4 replies to this topic

[dhns]

Hai all,

Am the trainee person for the designing of control valves., in that activity ..Is the Cv is the major criteria ?What basis i should select that Cv ? can you indicate reference materials.,

with best Regards..,
Dhanasekaran.R

[JEBradley]

The best way to answer your question is probably to refer you to the Emerson Control Valve Handbook - it explains Cv's and should be able to answer pretty much any valve questions you might have.

http://http://www.documentation.emersonprocess.com/groups/public/documents/book/cvh99.pdf

[Padmakar Katre]

Dear,
Cv in case of control valve indicates its size (Port Area) for the certain design value of flow with the required pressure drop.The standard defination of "Cv is “the number of U.S. gallons per minute of water which will pass through a given flow restriction with a pressure drop of 1 psi.
 E.g. : A control valve which has a Cv of 12 has an effective port area in the full open position such that it passes 12gpm of water with 1 psi pressure drop.
The value of control Cv increases with increase in flow and decreases with increase in pressure drop (Across the control valve).The main factors which are required for calculation are
1.The inlet flow (max/min/norm)
2.Inlet Pressure
3.Delta P
4.Tempearture,Mol Wt. -(Or The sp.Gr.)
And so on the list minimum required but not limited to as it varies as per the case like for liquids,for air and other gases for sat steam/superheated steam.For the sake of better understanding of the different formulas to calculate the Cv here is the link

http://www.engineeri...ents-d_277.html

As well the Cf i.e. critical flow factor is also taken into consideration while design the valve which brings the relationship between the inlet,outlet and the vena contracta pressure.Its significance is high value of Cf will have low pressure recovery and the low value of the Cf will have high pressure recovery.
I hope that it will help you a little.Still you have any doubt please let us know.

[dhns]

Thanks sir.,
i feel your reply is so helpful to design the control valves
also i have expecting one help you.,
plz, send me the excel worksheet for designing process pipelines sizing for offshore sector.

Regards,
dhns
dhnsekaran@gmail.com

[dhns]

Dear mr.Patmaker,

My kind thanks for your belevable reply and information.

Reg,
Dhns.