What is Weld Neck Flange?

What is Flange? The weld neck flange (WN flange) has a neck that relocates the pipe’s stress, thereby reducing the pressure collected in the flange bottom. This product is compatible with pipelines that work in high- or low-temperature conditions and bear high pressures. When the PN is greater than 2.5 MPa, it is specially designed for the pipe or the valve.

Two Shapes of Welding Neck Flange

A welding neck flange with hub comes in two shapes, one that has a reducing neck, referred to as a reducing weld neck flange manufacturers, and one that has a typical long neck, referred to as a long neck weld flange.A welding neck flange comes in two shapes, one that has a reducing neck, referred to as a reducing weld neck flange weld, and one that has a typical long neck, referred to as a long neck weld flange. Ss weld neck flange dimensions. Welded neck flange, Weldneck flanges, long weld necks, long weld neck flange.

Reducing Weld Neck Flange

Due to its name, it is like a combination of a pipe reducer and flange, so it could be directly welded to a smaller pipe.

Long Weld Neck Flange

Often referred to as LWN flanges, the neck part resembles an elongated pipe with a flange attached. As a result, it is typically used as a nozzle for a column or barrel.

If you need a heavy LWN flange with a larger thickness and a different shape, you can choose from a normal thickness long welding neck flange.

Types of Flanges

Slip On flange

Slip On flanges have a calculated strength of two-thirds that of Welding Neck flanges, and their fatigue life is one-third as long as Welding Neck flanges.

A flange is connected to a pipe by two fillet welds, both on the outside and on the inside.

Socket Weld flange

Initially, socket weld flanges were developed to be used on small-sized high pressure piping. The static strength of these flanges is the same as that of Slip On flanges, but their fatigue strength is 50% higher than that of double-welded Slip On flanges.

In order to connect the pipe to the flange, there is one fillet weld at the outside of the flange. A space must be created between the pipe and the flange or fitting prior to welding.

According to ASME B31.1 1998 127.3, Preparation for Welding (E) Socket Weld Assembly.

Prior to welding, the pipe or tube should be inserted into the socket to maximum depth and then withdrawn approximately 1/16″ (1.6 mm) away from contact between the end of the pipe and the socket shoulder.

Lap Joint flange

There are no raised faces on the lap joint flanges, therefore they are used in conjunction with “Lap Joint Stub Ends” to achieve the same dimensions.

With the exception of the radius at the intersection of the flange face and the bore to accommodate the flanged portion of the Stub End, these flanges are nearly identical to Slip On flanges.

Stub End

Stub Ends are always used with Lap Joint flanges as backing flanges.

As a cheap method of flanging, this flange connection can be used in low-pressure and non-critical applications.

Because carbon steel flanges do not come in contact with the product in the pipe, they can be used in stainless steel pipe systems.

Almost all pipe diameters are available with stub ends. According to ASME B.16.9, dimensions and dimensional tolerances must be met. Stub Ends (fittings) with lightweight corrosion resistance are defined in MSS SP43.

Threaded flange

The main advantage of threaded flanges is that they can be attached to the pipe without welding. As well as threaded connections, seal welds are sometimes used.

Despite still being available in most sizes and pressure ratings, screwed fittings are almost exclusively used in smaller pipes.

Blind flange

Flanges without a bore are used to blank off the ends of piping, valves, and pressure vessels.

Blind flanges, particularly in larger sizes, are the most highly stressed flange types because of internal pressures and bolt loads.

Materials of WN Flanges

Welding neck flanges are available in a variety of materials. Standards will have to be followed for these materials. Material quality should also be in compliance with ASTM or ASME standards.

Flange thickness and inner diameter will be determined by the size of the pipe for which this welding neck flange is designed.

Carbon alloy is a popular material for these flanges because it is resistant to extreme temperatures as well. Materials ASTM A 181 and ASTM A 105 are available. Flanges are available in a variety of grades, such as ASME B16 47 ‘A’ and ‘B’ series, to meet the needs of clients.

In addition to this material, welding neck flanges are made of stainless steel as well. ASME B165, F304, 316L, 347H, 310S, ASTM A182, and F304 are the materials used to manufacture the flanges.

UNS S31803 is also used as a duplex steel material. Other than stainless steel, welding neck flanges are also available in carbon alloys and nickel.

Materials such as Inconel 600 and 625, Hastelloy C22, C276 and other nickel alloys are available for nickel alloy welding neck flanges.

