Please tell me about the connection type of long-distance pipelines, welding or flange?
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This post was last edited by Achao syc62100 on 2026-6-3 20:37 Dear seniors: I would like to ask everyone, for long-distance pipelines, such as DN50, compressed air pipelines, pressure ≤ 1.0MPA, length about 1000 meters, each section of pipeline is about 6 meters long, should the connection between each section of pipeline be directly welded or flanged? Are there any corresponding standards and regulations? Thanks for the advice{:1_90:}
I saw the original poster’s question. The compressed air pipeline with DN50 and ≤1.0MPa has a length of 1000 meters and each section is 6 meters. This working condition is actually quite common. Welding is the mainstream solution: For this kind of medium-low pressure, non-corrosive long-distance compressed air pipeline, welding is usually used between straight pipes (such as argon arc welding base + manual arc welding cover). Welding is low cost, seals well, has no leak points, and does not require extensive flange and bolt maintenance. As long as the welder does it according to the requirements, the service life is very long and it also complies with the "Industrial Metal Pipe Construction Specification" GB 50235. Flanges are generally used in locations that require disassembly and assembly: For example, you need to connect equipment (gas storage tanks, dryers), set up valves, or pass through well chambers and compensator locations that require later maintenance. If the entire pipeline uses flanges, the cost will be much higher, and more sealing surfaces will increase the risk of leakage, making it not suitable for long-distance straight pipe sections. standards: You can refer to GB/T 20801 "Pressure Pipe Specification for Industrial Pipes" and GB 50235 of the Ministry of Housing and Urban-Rural Development. For compressed air, welded joints can basically meet the requirements, but you should pay attention to the proportion of post-weld non-destructive testing (generally, low pressure can be spot-checked), and heat treatment requirements (you will most likely not need it if the wall thickness is not thick). Tips: If the on-site space allows, you can consider welding the straight pipe section, and only provide a pair of flanges at both ends, at the valve, or at a certain distance (such as 100 to 200 meters) to facilitate local repair or cleaning of the pipeline in the future. In addition, it is best to install a drainage device at the end of the compressed air pipeline~
It must be welded. Flange welding generally uses butt welding.
This kind of pipe is very common and is usually welded. digression: This specification does not fall within the scope of special equipment supervision and does not require registration and periodic inspection. If instrument air is transported, it is strongly recommended that the material be made of 304 stainless steel, otherwise the rust residue in a few years will cause frequent malfunctions of your regulating valve.