The slip-on welding flange which neck is lower, the stiffness and bearing capacity of flange is improved compared to the plate flange. Compared with the Welding Neck Flange, welding workload, welding rod consumption is higher, can not afford the high temperature and pressure and repeated bending and temperature fluctuations, but the field installation more convenient, can omit weld stake knead injury process, which is more popular used.