What are the standard requirements for stainless steel pipes in the Xizang region

The requirements for the use of stainless steel pipes in the Xizang region mainly follow the relevant national standards, while also taking into account local specific application scenarios and environmental characteristics, etc. There are certain requirements in terms of material, size, performance, etc. Specifically as follows: 

Material Requirements

Common Materials: Depending on the application scenario, stainless steel grades such as 304 and 316 are often used.Element Content: Taking 304 stainless steel as an example, the chromium (Cr) content is typically between 18% and 20%, nickel (Ni) content between 8% and 10.5%, and carbon (C) content no more than 0.08%. The precise proportion of each element ensures the corrosion resistance, strength, and other properties of the pipes. 

Dimensional tolerance requirements

Pipe diameter deviation: When the nominal outer diameter is less than or equal to 50mm, the allowable deviation is usually ±0.5mm; when the nominal outer diameter is greater than 50mm, the allowable deviation is generally ±1%.

Wall thickness tolerance: The tolerance range for thinner-walled pipes is relatively stricter to ensure the applicability and safety of the pipes in different application scenarios. 

Performance Requirements

Mechanical Properties: Must meet the corresponding national standards. For example, stainless steel seamless pipes for fluid transportation should comply with the requirements of GB/T14976-2012, including having certain tensile strength, yield strength, and elongation, etc. 

Corrosion resistance: Stainless steel pipes generally need to undergo intergranular corrosion tests to evaluate their corrosion resistance in specific environments, ensuring that they can meet the requirements of service life and safety in actual use. 

Pressure resistance performance: A hydrostatic test is required to verify the pressure resistance capacity of the pipe. The test pressure and pressure-holding time should be carried out in accordance with the standards. 

Process and Quality Requirements

Welding Process: Use appropriate welding methods such as Tungsten Inert Gas (TIG) welding or Plasma Arc Welding (PAW), strictly control parameters such as welding current, voltage, and welding speed to ensure uniform and smooth weld seams free of defects like pores, cracks, and slag inclusions. At the same time, ensure that the flow rate of shielding gas meets requirements to prevent oxidation of the welding area. 

Surface quality: The surface of the stainless steel pipe should be smooth and clean, without obvious scratches, dents, deformations, etc. The surface roughness must reach a certain level of smoothness to meet the requirements of different application scenarios. 

Sanitary requirements: For water pipes used for drinking water and domestic water supply, the post-immersion sanitary requirements shall comply with the provisions of GB/T17219. 

Installation requirements: When thin-walled stainless steel pipes are connected to pipes, pipe fittings and accessories made of other materials, measures should be taken to prevent electrochemical corrosion. When thin-walled stainless steel pipes of different nominal diameters are connected to pipes made of other materials, corresponding special conversion connectors should be used according to the diameter size, such as threaded conversion connectors, flange conversion connectors, grooved pipe fittings, etc. 

In addition, there are also corresponding standard requirements in some specific engineering fields. For instance, in DBJ540005-2018 "Code for Construction and Acceptance of Civil Oxygen Supply Engineering in Xizang Autonomous Region", specific regulations are made on the quality of pipe fittings, welding techniques, welding environment, appearance quality of weld seams and chloride ion content of stainless steel pipes in civil oxygen supply engineering.