The Difference between Integral Flange and Weld Neck Flange

Different appearance
The end of the integral flange is thicker than that of the weld neck flange. The inner diameter of the integral flange is the same as the nominal diameter except for PN1.6 MPa and DN450. The integral flange has higher neck and thicker wall thickness, which can be clearly seen referring to the standard of the weld neck flange.

Different applications
1. The integral flange is a flange connected with equipment, such as a flange on a valve, which is an integral part of the valve and is not connected by welding. Integral flanges are mostly used in equipment manufacturing, hardly used in pipeline design.
2. The weld neck flange is used when connecting with valves, pumps and other equipment. When the WN flange is welded to the pipeline, the size of its tail interface is consistent with the outer diameter and wall thickness of the corresponding pipeline, so it can be directly butt welded.

Different technical requirements
1. Integral flange
Another meaning of the national standard flange is that flanges produced according to the size and tolerance range required by the national standard are different from flanges not produced according to the standard size, which are also called second standard flanges (it is incorrect for some people to call them non-standard flanges). Usually, some unscrupulous merchants will reduce the thickness and outer diameter of flanges to save materials.
 
They also use waste steel or scrap steel to process flanges. Usually, this kind of steel is a waste material with substandard chemical composition and mechanical properties, and even the flange is produced by private steelmaking in underground steel mills. The old steelmaking technology used in this private steelmaking can not guarantee the mechanical properties and weldability so that the flange may not be welded with steel pipes when in use, or the steel itself may leak after welding.
Therefore, when purchasing flanges, we should choose national standard flanges as much as possible. If the funds are limited, we must carefully observe and measure the flange size and test its material to avoid being fooled.

2. Weld neck flange
1) Weld neck flange shall be subject to ultrasonic inspection without delamination defects.
2) The steel shall be cut into strips along the rolling direction, bent and butt welded into a ring, and the steel shall form a cylindrical surface. Welded flange with neck shall not be machined directly from steel plate.
3) Full penetration welds shall be adopted for butt welds of circular rings.
4) The butt weld of the circular ring shall be heat treated after welding, and 100% radiographic or ultrasonic inspection shall be conducted. The radiographic inspection shall meet the Class II requirements of JB4730, and the ultrasonic inspection shall meet the Class I requirements of JB4730.