What is the wall thickness of SCH20 stainless steel pipe?
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Question: On the single-pipe diagram, the wall thickness of the stainless steel pipe is indicated as SCH20. But isn’t the wall thickness of stainless steel pipes usually denoted by a number followed by the letter S? There is no standard specifying a thickness of SCH20S either. Can it be assumed that the wall thickness is equivalent to that of ordinary steel pipes with SCH20 specification? For example, for pipes of types PIPE, SMLS, PE, GB/T 14976 022Cr17Ni12Mo2, SH/T 3405, 14” with SCH20, is it correct to convert this to a steel pipe specification of 355.6×7.92 mm?
The thickness of SCH20 and SCH20S with the same pipe diameter is different; the thickness of stainless steel pipes designated as SCH20 is the same as that of ordinary carbon steel pipes, right?
The design institute should be contacted to check whether there is a missing ‘S’ in the design. According to specification B36.19, stainless steel pipe sizes are used, and each SCH designation is accompanied by an S.
Your understanding is correct; if it doesn’t have an “S”, refer to Table 3.1, and if it does, refer to Table 3.2. The version without the “S” is used when it’s not possible to choose the version with the “S” for stainless steel; for stainless steel, it’s preferable to use the wall thickness series with the “S”. However, sometimes using the version with the “S” for wall thickness calculations is not appropriate – the wall thickness might end up being either too thick or too thin – in such cases, the version without the “S” is chosen. For example, in your case, 10S is too thin while 40S is too thick, so 3.1 was chosen instead. Those with an S are only 5S, 10S, 40S, and 80S – four types in total.
Stainless steel pipes have the thickness grade marked with “S”, while carbon steel and alloy steel pipes do not have this mark