Selection of gaskets
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What gasket should be used for the manhole of a pressure vessel with DN500 PN40? What gasket should be used for the inspection hole of a pressure vessel with DN600 PN40?
Manhole flanges, as well as the type of sealing surface, are all related to the choice of gasket.
Composite wave-shaped gaskets, wound gaskets, etc. can be used.
For this pressure rating, it is recommended to use wound gaskets.
You forgot two important parameters: medium, temperature
Refer to the manhole standards; HG/T 21518 should be a suitable choice. 21521 and 21524 can also be used as references, and they all specify requirements regarding the selection of gaskets
The choice of gasket depends on the material being handled and the temperature. The most commonly used types are PTFE gaskets (3 mm thick), rubber gaskets (5 mm thick, usually made of nitrile), metal-PTFE wound gaskets (4.5 mm thick; the type of metal used depends on the medium – 304, 316, or 2205 can all be used), and metal-graphite wound gaskets (4.5 mm thick, suitable for higher temperatures). Metal wound gaskets come in versions with inner rings, outer rings, or without any rings at all (where PTFE or graphite is wound directly around the metal). The role of the metal rings is to serve as a support and for fixing; they do not provide sealing functionality. Without rings, the graphite material tends to scatter easily. As for whether inner or outer rings are used, it depends on the design of the flange sealing surface – flanges with male and female surfaces generally require inner and outer rings, while butt-welded flanges usually do not need rings
For PN40, wound gaskets are generally chosen; the specific material to be used depends on the medium and temperature. Generally, when the pressure is high, a higher specific pressure as well as greater resilience are required. Wound gaskets are generally better!