Lap Joint Stub End Flange Set

Standard flanged systems often force full material upgrades, even when corrosion resistance is only needed at weld joints. Our Lap Joint Stub End Flange Set reduces cost by combining a corrosion-resistant stub end with a carbon steel backing flange.

Standard Specification

ASME B16.9 (Stub End), ASME B16.5 (Lap Joint Flange), MSS SP-43

Pressure Rating

Class 150 to 1500 (PN10 to PN250) [Determined by stub end]

Material

Carbon Steel (A403 WP316), Stainless Steel (A403 WP316), Duplex (A815 UNS S31803)

Nominal Size

½” to 48″ (DN15 to DN1200) [Stub end length per ASME B16.9]

Flange Type

Lap Joint Flange + Stub End (2-piece assembly)

Product Description

This 2-piece design simplifies alignment in large or offset piping runs while retaining full ASME B16.5 compatibility. Available in sizes from ½ inch to 48 inch, it meets pressure class ratings up to 1500 and supports full-face gaskets. 

Facing Type

Flat Face (FF) on flange [Stub end matches pipe facing]

Dimensions

Stub end thickness = 1.25×pipe wall [Per MSS SP-43]

Bolt Circle Diameter

Matches standard flange [ASME B16.5 Table 4]

Number & Size of Bolt Holes

Matches standard flange [Clearance for stub end rotation]

Surface Finish

125-250 μin RA (flange), 32-63 μin Ra (stub end weld bevel)

Corrosion Resistance

Stub end typically corrosion-resistant material [Flange often carbon steel]

Temperature Rating

-29°C to +538°C [Limited by stub end material]

Material Certification

EN 10204 3.1, NACE MR0175 (stub end), PED 2014/68/EU

Gasket Compatibility

Full-face gaskets [Matching stub end OD]

Coating/Plating

Flange: HDG/Xylan [Stub end uncoated for welding]

Manufacturing Method

Stub end: Forged + Machined [Flange: Plate-cut or forged]

Technical Advantages

The stub end-to-flange interface maintains bolt load without transmitting pipe stress to the flange body. This avoids fatigue cracking in vibration-prone systems. Using forged stub ends with 1.25× wall thickness ensures weld strength continuity across high-pressure joints. 
Each stub end meets ASME B16.9 tolerances, while backing flanges match bolt circles per B16.5 Table 4. Surface finish control at both gasket and weld prep zones supports leak-free sealing and X-ray quality welds. 

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Industry Applications

Chemical Process Units

The stainless stub end prevents corrosion at critical weld zones, reducing turnaround downtime in acid-handling systems.

Power Generation Plants

Thermal expansion tolerance in the stub-flange interface helps avoid stress failures in superheated water lines.

Marine Ballast Systems

Stub ends resist seawater attack, while coated backing flanges avoid unnecessary material costs in non-wetted areas.

Food and Beverage Pipelines

Clean weld prep surfaces (32–63 μin Ra) meet hygienic welding standards in high-purity processing.

Oil and Gas Skids

The rotating flange simplifies field adjustments during on-site bolt alignment under tight space constraints.

Pulp and Paper Lines

Stub ends in duplex material withstand high chlorides in bleach plant applications, with flanges coated for external humidity.

Reliable and Cost-Saving Assembly Sets

Sourcing teams gain flexibility by decoupling weld metallurgy from bolting material. Our sets come matched and inspected as per EN 10204 3.1 certification, ready for welding and assembly. 
We maintain large-size inventory up to 48 inches with stub end lengths per ASME B16.9, which reduces fabrication time. Optional coatings like hot-dip galvanizing or Xylan offer external protection in buried or corrosive environments. 

Lap Joint Stub End Flange Set

Having Doubts? Our FAQ

Check all our Frequently Asked Question

Can I combine a stainless steel stub end with a carbon steel flange?

Yes, this is a standard configuration. The stub end handles corrosion while the flanges provides mechanical strength at a lower cost. This pairing meets ASME and NACE guidelines when material compatibility is verified.

Does the stub end thickness meet process piping weld strength requirements?

Yes, each stub end uses 1.25 times the pipe wall thickness. This ensures full strength through the weld zone under pressure and thermal load. All dimensions comply with MSS SP-43 standards. 

Will the flange rotate freely for alignment after welding the stub end?

Yes, the lap joint flange remains loose over the stub end until bolting. This allows 360° adjustment to align bolt holes during installation. It saves time especially in tight or misaligned pipe runs.

Do I need to specify different coatings for flange and stub end?

No coating is applied to the stub end to maintain weld quality. However, you can request external coatings like Xylan or HDG for the flange. This protects against corrosion without affecting weld integrity. 

Can you provide both stub end and flange as a matched set from one supplier?

Yes, we supply fully matched flange-stub sets with size and class pairing verified before dispatch. This avoids mismatch issues during assembly. You also get single-source for easier documentation. 

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LOCATIONS

Global Sales Office

818, Preakness lane, Coppell, Texas, USA – 75019

Registered Office

10-A, First Floor, V.V Complex, Prakash Nagar, Thiruverumbur, Trichy-620013, Tamil Nadu, India.

Operations Office

9/1, Poonthottam Nagar, Ramanandha Nagar, Saravanampatti, Coimbatore-641035, Tamil Nadu, India. ㅤ

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Lap Joint Stub End Flange Set

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Lap Joint Stub End Flange Set

Need reliable Machining for your next project? Get in touch with us today, and we’ll help you find exactly what you need!

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