Flexible Pipe Couplings

April 4, 2006
Pipe strain can cause premature failure of pumps. This can frequently be absorbed by a flexible pipe coupling... but only if that pipe coupling is properly installed. Merely putting it into the line without any support, will not achieve any significant relief from the pipe strain. In order to protect the pump against the pipe strain, it must be anchored.

In an earlier article, we discussed the problem with pipe strain when the pipes are not accurately aligned to the pump. As many will be aware, there are applications where temperature changes within a pump system cause the piping to move from it’s originally installed position The pipe strain that can be created will cause premature failure of the pump. This can frequently be absorbed by a flexible pipe coupling..... but only if that pipe coupling is properly installed.

Merely putting it into the line without any support, will not achieve any significant relief from the pipe strain. In order to protect the pump against the pipe strain, it must be anchored.

The question that is frequently raised is whether the flexible pipe coupling should be anchored at the end closest to the pump, or the end furthest from the pump.

The rule for the effective use of a flexible pipe coupling is to anchor the end of the coupling closest to the item you need to protect.

If you want to protect the pump from movement of the pipework, then you must secure the end of the flexible coupling closest to the pump. This allows the movement of the pipework to be absorbed by the pipe coupling, but the flange on the pump side of that coupling is fixed, therefore no strain is being passed to the pump.

Similarly, if you want to protect the pipework from movement of the pump, the you must secure the end of the flexible coupling closest to the pipework. This allows expansion of the pump flange to be absorbed by the pipe coupling, but the flange on the piping side of that coupling is fixed, therefore no strain is being passed to the piping.

In the even you have the worst condition of having movement of both the pump and the piping, you may wish to consider to flexible pipe joints mounted one after another. The two pipe joints can be bolted together and secured at that point, thus allowing the pump and the piping to move independently, with no effect of one being transferred to another.


Author of “The Practical Pumping Handbook” and a specialist in Pumping Reliability, Ross Mackay can be reached at www.practicalpumping.com or at 1-800-465-6260

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