PSV on a minimum flow line

[silvz71]

Hello, I am trying to size a relief valve for a "minimum flow/sample" loop. I have a pump operating at around 600psi feeding boilers. There is a small loop just off the discharge of the pump that is regulated to 50psi, and then ties back into the suction of the pump. The idea is to protect the 50psi side since the pipe spec is different from the 600psi side. The fluid is boiler feed water, coming off a deaerator and feeding the boilers. An additional point of concern is that the desired discharge point of the relief is an atmospheric blowdown tank, that is nearly 200ft away.

Any tips on what to consider for this case? I've sized several relief valves in the past, but they have all been more "conventional" applications (i.e. PSV on a vessel where the fire case is governing, etc).

Any help is much appreciated! Thanks!

-David

 

[LittleInch]

The key to it is what is the max flow you can get through whatever the device is that is regulating your 600psi down to 50psi. Normally you size for max flow through that device (100% open or max differential) assuming a blocked line Back to the inlet. If there is no valve between the regulating device and your inlet line then you don't really have a concern so long as your system is confined to one pump. We can't see your system so we can't tell if there is a case to answer or not.

A sketch or snap shot of your P &ID would help...

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[SeanB]

So you have a sample loop that comes of your pump discharge is regulated down to 50 psi and then returns to the suction side. So to see greater than 50 psi you would have to have your regulator fail, the pump suction valve closed and the valve closed at the deaerator closed as well?? A sketch would help but my first though is that there is no issue and you don't need a PSV. It is quite common to have sample loops as you describe but I have yet to see one with a PSV installed. But again, without a sketch I can't say with certainty whether or not it is an issue.