Weld neck flanges can significantly save space and reduce weight. Moreover, they can prevent leakage at the joints and boast excellent sealing performance. The reduced size of weld neck flanges is due to the smaller diameter of the sealing elements, which in turn decreases the cross-sectional area of the sealing surface. In addition, flange gaskets have been replaced with sealing rings to ensure the perfect fit between mating sealing faces.

The main functions of weld neck flanges are classified as follows:

1.Facilitating disassembly and inspection when pipeline malfunctions occur.

2.Enabling replacement of a specific pipeline section in case of localized faults.

3.Connecting pipelines while maintaining reliable sealing performance.

Weld neck flanges have specific technical requirements and parameters for manufacturing and application, and must be produced and processed in strict accordance with established procedures:

1.Steel plates used for manufacturing weld neck flanges shall undergo ultrasonic flaw detection to ensure the absence of laminar defects, thus guaranteeing sound quality and performance. Production and inspection must comply with specified quality standards to ensure the steel plates are free from quality defects.

2.Butt welds of the ring forgings shall be heat-treated after welding and subjected to 100% radiographic or ultrasonic inspection. Radiographic inspection shall conform to Grade Ⅱ requirements specified in JB4730, while ultrasonic inspection shall meet Grade Ⅰ requirements of the same standard. Weld neck flanges shall be manufactured and welded in accordance with relevant welding specifications and techniques, complying with the corresponding national production standards and requirements.

3.Steel plates shall be cut into strips along the rolling direction and then bent and butt-welded into rings, with the surface of the steel forming the cylindrical surface of the ring. During production, it is prohibited to directly machine steel plates into necked flanges; the manufacturing must follow designated processes and procedures.