LAPJ Flange/Backing Ring

Description

Lap Joint Flange systems combine two distinct components—a backing flange (lap joint flange) and a stub end—to create a unique connection solution that offers unparalleled alignment flexibility, corrosion resistance optimization, and maintenance accessibility. This modular design allows rotation of the flange independent of the stub end, facilitating easy bolt hole alignment while enabling the use of cost-effective materials in corrosive services.

Technical Specifications & Standards:

Material Specifications:

• Backing Flange Materials: ASTM A105 (Carbon Steel), A36 (Plate), A283 (Low Carbon)

• Stub End Materials: ASTM A312 (Pipe), A403 (Wrought Fittings), A182 (Forged)

• Common Combinations: CS Backing Flange + SS Stub End for cost optimization

• Stub End Types: Type A (Long Pattern), Type B (Short Pattern), Type C (Plate Lap)

Design & Manufacturing Standards:

• Dimensional Standards: ASME B16.9 (Stub Ends), ASME B16.5 (Lap Joint Flanges)

• Pressure Classes: 150#, 300#, 600#, 900# (Common), 1500#, 2500# (Available)

• Stub End Lap Dimensions: Controlled thickness and radius per MSS SP-43

• Facing Types: Flat Face (FF) standard, Raised Face (RF) available

• Assembly: Stub end laps over flange face with close tolerance fit

Critical Design Features:

• Rotational Capability: Flange rotates freely around stub end for bolt hole alignment

• Modular Construction: Separable components for material optimization

• Stub End Lap: Machined radius matches flange face for smooth contact

• Gasket Surface: Provided by stub end lap, not flange face

• System Flexibility: Easy disassembly and reassembly for maintenance

Manufacturing Excellence:

• Stub End Forming: Cold or hot forming from pipe or plate

• Flange Machining: Precision face and bore machining for proper stub end fit

• Surface Finish: Controlled facing on stub end lap (critical sealing surface)

• Dimensional Control: Tight tolerances for lap-to-flange interface

• Quality Assurance: Separate certification for flange and stub end components

Performance Characteristics:

• Pressure Rating: Determined by stub end thickness and material

• Temperature Range: Limited by gasket and stub end material compatibility

• Corrosion Optimization: Expensive materials only in contact with process fluid

• Alignment Flexibility: 360° rotation capability during installation

• Maintenance Advantage: Easy disassembly without pipe cutting

Quality Assurance Protocol:

• Material Certification: Separate MTRs for flange and stub end

• Dimensional Verification: Lap thickness, radius, and fit-up verification

• Surface Inspection: Critical examination of stub end sealing surface

• Fit-Up Testing: Sample assembly verification for production lots

• Marking: Clear identification of both components