A 12D pipe bending is a pipe bend that the bend radius is 12 times the pipe outside diameter. What is 12D in bend pipe? The RADIUS of a 12D pipe bend is actually what is 5 times the nominal diameter. So if you had a 10" diameter pipe, the radius of the centerline of the bend would be 50 inches. How do you know a 3d or 12d bend? It is the radius of bend of the elbow with reference to a point,the point is determined by the intersection of two lines from the elbows socket end (which makes the shape of one quater of a circle). Methods of bends in carbon steel While the industry provides various means for bending the carbon steel pipe to the 5D bend, heat induction is the most widely-known–but not the most popular–technique in the industry. The pipe to be bent is subjected to extreme temperature, and when at the desired heat, a mode or model in the dimensions of the 5D bends is forced through the heated pipe, causing the pipe to conform to the bend of the 5D pipe dimensio...