Lap Joint Flange

Lap Joint Flange

The Lap Joint Flange by LOCUS is a two-piece assembly consisting of a stub end and a loose backing flange. Ideal for systems requiring frequent disassembly, inspection, or cleaning, it allows for flange rotation for easy bolt alignment.

Brand: LOCUS
Material: Carbon Steel / Stainless Steel / Alloy Steel
Sizes Available: ½” to 24” (DN15 to DN600)
Pressure Rating: Class 150, 300, 600, 900, 1500
Standard Compliance: ASME B16.5, EN1092, DIN, ANSI, JIS
Finish: Rust preventive oil / Black paint / Galvanized
Connection Type: Welded Stub End + Free Rotating Flange
Manufactured By: Locus International Exports
Certification: ISO 9001:2015, CE Marking, MSME, IEC, BIS

Description

1. Description

2. Specification

Parameter	Details
Design Standard	ASME B16.5, ANSI B16.47, DIN, EN1092
Materials	SS304, SS316, ASTM A105, ASTM A182, A350 LF2
Size Range	½” to 24” (DN15 to DN600)
Pressure Ratings	Class 150 to 1500 / PN6 to PN100
Face Type	Raised Face (RF) / Flat Face (FF)
Stub End	Machined to match the pipe bore
Surface Finish	3.2 – 6.3 Ra (as per application)

3. Working

Lap Joint Flanges work in combination with a stub end, which is butt-welded to the pipe. The loose flange slips over the pipe and rests against the back of the stub end. Since the flange is not welded or fixed, it can rotate freely, allowing easy bolt hole alignment.

4. Principle

The principle behind a Lap Joint Flange is ease of installation and alignment. Because the flange is loose, it compensates for misalignment, making assembly simple. The sealing surface is provided by the stub end, not the flange itself, reducing flange wear and allowing reuse.

5. Assembly

Butt weld the stub end to the pipe.
Slide the lap joint flange over the pipe before welding.
Align the bolt holes by rotating the flange.
Place gasket between mating faces.
Insert bolts and tighten to the specified torque.

6. Installation Process

Step 1: Clean pipe ends, stub end, and flange.
Step 2: Weld stub end to the pipe.
Step 3: Slide flange onto the pipe so it rests against the stub end.
Step 4: Align bolt holes.
Step 5: Place gasket and bolt together with mating flange.
Step 6: Torque bolts evenly in a criss-cross pattern.

7. Technical Specifications

Technical Parameter	Value / Description
Temperature Range	-29°C to 425°C (Material Dependent)
Pressure Capacity	As per Class Rating (e.g. Class 150 = 285 psi)
Corrosion Resistance	High (with SS stub end)
Reusability	High (flange can be reused with new stub end)
Bolt Hole Tolerance	±0.8 mm
Dimensional Accuracy	±0.5 mm
Manufacturing Tolerance	As per ASME / DIN standards

8. Troubleshooting

Problem	Cause	Solution
Misalignment of bolt holes	Improper stub end positioning	Rotate the flange for correct alignment
Leakage at joint	Improper gasket or loose bolts	Use correct gasket & retighten bolts
Rust on carbon steel flange	Exposure to moisture	Use rust preventive coating / galvanization
Stub end wear	Repeated use or chemical attack	Replace stub end
Flange face damage	Mishandling during storage/transport	Inspect and reface or replace if necessary

9. HS Code

HS Code: 73072100
Description: Flanges of Iron or Steel, Forged or Cast
(Used for customs declaration and export documentation)

10. FAQs

Q1: Can the flange be reused?
A1: Yes, the flange is reusable; only the stub end needs to be replaced.

Q2: What is the main advantage of lap joint flanges?
A2: Easy alignment and maintenance-friendly; ideal for corrosive systems.

Q3: Are these suitable for high-pressure applications?
A3: Mostly used for low to moderate pressure. For high pressure, weld neck flanges are recommended.

Q4: What gaskets are recommended?
A4: Spiral wound, PTFE, or rubber gaskets depending on media.

Q5: Does LOCUS offer custom sizes?
A5: Yes, LOCUS can manufacture custom sizes and finishes as per buyer drawings.

11. Applications