machinery space, with the shaft passing through a gas-tight seal in the bulkhead. Oil content reading of the discharge is fed into the control computer together with discharge rate and ship’s speed to give a permanent record.
Seris Monitoring System for Tanker Ballast
Seris Monitoring System for Tanker Ballast (Figure-3)

Q) With reference to oil monitoring of bilge and tanker ballast discharges: State the Inputs that are recorded and output operation.

Ans:- List of items to be recorded:- (Marpol Annex I)

(A) Ballasting or cleaning of oil fuel tanks

  • Identity of tank(s) ballasted.
  • Whether cleaned since they last contained oil and, if not, type of oil previously carried.
  • Cleaning process:
    • position of ship and time at the start and completion of cleaning;
    • identify tank(s) in which one or another method has been employed (rinsing through, steaming, cleaning with chemicals; type and quantity of chemicals used, in cubic metres);
    • identity of tank(s) into which cleaning water was transferred.
  • Ballasting:
    • position of ship and time at start and end of ballasting;
    • quantity of ballast if tanks are not cleaned, in cubic metres.

(B) Discharge of dirty ballast or cleaning water from oil fuel tanks referred to under section (A)

  • Identity of tank(s).
  • Position of ship at start of discharge.
  • Position of ship on completion of discharge.
  • Ship’s speed(s) during discharge.
  • Method of discharge:
    • through 15 ppm equipment;
    • to reception facilities.
  • Quantity discharged, in cubic metres.

(C) Collection and disposal of oil residues (sludge and other residues)

  • Collection of oil residues: Quantities of oil residues (sludge and other oil residues) retained on board. The quantity should be recorded weekly:* (This means that the quantity must be recorded once a week even if the voyage lasts more than one week)
    • identity of tank(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
    • capacity of tank(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . .m3
    • total quantity of retention . . . . . . . . . . . . . . . . . . . . . . m3
  • Methods of disposal of residue. State quantity of oil residues disposed of, the tank(s) emptied and the quantity of contents retained in cubic metres:
    • to reception facilities (identify port);
    • transferred to another (other) tank(s) (indicate tank(s) and the total content of tank(s));
    • incinerated (indicate total time of operation);
    •  other method (state which).

(D) Non-automatic discharge overboard or disposal otherwise of bilge water which has accumulated in machinery spaces

  • Quantity discharged or disposed of, in cubic metres.
  • Time of discharge or disposal (start and stop).
  • Method of discharge or disposal:
    • through 15 ppm equipment (state position at start and end);
    • to reception facilities (identify port);
    • transfer to slop tank or holding tank (indicate tank(s); state quantity retained in tank(s), in cubic metres).

(E) Automatic discharge overboard or disposal otherwise of bilge water which has accumulated in machinery spaces:-

  • Time and position of ship at which the system has been put into automatic mode of operation for discharge overboard, through 15 ppm equipment.
  • Time when the system has been put into automatic mode of operation for transfer of bilge water to holding tank (identify tank).
  • Time when the system has been put into manual operation.
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Q) For a fully automatic provisions refrigeration system incorporating a number of rooms: Sketch a line diagram detailing the devices incorporated into the refrigeration system to protect the machinery and equipment against malfunction.

Main Components of Refrigeration Plants
Main Components of Refrigeration Plants

Main Components of Refrigeration plants:- Any refrigeration unit works with different components inline to each other in series. The main components are:

  1. Compressor: Reciprocating single or two stage compressor is commonly used for compressing and supplying the refrigerant to the system.
  2. Condenser: Shell and tube type condenser is used to cool down the refrigerant in the system.
  3. Receiver: The cooled refrigerant is supplied to the receiver, which is also used to drain out the refrigerant from the system for maintenance purpose.
  4. Drier: The drier connected in the system consists of silica gel to remove any moisture from the refrigerant.
  5. Solenoids: Different solenoid valves are used to control the flow of refrigerant into the hold or room. Master solenoid is provided in the main line and other solenoid is present in all individual cargo hold or rooms.
  6. Expansion valve: An Expansion valve regulates the refrigerants to maintain the correct hold or room temperature.
  7. Evaporator unit: The evaporator unit acts as a heat exchanger to cool down the hold or room area by transferring heat to the refrigerant.
  8. Control unit: The control unit consist of different safety and operating circuits for safe operation of the refer plant.

