Selection of manhole gaskets
Thread Content
What gasket should be used for a manhole with a design pressure of 10 MPa and DN=400? Can weld flanges with JB/T82.4-94 ring connection faces be used? What to do if there is no corresponding standard for the manhole cover?
Reply to 1# 20080818: Use metal wound gaskets when the pressure is high; they can be reused, while metal gaskets may not work.
It is recommended to use stainless steel spiral wound gaskets, which yield good results.
For a pressure of 10MP, the thickness of the inner cylinder can be used as a reference; if the inner cylinder is 12 units thick, it is recommended to use gaskets that are 8 units thick for the manholes. It is acceptable to use ring-connected face-welded flanges in accordance with JB/T82.4-94, but after the flanges are welded together, stress-relief heat treatment must be carried out (due to the thick thickness of the plates), followed by 100% RT or UT inspection.
Manholes also use PTFE gaskets, which can be reused.
Standard American flanges, flange covers, and wound gaskets can be used
The flange can be a recessed flange, with the flange cover having a convex surface for sealing; wave-patterned gaskets are used for safety reasons. For example, if the design pressure of a medium-pressure steam generator drum is 10 MPa, there is no problem using concave-convex surfaces together with wavy toothed gaskets.