I come from an inline inspection pigging background. We always refer to bends as 1.5D or 3D, etc. A lot of field maintenance or pipeline construction personnel refer to them as 1.5R or 3R. I have always been curious why they use R instead of D.
I have been told that a pipeline 3D bend is equivalent to a bend with a radius of 3 x the outside diameter of the pipe, hence 3D. I have also been told that a 3R bend means the same thing as a 3D bend. They are both 3 x the outside diameter of the pipe. A lot of people get confused about the R...
