ASME 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 Bolts Diameter of Bolts(inches) Diameter ofBolt Holes (inches) Bolt Circle(inches) 1/4 3-3/8 4 1/2 0.62 2-1/4 1/2 3-1/2 4 1/2 0.62 2-3/8 3/4 3-7/8 4 1/2 0.62 2-3/4 1 4-1/4 4 1/2 0.62 3-1/8 1-1/4 4-5/8 4 1/2 0.62 3-1/2 1-1/2 5 4 1/2 0.62 3-7/8 2 6 4 5/8 0.75 4-3/4 2-1/2 7 4 5/8 0.75 5-1/2 3 7-1/2 4 5/8 0.75 6 3-1/2 8-1/2 8 5/8 0.75 7 4 9 8 5/8 0.75 7-1/2 5 10 8 3/4 0.88 8-1/2 6 11 8 3/4 0.88 9-1/2 8 13-1/2 8 3/4 0.88 11-3/4 10 16 12 7/8 1 14-1/4 12 19 12 7/8 1 17 14 21 12 1 1.12 18-3/4 16 23-1/2 16 1 1.12 21-1/4 18 25 16 1-1/8 1.25 22-3/4 20 27-1/2 20 1-1/8 1.25 25 24 32 20 1-1/4 1.38 29-1/2
Nominal Pipe Size NPS (inches) Diameter of Flange (inches) No. of Bolts Diameter of Bolts(inches) Diameter ofBolt Holes (inches) Bolt Circle(inches) 1/4 3-3/8 4 1/2 0.62 2-1/4 1/2 3-3/4 4 1/2 0.62 2-5/8 3/4 4-5/8 4 5/8 0.75 3-1/4 1 4-7/8 4 5/8 0.75 3-1/2 1-1/4 5-1/4 4 5/8 0.75 3-7/8 1-1/2 6-1/8 4 3/4 0.88 4-1/2 2 6-1/2 8 5/8 0.75 5 2-1/2 7-1/2 8 3/4 0.88 5-7/8 3 8-1/4 8 3/4 0.88 6-5/8 3-1/2 9 8 3/4 0.88 7-1/4 4 10 8 3/4 0.88 7-7/8 5 11 8 3/4 0.88 9-1/4 6 12-1/2 12 3/4 0.88 10-5/8 8 15 12 7/8 1 13 10 17-1/2 16 1 1.12 15-1/4 12 20-1/2 16 1-1/8 1.25 17-3/4 14 23 20 1-1/8 1.25 20-1/4 16 25-1/2 20 1-1/4 1.38 22-1/2 18 28 24 1-1/4 1.38 24-3/4 20 30-1/2 24 1-1/4 1.38 27 24 36 24 1-1/2 1.62 32
Nominal Pipe Size NPS (inches) Diameter of Flange (inches) No. of Bolts Diameter of Bolts(inches) Diameter ofBolt Holes (inches) Bolt Circle(inches) 1/4 3-3/8 4 1/2 0.62 2-1/4 1/2 3-3/4 4 1/2 0.62 2-5/8 3/4 4-5/8 4 5/8 0.75 3-1/4 1 4-7/8 4 5/8 0.75 3-1/2 1-1/4 5-1/4 4 5/8 0.75 3-7/8 1-1/2 6-1/8 4 3/4 0.88 4-1/2 2 6-1/2 8 5/8 0.75 5 2-1/2 7-1/2 8 3/4 0.88 5-7/8 3 8-1/4 8 3/4 0.88 6-5/8 3-1/2 9 8 7/8 1 7-1/4 4 10 8 7/8 1 7-7/8 5 11 8 7/8 1 9-1/4 6 12-1/2 12 7/8 1 10-5/8 8 15 12 1 1.12 13 10 17-1/2 16 1-1/8 1.25 15-1/4 12 20-1/2 16 1-1/4 1.38 17-3/4 14 23 20 1-1/4 1.38 20-1/4 16 25-1/2 20 1-3/8 1.5 22-1/2 18 28 24 1-3/8 1.5 24-3/4 20 30-1/2 24 1-1/2 1.62 27 24 36 24 1-3/4 1.88 32
