F i t t i n g s 153

NominalPipeSize

FlangeOD

Dia of Bolt

CircleDia of Bolts

No.of

Bolts

Lengthof Studs 1/16 in RaisedFace

BoltLength

Length Thru Hub Thickness

Weld Neck1

SOThreaded

SW1 Lap Joint Blind1

in in in in in in in in in in

1/2 3 1/2 2 3/8 1/2 4 2 1/4 1 3/4 1 7/8 5/8 5/8 7/16

3/4 3 7/8 2 3/4 1/2 4 2 1/4 2 2 1/16 5/8 5/8 1/2

1 4 1/4 3 1/8 1/2 4 2 1/2 2 2 3/16 11/16 11/16 9/16

1 1/4 4 5/8 3 1/2 1/2 4 2 1/2 2 1/4 2 1/4 13/16 13/16 5/8

1 1/2 5 3 7/8 1/2 4 2 3/4 2 1/4 2 7/16 7/8 7/8 11/16

2 6 4 3/4 5/8 4 3 2 3/4 2 1/2 1 1 3/4

2 1/2 7 5 1/2 5/8 4 3 1/4 3 2 3/4 1 1/8 1 1/8 7/8

3 7 1/2 6 5/8 4 3 1/2 3 2 3/4 1 3/16 1 3/16 15/16

3 1/2 8 1/2 7 5/8 8 3 1/2 3 2 13/16 1 1/4 1 1/4 15/16

4 9 7 1/2 5/8 8 3 1/2 3 3 1 5/16 1 5/16 15/16

5 10 8 1/2 3/4 8 3 3/4 3 1/4 3 1/2 1 7/16 1 7/16 15/16

6 11 9 1/2 3/4 8 3 3/4 3 1/4 3 1/2 1 9/16 1 9/16 1

8 13 1/2 11 3/4 3/4 8 4 3 1/2 4 1 3/4 1 3/4 1 1/8

10 16 14 1/4 7/8 12 4 1/2 3 3/4 4 1 15/16 1 15/16 1 3/16

12 19 17 7/8 12 4 1/2 4 4 1/2 2 3/16 2 3/16 1 1/4

14 21 18 3/4 1 12 5 4 1/4 5 2 1/4 3 1/8 1 3/8

16 23 1/2 21 1/4 1 16 5 1/4 4 1/2 5 2 1/2 3 7/16 1 7/16

18 15 22 3/4 1 1/8 16 5 3/4 4 3/4 5 1/2 2 11/16 3 13/16 1 9/16

20 17 1/2 25 1 1/8 20 6 5 1/4 5 11/16 2 7/8 1 11/16

22 29 1/2 27 1/4 1 1/4 20 6 1/2 5 1/2 5 7/8 3 1/8 1 13/16

24 32 29 1/2 1 1/4 20 6 3/4 5 3/4 6 3 1/4 1 7/8

26 34 1/4 31 3/4 1 1/4 24 7 6 5 3 3/8 2

30 38 3/4 36 1 1/4 28 7 1/4 6 1/4 5 1/8 3 1/2 2 1/8

34 43 3/4 40 1/2 1 1/2 32 8 7 5 5/16 3 11/16 2 5/16

36 46 42 3/4 1 1/2 32 8 1/4 7 5 3/8 3 3/4 2 3/8

42 53 49 1/2 1 1/2 36 8 3/4 7 1/2 5 5/8 4 2 5/8

1 The 1/16” raised face is included in the “Length thru Hub” dimension of the Weld Neck (WN), Slip On (SO), Threaded, and Socket Weld (SW) flange, and also in the “Thickness” dimension of the Blind flange.

TABLE 7.2 ANSI B16.5 Flange dimensions for 150 lb flanges. Bolting arrangement for 125 lb cast iron (ANSI B 16.1) flanges are the same as for 150 lb ANSI B16.5 steel flanges.

