expansion joints

[SWMechanical]

hi all,

I am doing a stress analysis for pump suction piping. The pipe is connected directly to an expansion joint. Then there is an elbow next to the expansion joint. A support is installed at the piping right after the elbow. I would like add an directional anchor at the support to limit the lateral movement of the expansion joint. Is this a common pratice?

Thanks,

 

[ColonelSanders83]

If you present a scketch of your layout with the proposed direction of restraint for clarity I would be happy to coment on its acceptability.

The pressure and temperature involved would be usfull. The type of bellows is also necesary information, i.e. does it have tie rods? control rods, is it metal?, or is it rubber?

 

[SWMechanical]

Thank you ColonelSanders.

Here is a sketch of it. The temperature is 100C. Pressure is 690kPa.

 

[pennpiper]

Just my opinion!

I think you should:
a. remove the expansion joint
b. use a guide to restrict lateral movement in the approach pipe run but allow movement away from the pump.

Next time please include a North Arrow on your sketch

 

[ColonelSanders83]

I aggree with pennpiper's opinion.

Your layout shows a bellows directly atached to the pump suction coming in from a 90 deg elbow. This is bad practice due the flow disruption caused by bellows joints (as well as the elbow although some would argue this point). You are likely to see long term cavitaion and flow disruption problems.

Just my 2 cent's worth.

 

[Artisi]

Flow disruption problems - possibly yes, cavitation Why?

 

[rmw]

A pump with properly designed piping does not need expansion joints at the connections. Too often EJ's are used as crutches for poor pipe support design.

Ever so occasionally a pump will have a growth characteristic that requires an EJ to allow it to move, but not as an excuse for poor piping design.

rmw

 

[rneill]

You might want to look at Welding Research Council Bulletin 449 "Guidelines for the Design and Installation of Pump Piping Systems" and/or API 686 "Recommended Practices for Machinery Installation and Installation Design"

http://www.forengineers.org/wrc/wrcpvrcbulletin.htm