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Various valves arrangement for machinery spaces piping system
Different type valves for ships use :
Valves are provided in a piping system to regulate or stop the liquid
flow. Various types exist in a machinery space with their associated particular function or
A cock is used in small-bore pipework and is joined to adjacent pipework
by a compression coupling. A cock can restrict or close an internal
passage by moving a central plug, usually by an external lever. An
example of a straight-through cock is given in Figure
Fig: A straight-through cock
Fig: A Globe valve
A globe valve has a somewhat spherical body enclosing the valve seat and
valve disc . Flanges are provided at either side for
connecting to adjacent pipework, and internal passages guide the liquid
flow through the valve seat. Liquid flow is always arranged to come from
below the valve seat so that the upper chamber is not pressurised when
the valve is closed. A screw lift valve arrangement is shown where the
spindle is joined to the valve disc. A gland with appropriate packing
surrounds the spindle where it leaves the valve bonnet. The upper part
of the spindle is threaded and passes through a similarly threaded
A circular handwheel is used to turn the spindle and raise
or lower the valve disc. The valve disc and seat are a perfect match and
may be flat or, more commonly, mitred. The material for both is often
provided with a very hard stellite coating. Globe valves also exist in a
right-angled form where the inlet and exit flanges are at 90° to each
Fig: A Non-return valve
Non-return or check valves are arranged in various pipelines to
prevent reverse flow. Where the valve disc is not attached to the spindle
it is known as screw-down non-return (SDNR). The valve disc in such a
valve must have some form of guide or wings to ensure it can reseat
correctly when screwed closed. Non-return valves are sometimes
arranged without spindles, in which case they are liquid operated and can not be manually closed . A free lifting valve may be used or a hinged flap.
Fig: A Gate valve
A gate valve should be fully open or closed; it is not suitable for flow
control. When open it provides a clear full-bore internal passage for the
liquid since the valve or gate is raised clear . The spindle is
threaded over its lower portion and when turned causes the gate to raise
or lower. The gate may be parallel or wedge-shaped in section fitting
against a matching seat. Larger valves have replaceable seat rings and
Fig: A Relief valve
Excess pressure is avoided in pipe systems by the use of relief valves. The
valve disc is held closed by a spring arrangement on the stem . The spring compression can be adjusted to enable the valve to
open at the appropriate pressure. Boiler safety valves are a special case
of relief valve .
Oil tank suction valves are arranged for rapid closing from a remote
point by the use of quick-closing valves. The collapsing of the 'bridge'
results in the valve closing quickly under the combined effects of gravity
and an internal spring. A manually operated wire or a hydraulic cylinder
can be used to collapse the bridge.
Valve chests are a series of valves all built into a single block or manifold.
Various arrangements of suction and discharge connections are possible
with this assembly.
- 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....
- 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
- 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
- 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
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