Registered: 12/13/99
Posts: 6226
Loc: Houston, Texas, USA
"Seating" is the initial "bolt up" operation which "seats" the gasket. This and all other terms are defined in Appendix 2 of the ASME code. You may also find the Taylor Forge bulleting useful in providing an overall summary of flange behavior.
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Regards, Richard Ay - Consultant