ISA control valves Kv vs Pneumatic Kv
ISA control valves Kv vs Pneumatic Kv
(OP)
Hi, I'm checking some formulas for Kv and I've seen different formulas.
I use Norgren and ASCO formulas for pneumatic Kv value:
Kv = (Q/514) · sqrt(T1/(Dp·p2))
Now the ISA control valve handbook is:
Kv = (Q/(482·Y))·srqt(T1·Z/(Dp·p1))
So, if Y and Z are approximately 1 for air this is:
Kv = (Q/(482))·srqt(T1/(Dp·p1))
How is it that one is sqrt(T1/(Dp·p1)) and the other sqrt(T1/(Dp·p2))
Maybe I shouldn't use ISA formulas for pneumatic valves, but should't they be the same?
Regards,
I use Norgren and ASCO formulas for pneumatic Kv value:
Kv = (Q/514) · sqrt(T1/(Dp·p2))
Now the ISA control valve handbook is:
Kv = (Q/(482·Y))·srqt(T1·Z/(Dp·p1))
So, if Y and Z are approximately 1 for air this is:
Kv = (Q/(482))·srqt(T1/(Dp·p1))
How is it that one is sqrt(T1/(Dp·p1)) and the other sqrt(T1/(Dp·p2))
Maybe I shouldn't use ISA formulas for pneumatic valves, but should't they be the same?
Regards,





RE: ISA control valves Kv vs Pneumatic Kv
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RE: ISA control valves Kv vs Pneumatic Kv
ISA-75.01.01-2007 (IEC 60534-2-1 Mod)
Regards,
RE: ISA control valves Kv vs Pneumatic Kv
My two cents is that any of the formulas would work if they were applied properly. Go with which ever you want to use. However, if you're designing valves, I recommend that you consider testing them to confirm that your actual Kv meets your stated Kv.
Want to know the do's and don'ts of Eng-Tips? Read FAQ731-376: Eng-Tips.com Forum Policies.
English not your native language? Looking for some help in getting your question across to others or understanding their answers? Go to forum1529: Translation Assistance for Engineers.