Machinery Spaces
Home || Diesel Engines ||Boilers||Feed Systems ||Steam Turbines ||Fuel Treatment ||Pumps ||Refrigeration ||

Various valves arrangement for machinery spaces piping system

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 advantages.

Cock: 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

ships machinery spaces
container ships machinery info
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 bridge piece.


Fig: A straight-through cock

Globe valve

Fig: A Globe valve

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 other.

Non-return valves

Fig: A Non-return valve

Non-return valves

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.

Gate valve

Fig: A Gate valve

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 gate facings.

Relief valve

Fig: A Relief valve

Relief valves

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 .

British standard symbols various valves

Quick-closing valves

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.

Butterfly valve – A rotary stem valve with a centrally-hinged disc of the same dimension as the pipeline. The valve opens into the pipeline and therefore takes up little space, permits large flow rates and gives minimum pressure drop.

Valve chests

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.

All ships side valves are to be maintained in good working order. Testing and lubrication of the valves is to also to be in accordance with the PMS system requirements. This is to include a weekly test of all shipside valves which are to be systematically closed and re-opened under the supervision of the Chief Engineer.

All valves must be properly identified and labelled in order to minimise the risk of incorrect operation and relevant staff briefed in their correct function, where appropriate.

Related Info:

  1. Dealing with pipe failure and related guideline
  2. Pipes corrode internally and externally. Internally, they may be affected by erosion, uniform and abrasive corrosion, fatigue and galvanic action. Externally, corrosion is caused mainly by atmospheric conditions, but pipes can corrode locally where liquids drip onto them. .....

  3. Mud boxes, Suction pipes, Steam traps, Expansion pieces & Drains for Machinery space piping system
  4. 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.....

  5. Piping maintenance guideline
  6. It is important to identify failing pipes before leakage occurs; maintenance of piping is as much about procedural checks and pressure tests to locate weak points as it is about actual repair......

  7. Reciprocating displacement pumping system for ships use
  8. 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.

  9. Centrifugal pump principles and working procedure
  10. 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 impeller rotation....

  11. How a pneumatically control valve works ?
  12. 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 in.....

  13. Domestic water systems for general cargo ship
  14. 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 air...

  15. Bilge and ballast systems for general cargo ships
  16. 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.....

  17. Find out more on bilge and ballast system sketches

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 || Propellers || Power Plants || Starting air system || Steam turbines || Steering gear || Sulzer engine || Turbine gearing || Turbochargers || Two stroke engines || UMS operations || Drydocking & major repairs || Critical machinery || Deck machineries & cargo gears || Control and instrumentation ||Fire protection ||Engine room safety ||

Machinery 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 Contact us

Copyright © 2010-2016 Machinery All rights reserved.
Terms and conditions of use
Read our privacy policy|| Home page||