As with vulcanization, there are several types of mechanical fastener, each created for use with different belt widths, lengths, thicknesses, speeds, tensions and belt cleaners.
Identifying the correct fastener for the application is essential to ensure maximum splice life and performance. Mechanical fasteners are available in two types – hinged and solid plate – and with a variety of attachment methods, including rivets, bolts and staples.
For extractive applications, rivet-hinged fasteners allow for the greatest versatility. They combine top and bottom fastener plates, which are joined at one end by two wide hinge loops. Each pair of plates sandwiches the belt end and is secured to the belt with a staggered pattern of rivets. The rivets penetrate the belt without damaging or weakening the belt carcass, because they slip between the load-bearing carcass fibres. The rivets are installed in a staggered pattern to provide maximum resistance to pull-out and to distribute splice tension evenly across the width of the belt.
No matter what the belt condition, mechanical fasteners are a good choice for both new and older, worn belts. Rivet-hinged fasteners can be used on belt thicknesses ranging from 3mm to 25mm with minimum pulley diameters of 230mm.
Concerns about comparable vulcanized splice strength can also be dismissed: rivet-hinged fasteners have a long history of service on belts, with mechanical fastener ratings of up to 350kN/m or 2,000 pounds per inch of width (PIW).
Because removing the hinge pin can easily separate hinged fasteners, these designs are essential in mining and quarrying applications where belts must frequently be removed, extended or shortened. In addition, hinged fasteners provide several installation benefits in these applications.
For example, the hinged fastening system permits separate halves of the belt to be pre-spliced, requiring only the hinge pin to be inserted at the job site. Also, if belts of different thicknesses must be joined, hinged fasteners can often satisfy this need by allowing two different fastener halves to be joined by a hinge pin acceptable to both. Moreover, mechanical fasteners can be installed quickly and easily, on-site, by in-house maintenance crews, usually in less than 60min.
Mechanical splice installation tools are easily transported to the job site and offer splice installers versatility in installation methods. Depending on the site’s available power source, mechanically attached rivet-hinged splices can be installed with as little as a basic installation tool and hammer, or with a modified installation tool and choice of electric or air-actuated power source.
Mechanical fasteners can also be countersunk during the installation process, so the fastener plates are flush with the belt’s cover, which eliminates interference with tight-fitting scrapers, skirt boards and other conveyor components. Countersinking also strengthens the fastener-to-belt attachment by positioning the plates closer to the belt’s load-bearing carcass fibres. The belt strength remains intact, as only a portion of the top cover material is removed, while the belt’s vital carcass fabric is left intact.
Besides virtually eliminating fastener rip-outs, rivet-hinged splicing cuts downtime by giving maintenance crews more freedom in deciding when to replace a splice. Any splice damage or wear and tear is very visible on a mechanical splice, and operators can finish a shift even with a few plates missing and not have to worry about belt failure.