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Sheave Alignment on Equipment that is V-Belt Driven It is extremely important that new or replacement pulleys be installed and aligned properly. Any pulley types used in industry must be properly assembled, and bolts or setscrews tightened to the correct torque. Most pulleys are attached to the shaft with a tapered bushing which fits a mating tapered bore in the pulley. This type of system consists of a bushing, a pulley and often a setscrew and key. Bushings come in several diameters. This allows for a reduction in the parts inventory required in your plant because one bushing can used with a number of different size pulleys.
V-Belt drives do not require alignment to as close tolerances as most other types of drives-but unless the belts enter and leave the sheaves in a relatively straight line, wear is accelerated. The two most common causes of misalignment are shown above: (a) the shafts of the driver and driven machines are not parallel, and (b) the sheaves are not located properly on the shafts. To check alignment all you need is a straight-edge or, for drives with longer centers, a steel tape. If these aren’t available, you can, as a last resort, even use heavy string. Just line the straight-edge or tape along the outside face of both sheaves as shown in the illustration. Misalignment will show up as a gap between the sheave face and straight-edge, or perhaps as a "break" in the tape or string. Make sure that the width of the outside land is equal on both sheaves when using this method. A third cause if misalignment in "titled" or improperly mounted sheaves. Sheaves that are already installed can be checked for "tilt" by using a spirit level. Posted 7 January 2002 |
