Dimensions of Class Flanges:- Class 300 & Class 150
This diagram illustrated the arrangement but not necessarily the correct number of bolt holes.
Refer to the column 'Bolting number' in the table for the actual number.
For raised face diameter and different types of flange faces see: Dimensions of Steel Flange Faces
 
Dimensions of Class 150 Flanges
 
Nominal
Size

DN        in

Mating
Dimensions
                         
Outside
Diameter
D [mm]
Diameter of
Bolt Circle
K [mm]
Diameter of
Bolt Hole
L    in (mm)
Bolting
Number
Bolting
Size
[in]
Flange
Thickness
C [mm]

15

1/2
95 66.7 5/8       (15.9) 4 1/2 14.3
20
3/4
117 82.6 3/4      (19.0) 4 5/8 15.9
25
1
124 88.9 3/4     (19.0) 4 5/8 17.5
40
1 1/2
156 114.3 7/8     (22.2) 4 3/4 20.6
50
2
165 127.0 3/4     (19.0) 8 5/8 22.2
65
2 1/2
190 149.2 7/8     (22.2) 8 3/4 25.4
80
3
210 168.3 7/8     (22.2) 8 3/4 28.6
100
4
254 200.0 7/8     (22.2) 8 3/4 31.8
125
5
279 235.0 7/8     (22.2) 8 3/4 34.9
150
6
318 269.9 7/8     (22.2) 12 3/4 36.5
200
8
381 330.2 1        (25.4) 12 7/8 41.3
250
10
444 387.4 1 1/8   (28.6) 16 1 47.6
300
12
521 450.8 1 1/4   (31.8) 16 1 1/8 50.8
350
14
584 514.4 1 1/4   (31.8) 20 1 1/8 54.0
400
16
648 571.5 1 3/8   (34.9) 20 1 1/4 57.2