CLASS 250 CAST IRON FLANGES DIMENSIONS CHART


Flanges, bolt holes and bolting dimensions chart of class 250 cast iron flanges per ASME B16.1.


Class 250 Cast Iron Flanges
Flange Dimensions (inches)
NPS Flanges Blind
Flanges Note 1
Hubs
O Qmin  W I V Xmin Ymin Tmin
1 4.88 0.69 2.69 1.00 - 2.06 0.88 0.68
1 1/4 5.25 0.75 3.06 1.25 - 2.50 1.00 0.81
1 1/2 6.12 0.81 3.56 1.50 - 2.75 1.12 0.87
2 6.50 0.88 4.19 2.00 - 3.31 1.25 1.00
2 1/2 7.50 1.00 4.94 2.50 - 3.94 1.43 1.13
3 8.25 1.12 5.69 3.00 - 4.62 1.56 1.19
3 1/2 9.00 1.19 6.31 3.50 - 5.25 1.62 1.25
4 10.00 1.25 6.94 4.00 - 5.75 1.75 1.31
5 11.00 1.38 8.31 5.00 - 7.00 1.88 1.44
6 12.50 1.44 9.69 6.00 - 8.12 1.94 1.56
8 15.00 1.62 11.94 8.00 - 10.25 2.19 1.75
10 17.50 1.88 14.06 10.00 0.94 12.62 2.38 1.94
12 20.50 2.00 16.44 12.00 1.00 14.75 2.56 2.19
14 23.00 2.12 18.94 13.25 1.12 16.25 2.69 2.25
16 25.50 2.25 21.06 15.25 1.25 18.38 2.88 2.50
18 28.00 2.38 23.31 17.00 1.38 - - -
20 30.50 2.50 25.56 19.00 1.50 - - -
24 36.00 2.75 30.31 23.00 1.62 - - -
30 43.00 3.00 37.19 29.00 2.00 - - -

Notation: NPS - Nominal Pipe Size, O - Diameter of flange, Q - Thickness of flange, W= Diameter of Raised Face, I - Diameter of Port, V - Wall thickness,  I - Diameter of Port, V - Wall Thickness, X - Hub Diameter, Y - Length through hub,  T = Length of Threads

Note 1: All blind flanges for NPS 10 and larger must be dished with inside radius equal to the port diameter.


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 Note 2
Length
of
Stud
Bolt Note 2
1 3.50 0.75 4 0.62 2.50 -
1 1/4 3.88 075 4 0.62 2.50 -
1 1/2 4.50 0.88 4 0.75 3.00 -
2 5.00 0.75 8 0.62 3.00 -
2 1/2 5.88 0.88 8 0.75 3.50 -
3 6.62 0.88 8 0.75 3.50 -
3 1/2 7.25 0.88 8 0.75 3.50 -
4 7.88 0.88 8 0.75 4.00 -
5 9.25 0.88 8 0.75 4.00 -
6 10.62 0.88 12 0.75 4.00 -
8 13.00 1.00 12 0.88 4.50 -
10 15.25 1.12 16 1.00 5.50 -
12 17.75 1.25 16 1.12 5.50 -
14 20.25 1.25 20 1.12 6.00 -
16 22.50 1.38 20 1.25 6.50 -
18 24.75 1.38 24 1.25 6.50 -
20 27.00 1.38 24 1.25 7.00 -
24 32.00 1.62 24 1.50 7.50 9.50
30 39.25 2.00 28 1.75 8.50 10.50

Note 2: When bolting to steel flanges, longer bolts or studs shall be used.


Reference:

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