Flaring Control Valves

[oilersfan007]

Hi, I am trying to calculate how much flow goes through a control valve that ends up as flare gas. I have used data sheets to identify thy type of control valve (linear, equal % or quick opening). I need a way to relate the flow coefficient (Cv) to the opening of the valve which will tell me how much flow is in the valve. Can someone please help? I am stuck!
Apparently there are equations for each different type of valve but I can't seem to find it!

 

[LittleInch]

Find the valve data sheet from the vendor fully filled in. This will tell you all you need to know.

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

 

[SNORGY]

If it's a Fisher valve or equivalent, you might be able to find the tables relating Cv to % Open in a document called (if memory serves) Catalogue 12 in Emerson Process Management, on line. Also, I think that the Fisher sizing software, SizeMaster (also downloadable on line) will generate the curve. If I need an equation for that data (although it's usually discretized to increments of 10% so interpolation is normally sufficient), I invariably fit it to a cubic polynomial. Several utilities exist in the public domain for that, but I personally use software that I purchased for a nominal price. You should be able to get the valve vendor to give you the curve or the data if it isn't published somewhere; they can't really size their valves without it.