Weld Neck Flange

Weld Neck Flange is a high-strength flange with a long neck, which is connected to the pipeline through full penetration butt welding. It is widely used in pipeline systems with high pressure, high temperature, and flammable and explosive media. Its structural feature is the integrated forging of flange and long neck, with the neck wall thickness consistent with the pipeline, which can effectively disperse stress and is the first choice for industrial pipelines with extremely high safety requirements.

Structure and Manufacturing

The butt welding flange consists of a flange plate, a sealing surface, and a long neck

The long neck is perfectly matched with the outer diameter and wall thickness of the pipeline, forming a continuous metal structure during welding without stress concentration points;

The sealing surface is mostly a protruding surface (RF), a concave convex surface (MFM), or a tenon groove surface (TG), suitable for metal gaskets or wrapped gaskets to ensure sealing under high pressure;

The manufacturing process adopts forging technology (carbon steel A105, stainless steel 304/316, alloy steel pipe WP22, etc.), which eliminates forging stress through heat treatment to ensure material uniformity.

Performance advantages

High pressure tolerance: The fully welded structure between the neck and the pipeline can withstand pressures ranging from Class 150 to Class 2500 (1.6MPa to 42MPa), which is much higher than that of sliding flanges and suitable for high-pressure systems such as steam and oil and gas.

Strong fatigue resistance: The long neck design ensures a smooth transition of stress along the neck, making it less prone to cracking due to thermal expansion and contraction under temperature fluctuations (such as -196 ℃ to 650 ℃).

Excellent sealing performance: The continuous sealing surface formed by butt welding reduces the risk of leakage, especially suitable for toxic and corrosive media such as chlorine gas and hydrogen sulfide.

Applicable scenarios

Connection of hydrogenation units and high-pressure reactors in petrochemical industry;

The main steam pipeline of a thermal power plant (made of 12Cr1MoV material with welded flanges that can withstand high temperatures of 540 ℃);

Station connection of natural gas long-distance pipelines (resistant to high pressure and frequent pressure fluctuations).