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Choice of batteries for ships machinery spaces - Lead acid and alkaline batteries
Requirement of appropriate batteries on board:
The battery is a convenient means of storing electricity. It is used on
many ships as an instantly available emergency supply. It may also be
used on a regular basis to provide a low-voltage d.c. supply to certain
equipment. To provide these services the appropriate size and type of
battery must be used and should be regularly serviced. Two main types
of battery are used on board ship: the lead—acid and the alkaline type,
together with various circuits and control gear.
The lead - acid battery is made up of a series of cells. One cell consists of
a lead peroxide positive plate and a lead negative plate both immersed in
a dilute sulphuric acid solution. The sulphuric acid is known as the
'electrolyte'. A wire joining these two plates will have a potential or
voltage developed across it and a current will flow. This voltage is about
2.2V initially with a steady value of about 2V. A grouping of six
separate cells connected in series will give a 12V battery. The word
'accumulator* is sometimes used instead of battery.
Actual construction uses interleaved plates in the cell in order to
produce a compact arrangement with a greater capacity. The complete
battery is usually surrounded by a heavy-duty plastic, hard rubber or
In the charged condition the battery contains lead, lead peroxide and
sulphuric acid. During discharge, i.e. the providing of electrical power,
some of the lead peroxide and the lead will change to lead sulphate and
water. The sulphuric acid is weakened by this reaction and its specific
When the battery is charged, i.e. electrical power is put into it, the
reactions reverse to return the plates to their former material and the
water produced breaks down into hydrogen gas which bubbles out.
The basic cell of the alkaline battery consists of a nickel hydroxide
positive plate and a cadmium and iron negative plate immersed in a
solution of potassium hydroxide. The cell voltage is about 1.4V. A
grouping of five cells is usual to give about seven volts.
An interleaved construction is again used and each cell is within a steel
casing. This casing is electrically 'live' being in contact with the
electrolyte and possibly one set of plates. A battery consists of a group of
cells mounted in hardwood crates with space between each. The cells are
connected in series to give the battery voltage.
In the charged condition the positive plate is nickel hydroxide and the
negative plate cadmium. During discharge oxygen is transferred from
one plate to the other without affecting the specific gravity of the
potassium hydroxide solution. The negative plate becomes cadmium
oxide and the positive plate is less oxidised nickel hydroxide. Charging
the battery returns the oxygen to the positive plate.
Choosing lead—acid or alkaline type
Large marine battery applications are provided by the following types:-
The use/storage of the two different types in the same system/room is not permitted.
The maker’s instructions are to be carefully adhered to.
- Non Sealed - Lead Acid
Sealed - Alkaline e.g. Nickel Cadmium or Nyffe cells
The choice between the lead—acid or alkaline type of battery for various running machinery onboard will be
based upon their respective advantages and disadvantages.
The lead-acid battery uses fewer cells to reach a particular voltage. It
is reasonably priced but has a limited life. It does, however, discharge on
open circuit and requires regular attention and charging to keep it in a
fully charged condition. If left in a discharged condition for any period
of time a lead-acid battery may be ruined.
The alkaline battery retains its charge on open circuit and even if
discharged it can be left for long periods without any adverse effect.
Although more expensive it will last much longer and requires less
attention. Also a greater number of cells are required for a particular
voltage because of the smaller nominal value per cell.
Both types of battery are widely used at sea for the same basic duties.
- A.C. motors for ships machinery
Supplying alternating current to a coil which is free to rotate in a magnetic field will not produce a motor effect since the current is constantly changing direction. Use is therefore made in an induction or squirrel cage motor of a rotating magnetic field produced by three separately phased windings in the stator. ...
Use of A.C. generatorsA coil of wire rotating in a magnetic field produces a current. The current can be brought out to two slip rings which are insulated from the shaft. Carbon bushes rest on these rings as they rotate and collect the current for use in an external circuit. Current collected in this way will be alternating, that is, changing in direction and rising and falling in value. To increase the current produced, additional sets of poles may be introduced....
D.C. motors for ships machinery When a current is supplied to a single coil of wire in a magnetic field a force is created which rotates the coil. This is a similar situation to the generation of current by a coil moving in a magnetic field. In fact generators and motors are almost interchangeable, depending upon which two of magnetic field, current and motion are provided.....
Use of D.C. generatorsA current is produced when a single coil of wire is rotated in a magnetic field. When the current is collected using a ring which is split into two halves (a commutator), a direct or single direction current is produced. The current produced may be increased by the use of many turns of wire and additional magnetic fields....
Emergency power supply for ships machinery operation
In the event of a main generating system failure an emergency supply of electricity is required for essential services. This can be supplied by batteries, but most merchant ships have an emergency generator. The unit is diesel driven and located outside of the machinery space .
Maintenance requirement for ships electrical equipment
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. ...
Choice of batteries for ships machinery spaces - Lead acid and alkaline batteries
The battery is a convenient means of storing electricity. It is used on many ships as an instantly available emergency supply. It may also be used on a regular basis to provide a low-voltage d.c. supply to certain equipment.....
Ships battery maintenance guidance The electrolyte level should be maintained just above the top of the plates. Any liquid loss due to evaporation or chemical action should be replaced with distilled water. Only in an emergency should other water be used. It is not usual to add electrolyte to batteries.....
Operating characteristics of battery for ships machinery spaces
Having been 'discharged' by delivering electrical power a battery must then be 'charged' by receiving electrical power. To charge the battery an amount of electrical power must be provided in the order of the capacity.....
Insulation resistance measurement
Good insulation resistance is essential to the correct operation of electrical equipment. A means must be available therefore to measure insulation resistance. Readings taken regularly will give an indication as to when and where corrective action, maintenance, servicing, etc., is required....
Use of navigational light circuitsThe supply to the navigation lights circuit must be maintained under all circumstances and special provisions are therefore made. To avoid any possibility of accidental open circuits the distribution board for the navigation lights supplies no other circuit.....
Ward—Leonard speed control system
As a very flexible, reliable means of motor speed control the Ward-Leonard system is unmatched.The system is made up of a driving motor which runs at almost constant speed and powers a d.c. generator .....
- Danger of electric shock to human bodyThe resistance of the human body is quite high only when the skin is dry. The danger of electric shock is therefore much greater for persons working in a hot, humid atmosphere since this leads to wetness from body perspiration.....
Marine machineries - Useful tags
Marine diesel engines ||Steam generating plant ||Air conditioning system ||Compressed air ||Marine batteries ||Cargo refrigeration ||Centrifugal pump ||Various coolers ||Emergency power supply ||Exhaust gas heat exchangers ||Feed system ||Feed extraction pump ||
Flow measurement || Four stroke engines || Fuel injector || Fuel oil system || Fuel oil treatment ||Gearboxes || Governor ||
Marine incinerator ||
Lub oil filters ||
MAN B&W engine ||
Marine condensers ||
Oily water separator ||
Overspeed protection devices ||
Piston & piston rings ||
Crankshaft deflection ||
Marine pumps ||
Various refrigerants ||
Sewage treatment plant ||
Starting air system ||
Steam turbines ||
Steering gear ||
Sulzer engine ||
Turbine gearing ||
Two stroke engines ||
UMS operations ||
Drydocking & major repairs ||
Critical machinery ||
Deck machineries & cargo gears
|| Control and instrumentation
||Engine room safety ||
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