Disadvantages of Mechanical Splices
If the materials to be conveyed are hot, the transmission of heat through a metal fastener may be a factor that leads to the selection of a vulcanized splice. When the material temperature exceeds 121 degrees Celsius (250 degrees F), the amount of heat passing through the metal fastener into the belt carcass can weaken the fibers, ultimately allowing the fastener to pull out. In these applications, a vulcanized splice would be preferable.
Failure to inspect fasteners and the resulting failures of those fasteners can result in severe belt damage. If the fasteners begin pulling out on a portion of the splice width, longitudinal ripping of the belt may occur. When belt and fasteners have been properly selected, pullout is usually due to insufficiently tight bolts or worn hooks or plates. Plate-type mechanical fasteners typically allow the replacement of individual plates, which, if performed when damage is first observed, may eliminate the need to cut out and replace the entire joint.
Using the wrong size or type of mechanical fastener can greatly reduce the operating tension capacity of a belt. The extra thickness of a mechanical splice not properly recessed or of the wrong specification will make sealing the transfer point almost impossible. Splices that are oversized and too thick to pass through the transfer-point area can catch on the wear liner or skirtboard, abusing the splice and shortening its life. These splice issues sometimes require the wear liner and skirtboard to be higher above the belt, allowing more material to reach the edge-sealing system. This, in turn, results in accelerated wear and spillage. Often, the fasteners used in the splice will not be properly trimmed, and these extended rivets or bolts can catch on other components like skirtboard-sealing systems or belt cleaners.
Most, if not all, mechanical splices will allow some small quantity of the conveyed material to filter through the joint itself. This material will fall along the run of the conveyor, resulting in cleanup problems and the potential for damage to idlers, pulleys, and other conveyor components. Plate-type fasteners, in a well-made joint, are quite free of material leakage. The hinge-type fasteners are all subject to problems with fine materials sifting through the joint; this problem is eliminated with vulcanized splices.
While it does provide greater strength, the V-shaped splice does have its costs. It can require up to 3 meters (10 ft) of belting for completion. That may be a significant amount of expensive belting to be discarded.
Mechanical splices are used on fabric belts for making the belt endless or for repairing rips and holes; however, on steel-cable belts, they can be used only for temporary repairs.
Safe Splice Design
Both mechanical and vulcanized splices must be designed with factors of safety when compared to the expected belt tension. These design factors for mechanical fasteners are built into the manufacturers’ selection tables. Vulcanized splices on high tension steel cable belts are often individually designed by the belt manufacturer or consultant failure to match the splice with the belt and account for the correct service and safety factors can result in catastrophic splice failures leading to injury, death, loss of production, and equipment damage.
Maintenance and Installation Stations
Some operations develop what is called a belt-splicing station along the conveyor. Here, tolls and equipment are stored for splice maintenance, and the space and work surfaces are available for splice installation. This may also be the point at which a new belt is pulled onto the conveyor.
A splice should be located where there is plenty of room, ideally including workspace on both sides of the conveyor structure. The station should provide protection for the belt from climate conditions and fugitive material. The space should be placed at a point where there is a distance of at least five belt widths of straight conveyor stringer on either side of the point where the splice will be made. Power should be readily available, including outlets for hand tools.
See Also: Notching the Trailing Side of a Conveyor Belt Splice Part 1 | Part 3.
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