About pressure gauges
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I’ve started working in a new factory, and all the ordinary pressure gauges there are sealed with packing tape. In the past, I’ve worked with ones that were sealed using PTFE gaskets. Are there any specifications regarding this? Replacing the pressure gauge is extremely troublesome: if you use too much force, the panel ends up in the wrong orientation, and the tape used for sealing doesn’t work properly; if you use too little force, there’s a risk of leakage. One more question: regarding the selection of valves for ordinary pressure gauges, some use needle valves, some use ball valves, and others use gate valves. Is this decision based on the type of medium, the pressure level, or something else?
Whether to use a PTFE tape or gaskets depends on the process connection type of the pressure gauge. Shims are required for M20x1.5, and PTFE tape is needed for 1/2 NPT.
Thank you for the answer. Why is a PTFE tape necessary for 1/2 NPT?
This post was last edited by jujiangliu on 2018-4-4 at 11:16. The M20x1.5 thread is a straight, unsealed type, so gaskets are required； 1/2 NPT is a tapered pipe sealing thread, so PTFE tape must be used.
For those new to the factory: if the pressure gauge interface uses thread sealing such as NPT, use tape; if it uses face sealing like M20X1.5, use PTFE gaskets. All of these can use swivel joints as transition interfaces, allowing you to orient the pressure gauge however you wish. For valve selection, options include needle valves, ball valves, gate valves, etc.: the choice is determined by the medium, pressure, temperature, location, and preferred specifications...
For M20x1.5 threads, use PTFE gaskets or other flat gaskets; for G1/2 threads, use PTFE gaskets or other flat gaskets; for ZG1/2 threads, use tape; for NPT1/2 threads, in theory no sealant is needed – tightening the thread is sufficient for sealing.