Why is a three-way ball valve used in diaphragm pressure gauges?
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I saw a flange-connected three-way ball valve used under a gauge that measured some type of differential pressure at the site; I don’t understand why a three-way ball valve was used What is its function? Can’t a regular two-way ball valve be used?
May I ask, what medium is the diaphragm pressure gauge seen by the original poster used to measure?
This diaphragm pressure gauge is used to measure methanol.
Reply to 1# spacerover: How was it installed? Are there any diagrams or photos from the installation site?
It might be aimed at the air; check whether the instrument can return to zero under normal pressure.
Reply to 5# lant: Three-way valves are generally used for pressure measurement, sampling, and drainage. Generally, two-way valves can only be used for pressure measurement; to drain waste fluid, the gauge has to be removed. With a three-way valve, there is no need to remove the gauge; by rotating the three-way valve to another position, waste can be discharged online. But be careful about safety too.
Agree with what was said above; a three-way valve can be used for sewage discharge； Alternatively, instead of using a three-way valve, it is also a common practice to use two straight-through valves: one for root isolation and the other for drainage~~~
Three-way valves can also be used for pressure tapping with purging.