
A steel flange is a pipe fitting used to connect pipes, valves, pumps, and other equipment in a piping system. It provides easy assembly, disassembly, and maintenance while ensuring a leak-proof seal under high pressure and temperature conditions.
1. Classification of Steel Flanges
A. By Connection Type
Weld Neck Flange (WN)
Features a long tapered hub for smooth stress distribution.
Used in high-pressure and high-temperature applications (oil & gas, petrochemical).
Slip-On Flange (SO)
Slides over the pipe and is welded on both sides.
Easier to align but less robust than weld neck flanges.
Socket Weld Flange (SW)
Pipe is inserted into the flange and welded for a strong joint.
Ideal for small-diameter, high-pressure piping.
Lap Joint Flange (LJ)
Used with a stub end, allowing easy rotation for alignment.
Common in systems requiring frequent dismantling.
Threaded Flange (TH)
Screws onto pipes without welding.
Used in low-pressure, non-critical applications.
Blind Flange (BL)
Seals the end of a piping system.
Used for pressure testing, isolation, or future expansion.
Orifice Flange
Designed for flow measurement (used with orifice plates).
B. By Facing Type
Flat Face (FF) – For low-pressure applications.
Raised Face (RF) – Most common, provides better sealing.
Ring-Type Joint (RTJ) – Used in high-pressure, high-temperature systems.
Tongue & Groove (T&G), Male & Female (M&F) – For precise alignment.
2. Materials Used in Steel Flanges
Material Grade | Properties | Common Applications |
---|---|---|
Carbon Steel (A105) | Good strength, cost-effective | General industrial piping |
Stainless Steel (304/316) | Corrosion-resistant, hygienic | Food, chemical, marine |
Alloy Steel (F11, F22) | High-temperature resistance | Power plants, boilers |
Duplex Steel (S31803) | High strength, corrosion-resistant | Offshore, oil & gas |
Nickel Alloys (Inconel, Monel) | Extreme corrosion/heat resistance | Aerospace, chemical processing |
3. Applications of Steel Flanges
✔ Oil & Gas Industry – Pipeline connections, refineries.
✔ Chemical & Petrochemical Plants – Corrosive fluid handling.
✔ Water Treatment & HVAC – Pump and valve connections.
✔ Power Plants – High-pressure steam systems.
✔ Shipbuilding & Marine – Saltwater-resistant piping.
✔ Food & Pharmaceutical – Hygienic, easy-to-clean systems.
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