Electrical deck auxiliaries on ships

These auxiliaries, in the main, comprise cargo winches (which may include warping as a subsidiary duty), cranes, capstans, warping winches, windlasses and hatch-cover winches. Except for cranes, each of these may sometimes be used for duties other than those for which they are primarily intended. The systems of control as between these various applications bear a similarity but with variations to suit the operating conditions. It will be convenient to deal with them under their different headings, but there are divergencies between the methods favoured by different makers and descriptions will therefore be confined to representative schemes.

Electro-hydraulic winches do not call for special mention as they use a continuous running motor, which can be either a.c. or d.c. They can be operated either singly or in groups from one pump. Many electrical deck auxiliary schemes make use of contactors for control purposes and where these are of such size and numbers as to warrant it they can be accommodated in a separate contactor deckhouse instead of in the winch assembly. This increases the amount of cabling but on the other hand it economises deck space in the vicinity of the winch, making for cleaner lines and unobstructed viewing by the operator. It also facilitates maintenance work which in any case is not always opportune to carry out when the ship is in port and when the winches are in use. While at sea maintenance can be carried out under protection from the elements. In every winch, etc., in which the load is lowered while the motor is mechanically coupled such as in systems employing power lowering it is essential to prevent the load taking charge and lowering at a speed which will damage the motor armature. To safeguard against this contingency centrifugal brakes are provided in some cases and they are so set as to enable heavy loads to be lowered with an assurance that the safe speed cannot be exceeded. Provision must also be made to stop the load running back if the power supply should fail or the overload relay operate and in this event the winch, etc., must not restart when power is restored unless the controller has been returned to the starting point, usually the "off " position.

Variable Voltage Control. Ward-Leonard control

Where fine control of both hoisting and lowering speed is required either booster control or a modified form of Ward-Leonard control is suitable and footbrakes are not essential. 

A magnetic brake provides against power failure or when returning the controller to off. Generally speaking for straightforward Ward-Leonard schemes the motor for the generator set can be either a.c. or d.c. and as the set runs continuously and in one direction only it is started in the conventional manner. If the supply is a.c. the exciter would be replaced by a static rectifier.

Under these Regulations vessels of 200 gross tons or less must have two lines of hawsers, one at the bow and the other at the stern quarter, each leading through a closed chock. Larger vessels must have at least four lines so arranged that they can be used on either side of the vessel. Two must lead from the bow and two from the stern quarters and not from the extreme bow or stern. For vessels between 200 and 300 gross tons the windlass forward and the capstan aft may be used for the two lines ahead but those leading aft must run from the main drum of power-driven winches and not from capstans. For all larger vessels all four lines must be power-operated and run from the main drum of power-driven winches and not from capstans.

Alarm Measuring System on the ship

1. The electronic and alarm measuring systems are designed for centralized supervision of processes on board ships.

2. Such systems are designed to meet the special requirements in marine applications.

3. The design of the alarm systems comprises a limited number of standard modules, and offers an economical and flexible solution for all system sizes — from small alarm systems with a few channels, to complex systems with data logging and alarm print-out functions.

4. The signals from analog and digital transducers are processed in the system and allow for simple and clear monitoring of process activities. The occurrance of abnormal conditions initiates audible and visual alarm signals.

Synchronous up/down counters

1. Synchronous up/down counters count number of pulses applied on the clock input. They consist of flip-flops and steering logic.

2. The reversible counters have the; following inputs and outputs: clock pulses inputs for counting down and counting up; clear input for resetting counter at any time; data and load inputs for presetting counter to desirable initial number before counting of clock pulses; data out puts for indicating in binary code current number in counter; carry output for indicating overflow of counter and borrow output for indicating underflow of counter. 

3. The outputs of all flip-flops are triggered by a low-to-high level transition of either count (clock) input. The direction of counting is determined by which count in put is pulsed while the other count input is high.

Thermocouple meters

Thermocouple meters convert applied current (a-c or d-c) by thermoelectric effects into deflection currents which register on a PM moving-coil couple actuated by heat generated at the junction formed by two strips of dissimilar metal. One strip carries the heat-generating input currents, the other carries heat-produced currents to the meter movement.

Thermocouple meters are used to measure a wide range of either a-c or d-c currents and give an accurate picture of the effective, or heats producting, value of a current no matter what its nature. The meters are relatively expensive and the thermal delay in converting input electricity to heat makes them sluggish.

