Page 332 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

312 Major Process Equipment Maintenance and Repair

Sheave grooves must be
like this not this
I

Figure 7-2. Good vs. bad grooves in a V-belt sheave.

A shiny groove bottom indicates that either the sheave, the belt or both
are badly worn and the belt is bottoming in the groove.
Badly worn grooves cause one or more belts to ride lower than the rest
of the belts, and the effect is the same as with mismatched belts. This is
called “differential driving.” The belts riding high in the grooves travel faster
than the belts riding low. In a drive under proper tension, a sure sign of dif-
ferential driving is when one or several belts on the tight side are slack. Note
Figure 7-2 for groove details.
Check alignment of drive. Sheaves that are not aligned properly cause
excessive belt and sheave wear. When the shafts are not parallel, belts on
one side are drawn tighter and pull more than their share of the load.
These overloaded belts wear out faster, reducing the service life of the
entire set. If the misalignment is between the sheaves themselves, belts
will enter and leave the grooves at an angle, causing excessive cover and
sheave wear and premature failure.