By Carol Wasson
Whether it’s coal mining or power plant applications, material handling systems are integral to overall efficiency. Rather than merely moving material from point A to point B, today’s optimum conveyor performance must meet a myriad of standards—from ensuring specified flow rates, to achieving operational goals of minimizing vibration, noise, and belt wear and tear—while maximizing plant capacities and uptime. Today’s maintenance teams are finding that consistently meeting the latter requirements via existing conveyor systems can be as simple as undergoing a few strategic component upgrades. A current example involves looking beyond the traditional or standard wing pulley designs to the use of the new V-shaped wing pulley—an upgrade that significantly boosts uptime and safety initiatives.
The Five Star mine in southern Indiana has replaced traditional pulleys with Chevron Wing Pulleys, manufactured by Superior Industries. According to Randy Smith, maintenance planner for the mine, the new V-shaped pulleys are replacing plain steel flat face pulleys or rubber lag pulleys in multiple locations that include tail, gravity take-up, bend and snub functions. “The main reason we wanted them—especially on the bend rollers and on the tail—is that they are self cleaning and this prevents ice buildup on the pulley face in the wintertime,” said Smith. He explains that the V-shaped wings deflect material out and away. “Ice buildup can cause severe belt damage or mistracking—and ice buildup is even a problem with rubber lag pulleys. There will always be some moisture retention on a belt, especially on a bend roller, as it is contacting the top side of the belt. You can’t get that 100% clean, and that ice just keeps building up. With the Chevron pulleys we have eliminated any ice buildup, and we’ve extended the life of our belts while minimizing any downtime,” he said.
A major power plant in western Pennsylvania installed the Chevron Wing Pulley on a main belt line. Group Supervisor Clyde Hopkins said they had heard of the successful operation of the new V-shaped pulley at another power plant facility. “We decided to replace a failing drum pulley on our main yard belt with the Chevron pulley,” Hopkins said. This conveyor system is at the center of their operation and distributes coal to the cleaning plant and back to the main belt line that feeds the plant. Past component failures on this main belt caused costly downtime and major headaches for the crew as they had to fire up several smaller conveyors to continue to feed the plant. So the failing drum pulley was replaced with a Chevron Wing Pulley sized at 36- x 51-in. and engineered with five 7/16-in. bushings within the shaft.
“We’re very pleased with the performance of this pulley,” Hopkins said. “First, it’s a self-cleaning component, and that makes the belt track really well because it doesn’t allow material to lodge between the belt and the drum itself,” he said. But most importantly, Hopkins said, the Chevron pulley has dramatically re-duced noise levels. “In fact, it is so quiet, we often check to see if the belt is even running,” he said.
Engineering Perspective
Jarrod Felton, chief engineer of standard products for Superior Industries, said that in comparison to the standard wing pulley, for example, the V-shaped Chevron Wing Pulley provides smooth operation with less vibration, less belt wear, less of an impact and load on the bearings, and less noise. Felton points to the fact that the Chevron wing pulley has a round end view, which allows continuous belt contact. The belt is essentially rolling around a circle, which significantly reduces any beating action on the belt. On the other hand, the standard wing pulley is “apexed” or shaped as a many-sided polygon. So the belt is always raising and lowering over one or two wings as the pulley is going around, which causes the belt to flap and results in more belt wear, and much more vibration and noise. As to the latter, Felton said it’s similar to comparing a jet engine to a vacuum. Tests have shown the standard wing pulley operates at an average 120-dBa noise level, while a Chevron Wing Pulley averages only 70 dBa.
According to Felton, when a conveyor belt stretches around a traditional wing pulley, it stretches over each wing bar. “That stretching is hard on the belt and the splice, and can cause damage. Our third-party testing (provided by Fenner Dunlop) revealed that the Chevron pulley’s continuous belt contact greatly extends belt life over that of traditional options; and the resulting reduction in beating action means less vibration, and less potential for mistracking, rubbing, and creating sparks and fire hazards.”
Additionally, said Felton, the round end view design of the Chevron Pulley means it can be applied in a number of applications, including its use as a bend or snub pulley. “According to CEMA, a wing pulley should be used in a non-drive situation—either as a tail or take-up pulley—where there is 180° of wrap angle. But since the round surface of the Chevron Pulley allows it to operate so differently than the traditional wing pulley, we can use it in non-180° wrap angle applications (bends and snubs) quite successfully.”
When downtime is so costly, it is extremely critical to prevent material buildup, wear and tear on a splice, or a breakdown of the belt carcass. With safety as an ongoing priority, reducing hazardous vibration and harmful noise levels is imperative. Upgrading operations with new conveyor component technologies is a welcome alternative. Boosting uptime and safety is a valuable payback.
About the Author
Wasson is a freelance writer who routinely writes about industrial applications. She wrote this article on behalf of Superior Industries and can be reached at: carolwasson@hotmail.com.
