Understanding Flange Types, Face Types & Pressure Ratings

What is a Flange?

A flange is a protruding rim or collar used to connect pipes, valves, and equipment in a piping system. Flanges allow easy assembly, disassembly, and maintenance.

Flange Types

1. Weldneck Flange (WNRF)

The most popular flange type for high-pressure, high-temperature applications. The long tapered hub provides stress distribution.

2. Slip-On Flange (SORF)

Slides over the pipe end and is fillet-welded on both sides. Cost-effective for low-pressure applications.

3. Blind Flange (BL)

Used to close the end of a piping system or vessel opening. Must withstand full system pressure.

4. Socket Weld Flange (SWRF)

The pipe inserts into the socket before welding. Used for small-bore, high-pressure applications.

5. Lap Joint Flange

Used with a stub end for applications requiring frequent dismantling. The flange itself is not in contact with the media.

6. Threaded Flange

Connected via NPT threads. Used for low-pressure, non-critical applications where welding is not feasible.

Face Types

Pressure Ratings (ASME B16.5)

Flanges are rated by pressure class:

150# — Up to 285 psi at 100°F

300# — Up to 740 psi at 100°F

600# — Up to 1480 psi at 100°F

900# — Up to 2220 psi at 100°F

1500# — Up to 3705 psi at 100°F

2500# — Up to 6170 psi at 100°F

Material Standards

Stainless Steel: ASTM A182 (F304, F316, F304L, F316L)

Carbon Steel: ASTM A105

Alloy Steel: ASTM A182 (F11, F22, F91)

Conclusion

Understanding flange types and ratings is essential for safe piping design. Swastik Metal Industries supplies all flange types in sizes from 1/2" to 60" across all pressure ratings.