5 replies to this topic

[Sridhar P]

Dear Sir,

Is there any special requirement for the isolation valve used for pressure gauge.

I have seen in many places globe valves are used for pressure gauge isolation valve. What is the purpose of using globe valve in PG isolation instead of ball or gate valves.

Pl. clarify

Regards,
P.Sridhar

[fallah]

Dear Sir,

Is there any special requirement for the isolation valve used for pressure gauge.

I have seen in many places globe valves are used for pressure gauge isolation valve. What is the purpose of using globe valve in PG isolation instead of ball or gate valves.

Pl. clarify

Regards,
P.Sridhar

In the cases i have ever seen small ball valve being used as pressure gauge isolation valve.

[manchester]

I ever seen many application using gate valve for this purpose. For rating 900 or higher, double block gate valve is used

[demank]

Commonly use ball valve,
In case for very high pressure above 3000 psig, we usually use needle valve.

[joesteam]

Normally I have seen needle valves. For some guages you need to dampen the gauge action - sort of like using a snubber before the guage - which is really just an orifice. So with a globe valve instead of a gate or globe you are able to open it partially and get some 'snubbing' action. With gauge isolation there is no flow, just a transmittal of pressure, so restrictions in the piping are OK and sometimes beneficial.

[Dazzler]

Hi Sridhar

In my experience working in many chemical plants, there are times when restricting the opening (needle valve) to a PG is useful to dampen and perhaps prevent a cycling reading due to pulsations, so a steady pressure can be read. Gate valves are often used as they are "multi-turn" and can not be bumped open by accident causing a hazard. Gates valve more often have all metal components so are less likely to leak or pass due to chemical attack of soft materials (non metals).

Common choice is a "gauge keeper" or valve block. This is often used between the main pipe isolation valve and the PG or other instrument. The Gauge keeper typically looks like a block of stainless with some T handles. It has built in single or doudle isolation valves (including needle) and a vent. It makes the job of changing a PG quick, safe, and easy.

Sometimes to dampen or other wise protect a PG, a diaphragm seal immediately upstream of the PG is also used.

Dazzler