PSV for a piping line

[wormhhh]

Hi, everyone:

I need to size a PSV for a piping line which has two pumps working in Parallel, two different chemicals transferred by pumps and mixed in the protected pipe. The pumps have different operation parameters. I am going to do Liquid thermal expansion calculation for the protected piping. My questions are:

1. Do I need to know the flow-rate in the protected pipe for PSV sizing? if I do, how do I calculate it from two pumps, using pump performance curve or there is simplified one?

2. Can I only consider Liquid thermal expansion and do the calculation with mixture thermal properties?

thanks for help.

 

[Montemayor]

wormhhh:

If your pumps are of the centrifugal type, PSVs are normally not required since the system is typically designed for withstand pressure well above the deadhead pump pressure.

There are no calculations normally required - or done - for the thermal expansion case. Thermal expansion has nothing whatsoever to do with flow rate, and even less with a pump performance curve.

What are mixture thermal properties?

If you have not done a pressure relief problem before, it might be wiser to seek the advice or help of someone experienced in this application.

 

[SmartEngineer]

Your question needs further elaboration

I got questions for you:
- Are there isolation valves causing blocked discharge of cold fluid
- If yes, then pumps are not of a problem as you will look for the trapped or blocked volume of liquid in the piping having isolation valves from both sides.

Hope you can elaborate a little as we try to help you out

Cheers
SmartEngineer

 

[wormhhh]

Thanks for you guys response. One pump is protected by a PRV and the other doesn't. What I am assigned to do is to protect, using a PRV, the pipe line after two chemicals mixed from liquid thermal expansion, I am thinking to use the total flow rate of mixed chemicals and pressure to size the PRV. Is it the right way or not? Thanks.