Back pressure valve pressure setting 1

[Nixon509]

Hi,
I am testing a back pressure valve with water.
My valve came with 50psi factory setting which I assume that it requires 50psi to open the spring inside the valve and thus the maximum downstream pressure would not exceed 50psi.

However, no matter what the upstream pressure is downstream pressure always stays on 20psi. I increased the inlet pressure from 30~100psi but the downstream pressure would not exceed 20psi(it varies very little). I tried to readjust the spring on the valve but adjusting the spring only changes my upstream pressure.

However, I can half close the ball valve which is installed after my back pressure valve and increase the outlet pressure by generating some back pressure but in that case my downstream pressure keeps changing whenever I change my inlet pressure.

Is my valve broken?

I want to measure the pressure drops across the valve while I am keeping the constant outlet pressure using the valve and changing the inlet pressure.

I know how back pressure valves work but I don't understand why my valve behaves like this.

Any comment would be really really appreciated!

Thank you

 

[Pumpsonly]

From your description, I am not sure if you thoroughly understand how a back pressure valve -BPV work.

http://www.plastomatic.com/bprvspr.html

http://www.plastomatic.com/pomrelief.html

http://www.plastomatic.com/pomfaq.html#q&a

A BPV is used to maintain or control the pressure up stream of the valve at the set point of the valve.
When you increase the up stream supply pressure, you are increasing the flow rate to the valve. The valve need to open up more to let more water pass and hence relieve the pressure. When you reduce the the up stream supply pressure, the valve reduces the opening.

If the valve is set at 50PSI , you will not get any flow if the up stream pressure is below 50PSI. You also will not be able to increase the up stream pressure much above 50PSI. Otherwise you will encounter choked flow.


The down stream pressure will depends on the flow rate and the resistance / friction of the piping and fitting down stream of the BPV.