154 C h a p t e r 7

NominalPipeSize

FlangeOD

Diamof Bolt Circle

Diamof

BoltsNo. of Bolts

Lengthof

Studs1/16”RaisedFace

BoltLength

Length Thru Hub Thickness

Weld Neck1

SOThreaded

SW1 Lap Joint Blind1

in in in in in in

1/2 3 3/4 2 5/8 1/2 4 2 1/2 2 2 1/16 7/8 7/8 9/16

3/4 4 5/8 3 1/4 5/8 4 2 3/4 2 1/2 2 1/4 1 1 5/8

1 4 7/8 3 1/2 5/8 4 3 25 1/2 2 7/16 1 1/16 1 1/16 11/16

1 1/4 5 1/4 3 7/8 5/8 4 3 2 3/4 2 9/16 1 1/16 1 1/16 3/4

1 1/2 6 1/8 4 1/2 3/4 4 3 1/2 3 2 11/16 1 3/16 1 3/16 13/16

2 6 1/2 5 5/8 8 3 1/4 3 2 3/4 1 5/16 1 5/16 7/8

2 1/2 7 1/2 5 7/8 3/4 8 3 3/4 3 1/4 3 1 1/2 1 1/2 1

3 8 1/4 6 5/8 3/4 8 4 3 1/2 3 1/8 1 11/16 1 11/16 1 1/8

3 1/2 9 7 1/4 3/4 8 4 1/4 3 3/4 3 3/16 1 3/4 1 3/4 1 3/16

4 10 7 7/8 3/4 8 4 1/4 3 3/4 3 3/8 1 7/8 1 7/8 1 1/4

5 11 9 1/4 3/4 8 4 1/2 4 3 7/8 2 2 1 3/8

6 12 1/2 10 5/8 3/4 12 4 3/4 4 1/4 3 7/8 2 1/16 2 1/16 1 7/16

8 15 13 7/8 12 5 1/4 4 3/4 4 3/8 2 7/16 2 7/16 1 5/8

10 17 1/2 15 1/4 1 16 6 5 1/4 4 5/8 2 5/8 3 3/4 1 7/8

12 20 1/2 17 3/4 1 1/8 16 6 1/2 5 3/4 5 1/8 2 7/8 4 2

14 23 20 1/4 1 1/8 20 6 3/4 6 5 5/8 3 4 3/8 2 1/8

16 25 1/2 22 1/2 1 1/4 20 7 1/4 6 1/2 5 3/4 3 1/4 4 3/4 2 1/4

18 28 24 3/4 1 1/4 24 7 1/2 6 3/4 6 1/4 3 1/2 5 1/8 2 3/8

20 30 1/2 27 1 1/4 24 8 7 6 3/8 3 3/4 5 1/2 2 1/2

22 33 29 1/4 1 1/2 24 8 3/4 7 1/2 6 1/2 4 6 2 5/8

24 36 32 1 1/2 24 9 7 3/4 6 5/8 4 3/16 2 3/4

26 38 1/4 34 1/2 1 5/8 28 10 8 3/4 7 1/4 7 1/4 3 1/8

30 43 39 1/4 1 3/4 28 11 1/4 10 8 1/4 8 1/4 3 5/8

34 47 1/2 43 1/2 1 7/8 28 12 1/4 10 3/4 9 1/8 9 1/8 4

36 50 46 2 32 12 3/4 11 1/4 9 1/2 9 1/2 4 1/8

42 57 52 3/4 2 36 13 3/4 13 1/2 10 7/8 10 7/8 4 5/8

1 The 1/16” raised face is included in the “Length thru Hub” dimension of the Weld Neck (WN), Slip On (SO), Threaded, and Socket Weld (SW) flange, and also in the “Thickness” dimension of the Blind flange.

TABLE 7.3 ANSI B16.5 Flange dimensions for 300 lb flanges. Bolting arrangement for 250 lb cast iron (ANSI B 16.1) flanges are the same as for 300 lb ANSI B16.5 steel flanges.

F i t t i n g s 155

NominalPipe Size

FlangeOD

Diamof Bolt Circle

Diamof

BoltsNo. of Bolts

Lengthof

Studs1/4”