Nominal Pipe Size NPS (inches) Diameter of Flange (inches) No. of Bolts Diameter of Bolts(inches) Diameter ofBolt Holes (inches) Bolt Circle(inches) 1/4 3-3/8 4 1/2 0.62 2-1/4 1/2 3-3/4 4 1/2 0.62 2-5/8 3/4 4-5/8 4 5/8 0.75 3-1/4 1 4-7/8 4 5/8 0.75 3-1/2 1-1/4 5-1/4 4 5/8 0.75 3-7/8 1-1/2 6-1/8 4 3/4 0.88 4-1/2 2 6-1/2 8 5/8 0.75 5 2-1/2 7-1/2 8 3/4 0.88 5-7/8 3 8-1/4 8 3/4 0.88 6-5/8 3-1/2 9 8 7/8 1 7-1/4 4 10-3/4 8 7/8 1 8-1/2 5 13 8 1 1.12 10-1/2 6 14 12 1 1.12 11-1/2 8 16-1/2 12 1-1/8 1.25 13-3/4 10 20 16 1-1/4 1.38 17 12 22 20 1-1/4 1.38 19-1/4 14 23-3/4 20 1-3/8 1.5 20-3/4 16 27 20 1-1/2 1.62 23-3/4 18 29-1/4 20 1-5/8 1.75 25-3/4 20 32 24 1-5/8 1.75 28-1/2 24 37 24 1-7/8 2 33
Nominal Pipe Size NPS (inches) Diameter of Flange (inches) No. of Bolts Diameter of Bolts(inches) Diameter ofBolt Holes (inches) Bolt Circle(inches) 1/2 4-3/4 4 3/4 0.88 3-1/4 3/4 5-1/8 4 3/4 0.88 3-1/2 1 5-7/8 4 7/8 1 4 1-1/4 6-1/4 4 7/8 1 4-3/8 1-1/2 7 4 1 1.12 4-7/8 2 8-1/2 8 7/8 1 6-1/2 2-1/2 9-5/8 8 1 1.12 7-1/2 3 9-1/2 8 7/8 1 7-1/2 4 11-1/2 8 1-1/8 1.25 9-1/4 5 13-3/4 8 1-1/4 1.38 11 6 15 12 1-1/8 1.25 12-1/2 8 18-1/2 12 1-3/8 1.5 15-1/2 10 21-1/2 16 1-3/8 1.5 18-1/2 12 24 20 1-3/8 1.5 21 14 25-1/4 20 1-1/2 1.62 22 16 27-3/4 20 1-5/8 1.75 24-1/2 18 31 20 1-7/8 2 27 20 33-3/4 20 2 2.12 29-1/2 24 41 20 2-1/2 2.62 35-1/2
Nominal Pipe Size NPS (inches) Diameter of Flange (inches) No. of Bolts Diameter of Bolts(inches) Diameter ofBolt Holes (inches) Bolt Circle(inches) 1/2 4-3/4 4 3/4 0.88 3-1/4 3/4 5-1/8 4 3/4 0.88 3-1/2 1 5-7/8 4 7/8 1 4 1-1/4 6-1/4 4 7/8 1 4-3/8 1-1/2 7 4 1 1.12 4-7/8 2 8-1/2 8 7/8 1 6-1/2 2-1/2 9-5/8 8 1 1.12 7-1/2 3 10-1/2 8 1-1/8 1.25 8 4 12-1/4 8 1-1/4 1.38 9-1/2 5 14-3/4 8 1-1/2 1.62 11-1/2 6 15-1/2 12 1-3/8 1.5 12-1/2 8 19 12 1-5/8 1.75 15-1/2 10 23 12 1-7/8 2 19 12 26-1/2 16 2 2.12 22-1/2 14 29-1/2 16 2-1/4 2.38 25 16 32-1/2 16 2-1/2 2.62 27-3/4 18 36 16 2-3/4 2.88 30-1/2 20 38-3/4 16 3 3.12 32-3/4 24 46 16 3-1/2 3.62 39
Nominal Pipe Size NPS (inches) Diameter of Flange (inches) No. of Bolts Diameter of Bolts(inches) Diameter ofBolt Holes (inches) Bolt Circle(inches) 1/2 5-1/4 4 3/4 0.88 3-1/2 3/4 5-1/2 4 3/4 0.88 3-3/4 1 6-1/4 4 7/8 1 4-1/4 1-1/4 7-1/4 4 1 1.12 5-1/8 1-1/2 8 4 1-1/8 1.25 5-3/4 2 9-1/4 8 1 1.12 6-3/4 2-1/2 10-1/2 8 1-1/8 1.25 7-3/4 3 12 8 1-1/4 1.38 9 4 14 8 1-1/2 1.62 10-3/4 5 16-1/2 8 1-3/4 1.88 12-3/4 6 19 8 2 2.12 14-1/2 8 21-3/4 12 2 2.12 17-1/4 10 26-1/2 12 2-1/2 2.62 21-1/4 12 30 12 2-3/4 2.88 24-3/8
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.
