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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Low-Pressure Stainless Steel Unthreaded Pipe Flanges
Bolt two flat-surface flanges or two raised-surface flanges of the same size together with a
Slip-on weld flanges have no internal stop; slide a pipe through the flange and weld on both sides. Cast flanges are also called MSS flanges.
304 stainless steel flanges offer very good corrosion resistance, and 316 stainless steel flanges have excellent corrosion resistance.
For technical drawings and 3-D models, click on a part number.
- For Use With: Air, Water, Natural Gas, Oil
- Pressure Class: 150
- Specifications Met: MSS SP-51, ASTM A351
- Fittings: Use schedule 40 stainless steel
- Pipe Nipples and Pipe: Use Schedule 40 stainless steel
Bolt Hole | 304 Stainless Steel | 316 Stainless Steel | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Pipe Size  | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Max. Pressure | Each | Each | ||
| 1/2 | 3 1/2" | 1/2" | 5/8" | 4 | 2 3/8" | 230 psi @ 72° F | 000000000 | 000000 | 000000000 | 000000 |
| 3/4 | 3 7/8" | 1/2" | 5/8" | 4 | 2 3/4" | 230 psi @ 72° F | 000000000 | 00000 | 000000000 | 00000 |
| 1 | 4 1/4" | 1/2" | 5/8" | 4 | 3 1/8" | 230 psi @ 72° F | 000000000 | 00000 | 000000000 | 00000 |
| 1 1/4 | 4 5/8" | 1/2" | 5/8" | 4 | 3 1/2" | 230 psi @ 72° F | 000000000 | 00000 | 000000000 | 00000 |
| 1 1/2 | 5" | 1/2" | 5/8" | 4 | 3 7/8" | 230 psi @ 72° F | 000000000 | 00000 | 000000000 | 000000 |
| 2 | 6" | 5/8" | 3/4" | 4 | 4 3/4" | 230 psi @ 72° F | 000000000 | 00000 | 000000000 | 000000 |
| 2 1/2 | 7" | 5/8" | 3/4" | 4 | 5 1/2" | 230 psi @ 72° F | 000000000 | 000000 | 000000000 | 000000 |
| 3 | 7 1/2" | 5/8" | 3/4" | 4 | 6" | 230 psi @ 72° F | 000000000 | 000000 | 000000000 | 000000 |
Low-Pressure Stainless Steel Threaded Pipe Flanges
Also known as Pressure Class 150 flanges, these are designed for low-pressure pipe 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 within a line.
304 stainless steel flanges have very good corrosion resistance. 316 stainless steel flanges have excellent corrosion resistance. Cast flanges are also called MSS flanges.
For technical drawings and 3-D models, click on a part number.
- For Use With: Natural Gas, Steam, Oil, Water, Air
- Pressure Class: 150
- Specifications Met: MSS SP-51, ASTM A351, MSS SP-42
- Pipe Nipples and Pipe: Use Schedule 40 stainless steel
- Fittings: Use Class 150 stainless steel
Bolt Hole | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Pipe Size | Flange OD | For Bolt Dia. | Dia. | No. of | Bolt Circle Dia. | Max. Pressure | Max. Steam Pressure | Each | |
304 Stainless Steel | |||||||||
NPT | |||||||||
| 1/2 | 3 1/2" | 1/2" | 0.625" | 4 | 2 3/8" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 000000 |
| 3/4 | 3 7/8" | 1/2" | 0.625" | 4 | 2 3/4" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 00000 |
| 1 | 4 1/4" | 1/2" | 0.625" | 4 | 3 1/8" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 00000 |
| 1 1/4 | 4 5/8" | 1/2" | 0.625" | 4 | 3 1/2" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 00000 |
| 1 1/2 | 5" | 1/2" | 0.625" | 4 | 3 7/8" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 00000 |
| 2 | 6" | 5/8" | 0.75" | 4 | 4 3/4" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 00000 |
| 2 1/2 | 7" | 5/8" | 0.75" | 4 | 5 1/2" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 000000 |
| 3 | 7 1/2" | 5/8" | 0.75" | 4 | 6" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 000000 |
| 4 | 9" | 5/8" | 0.75" | 8 | 7 1/2" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 000000 |
316 Stainless Steel | |||||||||
NPT | |||||||||
| 1/2 | 3 1/2" | 1/2" | 0.625" | 4 | 2 3/8" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 00000 |
| 3/4 | 3 7/8" | 1/2" | 0.625" | 4 | 2 3/4" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 00000 |
| 1 | 4 1/4" | 1/2" | 0.625" | 4 | 3 1/8" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 00000 |
| 1 1/4 | 4 5/8" | 1/2" | 0.625" | 4 | 3 1/2" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 00000 |
| 1 1/2 | 5" | 1/2" | 0.625" | 4 | 3 7/8" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 000000 |
| 2 | 6" | 5/8" | 0.75" | 4 | 4 3/4" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 000000 |
| 2 1/2 | 7" | 5/8" | 0.75" | 4 | 5 1/2" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 000000 |
| 3 | 7 1/2" | 5/8" | 0.75" | 4 | 6" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 000000 |
| 4 | 9" | 5/8" | 0.75" | 8 | 7 1/2" | 230 psi @ 72° F | 150 psi @ 360° F | 000000000 | 000000 |