Selection of gaskets for British and metric pipe flanges
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The diameter of the pipe is D426X10; the pipe flanges use DN400-PN10 RF (Series II) GB/T 9116.1-2000. However, when selecting gaskets, according to GB/T 9126-2008, the inner diameter of the gasket corresponding to DN400 is 407. Personally, I think for a British standard pipe with a nominal diameter of DN400, a gasket with an outer diameter of 406 and an inner diameter of 407 is the appropriate choice. So, which size gasket should be used with metric pipe D426? It seems that all metric pipes have this problem. Additionally, I would like to ask everyone whether the pipeline is for natural gas with a pressure of 0.4 MPa, and if there are any issues with the flanges selected for it Which type of gasket is more suitable?
And where are oil-resistant rubber gaskets generally used?
The outer diameter of a metric pipe DN400 is already 406, so 407 works perfectly!
I checked the manual: according to the GB/T9126 standard, the inner diameter of the RF gaskets used for DN400 flanges is 407, while according to the HG/T20606 standard, the inner diameter of such gaskets is 426. So it depends on which standard’s gaskets you choose; for our HG standard, it’s better to follow the standards set by the Ministry of Chemical Industry, and you can refer to the national standards as well
Same question. This question is confusing. Standards for non-metallic and wound gaskets apply only to flanges for pipes in imperial units; it is better to use custom-made gaskets for flanges of pipes in metric units, especially wound gaskets