Pipe Flow Calculations Forum

Hi,
I want to calculate Natural gas flow through the Control valve at let say 50% Position.
Datas Available with me :
P1: Upstream pressure : 67 bar
P2: Down Stream Pressure :27 bar
Calculated CV of The Valve : 61.4
Compressibility factor : 0.92
NG MM: 17.0
Density of NG at STP: 0.74 kg/m3
Density : 35 kg/m3 ( Probably at P2 conidtion )

Control Valve Data sheet datas attached

Using Cv for natural gas is not very good approach. Cv is obtained with water as testing fluid and as water is incompressible it is a problem once you try to calculate gas flow rate. For gas control valves, Cg is flow coefficient that manufacturer should give, as Cg is measured with air as testing fluid.

Here is how flow rate can be calculated once you have gas flow coefficient value.

This equation is used in gas control valve calculator.

Also to know flow rate of control valve on some position like 50%, you should know flow characteristics, which is curve showing how flow coefficient is changing from 0 to 100%. So, when you know flow coefficient on 50% than you can calculate flow with above mentioned equation or calculator.

FOA,
Thanks for the reply

I need a calculated example of Control valve ( Attached Data Sheet) @ 50% Opening how much gas flow,
Can you please post it

thanks
regards

Viren
data given : attached valve data sheet &
I want to calculate Natural gas flow through the Control valve at let say 50% Position.
Datas Available with me :
P1: Upstream pressure : 67 bar
P2: Down Stream Pressure :27 bar
Calculated CV of The Valve : 61.4
Compressibility factor : 0.92
NG MM: 17.0
Density of NG at STP: 0.74 kg/m3
Density : 35 kg/m3 ( Probably at P2 conidtion )