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ANSI Flange Dimensions

Flange Standards
The most common flange standard in the oil and gas industry is arguably American National Standards Institute (ANSI) B16.5.
Other standards are used, e.g.
- British Imperial flanges BS 10,
- Metric flanges SABS 1123, BS 4504, DIN 2501,
- Japanese and Korean flanges JIS-B-2212, JIS-B-2214 & KS-B-1503
 
ANSI B16.5. Flange Dimensions
The following tables provide flange dimensions, diameters and drillings for the most common sizes and ratings.
 
ANSI 150#
Pipe NBBolt PCDNo. of BoltsBolt SizeFlange OD
1/2"2 3/8"41/2"3 1/2"
1"3 1/8"41/2"4 1/4"
2"4 3/4"45/8"6"
4"7 1/2"85/8"9"
6"9 1/2"83/4"11"
8"11 3/4"83/4"13 1/2"
10"14 1/4"127/8"16"
12"17 "127/8"19"
14"18 3/4"121"21"

ANSI 300#
Pipe NBBolt PCDNo. of BoltsBolt SizeFlange OD
1/2"2 5/8"41/2"3 3/4"
1"3 1/2"45/8"4 7/8"
2"5"85/8"6 1/2"
4"7 7/8"83/4"10"
6"10 5/8"123/4"12 1/2"
8"13"127/8"15"
10"15 1/4"161"17 1/2"
12"17 3/4"161 1/8"20 1/2"
14"20 1/4"201 1/8"23"

ANSI 600#
Pipe NBBolt PCDNo. of BoltsBolt SizeFlange OD
1/2"2 5/8"41/2"3 3/4"
1"3 1/2"45/8"4 7/8"
2"5"85/8"6 1/2"
4"8 1/2"87/8"10 3/4"
6"11 1/2"121"14"
8"13 3/4"121 1/8"16 1/2"
10"17"161 1/4"20"
12"19 1/4"201 1/4"22"
14"20 3/4"201 3/8"23 3/4"

ANSI 900#
Pipe NBBolt PCDNo. of BoltsBolt SizeFlange OD
2" *6 1/2"87/8"8 1/2"
4"9 1/4"81 1/8"11 1/2"
6"12 1/2"121 1/8"15"
8"15 1/2"121 3/8"18 1/2"
10"18 1/2"161 3/8"21 1/2"
12"21"201 3/8"24"
14"22"201 1/2"25 1/4"
* 2" Class 1500 is used for 2" Class 900

ANSI 1500#
Pipe NB Bolt PCD No. of Bolts Bolt Size Flange OD
2" 6 1/2" 8 7/8" 8 1/2"
4" 9 1/2" 8 1 1/4" 12 1/4"
6" 12 1/2" 12 1 3/8" 15 1/2"
8" 15 1/2" 12 1 5/8" 19"

Flange Class Equivalents
The above tables reveal the following equivalences:
- Classes 300 & 600 for sizes 1/2", 3/4" and 1"
- Classes 900 to 1500 for sizes 1/2" to 2 1/2"

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Further Reading

Flange Fittings and Piping Data
 
Pocket Guide to Flanges, Fittings & Piping Data
 

 

 
Piping Engineering Leadership for Process Plant Projects
 

 

 
Piping Handbook
Pipe flanges
 

C&I Resources

 
ATEX
Cable Gland Selector
CE Marking
Flange Dimensions
Ingress Protection
Pipe Schedules
Relief Valve Orifice Size
Temperature Class
Temperature Conversion
Thermocouple Types
Valve Leakage
Vortex Meters
Wires and Cables
 

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