High purity nitrogen gas has to be transported through pipelines to the point of use of the small air separation unit. In order to meet the quality requirements of the gas for the process, the selection of materials for the piping system and the quality of construction need to be paid more attention to during the construction process, provided that the gas export index is determined. The quality of the gas depends not only on the precision of the gas production or purification unit, but is also influenced to a large extent by many factors in the piping system. The piping of the high-purity nitrogen system requires the use of electrolytic polished (EP) low carbon (316L) stainless steel tubes with the same material as the bellows valves or diaphragm valves.
In the stainless steel melting process, approximately 200g of gas is absorbed per tonne of steel. After processing, stainless steel not only has various contaminants adhering to its surface, but also leaves a certain amount of gas in its metal lattice. When there is airflow through the pipeline, this part of the gas absorbed by the metal will re-enter the airflow and pollute the pure gas. When the airflow in the tube is discontinuous flow, the tube to the gas through the formation of pressure adsorption, the airflow stopped through, the tube adsorption of gas and the formation of pressure reduction analysis, and the analysis of the gas as impurities into the pure gas in the tube. The adsorption and resolution cycle makes the metal on the inner surface of the tube also produce a certain amount of powder, and this metal dust particles also contaminate the pure gas inside the tube. This characteristic of the tube in small air separation unit affects the purity of the gas conveyed, so the process requires not only an extremely smooth inner surface of the tube, but also a high degree of wear resistance.
Dear Air Separation refers to international industry standards in the selection of materials and piping, and adheres to the relevant industry principles in the selection of pipes, and indicates the material of the pipes in the drawings.
