ASTM A182 F321 / UNS S32100 / 1.4541 Stainless Steel Flange Lap Joint Flange RF

ASTM A182 F321 Stainless Steel Flange UNS S32100 Forged Steel Lap Joint Flange

ASTM A182 F321 Lap Joint Flange for a high-temperature piping system where you need the flexibility and easy alignment of a loose flange, and the material must resist intergranular corrosion after welding. 

A Lap Joint Flange is not a single-piece component like a Weld Neck or Slip-On flange. It is a two-part assembly consisting of: 1. The Flange Ring (Loose Flange): This is the part made from ASTM A182 F321. It looks similar to a Slip-On flange but has a radius at the bore on the back face. 2. The Stub End: This is a separate, short piece of pipe that is welded to the pipe. It has a curved lip that matches the radius on the flange ring.

Why F321 for high-temperature service?

1. Resistance to Sensitization:

The stub end requires welding to the pipe. If you used a standard 304 stub end, the heat from the welding could sensitize the material, making it susceptible to corrosion. F321's titanium stabilization prevents this.

2. High-Temperature Integrity:

The flange ring itself, while not in contact with the process fluid, is exposed to the ambient heat radiating from the pipe. F321 maintains its mechanical properties and structural integrity in this hot environment better than non-stabilized grades.

Advantages of the Lap Joint Design

• Ease of Alignment: Because the flange ring rotates, bolt holes are incredibly easy to align, which is a major advantage in field construction or when connecting to equipment with flanges that have fixed bolt holes.

• Cost Savings in High-Alloy Systems: You can use a less expensive material for the flange ring (e.g., carbon steel) while the wetted parts (the stub end and pipe) are made of the expensive alloy. However, in this specific case (F321), both parts would likely be F321 for a full high-temperature solution.

• Reduced Inventory: One set of flange rings can be used with stub ends of different schedules (wall thicknesses), as long as the bore of the ring is large enough.

Applications

• Heat Exchangers: Frequently used on the channels and shells of heat exchangers where thermal expansion and the need for frequent disassembly for cleaning are common. The loose flange can handle thermal stresses better than a fixed one, and the F321 material withstands the operating temperatures.

• Furnace Piping and Superheater Lines: Any piping system that operates consistently above 800°F (427°C).

• Aircraft and Aerospace Exhaust Systems: Where high heat and vibration are factors.

• Chemical and Petrochemical Plants: In processes involving high temperatures, especially where aqueous corrosion is not the primary concern but high-temperature strength is.