https://www.sstubecn.com/difference-among-weld-neck-flanges-socket-weld-flanges-slip-on-flanges.html What's the difference between weld neck and slip on flange? Weld neck vs slip on: Weld neck flanges, slip on flanges, socket weld flanges have different production standards, different applicable occasions. In addition, weld neck flange is the interface end pipe diameter and wall thickness is the same as the pipe to be welded. Slip on flange is the joint being processed to a concave table a little larger than the pipe outside diameter, pipe inserted in the inside for welding. Weld neck flange has better welding performance and less corrosion. Slip on flanges are generally used for low and medium pressure pipelines, weld neck flanges are used for connection of middle and high pressure pipelines, generally at least pn2.5mpa. Weld neck flanges are used to reduce stress concentration.