Conveyor Belting Design
Straight-warp belting
The straight-warp conveyor belt design provides a new type of belting material capable of withstanding high edge pressures. The straight-warp design, known as TunnelMax conveyor belting, is thinner in construction in order to reduce the required minimum diameter of the pulleys in the conveyor system. Reducing the physical size of the pulleys makes for easier installation—an advantage in restricted areas such as those often required in tunnel applications. In addition, the smaller size reduces the costs of the pulleys.
A conveyor system can consist of 24 – 50 or more pulleys, depending on the conveyor layout and configuration.
Reducing the size of all the pulleys throughout the conveyor system will serve to dramatically reduce the overall costs of the conveyor.
The TunnelMax conveyor belt is constructed with a lighter carcass and lighter rubber compound, making the physical weight of the conveyor belt lower. The lighter weight material decreases the required horsepower and also decreases the power consumption of the conveyor system. Using the lighter carcass and lighter rubber compounds gives the belting approximately a 5% decrease in overall weight without decreasing the strength and durability of the belting. Belting is designed and supplied in a single-ply construction up to 1000 PIW and up to 2000 PIW in a two-ply construction.
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By GlobalDataThe TunnelMax belt also has excellent properties of resistance to tearing and heavy impact loads. The straight-warp design also has better flexibility over multiple-ply designs, which allows the conveyor belt to trough in the carrying idlers for better material handling and minimized material spillage. The TunnelMax straight-warp design allows the belting to hold up to years of hard use, conveying hard rock in tunneling applications.
The belt is designed to take high-edge pressures applied by the self-adjusting curve idlers and guide idlers in horizontally curved sections of the tunnel. It is also designed to withstand the induced edge pressure and does not delaminate at the belt edges, because it has a higher adhesion between the belting covers and carcass than commonly-supplied belting. Delimitation of the belt edges reduces the belt capacity because it reduces the physical belt-width of the belting. Edge pressure is increased in smaller radius horizontal curves and having a belt that is designed to withstand this makes the conveyor belting easier to train in the horizontal curve sections of the tunnel, and also increases the life of the conveyor belting.
TunnelMax belting can be supplied to the jobsite ready to be installed into the conveyor system because the mechanical fasteners are installed at the belting factory before the conveyor belt is rolled for shipment. With the mechanical fasteners preinstalled, a roll of belting can be added into the conveyor system in approximately 30-40 minutes depending on the belt roll length. The mechanical splices that are used on the belting can be installed quickly if needed with a few hand tools and all of the required hardware preinstalled on the mechanical splice, without any loose screws or pins. The TunnelMax conveyor belt will retain the mechanical fasteners because the fabric weave has been designed in conjunction with the design of the mechanical fastener for maximum retention. The mechanical fastener can be easily installed by using only the fastener bed plate, hammer tool and a hammer onsite or in the tunnel if needed. Belting is also provided with a steel belt core so that the belt cores can be stored anywhere after the belting is removed without deterioration. The steel belt cores can be reused to remove and store the conveyor belting at the end of the project. These steel belt cores can be sized to match any existing belt winders or conveyor equipment as needed.
The typical stretch of a conveyor belt is approximately 2% of the length of the belting. TunnelMax conveyor belting has only about 1% belt stretch. The belt stretch is a major factor to consider, especially on a long tunnel conveyor system because the difference of 1% can be as much as 150m to 180m.
Conveyor Belting Safety
Due to the design of its fabric weave, TunnelMax conveyor belting has little to no belt edge-strings. If the belting starts to string at the edges it will only produce small strings for short periods of time because of the design of the fabric and its interlocking weave pattern (Figure 1). This design feature eliminates the long belt-strings that can and have caused equipment damage or injuries on the jobsite.
Conveyor belt strings are a major safety issue because the strings are traveling at speeds up to 3.56m/second and the strings can catch on and wrap around objects and equipment in the tunnel, including personnel. The belt strings can also get caught on the pull-cord cables or e-stop switches and cause an e-stop fault, which will shut down the conveyor system. Belting string problems are magnified when the conveyor is mounted in the crown of the tunnel or above areas where personnel are located because the strings can get wrapped around a piece of clothing or a body part and cause major damage. Fabric belt strings are extremely strong and they will usually take or remove anything that they get wrapped around without breaking. Belt strings are also known to damage or restrict the movement of the bearings and bearing seals of the belt structure idlers and the pulleys throughout a conveyor system.
Belt strings can also accumulate in certain areas to the extent that it sometimes makes maintenance nearly impossible without having to remove the strings. TunnelMax belting can be supplied with a molded edge, which eliminates belt edge strings completely and provides a sealed smooth belt edge without any belt fabrics being exposed.
TunnelMax conveyor belting is more flexible and is designed to withstand belt-edge pressure: both of these characterizations make the belt tracking better and easier to manipulate for belt-training purposes. A conveyor belt that tracks better and is easier to train means personnel are less exposed to the moving parts of a conveyor, thus decreasing the chance of an injury around the conveyor system.
TunnelMax conveyor belting can be made to any fire-resistant specifications necessary to achieve the requirements of projects. Having received MSHA approval Par 14, the TunnelMax belt also has other fire-resistance approvals for various countries throughout Europe and Asia.
Conclusions
TunnelMax conveyor belting has been specifically designed for the conditions encountered by tunnel conveyors and has been used on multiple tunnel conveyor projects. One of these projects has had TunnelMax belting in operation for over three years, removing an abrasive material with a conveyor availability of 95%. To date the belting is only showing minimal wear. Engineers are dedicated to developing the ultimate conveyor belt for the tunneling industry, and are working on improvements that will further reduce energy consumption, handle curves in complex conveyor systems even better, be able to run on smaller-diameter pulleys, and further eliminate potentially dangerous belt strings.
