Material issues for flanges on pipes and valves?
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When the experienced engineers in our company design systems, they use 20# material for the pipes and Q235A for the valve flanges. I think this can lead to potential corrosion; I believe it would be better to use the same material for everything. Could my thinking be wrong?
There should be no problems under normal circumstances, and using Q235A for the flanges can help save costs.
I don’t know what organization you belong to; if 20# is chosen for the pipes, then why is a lower grade used for just a small part of those pipes?
Potential corrosion is not likely to occur, but there is no need to design it in that way. Using 20# for all of them should be quite reasonable. Moreover, Q235A is no longer used in pressure pipelines these days
Flanges are almost never made of Q235 material, unless they are used on air ducts; pressure pipelines rarely use Q235
I’ve never chosen it, but I really have never seen Q235A used for pipe flanges!
Flanges made of Q235 are still used by some older factories when they design products; they were included in pipeline manuals in the past, but are no longer used in modern designs