I am analysing flange leakage calculation and facing problem in gasket seating stress, gasket is failing in seating stress itself. As per the input, flange facing is serrated finish ( facing sketch- 1b) in which it fails, however if i input raised nubbin-serrated finish (1d)it passes. Can i take this deviation from 1b to 1d.?? Can i take this deviation as it is mentioned in ASME SEC VIII-APPENDIX 2 TABLE 2-5.2 Notes: where serrations do not exceed 1/64 in depth and 1/32 in. width spacing, sketches 1b and 1d shall be used. If yes then what is the main factor which makes the design safe.