What material is required for the pipeline of the instrument air inlet valve?
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In some companies, plastic pipes are used for the pipelines leading to the valves that supply instrument air, while in other companies stainless steel pipes are used. Some experts have stated that plastic pipes should not be used as they cannot withstand fire; is there any clear standard requiring the use of stainless steel pipes? If the valve is fail-safe, and the plastic pipe is damaged, can’t the valve return to its safe position thanks to its built-in spring?
What experts say is the standard; even the real standards can’t overcome the \"experts\" who are in charge of you.
For the main pipes and trunk piping of the gas supply system, stainless steel pipes or galvanized steel pipes can be used. Stainless steel pipes are recommended for the piping on the downstream side of the air source ball valve.
Refer to the standard SH/T 3020-2013, Design Code for Gas Supply of Petrochemical Instruments
It is recommended to use stainless steel pipes for the connection tubes between instruments and gas sources (HG/T 20510-2014 Design Code for Instrument Gas Supply). This specification is a recommended standard. Stainless steel pipes are recommended for the connection tubes between instruments and gas sources, primarily to prevent rust from forming inside these tubes and eventually entering the instruments. In the past, copper pipes were recommended; now stainless steel is recommended. Using a nylon tube to connect to the air source should be fine, in my opinion. In the past, when pneumatic instruments were used, the signals from the control room to the field were connected using nylon pipes.
In applications subject to the fire protection requirements of 6.1.2 for SHT3020, stainless steel pipes should be used
The main pipe is galvanized; those connected to the positioner are made of stainless steel
In explosion-proof areas, stainless steel pipes or copper pipes should be used; in non-explosion-proof areas, stainless steel pipes, copper pipes, and PU pipes can be used