Weld Neck Flanges Specifications

Weld Neck Flanges Standards

Flanges are available in accordance with ANSI/ASME B16.5, B16.47 Series A & B, B16.48, BS4504, BS 10, EN-1092, DIN, and ISO standards as well as DIN, BS, DIN, EN, HPF, BS1560-3.1, API7S-15, API7S-43, API605, and API705.

ASME B16.5 Weld Neck Flanges Size Chart

15mm (15NB) to 48mm (1200NB) DN10~DN5000

Weld Neck Flanges Pressure Calculation in DIN

Flanges for 6Bar, 10Bar, 16Bar, 25Bar, and 40Bar / PN6, PN10, PN16, PN25, PN40, PN64

Weld Neck Flanges Pressure Rating ANSI

Class 150 LBS, 300 LBS, 600 LBS, 900 LBS, 1500 LBS, 2500 LBS Weld Neck Flanges


6Bar 10Bar 16Bar 25Bar 40Bar Weld Neck Flanges


Flanges for 5K, 10K, 16K, 20K, 30K, 40K, 63K Weldnecks


Cold and Hot Dip Galvanized Weld Neck Flanges with Oil Black Paint, Zinc Plated, Yellow Transparent, Zinc Plated, Copper Plated, and Anti-rust Paint


6Bar 10Bar 16Bar 25Bar 40Bar Weld Neck Flanges

Test Certificates

EN 10204/3.1B

Raw Materials Certificate

100% Radiography Test Report

Third Party Inspection Report, etc

Most common types of Weld Neck Flanges

Forged / Threaded / Screwed / Plate

Connect Type/ Flange Face Type

Ring Type Joint (RTJ), Flat Face (FF), Large Male-Female (LMF), Lap Joint Face (LJF), Small Male-Female (SMF), Small Tongue and Groove, Groove

Production technique

  • Forged, Heat treated and machined


Instruments like direct-reading spectrographs, hydrostatic testing machines, X-ray detectors, UI transonic flaw detectors, and magnetic particle detectors

Special design

Based on your drawing


NB(1/2″) to NB(8″)

Configurations of equal and reducing dimensions


Indian / West Europe / Japan / USA / Korean


Press machine, Bending machine, Pushing Machine, electric bevelling machine, Sand-blasting machine etc

Weld Neck Flanges Uses & application

  • Bitumen upgraders.
  • Heavy oil refineries.
  • Nuclear power (mostly seamless).
  • Petrochemicals and acids.

Manufacturer of

Standards like DIN, GOST, JIS, UNI, BS, AS2129, AWWA, EN, SABS, NFE, etc.

Our range of Weld Neck Flanges includes BS Flanges, EN Flanges, API 6A Flanges, ANSI Flanges, ASME Flanges, DIN Flanges, EN1092-1 Flanges, UNI Flanges, JIS/KS Flanges, BS4504 Flanges, GB Flanges, AWWA C207 Flanges, GOST Flanges, PSI Flanges, etc.

  • Standards: BS4504, BS3293, BS1560, BS10
  • Tables D, E, and H of AS 2129
  • MSS SP44, ASA, API-605, AWWA, ANSI B16.5, ANSI B16.47 Series A & B, and Custom Drawings
  • In ANSI, there are B16.5, B16.47 (API605), MSS SP44, B16.36, and B16.48.
  • Standards ANSI B16.5, ANSI B16.47, MSS SP44, ANSI B16.36 and ANSI B16.48
  • ANSI (American National Standards Institute)
  • (DIN) German
  • BS (British Standard)
  • The following DIN specification codes are available: DIN 2527, DIN 2566, DIN 2573, DIN 2576, DIN 2641, DIN 2642, DIN 2655, DIN 2656, DIN 2627, DIN 2628, DIN 2629, DIN 2631, DIN 2632, DIN 2633, DIN 2634, DIN 2635, DIN 2636, DIN 2637, DIN 2638.
  • Another standard is AWWA C207; EN1092-1; GOST12820; JIS B2220; KS B1503, SABS1123; NFE29203; UNI2276.

Export to

Saudi Arabia, Peru, Egypt, Indonesia, Brazil, Spain, USA, Canada, Ukraine, Singapore, Thailand, Oman, Ireland, Korea, Iran, India, Dubai

Material Test Certificates (MTC) as per EN 10204 3.1 and EN 10204 3.2, Test Certificates for NACE MR0103 and NACE MR0175

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