Plate Flange (PL)
Flat-type flange with simple structure, light weight and low cost — ideal for low-pressure pipeline systems.
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Lap Joint Flange (LJ)
Loose flange with stub end — convenient disassembly for large-diameter, low and medium pressure systems.
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LJSteel Pipe Flanges
Overview
Lap Joint Flange (LJ), also known as Loose Flange, is a flange composed of a flange ring and a Stub End (lap joint short section). The flange ring is loosely sleeved on the Stub End, which is welded to the pipe, and the flange ring is connected by bolting. It has the advantages of convenient disassembly, low cost, and no damage to the pipe during disassembly, and is suitable for large-diameter, low and medium pressure pipeline systems and scenarios that require frequent disassembly. As a flexible flange type, it is widely used in various industrial pipeline systems and large-diameter export projects.
Size Range
2" – 56" (DN50 – DN1400)
Pressure Class
Class 150 – 600 / PN10 – PN40
Key Features
- Convenient disassembly — flange ring removes quickly without damaging pipe or stub end
- Cost-effective — simple flange ring design, ideal for large-diameter systems
- Good adaptability — suits low and medium pressure, various media, slight pipeline displacement
- No pipe damage — disassembly involves only the flange ring, protecting welds and pipe life
- Global standard compliance — ISO, ASME, DIN, EN, JIS and GB manufacturing
- Two-piece set: loose flange ring + lap joint stub end (butt-welded to pipe)
- Sealing surfaces: RF (Raised Face) and FF (Flat Face)
Benefits
- Flange ring rotates freely for easy bolt-hole alignment during installation
- Economical — replace worn ring only without renewing stub end or pipe weld
- Ideal for lined, coated or frequent-disassembly pipeline systems
- Custom flange rings and stub ends per drawing, material and standard
Specifications
| Standards | ISO 7005, ASME B16.5, DIN 2501, EN 1092-1, JIS B2220, GB/T 9118, HG/T 20592, HG/T 20615 |
| Materials | Flange ring: A105, Q235B, 304, 316L; Stub end: 20#, 16Mn, 304, 316L — customizable per medium and conditions |
| Pressure Ratings | Class 150, 300, 600 / PN10, PN16, PN25, PN40 |
| Nominal Diameter | DN50 – DN1400 (NPS 2" – 56") |
| Sealing Surface | RF (Raised Face), FF (Flat Face) |
| Working Temperature | -20°C – 450°C (special grades on request) |
| Components | Loose flange ring + lap joint stub end |
Applications
Petroleum and petrochemical pipeline systemsNatural gas transmission and distributionWater supply, drainage and HVACChemical engineering and marine industriesMaintenance, inspection and medium replacement accessLarge-diameter low and medium pressure piping
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Standards
- • ISO 7005
- • ASME B16.5
- • DIN 2501
- • EN 1092-1
- • JIS B2220
- • GB/T 9118
- • HG/T 20592
- • HG/T 20615
Materials
- • Flange Ring — Carbon Steel: A105, Q235B
- • Flange Ring — Stainless Steel: 304, 316L
- • Stub End — Carbon Steel: 20#, 16Mn
- • Stub End — Stainless Steel: 304, 316L
Related Products
Slip On Flange (SO)
Sleeve-type flange slipped over the pipe and fixed by fillet welding — economical for medium and low pressure systems.
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Socket Weld Flange (SW)
Socket bore flange with fillet weld — compact and reliable for small-bore, high-pressure systems.
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