RaisedFace

Length Thru Hub Thickness

Weld Neck1

SOThreaded

SW1 Lap Joint Blind1

in in in in in in in in in

1/2 3 3/4 2 5/8 1/2 4 3

Use 600 lb

3/4 4 5/8 3 1/4 5/8 4 3 1/4

1 4 7/8 3 1/2 5/8 4 3 1/2

1 1/4 5 1/4 3 7/8 5/8 4 3 3/4

1 1/2 6 1/8 4 1/2 3/4 4 4

2 6 1/2 5 5/8 8 4

2 1/2 7 1/2 5 7/8 3/4 8 4 1/2

3 8 1/4 6 5/8 3/4 8 4 3/4

3 1/2 9 7 1/4 7/8 8 5 1/4

4 10 7 7/8 7/8 8 5 1/4 3 1/2 2 2 1 3/8

5 11 9 1/4 7/8 8 6 1/2 4 2 1/8 2 1/8 1 1/2

6 12 1/2 10 5/8 7/8 12 5 3/4 4 1/16 2 1/4 2 1/4 1 5/8

8 15 13 1 12 6 1/2 4 5/8 2 11/16 2 11/16 1 7/8

10 17 1/2 15 1/4 1 1/8 16 7 1/4 4 7/8 2 7/8 4 2 1/8

12 20 1/2 17 3/4 1 1/4 16 7 3/4 5 3/8 3 1/8 4 1/4 2 1/4

14 23 20 1/4 1 1/4 20 8 5 7/8 3 5/16 4 5/8 2 3/8

16 25 1/2 22 1/2 1 3/8 20 8 1/2 6 3 11/16 5 2 1/2

18 28 24 3/4 1 3/8 24 8 3/4 6 1/2 3 7/8 5 3/8 2 5/8

20 30 1/2 27 1 1/2 24 9 1/2 6 5/8 4 5 3/4 2 3/4

22 33 29 1/4 1 5/8 24 10 6 3/4 4 1/4 2 7/8

24 36 32 1 3/4 24 10 1/2 6 7/8 4 1/2 6 1/4 3

26 38 1/4 34 1/2 1 3/4 28 11 1/2 7 5/8 7 5/8 3 1/2

30 43 39 1/4 2 28 13 8 5/8 8 5/8 4

34 47 1/2 43 1/2 2 28 13 3/4 9 1/2 9 1/2 4 3/8

36 50 46 2 32 14 9 7/8 9 7/8 4 1/2

42 57 52 3/4 2 1/2 36 16 1/4 11 3/8 11 3/8 5 1/8

1 The 1/16” raised face is included in the “Length thru Hub” dimension of the Weld Neck (WN), Slip On (SO), Threaded, and Socket Weld (SW) flange, and also in the “Thickness” dimension of the Blind flange.

TABLE 7.4 ANSI B16.5 Flange dimensions for 400 lb flanges.

156 C h a p t e r 7

NominalPipeSize

FlangeOD

Diamof Bolt Circle

Diam of Bolts

No. of Bolts

Lengthof Studs

1/4”RaisedFace

Length Thru Hub Thickness

Weld Neck1

SOThreaded

SW1 Lap Joint1 Blind1

in in in in in in in in in

1/2 3 3/4 2 5/8 1/2 4 3 2 1/16 7/8 7/8 9/16

3/4 4 5/8 3 1/4 5/8 4 3 1/4 2 1/4 1 1 5/8

1 4 7/8 3 1/2 5/8 4 3 1/2 2 7/16 1 1/16 1 1/6 11/16

1 1/4 5 1/4 3 7/8 5/8 4 3 3/4 2 5/8 1 1/8 1 1/8 13/16

1 1/2 6 1/8 4 1/2 3/4 4 4 2 3/4 1 1/4 1 1/4 7/8

2 6 1/2 6 5/8 8 4 2 7/8 1 7/16 1 7/16 1

2 1/2 7 1/2 5 7/8 3/4 8 4 1/2 3 1/8 1 5/8 1 5/8 1 1/8

3 8 1/4 6 5/8 3/4 8 4 3/4 3 1/4 1 13/16 1 13/16 1 1/4

3 1/2 9 7 1/4 7/8 8 5 1/4 3 3/8 1 15/16 1 15/16 1 3/8

4 10 3/4 8 1/2 7/8 8 5 1/2 4 2 1/8 2 1/8 1 1/2

5 13 10 1/2 1 8 6 1/4 4 1/2 2 3/8 2 3/8 1 3/4

6 14 11 1/2 1 12 6 1/2 4 5/8 2 5/8 2 5/8 1 7/8

8 16 1/2 13 3/4 1 1/8 12 7 1/2 5 1/4 3 3 2 3/16

10 20 17 1 1/4 16 8 1/4 6 3 3/8 4 3/8 2 1/2

12 22 19 1/4 1 1/4 20 8 1/2 6 1/8 3 5/8 4 5/8 2 5/8

14 23 3/4 20 3/4 1 3/8 20 9 6 1/2 3 11/16 5 2 3/4

16 27 23 3/4 1 1/2 20 9 3/4 7 4 3/16 5 1/2 3

18 29 1/4 25 3/4 1 5/8 20 10 1/2 7 1/4 4 5/8 6 3 1/4

20 32 28 1/2 1 5/8 24 11 1/4 7 1/2 5 6 1/2 3 1/2

22 34 1/4 30 5/8 1 3/4 24 12 7 3/4 5 1/4 3 3/4

24 37 33 1 7/8 24 12 3/4 8 5 1/2 7 1/4 4

26 40 36 1 7/8 28 13 1/4 8 3/4 8 3/4 4 1/4

30 44 1/2 40 1/4 2 28 14 9 3/4 9 3/4 4 1/2

34 49 44 1/2 2 1/4 28 15 10 5/8 10 5/8 4 3/4

36 51 3/4 47 2 1/2 28 15 3/4 11 1/8 11 1/8 4 7/8

42 58 3/4 53 3/4 2 3/4 28 17 1/2 12 3/4 5 1/2

1 The 1/16” raised face is included in the “Length thru Hub” dimension of the Weld Neck (WN), Slip On (SO), Threaded, and Socket Weld (SW) flange, and also in the “Thickness” dimension of the Blind flange.

