How to Identify and Measure Fittings
Pipe size is an industry designation, not the actual size. View information about how to measure threaded and unthreaded pipe and pipe fittings.
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FM-Approved Low-Pressure Cast Iron Threaded Pipe Flanges
Suitable for use in fire-protection applications, these flanges are brittle and can be quickly opened with the strike of a sledge hammer. Bolt two flanges of the same size together with a gasket (sold separately) to create an access point within a line. Use in noncorrosive environments.
Reducing flanges transition your system to a smaller pipe size. Attach them to a flange with a larger pipe size but with the same flange dimensions.
- For Use With: Air, Natural Gas, Oil, Steam, Water
- Specifications Met:
3/4 Pipe Size: ASME B1.20.1, ASME B16.1, ASTM A126, FM Approved
All other sizes: ASME B1.20.1, ASME B16.1, ASTM A126, FM Approved, UL Listed - Pipe Nipples and Pipe: Use Schedule 40 steel
- Fittings: Use Class 125 iron and steel
Bolt Hole | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Pipe Size  | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Max. Pressure | Max. Steam Pressure | Material | Each | |
NPT | ||||||||||
| 3/4 | 3 7/8" | 1/2" | 5/8" | 4 | 2 3/4" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
| 1 | 4 1/4" | 1/2" | 5/8" | 4 | 3 1/8" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 00000 |
| 1 1/4 | 4 5/8" | 1/2" | 5/8" | 4 | 3 1/2" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 00000 |
| 1 1/2 | 5" | 1/2" | 5/8" | 4 | 3 7/8" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 00000 |
| 2 | 6" | 5/8" | 3/4" | 4 | 4 3/4" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 00000 |
| 2 1/2 | 7" | 5/8" | 3/4" | 4 | 5 1/2" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 00000 |
| 3 | 7 1/2" | 5/8" | 3/4" | 4 | 6" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 00000 |
| 4 | 9" | 5/8" | 3/4" | 8 | 7 1/2" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
| 5 | 10" | 3/4" | 7/8" | 8 | 8 1/2" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
| 6 | 11" | 3/4" | 7/8" | 8 | 9 1/2" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
| 8 | 13 1/2" | 3/4" | 7/8" | 8 | 11 3/4" | 125 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
- For Use With: Air, Natural Gas, Oil, Steam, Water
- Specifications Met: ASME B1.20.1, ASME B16.1, ASTM A126, ASTM A153, FM Approved
- Pipe Nipples and Pipe: Use Schedule 40 iron and steel
- Fittings: Use Class 125 iron and steel
Bolt Hole | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Pipe Size | For Flange Pipe Size | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Max. Pressure | Max. Steam Pressure | Material | Each | |
NPT | |||||||||||
| 2 | 2 1/2 | 7" | 5/8" | 3/4" | 4 | 5 1/2" | 175 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
| 2 | 3 | 7 1/2" | 5/8" | 3/4" | 4 | 6" | 175 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
| 2 | 4 | 9" | 5/8" | 3/4" | 8 | 7 1/2" | 175 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
| 3 | 4 | 9" | 5/8" | 3/4" | 8 | 7 1/2" | 175 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
| 4 | 6 | 11" | 3/4" | 7/8" | 8 | 9 1/2" | 175 psi @ 72° F | 125 psi @ 350° F | Iron | 000000000 | 000000 |
Low-Pressure Steel Threaded Pipe Flanges
Use these flanges for low-pressure applications in noncorrosive environments. Bolt two flanges of the same size together with a gasket (sold separately) to create an access point within a line.
- For Use With: Air, Natural Gas, Oil, Steam, Water
- Pressure Class: 150
- Specifications Met:
NPT: ASME B16.5, ASTM A105, MSS SP-25
BSPT: ASTM A105 - Fittings: Use Class 125 or 150 iron and steel
- Pipe Nipples and Pipe: Use Schedule 40 steel
Bolt Hole | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Pipe Size | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Max. Pressure | Max. Steam Pressure | Material | Each | |
BSPT | ||||||||||
| 1/2 | 3 1/2" | 1/2" | 5/8" | 4 | 2 3/8" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 000000 |
| 3/4 | 3 7/8" | 1/2" | 5/8" | 4 | 2 3/4" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 00000 |
| 1 | 4 1/4" | 1/2" | 5/8" | 4 | 3 1/8" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 00000 |
| 1 1/4 | 4 5/8" | 1/2" | 5/8" | 4 | 3 1/2" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 00000 |
| 1 1/2 | 5" | 1/2" | 5/8" | 4 | 3 7/8" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 00000 |
| 2 | 6" | 5/8" | 3/4" | 4 | 4 3/4" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 000000 |
| 2 1/2 | 7" | 5/8" | 3/4" | 4 | 5 1/2" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 000000 |
| 3 | 7 1/2" | 5/8" | 3/4" | 4 | 6" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 000000 |
| 4 | 9" | 5/8" | 3/4" | 8 | 7 1/2" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 000000 |
| 6 | 11" | 3/4" | 7/8" | 8 | 9 1/2" | 285 psi @ 72° F | 230 psi @ 300° F | Steel | 0000000 | 000000 |
FM-Approved Low-Pressure Cast Iron Unthreaded Pipe Flanges
- For Use With: Air, Diesel Fuel, Gasoline, Natural Gas, Oil, Steam, Water
- Pressure Class: 125
- Specifications Met: ASME B1.20.1, ASME B16.1, ASTM A126, FM Approved
- Pipe Nipples and Pipe: Use Schedule 40 steel
- Fittings: Use Class 125 or 150 iron and steel
FM-approved for fire protection applications, these flanges are cast iron, so they're brittle and can be quickly opened by hitting them with a sledge hammer. Bolt them together with a gasket (not included) to create an access point within a low-pressure pipe line. All are cap flanges, which are also known as blind flanges. Use them in noncorrosive environments.
Bolt Hole | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Pipe Size | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Max. Pressure | Max. Steam Pressure | Each | |
| 1 | 4 1/4" | 1/2" | 5/8" | 4 | 3 1/8" | 200 psi @ 72° F | 165 psi @ 300° F | 0000000 | 000000 |
| 1 1/2 | 5" | 1/2" | 5/8" | 4 | 3 7/8" | 200 psi @ 72° F | 165 psi @ 300° F | 0000000 | 00000 |
| 2 | 6" | 5/8" | 3/4" | 4 | 4 3/4" | 200 psi @ 72° F | 165 psi @ 300° F | 0000000 | 00000 |
| 2 1/2 | 7" | 5/8" | 3/4" | 4 | 5 1/2" | 200 psi @ 72° F | 165 psi @ 300° F | 0000000 | 00000 |
| 3 | 7 1/2" | 5/8" | 3/4" | 4 | 6" | 200 psi @ 72° F | 165 psi @ 300° F | 0000000 | 00000 |
| 3 1/2 | 8 1/2" | 5/8" | 3/4" | 8 | 7" | 200 psi @ 72° F | 165 psi @ 300° F | 0000000 | 000000 |
| 4 | 9" | 5/8" | 3/4" | 8 | 7 1/2" | 200 psi @ 72° F | 165 psi @ 300° F | 0000000 | 000000 |
| 6 | 11" | 3/4" | 7/8" | 8 | 9 1/2" | 200 psi @ 72° F | 165 psi @ 300° F | 0000000 | 000000 |