CLASS 25 CAST IRON FLANGES DIMENSIONS CHART


Flanges, bolt holes and bolting dimensions chart of class 25 cast iron flanges per ASME B16.1.


Class 25 Cast Iron Flanges
Flange Dimensions (inches)
NPS Flanges Hub
O Qmin  Xmin Ymin
4 9.00 0.75 5.31 1.31
5 10.00 0.75 6.44 1.44
6 11.00 0.75 7.56 1.56
8 13.50 0.75 9.69 1.75
10 16.00 0.88 11.94 1.94
12 19.00 1.00 14.06 2.19
14 21.00 1.12 15.37 2.25
16 23.50 1.12 17.50 2.50
18 25.00 1.25 19.62 2.69
20 27.50 1.25 21.75 2.88
24 32.00 1.38 26.00 3.25
30 38.75 1.50 - -
36 46.00 1.62 - -
42 53.00 1.75 - -
48 59.50 2.00 - -
54 66.25 2.25 - -
60 73.00 2.25 - -
72 86.50 2.50 - -
84 99.75 2.75 - -
96 113.25 3.00 - -

Notes:

NPS - Nominal Pipe Size, O - Diameter, Q - Thickness, X - Hub Diameter, Y - Hub Length

Bolt Holes and Bolting Dimensions (inches)
NPS Bolt Holes Bolting
Dia. of
Bolt
Circle
Dia. of
Bolt
Holes
Number
of
Bolts
Dia.
of
Bolts
Length
of
Bolts
4 7.50 0.75 8 0.62 2.50
5 8.50 0.75 8 0.62 2.50
6 9.50 0.75 8 0.62 2.50
8 11.75 0.75 8 0.62 2.50
10 14.25 0.75 12 0.62 3.00
12 17.00 0.75 12 0.62 3.00
14 18.75 0.88 12 0.75 3.50
16 21.25 0.88 16 0.75 3.50
18 22.75 0.88 16 0.75 4.00
20 25.00 0.88 20 0.75 4.00
24 29.50 0.88 20 0.75 4.00
30 36.00 1.00 28 0.88 4.50
36 42.75 1.00 32 0.88 5.00
42 49.50 1.12 36 1.00 5.50
48 56.00 1.12 44 1.00 6.00
54 62.75 1.12 44 1.00 6.50
60 69.25 1.25 52 1.12 6.50
72 82.50 1.25 60 1.12 7.00
84 95.50 1.38 64 1.25 7.50
96 108.50 1.38 68 1.25 8.00

Reference:

  • ASME B16.1-1998, Cast Iron Pipe Flanges and Flanged Fittings - Classes 25, 125, and 250