Flange roughness requirement for Spiral Wound Gasket (ASME B16.20) and Flat ring Gasket (B16.21)

[ligin18]

Dear All
For a brown filed project, the existing RF flange roughness was 6.3-12.5 micrometers. But the new mating flange roughness is 3.2 - 6.3 micrometers. The existing gasket was flat ring as per ASME B16.21. Please clarify whether Spiral Wound Gasket can be used as a gasket for these flanges of different roughness (any leakage due to the different roughness) or flat ring gasket as per ASME B16.21.

Thanks for the help

 

[mk3223]

It looks that the existing flange with higher surface roughness was for the "soft" gasket application, and it should be acceptable for the spiral wound gasket.