Compressor safety devices: The compressor is protected by three safety switches:-

  1. The OP switch or Oil Differential Pressure switch compares the measured lubricating oil pressure to the Suction (crankcase) pressure. Should the differential pressure fall below a pre-set minimum (about 1.2 bar) then the compressor will trip and require a manual reset to restart. A time delay is built into the circuit to allow sufficient time for the lubricating oil pressure to build up when starting before arming the circuit.
  2. The HP or High Pressure switch, is fitted to the outlet of the compressor before the isolating valve. On over pressurization (dependent on the refrigerant, up to about 24bar bar for R22) the switch will trip the compressor and a manual reset is required before restart.
  3. The LP or Low Pressure switch when activated (at about 1 bar for R22) will trip the compressor and require a manual reset before the compressor can be restarted.
  4. This normally takes the form of an LP cut out pressure switch with automatic reset on pressure rise. The cut out set point is just above the LP trip point says at about 1.4bar.
  5. An adjustable differential is set to about 1.4bar to give a cut in pressure of around 2.8 bar. The electrical circuit is so arranged that even when the switch has reset, if no room solenoid valves are open the compressor will not start. This is to prevent the compressor cycling due to a leaky solenoid valve.
  6. In addition to this extra LP switches may be fitted which operate between the extremes of the LP cut in and cut out to operate compressor unloaders.
  7. Some modern systems contain a rotary vane compressor with variable speed (frequency changing) control.

Q) For a fully automatic provisions refrigeration system incorporating a number of rooms: Explain how critical temperature restricts plant operation and how these limitations overcome?

Ans:- The Critical Point:- The critical point is the point above which:

  1. The gas will not liquefy by the action of pressure alone. This is an important temperature for refrigeration systems which rely on the change of state for heat transfer.
  2. The gas will not liquefy by cooling alone.

Working of Ship’s Refrigeration Plant:-

  • The compressor acting as a circulation pump for refrigerant has two safety cut-outs- Low pressure (LP) and High Pressure (HP) cut outs.
  • When the pressure on the suction side drops below the set valve, the control unit stops the compressor and when the pressure on the discharge side shoots up, the compressor trips.
  • LP or low pressure cut out is controlled automatically i.e. when the suction pressure drops, the compressor stops and when the suction pressure rises again, the control system starts the compressor. HP or high pressure cut out is provided with manually re-set.
  • The hot compressed liquid is passed to a receiver through a condenser to cool it down. The receiver can be used to collect the refrigerant when any major repair work has to be performed.
  • The master solenoid is fitted after the receiver, which is controlled by the control unit. In case of sudden stoppage of compressor, the master solenoid also closes, avoiding the flooding of evaporator with refrigerant liquid.
  • The room or hold solenoid and thermostatic valve regulate the flow of the refrigerant in to the room to maintain the temperature of the room.
  • For this, the expansion valve is controlled by a diaphragm movement due to the pressure variation which is operated by the bulb sensor filled with expandable fluid fitted at the evaporator outlet.
  • The thermostatic expansion valve supplies the correct amount of refrigerants to evaporators where the refrigerants takes up the heat from the room and boils off into vapours resulting in temperature drop for that room.
  • This is how temperature is maintained in the refrigeration plant of the ship.
  • A safety system includes alarm, cut offs, and trips which safeguards the machinery and its parts from getting damage.

Q) For a fully automatic provisions refrigeration system incorporating a number of rooms: What is the effect on the environment of the release of refrigerants into the atmosphere?

