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Conveyor Belting Repair

Many forms of belt damage lend themselves to relatively simple methods of repair.

For most operations, conveyor belt-life is measured in years. To achieve the lowest operating cost, inspection of the belt should be a scheduled maintenance procedure. Any belt damage noted during these inspections should be repaired promptly to prevent small problems from becoming big trouble. Damage to a belt can permit the entrance of moisture or foreign materials into the belting, and thus promote premature failure of the belt. To preserve the belt, it is important to make prompt and effective repairs of any damage.

Vulcanized repairs can be made during scheduled maintenance outages when sufficient conveyor downtime is available to allow the long time required to make a vulcanized joint. In nearly all cases, a vulcanized repair requires removal of a complete section of belt and then either re-splicing the remainder or adding an additional piece of belting, often called a “saddle.”

Fortunately, many forms of damage lend themselves to relatively simple methods of repair.

Repairable forms of damage include:

  1. Grooves in which the top cover is worn away by abrasion from material or a foreign object
  2. Longitudinal rips in which the belt is slit by a fixed object, such as a metal bar becoming wedged into the conveyor structure
  3. Profile rips in which a small tear in the belt edge extends inward
  4. Edge gouges in which blunt objects tear chunks of rubber out of the belt edge, generally caused by the mistracking of the belt into the conveyor’s structure

Repairs can be made with self­curing, adhesive­like repair materials to keep moisture or foreign material out of the carcass. Mechanical fasteners are another method for repairing damaged belting to restore service without significant downtime and extend the service­life of expensive belts.

Belt Repair Using Adhesives

Adhesives provide a cost-effective means to repair conveyor belting with a high quality bond. Use of adhesive compounds will save downtime and money in maintenance budgets without requiring heavy vulcanizing equipment or creating obstructions with repair hardware in the belt. Adhesive repair compounds offer simple solutions for belt maintenance that are durable, reliable, and easy to use. There are a number of products available to do this. They include solvent-based contact cements, heat-activated thermoplastics, and two-component urethane elastomers.

A black adhesive is spread over a section of the conveyor belt.
Specialized adhesives can be used to repair a damaged belt.

All of these systems require some degree of surface preparation, ranging from a simple solvent wipe to extensive grinding or sandblasting. Some may need an application of a primer to improve adhesion.

Most commonly used for standard cold vulcanized splices, solvent cements are also used for bonding repair strips and patches over damaged areas.

Thermoplastic compounds are “hot melts” that are heated to a liquid state and then harden as they cool, forming a bond. As they cool quickly from their application temperature of 120 to 150 degrees Celsius (250° to 300° F), the repair must be performed quickly, before the adhesive returns to the hardened (non-adhesive) condition. Problems encountered with thermoplastic adhesives include the possibility of shrinkage as the adhesive cools and the risk that high-temperature operations or cargo may cause a softening of the adhesive, leading in turn to failure of the repair.

Urethane products are typically two component systems that the user can mix and then spread like cake frosting directly onto the area to be repaired. They typically achieve operating strength in a short period, one to two hours, but will continue to cure for eight to twelve hours until full cure strength is reached.

All adhesive systems offer fairly simple applications, assuming the instructions are followed. Of course, it is critical that the adhesive manufacturer’s instructions be followed carefully as to surface preparation, component mixing, pot life, application technique, and cure time. The length of time for an operating cure and full cure may provide the basis for selecting any particular product.

It is important to get the profile of the repaired area down to match the profile of the original belt in order to preserve the repair and avoid more damage to the belt.

It is also important to identify and resolve the cause of the problem, removing the obstruction or correcting the mistracking that led to the belt damage in the first place. Otherwise, the resumption of operations after repair merely initiates a waiting period until the damage recurs and the repair must be made again.

Topics: Belt Conveyor System Maintenance

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