Expansion Joints

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The different joints as per the Strength of Material (related to civil engg ) are

Contraction- No initial gap, continuous reinforcement bars(no breaks)

Expansion: - Gap exist, permits contraction also, gap filled usually with plastic sealers.

Sliding- Movement along the joint plane.

Hinged- permits angular displacement.

Settlement- Allows the structures to displace vertically (eg foundation of building)

Hwoever never came across the "settlement joint" in mechanical aspect. All others yes.

Do we use settlement joints to piping ?

Pressure?

technically feasible for lower prassures.

Look at this link

http://www.royalpipe.com/pdfs/M_CTRLSET_BRV2.pdf

Where as expansion joints (most of the times) are bellow types to have more adaptibility to multiple expansion and contraction (you get other efatures like vibration isolation etc as bonus). And these usually can cater to much higher pressures.

Expansion Joints are used in piping for linear expansion due to thermal expansion when there is no other choice.

Other types of joints can be used when there is settlement or offset movement in a piping system.

However, both of these type of joints should be considered the last choice to compensate for the problem. The first choice is and should always be configuration (pipe routing).

To compensate for thermal expansion a "U" shaped loop is the most common configuration.

To compensate for offset (settlement) an "Z" shape is the most common configuration.

Why Configuration over Joint?

Configuration is ALL pipe and fittings. The pipe and fittings are stronger to begin with and will remain stronger over time. Joints are subject to fatigue failure and will thus become a hazard to the plant integrity as well as a safety issue for the worker.

Joints are also more costly then the extra pipe required for the configuration.

So, if you have the space and do not want to spend a lot of money use piping configuration. If you do not have the space and have the money then use the joint.