Elbow Terminology

CLR (centerline radius) – If the elbow were a complete circle, this would be the distance from the very middle of the circle to the centerline of the tube or pipe. The larger the circle, then obviously the CLR gets bigger also. If you are conveying abrasive material, you would want the CLR to be as big as possible to lessen the resistance through the corner.

Tangent- The tangent is the short run of straight on each end of the elbow. Without the tangent, couplings would not slide on properly or seal. A standard tangent is always twice the O.D. of the tube or twice the nominal size of pipe. For example a 4” OD elbow would have 8” long tangents and a 3” pipe would 6” long tangents (even though 3” pipe is not 3” OD but 3” ID instead).

If you are having trouble fitting an elbow into a specific location, usually adjusting the tangent length will help customize your fit.

Degree- This is pretty straight forward. People who bend elbows can make any degree you would like from 1 to 180, but the Center-Line-Radius would still have to be kept at a standard length (such as 12”, 18”, 24” and so on).

Diameter- This is simply the measurement from one side of the tube or pipe to the other side. Tubing is expressed in O.D., while pipe is expressed in I.D. For example, 6” tubing is 6”O.D. and 6” pipe is 6 5/8” O.D.. Tubing is straight forward, but people tend to get confused when talking about pipe. The #1 rule is to be consistent with your terminology, either always say “ 6” pipe” or 6 5/8” O.D.”.