Bolting Dimensions for API Flanges

3000 lb. W.P.

Nominal Size Inches Gasket API Number Number Of Studs Stud Bolt Size Inches
3-1/8 R31 8 7/8 X 6
4-1/16 R37 8 1-1/8 X 7
5-1/8 R41 8 1-1/4 X 7-3/4
7-1/16 R45 12 1-1/8 X 8
9 R49 12 1-3/8 X 9
11 R53 16 1-3/8 X 9-1/2
13-5/8 R57 20 1-3/8 X 10-1/4
16-3/4 R66 20 1-5/8 X 11-3/4
20-3/4 R74 20 2 X 14-1/2
26-3/4 BX168 24 2 X 17