Gasket dimensions for ASME B16.5 Pipe Flanges and Flange Fittings

Nominal Pipe Size	Gasket Inside Diameter (ID) (inch)	Gasket Outside Diameter (OD) (inches)
		Class 300	Class 400	Class 600	Class 900
1/2	0.84	2.12	2.12	2.12	2.50
3/4	1.06	2.62	2.62	2.62	2.75
1	1.31	2.88	2.88	2.88	3.12
1 1/4	1.66	3.25	3.25	3.25	3.50
1 1/2	1.91	3.75	3.75	3.75	3.88
2	2.38	4.38	4.38	4.38	5.62
2 1/2	2.88	5.12	5.12	5.12	6.50
3	3.50	5.88	5.88	5.88	6.62
4	4.50	7.12	7.00	7.62	8.12
5	5.56	8.50	8.38	9.50	9.75
6	6.62	9.88	9.75	10.50	11.38
8	8.62	12.12	12.00	12.62	14.12
10	10.75	14.25	14.12	15.75	17.12
12	12.75	16.62	16.50	18.00	19.62

 

The ASME B16.5 - 1996 Pipe Flanges and Flange Fittings standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings. The standard includes flanges with rating class designations 150, 300, 400, 600, 900, 1500, and 2500 in sizes NPS 1/2 through NPS 24, with requirements given in both metric and U.S units. The Standard is limited to flanges and flanged fittings made from cast or forged materials, and blind flanges and certain reducing flanges made from cast, forged, or plate materials. Also included in this Standard are requirements and recommendations regarding flange bolting, flange gaskets, and flange joints.