ASTM A182 F321 Lap Joint Flange LTF Flange EN 1.4541 / 08Х18Н10Т Stainless Steel Flanges
ASTM A182 F321 / UNS S32100 / 1.4541 Stainless Steel Lapped Flange Lap Joint Flange
ASTM A182 F321 Lap Joint Flange (LTF) is a forged stainless steel pipe-connecting component consisting of two separate, non-integral pieces:
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The Flange Ring (Loose Flange) – Manufactured to ASTM A182 F321, this ring slides freely over the pipe.
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The Lap Joint Stub End – A separate piece, typically manufactured to ASTM A403 WP321 or equivalent, which is butt-welded to the pipe end and features a radiused shoulder that mates with the back face of the loose flange.
When bolted to another flange, the pressure from the bolts compresses the stub end's gasket surface against the opposing flange, while the loose ring transmits the bolting load. The flange ring itself never contacts the process fluid – only the stub end does. This design allows the ring to rotate freely around the pipe, making bolt-hole alignment effortless during assembly.
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GOST
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JIS
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UNS
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EN
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08Х18Н10Т
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SUS 321
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F321 / S32100
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EN 1.4541
(X6CrNiTi18-10)
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Chemical Composition of ASTM A182 F321 Lap Joint Flange EN 1.4541 / UNS S32100 Stainless Steel Flanges
| Element % | C | Mn | P | S | Si | Ni | Cr |
| F321 | 0.08max | 2.0max | 0.045max | 0.03max | 1.00max | 9.0-12.0 | 17.0-19.0 |
Mechanical Properties of ASTM A182 F321 Lap Joint Flange EN 1.4541 / UNS S32100 Stainless Steel Flanges
| Tensile Strength, min,ksi (MPa) | yield Strength, min,ksi (MPa) | Elongation in 2in(50mm), min % | Reduction or Area, min, % | Brinell Hardness Number, HBW |
| 75 (515) | 30 (205) | 30 | 50 | -- |
Advantages of Choosing a Lap Joint Flange (LTF)
| Advantage | Reason |
|---|---|
| Easy Alignment | The loose backing ring rotates 360°, making bolt-hole alignment effortless during installation. |
| Cost-Effective for Expensive Materials | Only the short Stub End needs to be made of expensive corrosion-resistant alloy. The bulky backing ring can be made of carbon steel (though ASTM A182 F321 backing rings are often specified, carbon steel backing rings with F321 stubs are common in cost-sensitive projects). |
| No Field Welding on the Flange Face | Welding stress is isolated to the stub end. The backing ring is never subjected to weld heat, preventing distortion. |
| Easy Maintenance & Inspection | The flange can be easily slid back along the pipe, allowing full access to the gasket and stub end face for inspection or replacement without cutting the pipe. |
Applications
Due to its titanium stabilization and easy-assembly design, this LTF Flange combination is widely used in:
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Low to Medium Pressure Piping Systems (Class 150 – 300).
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Heat Exchanger and Vessel Nozzles where frequent disassembly is required for internal cleaning.
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Food Processing & Pharmaceutical (where easy dismantling and sanitation are critical).
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Chemical Plants handling oxidizing acids (e.g., nitric acid) at moderate temperatures.
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Cryogenic Services – F321 retains good toughness at sub-zero temperatures.
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