Pipes and fittings
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When determining the pipe grade, must pipes and fittings be welded or seamless, and must they correspond one-to-one? Is it necessary to use seamless pipes and fittings, as well as welded steel pipes and welded fittings? Is it possible to use them together? For example, using welded steel pipes for the tubes and seamless pipe fittings for the fittings – could someone please give some advice?
It’s necessary; it must be unified. Welded steel pipes can be used for the tubes, and seamless pipe fittings may work fine; however, the reverse approach might present problems.
The outer diameters of welded steel pipes and seamless steel pipes also differ, and mixing them cannot ensure consistency. Furthermore, the pressure-bearing capacity of seamless steel pipes is higher than that of welded steel pipes; it is possible to use a higher-grade pipe in place of a lower-grade one, but not the reverse.
For pressure pipeline components, whether they are welded or seamless depends on the design pressure class of the pipeline; as long as the pressure rating meets the requirements, either welded or seamless fittings will suffice. Seamed and seamless versions differ only in their manufacturing processes; the pressure resistance capability of both types of pipe fittings meets the same quality standards. GBT12459-2005 Steel butt-welded seamless pipe fittings and GB T13401-2005 Steel plate butt-welded pipe fittings. Currently, the two standards have been merged into one: one is a technical specification and the other is a material standard. It is GB/T 13401-2017, Technical Specification for Welded Steel Fittings, and GBT12459-2017, Types and Parameters of Welded Steel Fittings. I hope this is useful to you.