Instrument gas supply pipeline design

During actual on-site construction, valve No. 1 and valve No. 2 are usually installed on the branch pipe. Valve No. 1 is used to control the gas supply volume of the branch pipe to ensure stable gas supply. ； The No. 2 valve is used to cut off the connection between the air source ball valve and the branch pipe to facilitate maintenance and inspection of the branch pipe. Therefore, installing valve No. 1 and valve No. 2 at the same time can improve safety and reliability. .

No need. However, 7.2.1 in HG/T20510-2014 (approximately the same as SH/T3020), when the air supply system needs to draw out the air source from the air supply main pipe or main pipe, the source part should be set above the horizontal pipe, and the air source stop valve should be installed at the source part. The specification stipulates that the air source is led out from the main pipe or main pipe, so there is no need to install double valves for a single valve or gas equipment (except for large or dispersed gas consumption in Article 5.1.1). For specific design drawings, please refer to HGT20538 gas supply system diagram.

The ones I've seen generally only have No. 1 valve installed, not No. 2 valve.

Standards are required, but many people on site don’t pretend

The installation plan I adopted is the instrument air source main pipe voltage stabilization control. One #1 valve will be installed on each floor or one north and south main pipe on each floor. Generally, only the #2 valve will be installed on the instrument air source branch pipe. Considering that the possibility of many valves operating at the same time in a fine chemical plant is small, and the valves are selected as gas source fail-safe types, it is not necessary to install the #1 valve in the instrument gas source branch pipe, and it is not a mandatory requirement of the specification.

No need to use 2, just adjust the size with 3

Both No. 1 and No. 2 valves are required.

. 1. The construction depends on the drawings. Install if there is one on the drawing. If not, don’t install.； 2. Valve 1 on the branch pipe is not necessary. The relevant specifications are either recommended or do not make specific regulations. When encountering minor construction work on site, you can follow two principles:: At the position of valve 2, you can directly see the place where valve 1 should be installed, so valve 1 is not installed. ； When there is no difference between stopping one instrument on the same main pipe and stopping n instruments, the valve on the branch pipe does not need to be installed. .

In the design we do, valve 1 generally covers the range of the pipeline, and valve 2 covers the range of the instrument. If multiple air source lines are connected to a branch pipe, valve 1 is generally no longer required.

This post was last edited by qugd on 2023-6-16 13:43. The original poster asked a question about the design. During the design, it is necessary to consider the boundary between the process and the instrument, and determine the ownership of valve 1 and valve 2 based on the boundary. In the branch pipeline, if valve 1 and valve 2 are both responsible for the instrument professional and are also responsible for the instrument at the user's site, then one of valve 1 and valve 2 can be omitted. Because during maintenance and use, valve 1 and valve 2 have basically the same function, which is to shut off. If the dividing line between process and instrument is between valve 1 and valve, then neither valve 1 nor valve 2 can be canceled, because the switch of valve 1 is to control and isolate the gas supply from the branch pipe to the instrument, and valve 1 is the responsibility of the process party. ； Valve 2 is the control of the instrument on the branch pipeline. During maintenance, valve 2 can be closed, but valve 1 cannot be closed at will, because valve 1 is a control outside the instrument boundary.