TABLE 7.5 ANSI B16.5 Flange dimensions for 600 lb flanges.

F i t t i n g s 157

Pressure Class 25 125 250 800

Material ASTM A 126 ASTM A 126 ASTM A 126ASTMA 126

Class A A B A B BNPS (in) 4-36 42-96 1-12 1-12 14-24 30-48 1-12 1-12 14-24 30-48 2-12

Service Temp(°F)

Maximum Non-Shock Pressure(psig)

-20 to 150 45 25 175 200 150 150 400 500 300 300 800

200 40 25 165 190 135 115 370 460 280 250

225 35 25 155 180 130 100 355 440 270 225

250 30 25 150 175 125 85 340 415 260 200

275 25 25 145 170 120 65 325 395 250 175

300 140 165 110 50 310 375 240 150

325 130 155 105 295 355 230 125

375 145 265 315 210

425 130 270

450 125 250

Limitations:

Class 25: Maxi mum pressure shall be limited to 25 psig when Class 25 cast iron flanges and flanged fittings are used for gaseous service. Tabulated pressure-temperature ratings above 25 psig for Class 25 cast iron flanges and flanged fittings are applicable for non-shock hydraulic service only.

Class 250: When used for liquid service the tabulated pressure-temperature ratings in sizes 14 in and larger are applicable to Class 250 flanges only and not to Class 250 fittings.

Class 800: The tabulated rating is not a steam rating and applies to non-shock hydraulic pressure only.

TABLE 7.6 ANSI B16.1 Cast Iron Flange Temperature and Pressure Ratings.

Pressure Class 150 300 400 600 900 1500 2500PN Number 20 50 68 100 150 250 420

Service Temperature

(°F)

Maximum Non-Shock Pressure(psig)

100 285 740 990 1480 2200 3705 6170

200 260 675 900 1350 2025 3375 5625

300 230 655 875 1315 1970 3280 5470

400 200 635 845 1270 1900 3170 5280

500 170 600 800 1200 1795 2995 4990

600 140 550 730 1095 1640 2735 4560

650 125 535 715 1075 1610 2685 4475

700 110 535 710 1065 1600 2665 4440

750 95 505 670 1010 1510 2520 4200

800 NOT RECOMMENDED ABOVE 800

TABLE 7.7 ANSI B16.5 Temperature and Pressure Ratings for ASTM A105 Carbon Steel Flange.

158 C h a p t e r 7

Pressure classes of cast iron flanges are established by ANSI B16.1. These are rated at Classes 25,125, 250, and 800. The Class 125 flanges are always flat faced , and can be mated to 150 lb steel flanges. When this is done, there are two choices to prevent the cast iron flange from cracking due to the stress of bolting to a raised face flange:

1. Use low-strength bolting (less than 30 ksi minimum yield strength).

2. Machine off the raised face of the steel mating flange, and use a full face gasket as shown in Figure 7.1 with intermediate or high-strength bolts.

The same holds true for mating Class 250 cast iron flanges with 300 lb steel raised face flanges . Class 250 CI flanges have a raised face, and according to ANSI B16.5, both mating flange faces should be machined flat. In practice, sometimes you will see Class 250 CI raised face flanges installed against Class 300 steel flanges with ring gaskets as shown in Figure 7.2 and no machining. In these cases, the low-strength bolting should be used.

Most of what the average engineer deals with is at moderate temperatures and pressures, say up to 300°F and 200 psig. That is, it falls into the realm of Class 150, ASTM A105 flanges.

But sometimes we are faced with more demanding services, whether they are related to elevated temperatures, pressures, or corrosive fluids that require different metallurgy. In those cases, the reader is advised to obtain access to ANSI B16.5 (or B16.47) to determine the pressure rating at the particular temperature for that service. Do not rely on tables gleaned from generic sources, since these tend to generalize the term “carbon steel.” Carbon steel covers a lot of territory, and the difference in pressure rating for Class 300 flanges at 100°F can swing from 620 to 750 psig. Some tables list pressures for carbon steel flanges up to 1000°F, but ANSI B16.5 suggests that carbon steels not be used above 800°F. At those elevated temperatures, higher grades of stainless or the Group 3 nickel-molybdenum alloys should be used.