Stainless Steel Butt Weld Stub Ends Long Short Lap Joint Forged Pipe Fitting ASME

Stainless Steel Butt Weld Stub Ends Long Short Lap Joint Forged Pipe Fitting ASME

1.Product Description

Stainless Steel Stub Ends are essentially non-integral flanged connection adapters. They consist of a short straight pipe section and one end that is cold-extruded or hot-spun into a flared lip (lap). This product is not used independently and must be paired with Lap Joint Flanges. According to ASME B16.9 and MSS SP-43, they are generally classified into Long Pattern and Short Pattern. The Long Pattern is the industry standard, while the Short Pattern is mostly used in space-constrained environments or thin-wall piping systems (e.g., Sch 5S/10S). Based on the back contour of the lap, they are subdivided into Type A (with straight neck), Type B (curved transition), and Type C (integral forged thickened type).

2.Product Applications

1. Corrosive Media Transmission Pipelines: In strong acid, alkali, or seawater environments, only the stub end needs to be made of high-grade stainless steel (e.g., 316L, 904L), while the mating flange can be galvanized carbon steel, enabling zoned material selection (anti-corrosion on the media side, standard on the structural side).

2. Inlets/Outlets of Large-Diameter Vertical Equipment: Widely used in tower reactors, heat exchangers, and storage tank nozzles, solving the significant installation challenge of rotating large flanges for bolt hole alignment.

3. Process Sections Requiring Regular Dismantling & Cleaning: Applied in discharge lines for reactors in food, pharmaceutical, and fine chemical industries, allowing quick disassembly to flush out internal residues and ensure hygienic cleanliness.

4. Thermally Sensitive Pipelines: Suitable for steam or high-temperature thermal oil systems with large temperature differences. The slight clearance between the stub end and flange absorbs some axial thermal expansion displacement stresses.

​3.Product Advantages

1. Significant Procurement Cost Savings: For Class 300+ and large-bore (DN≥200) applications, using "SS Stub End + Carbon Steel Flange" instead of "All-SS Weld Neck Flange" can save 30%~50% in material costs.

2. Eliminates Welding Stress and Intergranular Corrosion: The lap is cold-formed, with no load-bearing weld seam exposed to the media, completely avoiding risks of intergranular corrosion and stress corrosion cracking found in traditional butt-weld flanges.

3. Zero Torque Transmission Protection: When tightening bolts, torque acts on the lap joint flange and transfers to the back of the stub end, rather than pulling on the pipe directly. This effectively protects thin-wall pipes (e.g., Sch 5S, Sch 10S) from deformation caused by excessive torque.

4. Flexible Maintenance Access: After disassembly, the lap joint flange can slide freely along the pipe, offering great convenience for replacing valves, instruments, or pipe sections later on without the need for hot work or re-cutting.

5. High-Precision Lap Sealing Face: The lap surface can be precision-machined to Ra 3.2~6.3μm finish, equipped with concentric serrations, ensuring zero-leakage sealing when paired with spiral wound gaskets or PTFE gaskets.

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4.Key Product Specifications

FAQ

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