Installation location of the root valve on the pressure gauge
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Recently, I encountered a problem: there is a discrepancy between the process drawings and the instrument drawings regarding the installation sequence of the valve at the base of the pressure gauge and the condensing ring. The **general standard atlas used in the process drawings specifies that the condensing ring should be installed first, followed by the control valve, and finally the pressure gauge； On the instrument diagram, the control valve is at the bottom; please share your opinions.
According to the instrument diagram, the control valve should be at the bottom, and then the condensation ring should be installed.
One should first connect the root valve, then the condensation coil, and finally the pressure gauge.
For earlier models, the pressure-regulating ring is installed first, followed by the valve. Now, control valves have been replaced with gate valves; the valve is installed first, followed by the pressure stabilizing ring. There is no problem with installing it first or later. (It shouldn’t be called a condensation ring, as it serves to protect the pressure gauge and acts as a buffer.)
The pressure gauge should be at the end, with a pressure stabilizing ring or isolation sleeve in the middle (for media that tend to condense), and a DN25 gate valve at the base
Indeed, I saw many instances on site where the root valve was connected first, followed by the condensation coil, and then the pressure gauge; I hardly ever saw a situation where the elbow was installed first and then another valve. Because once a failure occurs in the annular bend, the absence of a root valve ahead makes maintenance difficult. The equipment or pipeline can only be processed after being emptied.
It seems that anyway, it’s better to install a root valve first.