1、 Design Specification for Air Circuit Installation in Beijing Laboratory:

1. Centralized gas supply system

Gas should be introduced from a dedicated gas supply area outside the laboratory through pipelines, using main and backup gas supply bottles, and equipped with an automatic switching panel to ensure uninterrupted gas supply.

The main control valves and pressure reducing valves should be installed outside the laboratory for easy operation and maintenance.

2. Pipeline layout

Pipelines should be laid openly along the ceiling or wall, avoiding being laid on the same shelf as cables and conductive lines.

The pipeline route follows the principle of "shortest path, least bends", with a main pipeline slope of ≥ 1:100 to ensure smooth discharge of condensate.

When passing through walls or floors, the pipeline should be laid in a pre embedded sleeve, and there should be no welds inside the sleeve, which should be tightly sealed with non combustible materials.

3. Gas zoning

Flammable substances (such as acetylene and hydrogen) need to be introduced separately, with a distance of at least 5 meters from the combustion supporting gas (such as oxygen).

When hydrogen pipelines are laid parallel to other combustible gas pipelines, the spacing should be ≥ 0.5 meters; When cross laying, the spacing should be ≥ 0.25 meters; When laying in layers, the hydrogen pipeline is located above.

Corrosive gases such as chlorine and hydrogen sulfide should be kept away from precision instrument areas to avoid corrosion damage.

2、 Material Specification for Air Circuit Installation in Beijing Laboratory:

1. Pipeline material

High purity gas pipeline: BA grade seamless stainless steel pipes are preferred, with an inner surface roughness Ra ≤ 0.4 μ m. After argon arc welding, 5N high-purity nitrogen gas is required for purging.

Corrosive gas pipeline: using polytetrafluoroethylene (PTFE) or PVDF pipes, and passing the ASTM D1457 standard chemical corrosion resistance test.

End low pressure pipeline: EP grade copper pipes can be used, but contact with ammonia should be avoided to prevent the formation of copper ammonia complexes.

2. Valves and fittings

High pressure gas valve: using metal sealed ball valve, leakage rate; Needle valves are selected for micro adjustment applications, with a flow control accuracy of ± 1%.

Connection method: The high-pressure pipeline is connected with a sleeve, while the low-pressure pipeline is sealed with a VCR joint (metal gasket); Welded joints require X-ray inspection.

Identification management: All pipelines are labeled with gas names, flow arrows, and hazard levels. The weather resistance of the identification must meet the ISO 9227 salt spray test for 720 hours without detachment.