Should the pressure gauge bend be installed before or after the needle valve?
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But on site, I saw that in many cases the needle valve was installed first, followed by the elbow and pressure gauge – which method is correct? Are there any relevant standards stipulating this? ?
The specifications require the installation of a root valve. Think about it: if a root valve isn’t installed at the root, can it really be called a root valve? There is leakage at the bend in the left diagram – how can it be maintained online?
Normally, the pressure gauge bend should be installed behind the needle valve. The purpose of doing this is to control and shut off the pressure between the pressure gauge and the system using a needle valve, which facilitates the replacement and maintenance of the pressure gauge. It also prevents high pressure from acting directly on the pressure gauge for extended periods, thereby helping to extend its lifespan and enhancing its safety. Although it is possible to see needle valves installed first and then pressure gauges at the site, standard practice recommends using a needle valve to control the pressure gauge. For specific details, relevant industry standards and the recommendations of equipment manufacturers can also be referred to. .
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The image on the right is accurate; these days we no longer need to use welded globe valves or check valves – instead, we use flanged globe valves or flanged needle valves, which are easier to maintain. Threaded valves have been practically phased out in the chemical plants in our area, as their maintenance is too complicated
“\"Leakage at the curve in the left chart – how to perform online maintenance.\" Valves are more prone to leakage than annular elbows in high-temperature media.