A Socket weld flange could replace threaded flange, to minimize the risky of leakage.
B No need to beveling before welding.
C Welding work outside of the pipe, will not penetrate the pipe bore
D It is recommended for applications where internal welding operations are particularly difficult. This sock welded construction eliminates internal pockets while avoiding warpage of welding heat and damage to the flange face caused by weld spatter. It has the same internal pressure as the sliding on the flange, and has a better fatigue life.
A Socket welded flange requires higher skills for welder, which the welding need to make sure that the expanding gap between the pipe and shoulder is 1/16 inch.
B The expansion gap create the chances for the crack defects, especially for anti corrosive pipes as stainless steel pipes, so the cracks between the pipe and flange will cause the corrosive problems. So SW flange will not be compatible with corrosive or radioactive environment, as this solid buildup at the joint can cause operational and maintenance problems. So that's why people use but welding more often as the welding completely through the pipe from outside to inside, which makes the connects more strong and anti corrosive.
Socket Weld Flange vs Slip On Flange
Socket welded flange shape is similar to slip on flange, differently it has a shoulder at the inner bore.