How to calculate the valve flow rate??

[bzandy]

Is there anybody acquainted with the calculation of valve flow rate, the parameters at hand as follows:

1.Nominal diameters of control valve DN 50, DN 80, DN 100
Working media: gas condensate with water, methanol and
2. mechanical impurities of size up to 100 microns
3. Density, kg/m3: 800-1000
4. Operation pressure, Bar: 118
5. Inlet working media temperature, ºC: -2 up to – 20
6. Ambient temperature, ºC: - 55 up to + 39
Aside from the above mentioned parameters, any other paratmeters are needed accordingly? Thanks in advance!

By the way, possibly Please recommend a control valve type in accordance with diameters and work parameters given above and indicate the possible condensate flow rate through a control valve.

 

[JimCasey]

You need also the downstream pressure. Differential pressure is a key factor in the Cv (or Kv) equation.
You'll also need to know the relative concentrations of the process mixture, and probably what "gas Condensate" is, whether methane, propane, butane, etc.

 

[proinwv2]

Most manufacturers will provide free programs to calculate valve sizing. If you are not familiar with sizing then I suggest that you talk to them or someone experienced in this to point out the many factors involved. Sometimes cook book equations can cause one to miss the point.

Also the ISA75 publications offer a good explanation of some of these points and there are various publications, ISA, Fisher Valve, etc. that can further familiarize you with these points.

Paul

http://www.ostand.com

 

[bzandy]

Thanks so much for you guys kind reply. i just found out that the pressure differential between the upstream and downstream as follows:
Pressure for the control valves installed:
1) At condensate discharge line from compressor plant dust collectors and from condensate collector of pig receiver to combustion:
max min
Inlet pressure, Bar 95 66
Outlet pressure, Bar 5 5
However, up to now i have not gotten any useful information as to the concentration of processed mixture. what can i do now? i will try Fisher, ISA, wait to see any further information there. Thanks again!

 

[gerhardl]

All control valves are selected from the flow you want to have through the valve, not the nominal size.

a: You need to know the actual (different) flow ranges/amount you want to control.

b: You need to know the actual Cv of the different control valves. ( A nominal size DN50 control valve need not necessarily have a DN50 throughlet. For control valves very often different trim can be selected in the manufacturing of the valve, 'downsizing' valve from nominal opening.)

With theese figures known (in addition to what is mentioned above) you can either calculate necessary cv from point a, and select suitable valve, or you can check actual max flow through a valve from b, and decide if the valve is OK.

 

[JLSeagull]

Search for Fisher Control Valve Handbook. You will find a few web sites with this book available free as a PDF download.

 

[roydm]

Bzandy,
90 bar, thats one heck of a pressure drop calling for a specialty valve. I suggest you do a data sheet with all the process data you can gather then send it to your projects valve vendors.
Ask your local Emerson rep for "Firstview" it's the Fisher sizing program, quite easy to use for liquids.
Regards
Roy

 

[gerhardl]

Roy is absolutely right. Under given circumstances some special constructions may mangege such a drop. But you will have to have suppliers/producers to verify, as Roy says.