There is no such thing as equivalent gaskets between different manufacturers. In fact, changing manufacturers means updating the ASME PCC-1 Appendix O assembly bolt stress determination.
Spending the day with Steve Bond at the Flexitallic lab proved it to me. The differences between the graphite from different manufacturers alone was eye-opening.
I once heard the procurement director for a major petrochemical company proclaim that they order from gasket suppliers A, B, C, and D to ensure that none of them go out of business. They know for a fact that gasket supplier D has issues with quality, but they buy them anyway just in case something like Covid happens again. This line of thinking is not conducive to leak-free joints and makes the job of engineers like me much more difficult.
These four gasket properties are not equivalent between different manufacturers:
Target Assembly Gasket Stress, SgT
Maximum Permissible Gasket Stress, Sgmax
Minimum Gasket Operating Stress, Sgmin-O
Minimum Gasket Seating Stress, Sgmin-S
