Bend Ovality

Published: March 25, 2017
by Charles Busada
Placing a machined metal ball inside of a tube to test its ovality

Ovality, or out-of-roundedness can be a problem in pneumatic conveying. Our tolerance of out of roundness varies with our tube outer diameter. Ovality can be checked with calipers (as usually the case checking the OD) but in certain circumstances, we need a machined ball (passing the ID). The example below is for conveyance of golf balls through tight radius CAB (butyrate) bends.

Chicago Metal Fabricators have a nice online ovality calculator.

Ovality is the out-of-roundness or difference between maximum and minimum dimensions (usually) of Outer Diameter. It is a measure of high and low points at any one section around the tube. Ovality tolerance is the total spread, inside which both the maximum OD dimension and minimum OD dimension must abide. At Busada, for pneumatic conveyance of paper cups where the general rule is a .250 clearance between tube ID and paper cut, our maximum out of roundness may not exceed 0.075”).

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