2 replies to this topic

[chemicalengineer1989]

Hi All,

 

I have a control valve controlling the upstream of a column at 52barg. Depending on the throughput of the column, the control valve regulates the flow to maintain upstream pressure at 52barg.

 

Looking at the control valve datasheet, it only states a normal flow of 4225kg/hr, upstream P of 52barg and pressure drop of 10 bar. Cv calculated as 1.65. The design Cv specified seems to be 2.0

 

(Density = 800, temp = 150C)

 

My question is, can you from the above be able to work out what the maximum flowrate is through the valve when 100% open, and also the downstream pressure (upstream pressure remains constant).

 

If you can point in the right direction that would be great.

 

Thanks in advance

[Saml]

You can calculate the maximum flow from the max Cv from manufacturer datasheet, that you say seems to be 2.

Probably you are looking at the spec sheet for purchase. You should look on the manufacturer information about the delivered valve. Instrument people should have it.

Or you can search on the manufacturer catalog

Or you can ask the valve manufacturer

Or you can do a test run (if possible without upsetting your plant)

The downstream pressure will depend on the downstream system characteristics, so it is impossible to tell unless you post an schematic of your system.

[shvet]

My question is, can you from the above be able to work out what the maximum flowrate is through the valve when 100% open, and also the downstream pressure (upstream pressure remains constant).

 

 

You don't obtain all required information. You need pressure drop across CV at 100% open to know max possible flowrate. For this you need to perform hydraulic calculations of piping system both upstrream and downstream of CV. After you do this work you should see ISA-75.01.01 and CV datasheet for coefficients and calculation method.