Level Control Valve Sizing

[rjd1452]

I am trying to size a LCV from a separator, The separator pressure is 75 psig and the downstream of LCV goes to a vessel where pressure is maintained by blanketing at 5 psig.

What DP should be considered for the control valve? should it be 75 - 5 = 70 psig or

for the downstream of LCV should we consider pr. drop across piping also??

Since LCV only maintain level, is the pressure downstream of LCV defined by system pressures?

If the pressure downstream of LCV suddenly rises to more than 5 psig and differential pressure acorss lcv reduces, what will happen in that case? will flow reduce and ultimately level will not be maintain?

 

[LittleInch]

On your LCV data sheet you can specify different pressures at different flow rates, but unless the DP is more than 2 to 3 psi at max flow its not worth it.



What DP should be considered for the control valve? should it be 75 - 5 = 70 psig .
YES

for the downstream of LCV should we consider pr. drop across piping also??
Only if the DP changes a lot due to flow, so unlikley

Since LCV only maintain level, is the pressure downstream of LCV defined by system pressures?
Correct

If the pressure downstream of LCV suddenly rises to more than 5 psig and differential pressure acorss lcv reduces, what will happen in that case? will flow reduce and ultimately level will not be maintain?
Yes, but the D/s pressure would need to rise quite a lot as the CV design is usually only 70-75% open at full flow, so there is some spare capacity. Would probably need pressure to rise up to about 25 to 30 psi before that happened.


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[zamakaze]

@little inch - thanks very much for your response. much appreciated.

 

[LittleInch]

Do you have two accounts or is this some sort of student posting?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.