References for the design of the gas supply path of the instrument

Analytical instruments, especially gas chromatographs and other instruments, usually have certain requirements such as safety, cleanliness, and pressure stability. Starting from these aspects, put forward some of our reference opinions.

I. Air source selection

Cylinder gas and gas generators (such gases are relatively pure).

Second, the venue selection

1, cylinder gas should be considered in an outdoor small room or dedicated cylinder room.

2, the end of the corridor of the building.

3, indoor partition of the small room.

Because the cylinder gas is a dangerous article, especially a cylinder filled with hydrogen gas, the gas path is designed to be considered as above.

Third, the choice of pipeline

1, the preferred external bright internal clean stainless steel tube, followed by copper (disadvantage is easy to oxidize) and plastic tube.

Avoid using plastic pipes in the outdoor section because plastic pipes are susceptible to aging, cracking, and environmental damage.

2. The stainless steel pipe should be used indoors as much as possible, and polytetrafluoroethylene or polyethylene pipe can be used for special needs.

3, in order to eliminate unnecessary hidden trouble and pipeline failure should reduce the possible leakage point, it is recommended to use long stainless steel hose, this pipe is easy to distort, sometimes in order to facilitate the construction and design needs can be Some two-way and three-way connectors are installed in the pipeline.

4. For 1 to 3 chromatographs, use a stainless steel tube with an outer diameter of 3mm (φ3) and an inner diameter of 2mm (φ2). The outer tube can be supplied to the room and then the three-way pressure can be supplied to the three instruments. For 3 to 6 instruments, the supply air pressure is 0.4Mpa, and a stainless steel tube with an outer diameter of 3mm and an inner diameter of 2.4mm is used. Before the gas enters each instrument, it is best to add a regulated valve (wyf-1) to prevent mutual influence.

(5) For more than 3 (or more than 6) instruments, stainless steel tubes with an outer diameter of 6mm and an inner diameter of 5mm shall be used. After entering the room, use a three-way reducer (φ6×φ6×φ3) to divert to each instrument. Of course, in order to reduce the mutual influence, it is necessary to install a pressure-regulating valve.

6. For users who use stainless steel pipe, the cost of construction, commissioning, and materials will be greatly increased (few times).

IV. Continuous supply of gas

1. Both gas cylinders and gas generators need to consider continuous gas supply.

2. Inverted valve installed on air inlet: It can perform timely conversion between A gas source or B gas source.

3. Special purifiers need to be added for special requirements.

V. Precautions

1. In order to ensure the reasonable use of the gas source, an on-off valve should be installed before the gas enters the instrument and can be closed when not in use, so as to save the gas source.

2. The air source is relatively safe and can be supplied at close range. Usually, the amount of air used by the chromatograph is 5-10 times that of other gases. Therefore, the thickness of the air pipe should be changed accordingly.

3, for special occasions, such as ECD detector, GC / MS, etc., need to do a further cleaning of stainless steel hose, such as alcohol soaking and other measures, sometimes installed special purifiers in order to achieve good results.

4. Installed gas pipelines should be strictly leak tested, especially flammable gas such as hydrogen.

This article is for reference only, please criticize and correct me.