4 replies to this topic

[Arslan Akram]

hi

I am sizing a control valve for non-chocked, turbulent flow, i have calculated Cv , but how to select the Valve size against this Cv. 

[chemks2012]

Arslanakram.np

 

Normally, for the better control, the size of the control valve selected is either smaller than the line size or equal to the line size.

However, as a process engineer, your job is to calculate the Cv based on three conditions 1) Maximum flow rate 2) Normal flow rate 3) Minimum flow rate and then give all the relevant information to the valve supplier.

Valve supplier will then feed all these data into the valve sizing software and/or check against the tables/catalogues and suggest you the valve size. Again, there are various types of control you can select i.e. linear, proportional etc depending on applications.

 

Hope this helps.

KS

[RoyenG]

Hi Arslan,

 

you have valve Cv, then you can select the control valve size (as the preliminary size) based on Cv vs NPS/DN table (Fisher, Samson, or other CV vendor).

 

Regards,

Royen

[Arslan Akram]

Thanks , it is really helpful

[afaruque]

A process enginner needs to select carefully the amount of pressure drop required across the control valve for proper controllability. You can go through Spirax-Sarco resources to get the whole picture. Good luck.

 

http://www.spiraxsar...ter-systems.asp