Ans:- Environmental and Safety properties of Refrigerants:- At present the environment friendliness of the refrigerant is a major factor in deciding the usefulness of a particular refrigerant. The important environmental and safety properties are:

  1. Ozone Depletion Potential (ODP): According to the Montreal protocol, the ODP of refrigerants should be zero, i.e., they should be non-ozone depleting substances.
  2. Global Warming Potential (GWP): Refrigerants should have as low a GWP value as possible to minimize the problem of global warming. Refrigerants with zero ODP but a high value of GWP (e.g. R134a) are likely to be regulated in future.
  3. Total Equivalent Warming Index (TEWI): The factor TEWI considers both direct (due to release into atmosphere) and indirect (through energy consumption) contributions of refrigerants to global warming. Naturally, refrigerants with as a low a value of TEWI are preferable from global warming point of view.
  4. Toxicity: Ideally, refrigerants used in a refrigeration system should be non-toxic. Toxicity is a relative term, which becomes meaningful only when the degree of concentration and time of exposure required to produce harmful effects are specified. In general the degree of hazard depends on:
    • Amount of refrigerant used vs total space
    • Type of occupancy
    • Presence of open flames
    • Odor of refrigerant, and
    • Maintenance condition
  5. Flammability: The refrigerants should preferably be nonflammable and non-explosive. For flammable refrigerants special precautions should be taken to avoid accidents.
  6. Chemical stability: The refrigerants should be chemically stable as long as they are inside the refrigeration system.
  7. Compatibility with common materials of construction (both metals and non-metals)
  8. Miscibility with lubricating oils: Oil separators have to be used if the refrigerant is not miscible with lubricating oil (e.g. ammonia). Refrigerants that are completely miscible with oils are easier to handle (R12).
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Q) Explain how paralleling of generator’s carried out.

Ans:- Parallel Operation of Generators:-

  • Depending upon the capacity and the electrical load, more than one alternator can be connected to the common Bus bars. The connecting process is called ‘Synchronising’ i.e. enabling the parallel operation of the alternators.
  • Following conditions must be fulfilled for paralleling the Alternators:
    • Voltage must be same.
    • Frequency must match.
    • Phase sequence must be correct.
  • In short, the incoming alternator should have the same parameters as the running alternator(s). If the speed of the incoming machine is different, the ‘governor control switch’ should be used to adjust the speed.
  • Departure from the above conditions will result in the formation of power surges and unwanted electro-mechanical oscillation of rotor which will damage the equipment.
  • To carry out the paralleling operation, following devices are provided:
    • Synchroscope
    • Lamps (Dark/Bright)
  • Following are the steps to carry out with paralleling using a synchroscope:
    • Check voltages are same.
    • Check frequency of incoming generator is same as running generator.
    • Put on synchroscope and see that pointer turns slowly in clockwise direction (may require to adjust speed of incoming generator using the ‘governor control switch’ for this).
    • When the pointer is at 11 o’clock position, close the breaker of incoming generator.
    • Now the load is equally distributed among the generators.
  • Advantages of Parallel Operating Alternators
    • For maintenance or inspection, one machine can be taken out from service and the other alternator can keep up for the continuity of supply.
    • Load supply can be increased.
    • During light loads, more than one alternator can be shut down while the other will operate in nearly full load.
    • High efficiency and operating cost is reduced.
    • Ensures the protection of supply and enables cost-effective generation.
    • Reliability of the whole power system increases.
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Electrical Distribution

Q) Sketch and describe a Typical Ships Electrical Distribution System.

