Stainless Steel 304/316L Lap Joint Stub Ends Butt Weld Fittings for Petrochemical Pipe

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

1.Product Description

Stainless Steel Stub Ends are critical transition fittings that convert the pipe end into a standardized flange sealing face. Its core value lies not in being a simple "flanged short pipe," but in the forming process of the lap (flare). They are divided into two manufacturing routes: Seamless (SMLS) – formed integrally from seamless steel pipes, featuring a dense grain structure with no longitudinal weld seam, suitable for high-pressure and highly corrosive conditions; Welded (WELD) – roll-formed from steel plates and welded, offering better cost-effectiveness for large-diameter low-pressure systems. For both types, the back of the lap is equipped with an R-angle or chamfer that matches the inner bore of the lap joint flange, ensuring uniform flange pressure during bolting without creating stress concentration points.

2.Product Applications

1. High-Pressure & High-Temperature Steam Networks: Used at the inlets and outlets of main steam and reheat steam pipes in power plants. The butt-weld connection of the stub end replaces direct welding of flanges to pipes, preventing fatigue fractures at the flange neck due to drastic temperature fluctuations.

2. Piping with Severe Vibration (Reciprocating Compressors): Used in the inlet/outlet lines of reciprocating compressors. Since the lap joint flange is not rigidly welded to the pipe, it effectively buffers the shear damage caused by vibration to the weld joints.

3. Replaceable "Sacrificial Sections": Used at pump inlet strainers, heat exchanger channels, and other high-erosion locations. The stub end acts as a replaceable sacrificial component, extending the service life of expensive equipment bodies.

4. Precision Instrument and Sampling Tube Branches: For small-bore (DN15~DN50) instrument branch lines, using a stub end with a lap joint flange allows easy adjustment of the instrument's orientation without twisting the precision instrument body itself.

​3.Product Advantages

1. 100% Intergranular Corrosion Risk Avoidance: The lap section undergoes Solution Annealing treatment to completely eliminate residual stress from cold working. Since the lap face and inner bore have no weld heat-affected zones (HAZ), they offer absolute safety advantages in media prone to intergranular corrosion, such as nitric and acetic acids.

2. Strict Dimensional Chain Control: The outside diameter of the lap and the root radius (radusing) are precision-formed in a single die, ensuring 100% fit with the counterbore shoulder of the standard lap joint flange, preventing off-center leakage caused by flange tilting after installation.

3. Fully Traceable NDT (Non-Destructive Testing): All butt-weld bevel ends and lap sections undergo Liquid Penetrant (PT) or Magnetic Particle (MT) inspection before shipment. The longitudinal seams of welded stub ends undergo Radiographic Testing (RT) to ensure no internal cracks, porosity, or slag inclusions.

4. Optimized Wall Thickness Transition Design: The wall thickness at the butt-weld end is flush with the connecting pipe (same ID), eliminating turbulence and vortex dead zones, reducing flow-accelerated corrosion, while also facilitating preheating and post-weld heat treatment.

5. High On-Site Weld Repair Rate: Only a single circumferential butt weld is required when connecting to the pipeline, eliminating the need for two fillet welds compared to weld neck flanges. This reduces welding workload by over 40% and makes achieving 100% full-penetration much easier.

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4.Key Product Specifications

FAQ

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