Back pressure valve test

[GogiBOB]

Hi,
I am testing a back pressure valve and trying to plot a pressure drop vs flow rate graph of the valve.
I have a setting as shown in the picture. I am going to use 1/2'' pipeline to test my 1/2'' valve. I am going to install my valve on position B and measure the pressure at PT3 and PT4 and the flow rate at FT2. My plan is keeping the outlet pressure PT4 constant at 50PSI and vary the inlet pressure at PT3 and measure the flow rate at FT2 as I change the inlet pressure. I don't have much pipework experience and am not sure where to begin. Can anyone give me a heads up? I am using a centrifugal pump.
Thanks.

 

[GogiBOB]

I am not sure how I can control the inlet pressure in this pipe system.

 

[Pumpsonly]

You don't have to and not practical to keep the out let pressure constant.You need to add another globe valve at the down stream of the PT4 to vary the flow rate. The existing valves shown in your P &ID should serves as isolation valve only.
I suppose you are performing 1 test at a time only and you will only need 1 FT at the common discharge line.

 

[GogiBOB]

I added a ball valve after PT4 to control the down stream flow rate.
Now I am measuring the pressure drops across B with no valve attached.
To control the flow rate I turn off and on the bypass pipe valves. Am I doing it right?
This pipe system was designed by someone else and I took over to test back pressure valves. I don't have much experience in piping and still having hard time figuring out what is going on. Any comment would be really appreciated. Thanks!!

3 line question summary
1) I am using bypass pipe valves to control the flow rate.
2) Am I doing right?
3) Any comment about the pipe system above would be really grateful.

 

[GogiBOB]

is there any book I can refer to for this project?

 

[Pumpsonly]

Ball valve is no good for flow control. Use globe valve.
Don't use the by pass line to control the flow rate.
Open the by pass valves only if the testing flow rate is too low compared to the pump BEP ( less than 20%)flow and you need to run it on a prolong situation.

 

[GogiBOB]

Thank you for your comment pumpsonly.
I am now testing my pressure valve on B.
To control the flow rate I am using the globes on B and A with all other valves closed.
But for some reason I can't control my outlet pressure with the back pressure valve. To increase my outlet pressure I create back pressure by half closing the ball valve I newly installed after the pressure valve. However, regardless of my BPV(back pressure valve) setting my outlet pressure fluctuates as I increase the inlet pressure...
Am I missing something?

Any comment would be really appreciated!

 

[Pumpsonly]

Ok I had a misunderstanding on your original posting on the type of valve you are testing. I misunderstood as a check valve and hence recommended the earlier piping.

By the understanding of a back pressure valve, it is used to maintain the pressure between the pump and the BPV. That is, the pressure up stream of the BPV.

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

If your BPV is set at 50PSI, It will maintain the up stream pressure . Not the down stream pressure.
You down stream pressure will fluctuate depending on the flow rate and the resistance of the piping and fittings down stream of the BPV.

The flow rate need to be varied by using a valve at the up stream of the BPV. Or by using the by pass valves