Flanges and Bolt Dimensions – Class 150 To 2500 – ASME/ANSI B16.5

flanges and bolts

The 130-year-old American Society of Mechanical Engineers (ASME) has set the standard for mechanical engineers in over 100 countries worldwide.

ASME also sets the standards for flanges and bolt dimensions through the ANSI accredited ASME Standard B 16.5 ensuring all gasket and flange fittings are consistent and fit for purpose allowing a high-quality seal.

Below are the standard measurements for flanges and their relevant bolts and holes size – a very useful tool for any onsite machinist.

Flange and bolt dimensions – Class 150 to 2500

Nominal Pipe Size NPS (inches)Diameter of Flange (inches)No. of BoltsDiameter of Bolts(inches)Diameter ofBolt Holes (inches)Bolt Circle(inches)
1/43-3/841/20.622-1/4
1/23-1/241/20.622-3/8
3/43-7/841/20.622-3/4
14-1/441/20.623-1/8
1-1/44-5/841/20.623-1/2
1-1/2541/20.623-7/8
2645/80.754-3/4
2-1/2745/80.755-1/2
37-1/245/80.756
3-1/28-1/285/80.757
4985/80.757-1/2
51083/40.888-1/2
61183/40.889-1/2
813-1/283/40.8811-3/4
1016127/8114-1/4
1219127/8117
14211211.1218-3/4
1623-1/21611.1221-1/4
1825161-1/81.2522-3/4
2027-1/2201-1/81.2525
2432201-1/41.3829-1/2
Nominal Pipe Size NPS (inches)Diameter of Flange (inches)No. of BoltsDiameter of Bolts(inches)Diameter ofBolt Holes (inches)Bolt Circle(inches)
1/43-3/841/20.622-1/4
1/23-3/441/20.622-5/8
3/44-5/845/80.753-1/4
14-7/845/80.753-1/2
1-1/45-1/445/80.753-7/8
1-1/26-1/843/40.884-1/2
26-1/285/80.755
2-1/27-1/283/40.885-7/8
38-1/483/40.886-5/8
3-1/2983/40.887-1/4
41083/40.887-7/8
51183/40.889-1/4
612-1/2123/40.8810-5/8
815127/8113
1017-1/21611.1215-1/4
1220-1/2161-1/81.2517-3/4
1423201-1/81.2520-1/4
1625-1/2201-1/41.3822-1/2
1828241-1/41.3824-3/4
2030-1/2241-1/41.3827
2436241-1/21.6232
Nominal Pipe Size NPS (inches)Diameter of Flange (inches)No. of BoltsDiameter of Bolts(inches)Diameter ofBolt Holes (inches)Bolt Circle(inches)
1/43-3/841/20.622-1/4
1/23-3/441/20.622-5/8
3/44-5/845/80.753-1/4
14-7/845/80.753-1/2
1-1/45-1/445/80.753-7/8
1-1/26-1/843/40.884-1/2
26-1/285/80.755
2-1/27-1/283/40.885-7/8
38-1/483/40.886-5/8
3-1/2987/817-1/4
41087/817-7/8
51187/819-1/4
612-1/2127/8110-5/8
8151211.1213
1017-1/2161-1/81.2515-1/4
1220-1/2161-1/41.3817-3/4
1423201-1/41.3820-1/4
1625-1/2201-3/81.522-1/2
1828241-3/81.524-3/4
2030-1/2241-1/21.6227
2436241-3/41.8832
Nominal Pipe Size NPS (inches)Diameter of Flange (inches)No. of BoltsDiameter of Bolts(inches)Diameter ofBolt Holes (inches)Bolt Circle(inches)
1/43-3/841/20.622-1/4
1/23-3/441/20.622-5/8
3/44-5/845/80.753-1/4
14-7/845/80.753-1/2
1-1/45-1/445/80.753-7/8
1-1/26-1/843/40.884-1/2
26-1/285/80.755
2-1/27-1/283/40.885-7/8
38-1/483/40.886-5/8
3-1/2987/817-1/4
410-3/487/818-1/2
513811.1210-1/2
6141211.1211-1/2
816-1/2121-1/81.2513-3/4
1020161-1/41.3817
1222201-1/41.3819-1/4
1423-3/4201-3/81.520-3/4
1627201-1/21.6223-3/4
1829-1/4201-5/81.7525-3/4
2032241-5/81.7528-1/2
2437241-7/8233
Nominal Pipe Size NPS (inches)Diameter of Flange (inches)No. of BoltsDiameter of Bolts(inches)Diameter ofBolt Holes (inches)Bolt Circle(inches)
1/24-3/443/40.883-1/4
3/45-1/843/40.883-1/2
15-7/847/814
1-1/46-1/447/814-3/8
1-1/27411.124-7/8
28-1/287/816-1/2
2-1/29-5/8811.127-1/2
39-1/287/817-1/2
411-1/281-1/81.259-1/4
513-3/481-1/41.3811
615121-1/81.2512-1/2
818-1/2121-3/81.515-1/2
1021-1/2161-3/81.518-1/2
1224201-3/81.521
1425-1/4201-1/21.6222
1627-3/4201-5/81.7524-1/2
1831201-7/8227
2033-3/42022.1229-1/2
2441202-1/22.6235-1/2
Nominal Pipe Size NPS (inches)Diameter of Flange (inches)No. of BoltsDiameter of Bolts(inches)Diameter ofBolt Holes (inches)Bolt Circle(inches)
1/24-3/443/40.883-1/4
3/45-1/843/40.883-1/2
15-7/847/814
1-1/46-1/447/814-3/8
1-1/27411.124-7/8
28-1/287/816-1/2
2-1/29-5/8811.127-1/2
310-1/281-1/81.258
412-1/481-1/41.389-1/2
514-3/481-1/21.6211-1/2
615-1/2121-3/81.512-1/2
819121-5/81.7515-1/2
1023121-7/8219
1226-1/21622.1222-1/2
1429-1/2162-1/42.3825
1632-1/2162-1/22.6227-3/4
1836162-3/42.8830-1/2
2038-3/41633.1232-3/4
2446163-1/23.6239
Nominal Pipe Size NPS (inches)Diameter of Flange (inches)No. of BoltsDiameter of Bolts(inches)Diameter ofBolt Holes (inches)Bolt Circle(inches)
1/25-1/443/40.883-1/2
3/45-1/243/40.883-3/4
16-1/447/814-1/4
1-1/47-1/4411.125-1/8
1-1/2841-1/81.255-3/4
29-1/4811.126-3/4
2-1/210-1/281-1/81.257-3/4
31281-1/41.389
41481-1/21.6210-3/4
516-1/281-3/41.8812-3/4
619822.1214-1/2
821-3/41222.1217-1/4
1026-1/2122-1/22.6221-1/4
1230122-3/42.8824-3/8

Flange maintenance Tools

Enerpac manufactures a wide range of tools for flange management. These include flange facing machines, tools for flange pulling, spreading and alignment, hydraulic torque wrenches. Browse the full range of flange tools on the Enerpac website.

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