7 replies to this topic

[ayan_dg]

What is the pressure drop criteria for sizing control valves which is in a system almost wholly governed by static pressure. The dynamic losses are very small compared to the static pressure drop.

[clarenceyue]

ayan_dg

I undersand from Luyben that pressure drop across a valve should be about 20-30% of the total pressure drop in the line. I don't know how good is that, but it might be a good starting point.

[breizh]

What is the pressure drop criteria for sizing control valves which is in a system almost wholly governed by static pressure. The dynamic losses are very small compared to the static pressure drop.

Ayan ,
Let you try to download from Internet Valves mnaufacturer handbook s, you will get the right answer .
I would suggest Masoneilan or Fisher. Probably somewhere between 0.5 and 1.5 bars
Regards
Breizh

[ankur2061]

What is the pressure drop criteria for sizing control valves which is in a system almost wholly governed by static pressure. The dynamic losses are very small compared to the static pressure drop.

Ayan_dg,

Please check out the following links. One is from our good old cheresources.

http://www.cheresour...m/valvezz.shtml

http://www.sbt.sieme...on/15370186.pdf

http://www.incyam.co...nload/dl_51.pdf

The above mentioned links provide a good insight about control valves and also have specific sections dealing with pressure drops.

Regards,
Ankur.

[ARAZA]

Dear,

If the dynamic losses are small, than use 10 psig as a minimum for the control valve pressure drop.
If the dynamic losses are high, than the delta P across the control valve is 25 % of the dynamic losses.

This criteria is used by many reputed EPC companies like Bechtel and SNC lavalin E&C.

Hope this helps.

ARAZA

What is the pressure drop criteria for sizing control valves which is in a system almost wholly governed by static pressure. The dynamic losses are very small compared to the static pressure drop.

[S.AHMAD]

What is the pressure drop criteria for sizing control valves which is in a system almost wholly governed by static pressure. The dynamic losses are very small compared to the static pressure drop.

Dear Ayan

We do not need any criteria under such situation. The pressure drop for sizing is determined by the differential static pressure between upstream and downstream.

regards

S.AHMAd

[ayan_dg]

Dear S.Ahmad,

this is OK if the source and destination pressure are fixed, so obviously you cannot do anything. But say you can increase the source pressure; so, for better control what is the pressure drop?

[djack77494]

But say you can increase the source pressure; so, for better control what is the pressure drop?

You might use control of the source pressure as a means of controlling your flowrate, if that is what you desire to control - you didn't tell us. With no controls, your flowrate would be such that the pressure + static head of the source vessel = the pressure + static head of the destination vessel - frictional losses. Add a control valve and the concept remains the same; you just add the control valve dP to the frictional losses. If frictional losses are truly negligable, the the CV pressure drop is just the difference between the two vessels' static + superimposed pressures.