Proper belt alignment must be ensured along the entire length of the conveyor, with special attention paid to the belt at the transfer point. The conveyor structure must be “true” (relative to the centerline) and “level” (side to side).
All pulleys, snub rollers, and carrying and return idlers must be “square” with the frame (i.e., perpendicular to the belt centerline) and parallel to each other. Finally, the conveyor belt must be straight (less than 0.5 percent camber) and in good working condition (no cupping or damage), and the ends must be squared and properly spliced.
Good conveyor belt tracking requires cleanliness—therefore, no buildup of carryback on the idlers or pulleys can be allowed. The pulley lagging should not be worn nor irregular in shape. Belt tension should be adjusted to meet the manufacturer’s recommendations.
The tension must be high enough to prevent slippage between the drive pulley and the belt while also causing the belt to conform to the pulley crowns. Slippage will cause excessive wear to both the drive pulley lagging and the bottom side of the belt.
If possible, operators should observe the belt being loaded and while it is operating, checking to ensure the belt is properly loading in the center and, if not, making any adjustments possible to correct this condition.
For safety, operators must ensure that the belt is stopped—following all lockout/tagout procedures—when making adjustments, remembering that making several small adjustments is preferable to making one or two large adjustments that may result in overcompensation.
Importantly, tracking adjustments to the conveyor belt should never be done by adjusting pulleys. This can cause uneven conveyor belt stretch and/or pulley and shafting problems. The following process is recommended.
- Spread tracking adjustments over some length of the conveyor preceding the problem area.
- Begin by tracking and adjusting idlers on the return run, working toward the tail pulley
- Adjust the idlers on the top run in the direction of belt travel. Start with the belt empty, and then begin loading the belt gradually while observing the operation of the belt up to full load condition.
If the belt runs to one side at a particular point or points along the conveyor structure, the cause will probably be due to the alignment or leveling of the structure, the idlers and pulleys immediately preceding that particular area, or a combination of these factors.
In such a circumstance, the belt will move toward the edge of the roll (idler) where it first comes in contact. In extreme cases, belt alignment devices may be required to overcome short-term tracking problems.
Finally, material spillage leads to fugitive material being piled around operating conveyors. This material poses a safety hazard and lends itself to being picked up by the wind and blown around and off the property, creating environmental issues and affecting nearby businesses or residences.
Reference
NIOSH Mining Program Report of Investigations, «Dust Control Handbook for Industrial Minerals Mining and Processing», second edition.
