Flow Control Valve Pressure Drop


Thread Starter

Tim Smith


I have specified a flowmeter and flowc ontrol valve to control very low process flows (1L/hr) but to also have the ability to be sterilised using steam. ie they must allow 121 degrees through them.

We have a supply pressure of 1.8bar and an inlet temperature into the flowmeter of 131 degrees.

From the flowmeter the steam then goes through the flow control valve. The flowmeter specs say we will get a pressure drop of 0.2 at 1.8bar. The Flow control valve says we should be able to get 3.5kg/hr steam through the valve.

However we are getting about 125 degrees through the flowmeter (flowmeter and valve not lagged, pipework is). We are only getting 102 degrees on the outlet of the valve.

The normal process CV of the valve is 0.01. The steam CV is 0.17 (by allow stem to come out of valve).

The flowmeter flow is 1.5kg/hr. We have also tried 2.5kg/hr but made no difference to the temperature on the outlet of the valve. It did make a difference to the flowmeter outlet temperature-it increased by 5 degrees.

This is a globe type valve and a coriolis flowmeter.

The flowmeter steam velocity is about 60m/s at 1.5kg/hr. The pressure drop at this flow is only supposed to be 0.1bar.

What could be the reason for the huge temperature drop across the flow control valve?

I am suspecting when the valve is open 100% we are not getting 0.17cv but these are new valves and flowmeter so you wouldn't think that would be the issue.

Could there be any process reason i am missing?
> Could there be any process reason i am missing?

Is the piping stainless, and if so, is it well insulated?