According to its radius of curvature, there are long radius elbow and short radius elbow. Long radius elbow refers to its radius of curvature is equal to 1.5 times the outside diameter of the pipe, that is, R=1.5D; A short radius elbow means that its radius of curvature is equal to the outer diameter of the pipe, that is, R= 1.0d.(D is the diameter of the elbow, and R is the radius of curvature).