Stainless Steel Lap Joint Stub End Fittings ASME B16.9 Corrosion Resistant Easy Maintenance Butt Weld Pipe Fitting

Stainless Steel Lap Joint Stub End Fittings ASME B16.9 Corrosion Resistant Easy Maintenance Butt Weld Pipe Fitting

1. Product Description 

A Stub End is a type of butt-weld pipe fitting used in conjunction with lap joint flanges to create a flanged pipe connection. It consists of a short section of pipe with one flared (lipped) end and one plain end. The flared end seats against the flange face and provides the sealing surface, while the plain end is butt-welded directly to the pipeline. The lap joint flange slides freely over the stub end and is not welded to it, allowing the flange to rotate freely for easy bolt-hole alignment.

Stub ends are manufactured in three primary types: Type A (ASME B16.9, standard/longer hub), Type B (MSS SP-43, shorter hub, lighter wall), and Type C (MSS SP-43, shortest hub, light wall). Available materials include carbon steel, stainless steel, alloy steel, copper-nickel, and specialty alloys such as Monel, Inconel, and titanium.

2. Product Applications 

Stub end fittings are widely used in piping systems across various industries, including:

• Oil & Gas / Petrochemical — pipeline connections in refining, processing, and transportation systems

• Chemical Processing — handling corrosive fluids and frequent maintenance operations

• Food Processing — sanitary connections requiring regular cleaning and disassembly

• Water & Wastewater Treatment — flanged connections for pumps, valves, and treatment equipment

• Power Generation — high-temperature and high-pressure piping systems

• Marine & Offshore — corrosion-resistant piping systems

• Pharmaceutical — sanitary and corrosion-resistant fluid handling

• Vacuum Systems — ISO-KF vacuum plumbing and process systems

Stub ends are particularly suitable for applications requiring frequent flange disassembly for cleaning, inspection, or rapid component replacement.

3. Product Advantages 

1. Cost Efficiency 
Only the stub end needs to match the pipe alloy; the lap joint flange never contacts the process fluid and can be made of lower-grade carbon steel. This significantly reduces the use of expensive alloys in high-grade piping systems. For a 10-inch Class 300 Inconel 625 connection, switching from weld neck flanges to stub ends with carbon steel lap joints can save 45–65% on each flanged joint.

2. Easy Assembly and Disassembly 
The lap joint flange can be removed without cutting any welds, saving significant time during maintenance, turnarounds, and cleaning cycles.

3. Free Bolt-Hole Alignment 
The lap joint flange rotates freely around the stub end hub, eliminating the alignment difficulties common with fixed weld neck flanges. This is especially valuable on large-diameter piping where rotating the entire pipe spool is impractical.

4. Corrosion Resistance 
Stub ends can be manufactured from corrosion-resistant materials such as stainless steel (304, 316, 316L), duplex, super duplex, and nickel alloys to match the service environment.

5. Wide Compatibility 
Stub ends are available in a broad range of sizes, materials, and pressure ratings, compatible with various flange standards and piping systems.

4.Key Specifications

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