The decision to use a v-guide on a belt is a decision that needs to be understood so a good choice can be made. V-Guides in general will not solve all problems that are associated with belt mistrack. In general it is best to use a non v-guided belt in most applications when one considers cost, durability, and performance.
V-Guide Limitations
V-guided belts include single or multiple profiles on the underside of the belt to aid in the piloting of the belt. Belt manufacturers never recommend the v-guide be the primary source for piloting a belt. The v-guide should be used for temporarily restraining the belt during operation from intermittent side loads on the belt that will create a situation where the belt will mistrack.
With the understanding of the use of v-guides, it can be understood that a v-guided conveyor design when compared to a crowned pulley design should expect to exhibit:
- Lower belt life due to abrasion.
- Greater difficulties in tracking due to flat pulleys.
- Increased side to side belt movement due to the clearance required for the v-guide.
- The possibility of the belt being lifted off the frame due to external forces successfully pushing the v-guide out of it track and up on to the frame.
- Lower capability in terms of belt speed due to the abrasion of the v-guide.
Crowned Pulleys
Controlling of flat conveyor belts is most commonly achieved by utilizing trapezoidal (crowned) shaped pulleys. The crowned pulley utilizes an even distribution of opposing lateral forces to provide sufficient tracking power to guide a conveyor belt.
The key to comparing crowned pulleys to v-guided is to understand that crowned pulleys are free from rubbing or scraping of the v-guide itself. Alignment adjustments on each side of the conveyor permit control of belt to pulley alignment. These adjustments allow independent control of each side to bring these opposing lateral forces into balance for true center tracking.
The use of crowned pulleys normally requires that the conveyor be capable of sustaining pre-tension belt elongation values of approximately .2% to .3%. Tension values below this will result in insufficient lateral steering forces, as well as lower tension forces on the belt that drive friction and carry the load.
The key point to understand is a crowned pulley will provide continual pilot action without inducing damaging wear or abrasion to the conveyor belt.
V-Guide Uses
When the forces greater than the lateral forces created by the crown act on the conveyor belt, an additional source for piloting the belt is required. There are many methods for this, edge guides for durable edge belts, cam rollers attached to fabric belts, and the v-guide — the most commonly used.
V-guided conveyor applications do exist; some applications are as follows:
- Where pulley flanges can not be used or may interfere with products being conveyed
- Conveyors with long center distance where true tracking is critical.
- Side loading or unloading applications.
- Where the belt runs on its edge in a vertical position instead of lying flat on a conveyor surface.
- When reversing applications are required.
In some cases, v-guides must be used; the designer must choose wisely to assure the application is a good fit with all items noted above being considered.
