Blow Down with Nitrogen Gas of Positive Displacement Liquid Flow Meter

[MechEng176]

Hi Folks,

I've got a 6'' FMC positive displacement liquid flow meter as part of some piping that I have to pressure test with Nitrogen gas. Once we've held the pressure and start the blow down, I will be opening a vent downstream of the flow meter. I know that this is bad for turbine flow meters because the turbine will spin way way faster than it is designed to (because they're for measuring liquid flow as opposed to gas flow) but what about positive displacement flow meters? I will be relieving the pressure as slowly as possible by cracking open a 3/4'' gate valve but wanted to know if there is a SOP for this type of stuff.

http://www.fmctechnologies.com/en/M...iquidProducts/PDMeters/DCPDMeters/DC2to8.aspx

Thanks!

 

[LittleInch]

Yes, the normal practise is to remove the meter and replace with a spool piece. It is difficult to control gas velocity, especially at low pressure and you could easily damage your meter, both turbine and pd.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[MechEng176]

Good to know. In that case, I'll just isolate the flow meter on either end with inline valves.

Thanks!!

 

[BigInch]

You may not want to test against closed valves either.
In general, everything, except an open valve, or a strainer, should be blanked off, or removed. Check valves held open.

I hate Windowz 8!!!!