Pipe cap, also known as plug, cap, etc., is a pipe fitting welded to the end of the pipe or installed on the external thread of the pipe end to cover the plugging pipe. According to the design, the pipe cap can be divided into convex pipe cap, conical shell, reducer section, flat cap and shrink mouth. Among them, the convex cap includes hemispherical cap, oval cap, dish-shaped cap and spherical crown cap.