Typical Ships Electrical Distribution System
Typical Ships Electrical Distribution System
  • The electrical power distribution system on board a ship is designed so as to provide a secure supply to all loads with adequate built in protection for the equipment and operating personnel. The general scheme of a ship’s electrical power system is common to nearly all ships.
  • Both the auxiliary and emergency services are supplied by the Main generators during normal operating conditions. In event of emergency, only the emergency services are supplied by the Emergency generator.
  • The below figure shows a typical electrical distribution system of a vessel.
  • The main generators are connected to the main bus bar via air circuit breakers. The main bus bar supplies 440V directly, 220V via transformers and 24V DC via transformers and rectifiers.
  • The main bus bar is connected to the emergency switch board via the tiebreaker. Emergency generator is also connected to the emergency switch board.
  • Arrangements are also made for shore supply to be connected.
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Steering Gears

Q) State some built in measures by which steering gear mechanism can be kept operational in the event of breakage of rudder actuator, pipe failures, motor burn out etc.

Ans:- Measures against steering gear failure: Some general requirements for steering gears, based on the various regulations and SOLAS 1974, are given below:

  1. Ships must have a main and an auxiliary steering gear, arranged so that the failure of one does not render the other inoperative. An auxiliary steering gear need not be fitted, however, when the main steering gear has two or more identical power units and is arranged such that after a single failure in its piping system or one of its power units, steering capability can be maintained. To meet this latter alternative the steering gear has to comply with the operating conditions of paragraph 2 — in the case of passenger ships while any one of the power units is out of operation. In the case of large tankers, chemical tankers and gas carriers the provision of two or more identical power units for the main steering gear is mandatory.
  2. The main steering gear must be able to steer the ship at maximum ahead service speed and be capable at this speed, and at the ship’s deepest service draught, of putting the rudder from 35 deg on one side to 30 deg on the other side in not more than 28 secs. (The apparent anomaly in the degree of movement is to allow for difficulty in judging when the final position is reached due to feedback from the hunting gear which shortens the variable delivery pump stroke.) Where the rudder stock, excluding ice strengthening allowance, is required to be 120 mm diameter at the tiller, the steering gear has to be power operated.
  3. The auxiliary steering gear must be capable of being brought speedily into operation and be able to put the rudder over from 15deg on one side to 15deg on the other side in not more than 60 sees with the ship at its deepest service draught and running ahead at the greater of one half of the maximum service speed or 7 knots. Where the rudder stock (excluding ice strengthening allowance) is over 230 mm diameter at the tiller, then the gear has to be power operated.
  4. It must be possible to bring into operation main and auxiliary steering gear power units from the navigating bridge. A power failure to any one of the steering gear power units or to its control system must result in an audible and visual alarm on the navigating bridge and the power units must be arranged to restart automatically when power is restored.
  5. Steering gear control must be provided both on the bridge and in the steering gear room for the main steering gear and, where the main steering gear comprises two or more identical power units there must be two independent control systems both operable from the bridge (this does not mean that two steering-wheels are required). When a hydraulic tele-motor is used for the control system, a second independent system need not be fitted except in the case of a tanker, chemical carrier or gas carrier of 10000 gt and over. Auxiliary steering gear control must be arranged in the steering gear room and where the auxiliary gear is power operated, control must also be arranged from the bridge and be independent of the main steering gear control system. It must be possible, from within the steering gear room, to disconnect any control system operable from the bridge from the steering gear it serves. It must be possible to bring the system into operation from the bridge.
  6. Hydraulic power systems must be provided with arrangements to maintain the cleanliness of the hydraulic fluid. A low level alarm must be fitted on each hydraulic fluid reservoir to give an early audible and visual indication on the bridge and in the engine room of any hydraulic fluid leakage. Power operated steering gears require a storage tank arranged so that the hydraulic systems can be readily re-charged from a position within the steering gear compartment. The tank must be of sufficient capacity to recharge at least one power actuating system.
  7. Where the rudder stock is required to be over 230 rnm diameter at the tiller (excluding ice strengthening) an alternative power supply capable of providing power to operate the rudder, as described in paragraph 3 above, is to be provided automatically within 45 seconds. This must supply the power unit, its control system and the rudder angle indicator and can be provided from the ships emergency power supply or from an independent source of power located within the steering compartment and dedicated for this purpose. Its capacity shall be at least 30 minutes for ships of 1O,OOO gt and over and 10 minutes for other ships.