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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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High-Pressure Steel Unthreaded Pipe Flanges
Forged for extra strength, these heavy duty flanges can withstand high-pressure applications. Bolt two flat-surface flanges or two raised-surface flanges of the same size together with a gasket (sold separately) to create an access point in a pipe line.
Slip-on weld flanges have no internal stop; slide a pipe through the flange and weld on both sides.
Cap flanges are also known as blind flanges.
For technical drawings and 3-D models, click on a part number.
Slip-On Weld Flanges

Front

Raised Surface on Back
- For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
- Pressure Class: See table
- Specifications Met: ASTM A105, ASME B16.5
- Certification: Material Certificate with Traceable Lot Number and Test Report
- Pipe Nipples and Pipe: Use Schedule 80 steel
- Fittings: Use Class 3000 and Schedule 80 steel
Bolt Hole | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Pipe Size | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Max. Pressure | Max. Steam Pressure | Material | Each | |
Pressure Class 300 | ||||||||||
12 | 20 1/2" | 1 1/4" | 1 1/4" | 16 | 17 3/4" | 600 psi @ 72° F | 300 psi @ 300° F | Steel | 00000000 | 0000000 |
Caps

Front

Raised Surface on Back
- For Use With: Air, Hydraulic Fluid, Natural Gas, Oil, Steam, Water
- Pressure Class: See table
- Specifications Met: ASTM A105, ASME B16.5
- Certification: Material Certificate with Traceable Lot Number and Test Report
- Pipe Nipples and Pipe: Use Schedule 80 steel
- Fittings: Use Class 3000 and Schedule 80 steel
Bolt Hole | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Pipe Size | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Max. Pressure | Max. Steam Pressure | Material | Each | |
Pressure Class 300 | ||||||||||
12 | 20 1/2" | 1 1/4" | 1 1/4" | 16 | 17 3/4" | 600 psi @ 72° F | 300 psi @ 300° F | Steel | 00000000 | 0000000 |