Overland conveyors can offer big energy savings

Contributed

January 16, 2018

Overland Conveyor
While truck transport is limited to grades of 6 percent or below, overland systems can take on inclines of up to 35 percent.

Overland conveyor systems deliver cost-effective operation within a wide spectrum of capacities, while offering quiet and environmentally sound material transport. When used in place of loaders and haul trucks, overland systems allow operations to significantly reduce fuel costs and expenses associated with labor, workers’ compensation, Mine Safety and Health Administration (MSHA) training, emissions, engine depreciation, ongoing maintenance, and more.

To optimize the time-and-money-saving advantages of overland systems, producers should consider several top maintenance strategies.

Protect the belt

On an overland system, the belt is the biggest investment — and it must be adequately protected against costly and unnecessary damage. One of the most effective belt protection solutions is that of the V-shaped wing pulley. While extending pulley life, the V-shaped design is engineered to prevent material buildup and belt damage while greatly minimizing noise and vibration during operation.

Versus the conventional wing pulley, the V-shaped pulley design delivers several advantages.

A conventional wing pulley is particularly susceptible to material buildup, wing bending, and noise and vibration during operation. Belts and tail pulleys are subject to damage and failures when fugitive material becomes entrapped between the belt and the tail pulley. If the material is not removed, several serious issues can occur. First, degraded material, which breaks into smaller parts, can be carried between the belt and the pulley, causing excess wear and tear on the belt; as well as potential belt slippage and mistracking. Large entrapped material with sharp edges can create an uneven belt surface and can puncture, gouge, or rip the belt. Also, trapped material can be ejected back onto the return side of the belt and can become entrapped in the pulley repeatedly until it finally degrades — or until it damages the pulley face, bends the pulley wings, or causes pulley or belt failure. Removing material buildup from the pulley or repairing or replacing pulleys and belts may result in significant downtime and maintenance costs.

The V-shaped wing pulley deflects material away from the pulley and belt, minimizing the potential of pulley or belt damage. Its V-shaped wing configuration also results in continuous belt contact, and its round-edged wings overlap along the length of the wing pulley to permit the conveyor belt to be supported by multiple wings along the belt width. This eases the transition of belt contact from one wing to the next, which, in turn, minimizes vibration to the belt, extends belt life, and reduces the amount of noise generated by the wings contacting the belt.

Conveyor Belt
Automatic return training idlers provide continuous alignment, centering the belt and reducing or eliminating belt damage.

Ensure proper belt tracking

There are numerous belt training products to choose from, the most common being self-aligning idlers, which are used to address mistracking caused by issues such as off-centered loads, wind, structural settling, belt splicing errors, idler installation errors, material buildup, and more. Self-aligning idlers are a lower cost belt training solution that’s targeted to both the carry and return side of the conveyor belt. When a belt mistracks, it contacts the side guide rollers, causing the self-aligner to pivot. This action brings the belt back to center. When choosing a self-aligner, look for designs with key features that protect belts from additional ripping, such as urethane (versus steel) side guide rollers that are softer on the belts and concave-shaped side guide rollers that are easier on belting edges.

Another innovative belt tracking solution is the automatic return training idler, which provides continuous alignment, centering the belt and reducing or eliminating any belt damage.

Consider how alignment issues may affect a multi-mile-long overland conveyor. For example, a maintenance crew is often required to continually monitor the system by driving back and forth along the conveyor route to check for potential mistracking. Manual adjustments to the idlers are frequently needed. On the occasions that problems are not caught in time, belts can be damaged. By installing automatic return training idlers in varying intervals, alignment issues can be eliminated, freeing up maintenance time for key efficiency gains.

When choosing a belt trainer, make sure that the return trainer is indeed automatic. If a trainer is not automatic, it requires frequent adjustments — and that really defeats the purpose.

Also, depending on the brand one chooses, the return training idler is either a contact or contact-free product. Much of the industry prefers a return trainer that is contact free, as this eliminates wear parts and any side contact to the belt. So, a contact-free trainer leads to longer wear life and less maintenance. Additionally, look for models featuring rubber lagging which sheds material and increases friction, keeping the belt aligned. Note that certain trainers operate by using the gravity of the belt weight. Using the weight of the belt to make the roller shift (and thus track the belt) is the optimum method. The misaligned belt puts pressure on one side of the training idler, and this pressure causes the training idler to tilt and guide the belt back to center.

V-Shaped Wing Pulley
V-shaped wing pulleys deflect material away from the pulley and belt, minimizing the potential of pulley or belt damage.
Overland System
Overland system capacities vary from a trickle all the way up to 30,000 tons per hour.

Avoid oversizing 

When specifying a system, bigger isn’t necessarily better. A common misconception is that oversized equipment lasts longer and requires less maintenance. Conveyors should be sized according to the expected load, yet allowing for a small capacity increase. For example, specifying a larger belt than what is truly required will ultimately result in additional belt and idler rolling resistance and less energy efficiency.

Use correctly-sized, efficient motors

Manufacturers typically install new premium efficiency motors on overland systems. Since these motors perform most efficiently near their designed power rating, it’s recommended to run at between 75 percent and near 100 percent of full-load rating. Alternatively, when a system is running at 50 percent of capacity or lower, the efficiency of the motor drops dramatically. Motor size should be matched to the horsepower requirements of the load. Again, some producers may oversize a motor thinking that it will require less maintenance; however, the energy savings realized from a properly-sized motor will outperform any maintenance savings derived from a larger model — especially in regions where energy costs are high.

Monitor and minimize rolling resistance

Pay close attention to various features and benefits when specifying belts and idlers. For example, manufacturers are now designing belts with special covers that help to counter rolling resistance. As to idlers, they all may seem alike, but they vary in performance. Ask your conveyor manufacturer to recommend the right bearing and seal type for your application. Proper idler spacing is also important, as it affects both the shape and support of the conveyor belt. Consult with the Conveyor Equipment Manufacturers Association (CEMA) or your conveyor manufacturer for idler spacing and rolling resistance formulas.

Maintain preventive maintenance

Bottom line: the efficiency of the overland system is only as good as one’s preventive maintenance program. As to motors, regular lubrication and cleaning helps minimize loss from friction and heat and extends motor life. Also, systems must be periodically checked for improper belt tensioning, belt slippage, non-rolling idlers, and material carryback. Each of these issues affects energy efficiency, while resulting in costly downtime and excessive wear and tear on overland systems and components.

Alan Schmidgall is vice president of customer service for Superior Industries.

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