Excessive Pump Suction Nozzle Loads 1

[FlashPurp]

Hello,

I am working on stress on pump suction piping coming from a tank. I am seeing high moments and nozzle loads on my pump during hot and cold operation. I believe the issue is with how my header is growing and contracting during the 2 cases, so I was wondering the best way to restrain without transferring loads to the pump nozzles? Or would it be best to reroute the header to add flex and reduce movement?

Information:
Fluid: Water
Low Temp: 30 F; Hot Temp: 150 F
Design Pressure: 50 PSIG
Material: A312 TP304
Header Size: 18" SCH 10S
Branch Size: 12" SCH 10S
Nozzle Size: 8"

This is the layout I currently have it:


Movement during cold operation:

Movement during hot operation:

 

[RVAmeche]

Agreed. In that example you can see the stresses go down but the nozzle loads still too high. Its not until the expansion loop is added that the nozzle loads are acceptable.

 

[FlashPurp]

Thanks for everyone's insight, it is very informative.

@RVAmeche I agree as I look through different forums and there's always an agreement that the high loads aren't always realistic due to different factors (gasket compression, nozzle stiffness being lower than Caesar's typical anchor). I just wish there was some sort of guide or standard to modeling that shows this to create more realistic model.

@KernOily unfortunately we do not have any FEA licenses. I am a little confused on the pump nozzle stiffness approach with 1E5 and why I would want 1". Say for example API 610 is limited to 0.01" would I be able to use the allowable loads to calculate stiffness from that? K=F/d?

 

[Piper Mike]

FlashPurp

Since this is still open I would like to add some comments.

This was a poor layout to start and having hot cold scenarios with 3 alternating running pumps is a very challenging task.

Looking at the output, the exaggerated displacement graphic shows the moment arms issue with the two outer pumps. For your curiosity run a model without the tank run leg and do your hot cold alternating pump scenarios with just the pump feed header. can you even get the pumps to work. Resolve the 3 pump layout, then fix the tank leg line to not apply excessive load or displacement into the pump header.

Good luck resolving.

 

[FlashPurp]

Thanks @Piper Mike I'll try working it like that one step at a time, I assume I'll still anchor as a boundary condition before adding my tank leg?