Xt value for a control valve.

C

Thread Starter

cps13

Hi,

I am trying to figure out how to get the correct valve size for a uni question.

What I am struggling with is the Xt value (critical pressure differential ratio).

From what I can figure out, you need the Xt value to find the Cv/Kv value. But it says in the Emerson Control Valve Handbook that you should pick the Xt value you think is appropriate.

How do you know what Xt value will be appropriate?

Thanks
 
Having worked in the Chemical Industry for a short time, we found it unusual for the Control Systems Engineer to spec/purchase valves. And where did he obtain the relevant information from ? - from the process engineer who knew what he wanted !

As for critical pressure differential ratio, try guessing from the parameters you have:
- Type of valve
- Size of valve
- Incoming pressure/allowable pressure drop
- Process media
 
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