Pipeline elbow and pipeline bend

An "elbow" is defined as a length of pipe with a sharp bend in it. Most commonly elbows have a 90 degree bend, but they could have bends larger or smaller than that and still be referred to as "elbows."

Elbows can be made out of metal, plastic or other materials. Metal elbows are sometimes cast or formed through a variety of processes.  The discussion here will be limited to forming elbows by steel pipe bending of a straight piece of pipe.

A pipe bend means a piece of pipe which are bent to some angle to join two pipings.  they can be nearly any bending radius and angles . Pipe bends are commonly produced on site to meet a specific need by hot induction bending or cold bending. Aelbow means a specific pipe bend as per the standard ANSI/ASME B16.9 (or EN 10253, or other pipe fittings standards). Commonly the elbows have a bending radius of 1.5D or 1D (Here the D means nominal diameter of this bend) ,which are called “Long Radius elbow (LR elbow)” or “Short Radius elbow(SR elbow)” . and the angle of an elbow is 45 degree or 90 degree usually, some times there are also custom-designed elbows which are 30 degree,60 degree ,180 degree or other angles.

The pipe bends should be as per the standard of  ANSI/ASME B16.49 which did not specific the bending radius and angle , the regular pipe bend radius are 2.5D, 3D ,5D ,7D or 8D , but it can be any other bending radius according to the design need, and bending angle can be in any degree, 5 ,10 ,15, 90 degree or any other. People said “All bends are elbows but all elbows are not bend”, it is not true . Actually “All elbows are pipe bends but not all bends are elbows”  is more reasonable.

Sources :

http://www.cmrp.com/pipe-elbows

http://thepipefitting.com/difference-between-pipe-bend-and-elbow.html