Sizing a control valve (liquid dump valve on 2 or 3 phase O&G separators)
Sizing a control valve (liquid dump valve on 2 or 3 phase O&G separators)
(OP)
Hi,
I have never had to size these valves before, but I would really appreciate any input.
I understand that many manufactures have sizing programs that maks it easier and faster to size their own valves. But I want to be able to size them from first principles or equations, charts, etc. because there are some supplier that do not have such programs or softwares for sizing.
So; if I have P1, P2, dP, Q, S.G (specific gravity), what are the steps.
1. I know that I can select a valve and look up it's Cv in the manual and plug into the equation Cv=Q*sqrt(S.G/dP). is there a way to verify that one of the variables needs to be increased or reduced to ensure that the valve size for which I picked Cv is appropriate, e.g. critical velocity, erosional velocity, etc. Just a way to know that I can plug in and solve for dP, Q, or Cv and know that I will be fine.
Or can I solve for Cv from the equation above and compare it to the manufactures Cv for a given valve and know at what range/ratioo to stay...any rule or thumb? or other equations? or variables?
Thank you.
I have never had to size these valves before, but I would really appreciate any input.
I understand that many manufactures have sizing programs that maks it easier and faster to size their own valves. But I want to be able to size them from first principles or equations, charts, etc. because there are some supplier that do not have such programs or softwares for sizing.
So; if I have P1, P2, dP, Q, S.G (specific gravity), what are the steps.
1. I know that I can select a valve and look up it's Cv in the manual and plug into the equation Cv=Q*sqrt(S.G/dP). is there a way to verify that one of the variables needs to be increased or reduced to ensure that the valve size for which I picked Cv is appropriate, e.g. critical velocity, erosional velocity, etc. Just a way to know that I can plug in and solve for dP, Q, or Cv and know that I will be fine.
Or can I solve for Cv from the equation above and compare it to the manufactures Cv for a given valve and know at what range/ratioo to stay...any rule or thumb? or other equations? or variables?
Thank you.
As much as possible, do it right the first time...





RE: Sizing a control valve (liquid dump valve on 2 or 3 phase O&G separators)
Everything you need to know is here,
http://www.documentation.emersonprocess.com/groups...
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: Sizing a control valve (liquid dump valve on 2 or 3 phase O&G separators)
When I solve for Cv and keep it within 30 to 75% of the valve's rated Cv, everything looks good. It appears the two things to worry about are:
1. Critical flow (choked flow?) for cavitation and flashing- where can I find a verification equation for this? the control valve handbook just what kind of valves to use, and not a way to tell that your valve sizing condition is sub-critical or has less chance of erosion
2. Noice, is there an industry standard for the minimum sound decibels and an equation to derive the same?
Thanks for you help
As much as possible, do it right the first time...
RE: Sizing a control valve (liquid dump valve on 2 or 3 phase O&G separators)
2---noise control, it is not so accurate calculation, it is just a prediction, it is related to velocity in the valve and pipe line. the standard can be searched on google. some formulars are recommended for noise estimation in those standards.
3---- 30%-75% is not always right, it actually depends on the charactor of the valve trim, for equal% time, normally 60%-80%, for linear trim 40%-60%, for quick opening trim, <30%?? depends on how quick you need the valve to open.----which means depends on how big your system is !
hope can help.
Get help and return with helps!!.
RE: Sizing a control valve (liquid dump valve on 2 or 3 phase O&G separators)
Get help and return with helps!!.