Technical Bulletin

Gasket dimensions for ASME flanges are cut to the dimensions provided in ASME B16.21, which have a slightly larger ID for 12” and smaller flanges (to prevent gasket intrusion into the process stream), and RING gasket outer diameters are calculated by subtracting the bolt diameter from the bolt circle diameter of the flange. This method ensures when the ring gasket pushes the bolts to the outer edge of the bolt holes in the flanges for proper alignment/centering.

  ASME vs AWWA Flanges - TECHNICAL BULLETIN.pdf