Blackout recovery

The following action have been carried out.

1. Inform the Bridge and Master.
2. Notify Chief Engineer.
3. Start STBY generator and cut-in power.
4. Check and stop Emergency Generator & STBY position mode activated.
5. Start SW pump cooling system.
6. Check cause of black out and rectify.
7. Start ME Auxiliary Blowers.
8. Start ME Auxiliary pumps, LO Pump, etc.
9. Check all pressures & temperatures are normal.
10. STBY pumps check and restore to STBY mode.
11. Steering system check and restore to STBY mode.
12. Check Main Starting Air Bottle and press-up.
13. Check LO System on all STBY and service machinery & top-up as needed.
14. Check and remedy caused on STBY generator failure to gain power upon black-out.
15. Check Bridge & Engine communication system.
16. Check control air system at 6.5 – 7 kg/sm².
17. Drain air bottle of water accumulation.
18. Confirm all machineries in good working condition.

Problems with cargo cranes

Some problems with cargo cranes that occur on the ship.

Deck crane hoisting limit switches

While checking hoisting limit switches, due to incorrect setting of the hoisting limit switch on deck crane no. 1, noticed that the system differs from the ones on other sister ships. Hoisting up limit switch is no longer activated by means of a small weight that slacks the chain when the hook touches it, thus activating the micro switch, as on the previous sister ships; instead it has been put on the cam limit switch together with lowering limit. This means that the hoisting up limit is no longer fixed, to hook being about 2 meters below the boom head regardless to the boom angle; but that it is activated when the exact amount of wire rope is wound up on the drum. 

Lighting on ships. General Requirements

In all rooms, spaces and locations of the ship where lighting is ne cessary to ensure the safety of navigation, operating of machinery and equipment, as well as accommodating and evacuation of passengers and crew, stationary fixtures of main lighting are to be installed.

Lighting fixtures installed in rooms and spaces, where mechanical damage is possible to the glass hoods are to be provided with' protect ing gratings.

Lighting fixtures are to be installed in such a manner as to prevent heating of cables and adjacent materials up to a temperature exceeding the permissible level.

Permanently-installed lighting fixtures in holds are to take their po wer supply from a special switchboard. Apart from the fuses and swit ches this switchboard is to be provided with visual signals to monitor individual lighting circuits.

In rooms or places illuminated with luminiscent lamps where visible rotating parts of machinery are located, all measures to be taken to prevent stroboscope effect.

When using d-c, a label indicating the voltage level is to be fitted on switchboards feeding the discharge lamps.

Capacitors

The capacity of a capacitor is measured in farads. A capacitor has a capacity of 1 farad when a charge of 1 coulomb increases the potential, between its plates, by 1 volt.

The capacity depends on four things: a) the higher the voltage used to charge the capacitor the more energy it will store; b) the larger the sizes of plates and the greater their number the more energy will be stored; c) the closer are the positive and negative plates the greater is the charge; d) some insulators store greater charge than others.

Capacitor in A-C Line

When a capacitor is connected into a circuit through which alternat ing current is flowing, the plates of the capacitor are charged negatively or positively.

In order to show the action of a capacitor, in an a-c line, connect a capacitor in series with a lamp and plug into the a-c lighting. The lamp will glow provided its resistance does not prevent. Then connect another capacitor in parallel and the lamp will glow brighter. 

Connecting more capacitors and increasing the capacity we increase the glow. Thus, capacitors oppose the flow of current.

A-C Indicating Meters

The moving iron-vane type is the most common a-c meter. In it induced eddy currents are used to produce magnetic force on a structure bearing a pivoted pointer and a thin iron element called a vane. The vane has no coil. The stationary magnetic field is produced by a single current-carrying coil surrounding both the fixed metal element and the pointer movement. This coil is so arranged that its own field induces a field in the moving vane and in addition generates attractive or repulsive magnetic forces with respect to its own self-produced magnetic field. Deflection is basically proportional to the current through the main coil.

Moving iron-vane meters usually have relatively low impedance and are simple and inexpensive. They measure either voltage or current, but their use must be restricted to the frequency for which they are designed.

Rectifier type meters utilize PM d-c movements actuated by current developed from rectifying the applied a-c being measured. Rectifier elements mounted within the meter case may be copper oxide, selenium, germanium, or silicon. The developed d-c is proportional to the applied a-c while the rectifiers and associated circuitry are designed for operation over as wide a band of frequency as possible.