February 13, 2014
Sheave Alignment Is the First Step in Making V-Belts Last
By Stan Riddle
VibrAlign recently released an excellent “how-to” video on its You Tube channel. This video explains not only how to use the VibrAlign Belt Hog laser sheave/pulley alignment tool, but also introduces the 3 concepts of sheave misalignment and how to correct them.
However proper sheave alignment is only one step in making belts last. To get the maximum life out of belts, be sure to:
Use the Right Belt Size – Belts come in many different widths, sizes, and profiles. Make sure the belts and sheave groove(s) match.
Never “Roll” Belts On! – It’s easy to get in a hurry and roll the belts on without loosening the motor. But it is very unsafe, can easily damage belts and sheaves, and induces hard loads on bearings and shafts.
Check Your Sheave Groove(s) for Wear – Sheave wear is often overlooked, because many people think a rubber belt could never wear out a cast iron or steel sheave. But they can, and do wear out. A sheave groove measuring tool is inexpensive, and can usually be picked up at your local power transmission supplier.
Assure Proper Sheave Alignment – Laser tools really are best for this. With a laser tool, you can correct not only the horizontal offset misalignment but also the vertical and horizontal angular misalignment which are difficult to detect with a straightedge or string.
Assure Proper Belt Tension – Proper belt tension is not an exact science, but is important for long belt life. Too little tension causes excessive heat and noise, and can cause the belts to slip and “pop”, reducing their life. Too much tension causes band breakage, and dramatically decreases bearing life, due to excessive radial loading. Invest in a belt tension tool, and become familiar with how to use it. These can also be picked up at your local power transmission supplier.
Assure Proper Ventilation – Belts can generate quite a bit of heat in their normal operation. Be sure that belt guarding is well ventilated to help dissipate this heat.
Recheck Belt Tension After Break-In – This step is often overlooked by mechanics, but is important. As belts match the groove profile of the sheave, stretch a little, and heat up, belt tension normally can change. A quick re-check and re-tightening if needed can increase belt life substantially. When re-tensioning belts use the laser tool to ensure the horizontal angular alignment is maintained.
These simple steps take a few more minutes, but can and will dramatically increase the life of belts, sheaves, and bearings.