Long Weld Neck Flange

Long Weld Neck Flange (LWN) is an extended form of butt welded flange with a neck, whose neck height is significantly higher than that of ordinary butt welded flanges. The neck is usually designed in a straight cylindrical shape, and the height is adjusted according to the nominal diameter (DN): when DN ≤ 100, the neck height is 229mm, and when DN>100, it is 305mm. The thickness of the neck wall gradually transitions to the thickness of the pipe wall, effectively improving stress distribution, enhancing the stiffness and load-bearing capacity of the flange, and suitable for working conditions with high pressure, high temperature, and frequent temperature fluctuations.

SIZE:

DN10(3/8") DN15(1/2") DN20(3/4") DN25(1") DN40(1-1/2")

DN50(2") DN80(3") DN100(4") DN125(5") DN150(6")

DN200(8") DN250(10") DN300(12") DN350(14") DN400(16")

DN450(18") DN500(20") DN550(22") DN600(24")

Customized Size Consult Us

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Product Description

Manufacturing standards and materials

Standard specifications: mainly follow HG/T20615-2009 (China Chemical Industry Standard) and ASME B16.5 (American Standard), and some designs also comply with international standards such as ISO 7005-1.
Material selection: Common materials include carbon steel, stainless steel (such as 304/316L), alloy steel, and duplex steel (such as 2205), and special working conditions can use Hastelloy or titanium materials.
Production process: Adopting integral forging or die forging technology, combined with high-precision CNC lathe processing, to ensure the density and dimensional accuracy of the flange.

Application Fields

Long weld neck flanges are widely used in the following scenarios:
Energy and Chemical Industry: High pressure pipelines for petroleum refining, LNG storage and transportation systems, acid washing equipment circulation circuits.
Electricity and nuclear power: Ultra high voltage transmission steel pipe towers and cooling systems for nuclear power plants must meet the first level welding seam standard.
Ships and pharmaceuticals: seawater cooling system, sterile fluid delivery, surface polished to Ra ≤ 0.8 μ m to meet hygiene requirements.
General Industry: High temperature boilers, pressure vessels, and pipeline connections for repeated loads.

Production process and welding technology

Welding method:
Manual gas shielded welding (GTAW/SMAW): used for root welding of small-sized flanges or complex working conditions.
Automatic submerged arc welding (SAW): Suitable for double-sided penetration welding of large diameter flanges, without the need for root cleaning, with high efficiency and a weld qualification rate of 98%.
Groove design: Single sided V-shaped or U-shaped grooves are commonly used, with blunt edges ≥ 7mm and a gap of 0-1mm between the joints to ensure full penetration of the weld and prevent burning through.
Quality control: 100% radiographic testing (RT) and ultrasonic testing (UT), hydrostatic testing up to 1.5 times the working pressure, materials must provide EN 10204 3.1 certification.

Analysis of advantages and disadvantages

Advantages:
High load-bearing capacity: The neck structure disperses stress, reduces leakage risk, and is suitable for high-pressure systems above PN16MPa.
Easy installation: on-site welding eliminates the process of weld seam inspection, especially suitable for modular equipment with limited space.
limitations:
High cost: The welding workload is large, the consumption of welding rods is high, and the processing cycle is long.
Weak fatigue resistance: Not recommended for pipelines with frequent bending or sudden temperature changes.

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Related Category

Product Tag

LWN Flange

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Contact Info

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Address

No. 4516, Binhai 3rd Road 8, Xinghai Street, Longwan District, Wenzhou City, Zhejiang Province, China
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Tel

+86-577-85886898
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E-mail

Julong@snflange.com

MATERIAL:

STAINLESS STEEL

A-182 - F-304

Dual Grade 304/304L

Dual Grade 316/316L

316

304H

Dual Grade 304/304H

Dual Grade 316/316H

316H

309

310

317L

321

347

347H

904L

DUPLEX STEET

F51/2205

F53/2507

CARBON STEEL

ASTM/ASME

SA-105

A-350

LF-2

LF-3

A694

SA-516-70

A36

TITANIUM

Gr2

Gr12

CHROME ALLOYS

A-182-F-1

F-5

F-6

F-9

F-91

F-11

F-12

F-22

ALUMINUM

3003

6061

5083

other grades upon request

HASTALLOY

B-2

C-276

C-22

INCONEL

600

601

625

718

MONEL

400

COPPER

90/10 (C70600)

70/30 (C71500)

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Long Weld Neck Flange

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