Pressure Gauge Isolation Valve

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.

From the original1Gate Valve.com
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