Maximum allowed leakage test calculation for a Class IV control valve

[JulioJ]

Hi,
I've seen some posts regarding control valve leakrate calculation for testing against FCI-70-2 for Class IV valves. Although it's pretty straight forward calculation, I'm not sure what differential pressure should I use in the flow sizing formula Q=Cv*SQRT(DP) if I want to calculate the maximum allowed leakrate for a 6" valve with a CV=3000 using water at 60 degF as test media and a test pressure of 50 psi.

I know, per FCI-70-2 class IV, the leakage is defined as 0.01% of the rated valve capacity, i.e. 0.01% of CV valve, or 0.3 in this valve case.

Also, what would it be the case if I want to calculate the same but using air as test media?

Thanks.

 

[JulioJ]

Should I use 1 psi differential pressure in the formula, resulting on 0.3 GPM?

 

[hacksaw]

you use the test pressure to estimate the leakage.

 

[JulioJ]

Thanks for your reply hacksaw and sorry for the my late response, I'm still new on using this forums.