What does that mean?
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When removing the high-pressure gauge, when the pressure is generally greater than 10 MPa, it is necessary to first close the root valve and open the discharge hole of the J29 needle valve to relieve pressure. Be sure to avoid pointing any part of the body toward the discharge hole; only after the pressure has been relieved can the gauge be removed for replacement or calibration. Are two valves required when measuring high-pressure media? If it are two valves, what is the installation sequence?
The specifications do not require that high-pressure gauges must have two valves; they only stipulate that the installation height should be above 1.8 meters. Of course, a root valve is necessary. In process systems, pressure guides are usually used to direct the gauge to an appropriate location and height, which is why another shut-off valve is installed!
1# The rujimmy J29 needle valve has its own drain port; this means that when the J29 needle valve is closed, the drain port of the J29 needle valve is opened
One root valve, one drain valve. When removing the pressure gauge, the root valve should be closed and the drain valve opened to release pressure, in order to avoid injury.
GB50093-2002: Section 5.4.3
Since the measurement range of pressure gauges is generally between 1/3 and 2/3, the Bourdon tube may deform when used in high-pressure environments for an extended period; as a result, even if the gauge reads 0, it may not represent the actual value. In such cases, it is necessary to use a drain valve to release the internal pressure, and one should stand to the side to avoid being injured by high-pressure steam or other corrosive gases. Some steam pressure gauges do not have a drain valve; in such cases, it is necessary to loosen them slightly to allow the internal gas to escape before removing them completely.
Most high-pressure gauges are equipped with dual valves, and a tee is also provided to connect a stop valve, which is used to release pressure when the gauge needs to be replaced in order to protect personal safety.
This is necessary – the principle of \"no harm to three parties\"; some control valves also come equipped with pressure relief valves