Home || Diesel engines
||Steam turbines ||Fuel treatment ||Pumps ||Valves ||Refrigeration ||
Raising liquids from a low point - Various type pumps for shipboard use
A pump is a machine used to raise liquids from a low point to a high
point. Alternatively it may simply provide the liquid with an increase in
energy enabling it to flow or build up a pressure. The pumping action
can be achieved in various ways according to the type of pump
employed. The arrangement of pipework, the liquid to be pumped and
its purpose will result in certain system requirements or characteristics
that must be met by the pump.
A pumping system on a ship will consist of suction piping, a pump and
discharge piping . The system is arranged to provide a
positive pressure or head at some point and discharge the liquid. The
pump provides the energy to develop the head and overcome any losses
in the system. Losses are mainly due to friction within the pipes and the
difference between the initial and final liquid levels.
To obtain the best operating
conditions for the pump it should operate over its range of maximum
Fig: Basic pumping system on board
HsucrrTANK= height of suction tank level above pump
(negative when tank level is below pump suction)
An important consideration, particularly when drawing liquids from
below the pump, is the suction-side conditions of the system. The
determination of Net Positive Suction Head (NPSH) is undertaken for
both the system and the pump. Net Positive Suction Head is the difference
between the absolute pump inlet pressure and the vapour pressure of
the liquid, and is expressed in metres of liquid. Vapour pressure is
temperature dependent and therefore NPSH should be given for the
operating temperature of the liquid.
There are three main classes of pump in marine use: displacement, axial
flow and centrifugal. A number of different arrangements are possible
for displacement and centrifugal pumps to meet particular system
The stroke of steam driven reciprocating pumps must be adjusted so that it is a maximum, as this then reduces "ridging" in the steam cylinders and pump barrels. Suction and delivery valves must be kept in good condition by regular attention.
Read more on Reciprocating displacement pumps
Centrifugal and other types of rotary pumps usually depend on the maintenance of fine clearances for their successful operation. Attention must be given to see that the correct clearances are maintained, it must also be remembered that fine clearances are often destroyed through fitting joints of too thick material.
The glands of rotary pumps are also important, in many cases the gland is arranged on the suction side of the pump and sealing connections are fitted. Again, if the pump efficiency is to be maintained, it is imperative that care and attention be given to this part.
After overhaul of rotary pumps, it is essential that the shaft alignment between the prime mover and the pumps is maintained, failure to maintain this alignment leads to gland trouble and excessive wear on shafts, and this is of particular importance to pumps fitted with gland seals.
- Various valves arrangement for machinery spaces piping system Straight-through cocks, Globe valve,Non-return valves,gate valves,Relief valves, quick closing valves, valve chests....
- Domestic water systems for general cargo ship Domestic water systems usually comprise a fresh water system for
washing and drinking and a salt water system for sanitary purposes
. Both use a basically similar arrangement of an automatic
pump supplying the liquid to a tank which is pressurised by compressed
- Mud boxes, Suction pipes, Steam traps, Expansion pieces & Drains for Machinery space piping system The mud box is a coarse strainer with a straight tailpipe down to the bilge..Suction pipes in tanks should be arranged with a bell mouth or foot..An expansion piece is fitted in a pipeline which is subject to considerable temperature variations..Drains are provided in pipelines and usually have small cocks to open
or close them.....
- Reciprocating displacement pumping system for ships use The displacement pumping action is achieved by the reduction or
increase in volume of a space causing the liquid (or gas) to be physically
moved. The method employed is either a piston in a cylinder using a
reciprocating motion, or a rotating unit using vanes, gears or screws.
- Centrifugal pump principles and working procedure
In a centrifugal pump liquid enters the centre or eye of the impeller and flows radially out between the vanes, its velocity being increased by the
- How a pneumatically control valve works ?
Many pneumatic devices use a nozzle and flapper system to give a
variation in the compressed air signal.A typical pneumatic control valve is shown in Figure . It can be considered as made up of two parts—the actuator and the valve. A flexible diaphragm forms a pressure tight
chamber in the upper half of the actuator and the controller signal is fed
- Bilge and ballast systems for general cargo ships
The bilge main is arranged to drain any watertight compartment other
than ballast, oil or water tanks and to discharge the contents overboard.
The number of pumps and their capacity depend upon the size, type
and service of the vessel.....
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 ||
Machinery Spaces.com is about working principles, construction and operation of all the machinery
items in a ship intended primarily for engineers working on board and those who working ashore . For any remarks please
Copyright © 2010-2016 Machinery Spaces.com All rights reserved.
Terms and conditions of use