Machinery spaces piping system - various fittings

Mud boxes

Mud boxes are fitted into the machinery space bilge suction piping. The mud box is a coarse strainer with a straight tailpipe down to the bilge . To enable the internal perforated plate to be cleaned when necessary, the lid of the mud box is easily removed without disconnecting any pipework.

Mud box

Fig:Mud box

Suction pipes

Suction pipes in tanks should be arranged with a bell mouth or foot. The bell end or foot should provide an inlet area of about one-and-a-half times the pipe area.

It should also be a sufficient distance from the bottom plating and nearby structure to provide a free suction area, again about one-and-a-half times the pipe area.

Steam traps

Steam trapFig:Steam trap

A steam trap does as its name implies and permits only the passage of condensed steam. It operates automatically and is situated in steam drain lines. Various designs are available utilising mechanical floats which, when floating in condensate, will enable the condensate to discharge . Other designs employ various types of thermostat to operate the valve which discharges the condensate.

Expansion pieces

Expansion bellows pieceFig:An Expansion bellows piece

An expansion piece is fitted in a pipeline which is subject to considerable temperature variations. One type consists of a bellows arrangement which will permit movement in several directions and absorb vibration . The fitting must be selected according to the variation in system temperatures and installed to permit the expansion and contraction required in the system.


Drains are provided in pipelines and usually have small cocks to open or close them. It is essential that certain pipelines are drained regularly, particularly in steam systems. When steam is admitted to a pipeline containing a reasonable surface of water it will condense and a partial vacuum occur: the water will then be drawn along the pipe until it meets a bend or a closed valve. The impact of the moving water in the pipework will create large forces known as 'water hammer', which can result in damage to pipework and fittings.

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