Page 331 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Installation and Maintenance of VBelr Drives 311

Any vibration in a system will cause the slack side of the belts to dance
up and down. Excessive vibration will also induce a vibration in the tight
side of the drive. The cause of the vibration should be determined and
corrected.
If a set of belts is perfectly matched, all belts will have the same
amount of sag. However, perfection is a rare thing and there will usually
exist some difference in sag from belt to belt. It is more important to look
at the tight side of a drive to be sure that all of the belts are running tight.
If one or more belts are running loose, the drive needs to be retensioned,
or the belts replaced with a matched set.
These conditions could also be caused by uneven wear of the grooves
in the sheave. These should be checked with sheave groove gauges.

Inspect Sheave8 Often

Keep all sheave grooves smooth and uniform. Burrs and rough spots
along the sheave rim can damage belts. Dust, oil, and other foreign mat-
ter can lead to pitting and rust and should be avoided as much as possible.
If sheave sidewalls are permitted to “dish out,” as shown in Figure 7-1, the
bottom “shoulder” ruins belts quickly by chewing off their bottom
comers. Also, the belt’s wedging action is reduced and it loses its grip-
ing power.

Figure 7-1. Dished-out V-belt grooves.