Carbon Steel Lap Joint Flange
Flanges: ASME B16.5, EN 1092-1 (DIN), JIS B2220, GB/T 9117
Short sections: ASME B16.9, MSS SP-43
Process accuracy:CNC lathe machining of sealing surface (Ra≤3.2μm) | Laser positioning drilling (hole spacing error ±0.1mm) | Flanging Angle 30°±0.5°
- Product Introduction
Professional manufacturing: High cost-performance Carbon Steel Lap Joint Flange (LJF)
Flexible disassembly and assembly · Stress relief · Economical and efficient - a smart solution for general-purpose pipe connections in medium and low pressure
As a seasoned flange manufacturing expert, we precisely grasp the dual demands of piping systems for cost control and installation flexibility. Carbon steel lap flanges (LJF) are forged/rolled from high-quality carbon steel and combined with precision machining techniques. With a unique loose sleeve structure design as the core, they perfectly solve the problems of frequent maintenance, thermal displacement compensation and bolt hole alignment, making them ideal for petrochemical, power energy, building HVAC, water treatment and other fields.
Product structure and working principle
Carbon steel lap flanges are composed of two independent components:
Carbon steel flange Hub
The material is ASTM A105, Q235B, 20# steel, etc. The surface can be galvanized or coated with epoxy resin for rust prevention
The inner diameter is greater than the outer diameter of the pipe, and it can rotate freely without a neck
Sealing surface type: raised face (RF) as the main type, compatible with concave-convex face (MFM), tenon groove face (TG)
Stub End
It should be of the same material as the pipe (e.g. Stainless steel/alloy steel) and butt-weld to the pipe
The front end is precisely machined into a flanged structure to fit the sealing surface of the flange body
Workflow: ① Lap short section welded to the pipe → ② Carbon steel flange body inserted into the pipe and slid to the flanged short section → ③ Bolt fastened flange body to the matching flange → Seal formed between the flanged and the body
Core advantages and applicable scenarios
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Advantages |
Customer value |
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Cost savings of over 30% |
The flange body is made of carbon steel (not pipe material), significantly reducing the cost of precious metal (such as stainless steel/nickel alloy) systems |
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5 minutes quick disassembly and assembly |
The loose sleeve design allows for 360° free rotation alignment of the bolt holes, eliminating the need to cut the weld seam during disassembly and improving maintenance efficiency by 50% |
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Zero thermal stress damage |
Allow the pipe to slide axially, completely eliminate the stress caused by thermal expansion and contraction, and extend the pipe's lifespan |
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Prefabricated modularization |
Factory pre-welded short sections + on-site bolted connections, project progress increased by 40%, welding quality 100% controllable |
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Zero inventory of spare parts |
Standardize the flange body (e.g. Class 150/300), replace the body alone in case of damage, no need to replace the short section |
Typical applications
Frequent maintenance scenarios
Heat exchangers, pumps and valves, filter interfaces | Instrument lines (pressure gauges/flowmeters)
Thermal displacement system
Steam pipe | Thermal network | HVAC
Cost-sensitive items
Water treatment plant | Fire protection piping | Building water supply and drainage | General industrial medium delivery
Prefabricated projects
Modular plants | Skid-mounted equipment | Marine piping
Detailed technical specification sheet
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Parameter category |
Technical Specifications |
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Flange body material |
Carbon steel: ASTM A105, Q235B, 20#, A350 LF2 |
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Lap joint short section material |
Match by pipe: 304/316L stainless steel, duplex steel 2205, nickel-based alloy, etc. (as specified by the customer) |
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Pressure rating |
PN series: PN6 to PN40 (commonly PN10/16/25) |
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Nominal diameter (DN) |
DN15 to DN1200 (½ "to 48"), DN300 and below are in regular stock |
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Sealing surface type |
Raised face (RF) (90% order) | Concave-convex face (MFM) | Tenon groove face (TG) | Ring joint face (RJ) |
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Short joint type |
Type A (Long, ASME B16.9) | Type B (short) | Type C (tenon lock type) |
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enforce standards |
Flanges: ASME B16.5, EN 1092-1 (DIN), JIS B2220, GB/T 9117 |
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Process accuracy |
CNC lathe machining of sealing surface (Ra≤3.2μm) | Laser positioning drilling (hole spacing error ±0.1mm) | Flanging Angle 30°±0.5° |
Why choose our Carbon steel lap flanges?
Strict material selection control
The flange body is made of raw materials from large steel mills (with MTC material report), tensile strength ≥485MPa
The short section material is 100% compatible with the pipe, eliminating the risk of electrochemical corrosion
Smart process assurance
Forged flanges with UT flaw detection (conforming to JB/T4730.3) | Full-size laser inspection of rolled flanges
Sealing surface hardness test (HB≥137) to ensure pressure-resistant sealing
Full scene coverage capability
Stock available: DN15-DN300 Class150/300 RF flanges (galvanized/epoxy)
Deep customization: non-standard diameter, special sealing surface, nuclear grade certification (RCC-M), low-temperature impact test
One-stop delivery
Pre-assembled kits (carbon steel flange + stainless steel short section + bolt pack) are available.
Support for global logistics (including Marine anti-rust packaging)
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