ANSI/ASME B16.5 and B16.47 Weld Neck Flange

What is Weld Neck Flange?

A Weld Neck Flange is a type of flange designed to transfer stress from the flange to the connected pipe. It is also known as a tapered hub flange or high-hub flange. Weld Neck Flanges are engineered to provide a secure and stress-relieving connection in demanding industrial applications. Their tapered hub design and butt-weld connection make them a preferred choice in situations where maintaining the integrity of the piping system is crucial.

A Long Weld Neck (LWN) Flange, also known as an extended weld neck flange, is a type of flange that shares similarities with the conventional welding neck flange but features an elongated neck. This elongation makes it well-suited for specific applications, particularly as a nozzle for columns or barrels in various industrial processes. Here are some key features and benefits of weld neck flanges:

1. Tapered Hub Design: One distinctive feature of a weld neck flange is its tapered hub or neck. This long, tapered extension provides a smooth and gradual transition from the flange to the pipe. The gradual taper helps in reducing stress concentrations at the base of the flange, enhancing the overall strength and durability of the joint.

2. Butt-Weld Connection: Weld neck flanges are intended for butt-welding to the end of a pipe. The weld neck extends from the flange, and the pipe is welded to both the inner and outer sides of the flange. This type of connection results in a robust and reliable joint, particularly suitable for high-pressure and high-temperature applications.

3. Stress Distribution: The design of the weld neck flange allows for the effective distribution of stress. By providing a smooth transition between the pipe and the flange, stress is spread out more evenly, minimizing the risk of localized points of failure. This is especially important in applications where pressure and temperature fluctuations can lead to thermal expansion and contraction.

4. Raised Face or Ring Type Joint (RTJ): Weld neck flanges can have a raised face (RF) or a ring-type joint (RTJ) on the flange face. The raised face allows for the use of gaskets, improving the sealing performance of the joint. The ring-type joint is a specialized sealing method often used in high-pressure applications.

5. Applications: Weld neck flanges are commonly used in critical applications where a strong and reliable connection is essential. Industries such as oil and gas, petrochemical, chemical processing, and power generation often utilize weld neck flanges due to their ability to handle high pressures and temperatures.

6. Code Compliance: Weld neck flanges are manufactured according to various industry standards, such as ANSI/ASME, DIN, AWWA, GOST, etc. It's important to select the appropriate standard and pressure class based on the specific requirements of the piping system.

Advantages of Weld Neck Flange?

1. High Structural Integrity: Weld neck flanges are known for their high structural integrity and strength. The long tapered hub provides reinforcement to the attachment weld, reducing the risk of leakage and ensuring a robust connection.

2. Reduced Stress Concentration: The smooth transition from the flange to the pipe reduces stress concentration at the base of the flange, minimizing the risk of fatigue failure.

3. Excellent Pressure Resistance: Weld neck flanges are suitable for high-pressure and high-temperature applications. The design helps distribute the pressure across the pipe, reducing the risk of failure under intense conditions.

4. Prevents Leakage: The welding of the neck to the pipe creates a continuous, smooth inner bore without any sharp corners or abrupt changes in direction, which helps prevent turbulence and reduces the risk of leakage.

5. Ideal for Extreme Conditions: Weld neck flanges are commonly used in critical applications, such as oil and gas pipelines, petrochemical plants, and power generation facilities, where reliability and durability are crucial.

6. Facilitates Radiographic Inspection: The long tapered hub of a weld neck flange allows for easy radiographic inspection of the weld, helping ensure the quality of the welding process.

7. Alignment Assistance: The extended neck of the flange facilitates easy alignment during the welding process. This is particularly useful when connecting pipes in complex systems.

8. Easy to Bolt: Weld neck flanges are easy to bolt due to the flange's circular shape and the availability of evenly spaced bolt holes. This simplifies the installation process.

9. Versatility: Weld neck flanges are available in a variety of materials and sizes, making them suitable for a wide range of applications and industries.

The Three Main Components of A WNRF Flanged Joint Are?

Two Mating Flanges ( WNRF Flange) :

This is the main component of the joint and is welded to the pipe. The weld neck flange has a long tapered hub, which provides reinforcement to the attachment weld. The flange also has a raised face that serves as the sealing surface when it comes into contact with the gasket.

Pipe:

The pipe is the second component of the joint and is connected to the weld neck flange through welding. The pipe carries the fluid or gas being transported through the system.

Gasket:

Placed between the raised face of the weld neck flange and the mating flange (which could be another weld neck flange or a different type of flange), the gasket provides a seal to prevent leakage from the joint. Gaskets are typically made of materials that are resistant to the specific fluid or gas being transported and are chosen based on the application's requirements.