The difference in structure between neck flat welding flanges and neck butt welding flanges lies in the different connection modes of the nooks and flanges. Neck flat welding flanges are generally nooks and flanges Angle connection, while neck butt welding flanges are flanges and nooks butt connection.
1, centrifugal pump flange connection method is different: neck flat welding flange and neck butt welding flange in the structure of the difference is the different connection way of the pipe and flange, neck flat welding flange is generally a pipe and flange Angle connection, and neck butt welding flange is flange and pipe butt butt.
Flat welding flanges generally can only be connected with the pipe, but can not be directly connected with the butt-welding pipe fitting; Butt-welded flanges can be directly connected to all butt-welded pipe fittings (including elbows, tees, reducers, etc.), including pipes, of course.
2, centrifugal pump flange weld forms are different: flat welding weld can not be radiographic inspection, and welding weld can be. The type of welding seam between pipe and flange with neck flat welding flange is fillet weld, while the type of welding seam between flange and pipe with neck is girth weld. Flat welding is two fillet girth welds and butt welding is one butt girth welds. The difference between flanges with neck and flanges without neck is that flanges with neck have one more place in the pipeline welding site than flanges without neck. Flanges without neck is also flat flanges. The boss without flange is also flat fillet weld. The welding seam of the butt-welding flange with neck and the pipe connection belongs to class B seam, and the welding seam of the flat welding flange with neck and the pipe connection belongs to class C seam, and the non-destructive testing is different after welding.

3, nominal pressure is different: the nominal pressure of neck flat welding flange: 0.6-- 4.0Mpa, and the nominal pressure of neck butt welding flange: 1- 25Mpa grade, obviously, the pressure grade of neck flat welding flange is lower.
4. The stiffness of butt welding flange with neck is larger than that of flat welding flange with neck. The strength of butt welding is higher than that of flat welding, and it is not easy to leak.
Flat welded flanges with neck and butt-welded flanges with neck cannot be replaced at will. From the perspective of manufacturing, flat welded flanges with neck (SO is the abbreviation of SLIPON) with large internal warp means small weight and low cost. In addition, neck butt-welded flanges with nominal diameter greater than 250mm (WN is the abbreviation of Weldingneck) should be tested, while flanges with SO do not need to be tested. So the cost is relatively low.