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　　All high-purity and high-clean gases in high-purity gas pipelines must be transported to the instrument point of use (POU) through pipelines. In order to meet the quality requirements of the instrument, under the condition of certain export indicators, more attention should be paid to the material selection and construction quality of the pipeline system. According to the accuracy of the gas or purification equipment, various factors of the pipeline system are greatly affected, so the selection of pipelines must comply with relevant industry principles and indicate the pipeline materials.

　　The key to maintaining the quality of high-purity gas pipeline delivery is to ensure that the gas system is reasonably designed, the accessories are correctly selected and installed, and that it has passed the inspection. The high-purity gas pipeline should use pipelines of corresponding quality according to the requirements of gas purity, allowable impurity content, particulate matter content, etc. in the process.

　　For example, the semiconductor industry, due to its complex production process and fine processing, not only has a clean production environment, but also has specific and strict requirements for various high-purity gases required in the production process. From micron technology to submicron and deep submicron (less than 0.35g.m) technology, the requirements for gas impurity content and water content are very strict, so it is necessary for the pipeline material properties to adapt to the requirements of high-purity and ultra-high-purity gases.

　　1. Pipe material properties

　　In the transportation of high-purity natural gas pipelines, the main characteristics of pipe materials that affect gas quality are gas permeability, ignition rate, adsorption, surface roughness, wear resistance and corrosion resistance.

　　2. Gas permeability

　　The phenomenon of gas flowing from the high pressure (or partial pressure) side to the low pressure (or partial pressure) side through the material is called gas permeation. Since the partial pressure of oxygen and nitrogen in the air is the largest and the gas molecules are relatively small, the gas permeability of the pipeline material is mainly manifested as the permeability of oxygen and nitrogen. Generally, there are many oxygen permeability tests. For the transmission of gases with purity above ppm level, stainless steel pipes or steel pipes should be used from the perspective of gas permeation. If we improperly select unqualified pipeline materials, no matter what purification measures we take, it will be of no avail.

　　3. Gas outlet rate

　　There are impurities between the crystals or inside the crystal lattices of the pipes formed during the material smelting process, which are slowly released during the transportation of high-purity gas and pollute the high-purity gas. In particular, impurities require high-purity gas above ppb. Usually, the flowering period of low-carbon stainless steel pipes is very low.

　　4. Adsorption

　　Impurities such as moisture are polar molecules, so they have strong adsorption. Rubber, plastic or some materials with rough surfaces easily absorb impurities such as moisture. Copper has a strong adsorption to water, and using these materials to transport high-purity gases is prone to contamination. Except for the use of copper pipes for transporting oxygen below the ppm level, high-purity gases do not use copper pipes or plastic pipes.