Weld Neck flange (WN RTJ WNRF WNFF)

Weld Neck Flange Introduction

Weld neck flanges are one of the most commonly used flange types in high pressure and high temperature piping systems. Featuring a long tapered hub that is welded to the pipe, weld neck flanges provide excellent structural integrity, smooth stress transition, and reliable sealing performance. They are widely applied in critical industries such as oil & gas, petrochemical, power generation, and chemical processing.

A Weld Neck Flange (WN flange) is a type of flange designed for high-pressure and high-temperature applications, commonly used in oil & gas, petrochemical, power plants, and pipeline industries.

According to Weld neck flange – Wikipedia,

A weld neck flange consists of a circular fitting with a protruding rim around the circumference. Generally machined from a forging, these flanges are typically butt welded to a pipe. The rim has a series of drilled holes that permit the flange to be affixed to another flange with bolts.

What Is a Weld Neck Flange?

A weld neck flange is designed with a long, tapered hub that is butt welded to the pipe. This design allows stress to be evenly distributed from the flange to the pipe, significantly reducing stress concentration at the joint. As a result, weld neck flanges are especially suitable for applications involving high pressure, high temperature, and cyclic loading.

Compared with other flange types, weld neck flanges offer superior mechanical strength, excellent fatigue resistance, and long service life, making them the preferred choice for critical piping systems.

Advantages of Weld Neck Flanges

Weld neck flanges provide several key advantages in industrial applications:

Smooth stress transition due to the tapered hub design
High resistance to pressure and temperature fluctuations
Excellent performance under cyclic and vibration conditions
Strong, leak-resistant welded connection
Long service life and high reliability

These advantages make weld neck flanges ideal for severe service conditions where safety and performance are critical.

Applications of Weld Neck Flanges

Weld neck flanges are widely used in critical piping systems, including:

Oil & Gas Pipelines
Petrochemical and Chemical Processing Plants
Power Generation Facilities
Refineries
Offshore and Marine Engineering
High Pressure and High Temperature Piping Systems

A Weld Neck Flange features a long tapered neck that is welded to a pipe, providing excellent stress distribution and structural integrity. It is ideal for critical applications where strength, reliability, and pressure resistance are required.

Types of Weld Neck Flanges Face type We Offer:

Flange Type	Description
WN RF (Weld Neck Raised Face)	Most common type for high-pressure pipelines.
WN RTJ (Weld Neck Ring Type Joint)	Used for severe, high-pressure applications, especially in oil & gas.
WN FF (Weld Neck Flat Face)	Suitable for low-pressure and non-critical piping systems.

Weld Neck Flange Face type

Raised Face Weld Neck Flange

RTJ Weld Neck Flange

Raised face weld neck flange bottom side has a small portion surrounding the bore that protrudes from the face. Gasket seat will be placed in this raised area. Depending on the different pressure ratings, different height of raised face will be adopted. For example, 150# and 300# flange raised face height is 1/6”, above 300# the height will be above 1/4”.

The ring-joint type of WN flange has a special made groove, here you can place a metal gasket seat to seal the connects. So this type of SW flange is used in high temperature and high pressure services.

WNRTJ Flange (Weld Neck Ring Type Joint)

A WNRTJ flange is a Weld Neck Flange with Ring Type Joint (RTJ) facing, designed for high-pressure and high-temperature applications. Unlike standard raised face flanges, RTJ flanges use a metal ring gasket that fits into a precisely machined groove on the flange face, providing a metal-to-metal seal. This makes them highly reliable for critical service conditions such as oil & gas pipelines, refineries, offshore platforms, and petrochemical plants.

Long Weld Neck Flanges

Long Weld Neck (LWN) Flanges are a variant of weld neck flanges with an extended neck that functions as a nozzle for tanks, vessels, or pressure equipment. Unlike standard weld neck flanges, which are butt-welded to pipe ends, LWN flanges are typically welded directly to the vessel body, offering reinforcement and smooth stress distribution.

Reducing Weld Neck Flanges

Reducing Weld Neck Flanges are a type of weld neck flange designed to connect pipes of different diameters, combining the functionality of a weld neck flange with a reducer. They are ideal for high-pressure systems that require a smooth flow transition between dissimilar pipe sizes.

Weld neck Flange Materials We Offer

Standard	Material Grade
Carbon Steel	ASTM A105, A350 LF2, A694 F52/F60/F65
Stainless Steel	ASTM A182 F304/L Weld neck flange, F316/L, F321, F347, A182 F51 Weld neck flange, F53, F55 Weld neck flange
Alloy Steel	ASTM A182 F11, F12,F22, F5, F9, A182 F91
Nickel Alloys	Inconel 625, Incoloy 825, Hastelloy C276
Duplex / Super Duplex	UNS S31803, S32205, S32750, S32760
Special Materials	904L (1.4539), Monel 400, Titanium, Aluminum, Copper-Nickel