Conveyor skirting is an important enough component to an aggregate or mining operation that it seems odd to find it is often a point of cost-cutting.
Conveyor skirting is an important enough component to an aggregate or mining operation that it seems odd to find it is often a point of cost-cutting. Ripped or torn skirting can mean rock and sand everywhere, or escaping dust endangering workers’ health. It can mean hours of labor cleaning up the spillage and a line shut down until the skirting is repaired or replaced Û cutting into profits.
In conveyors, the main source of trouble is the skirting material. In an effort to save costs, officials from Argonics Inc. contend, many companies are using rubber. Its potential pitfalls include a high amount of friction created between the skirting and the conveyor belt resulting in drag, overworked conveyor motors, and wear. Rubber is also porous, allowing fines to become embedded in the skirting. In effect, the skirting becomes abrasive and wears down the top cover of the conveyor belt.
We’ve had rubber skirting before, underneath the VSI [Vertical Shaft Impact] crushers where it’s real tight on the belt itself, says Jeremy Russell, crusher foreman with Knife River Corp.’s Deer Island, Ore., site, specializing in concrete sand and gravel as well as other products. The skirting creates heat, and by the end of the day, the rubber would melt to the belt. We’d have a hard time the next day firing up the belt.
There was also apparently so much dust coming from underneath the crushers that, along with down-force of air, the skirting would wear badly and blow out. Dust would then get into idlers and wear out the bearings.
Rubber on rubber Û as with rubber skirting and a rubber belt Û creates a high amount of friction, says Jeff Riddell, outside sales representative for Conveyor Care Co. of Portland, Ore. Basically more heat translates into more wear.
Today, an increasingly common solution to these problems is skirting composed of a more durable and longer-lasting material: polyurethane, lasting eight to 10 times longer than rubber in the same application.
We went to a polyurethane, and all our problems ceased, Russell reports. There was no heat buildup, and the skirting wasn’t melting. Other parts such as idlers were also saved as a result.
Polyurethane skirting has been in four or five years in our plant, and I can’t even see any wear, says Charlie Fobert, supervisor with Wilsonville Concrete Products in Wilsonville, Ore.
Polyurethane has a much lower coefficient of friction with rubber than does rubber itself. Because less heat is generated, you get less wear and longer life out of the skirting, says Riddell.
Both Knife River and Wilsonville Concrete obtained polyurethane skirting from Argonics, whose polyurethane is actually formulated with a proprietary chemistry that allows skirting to last two to three times longer than other polyurethane products, according to the company. Their polyurethane pretty much outlasts any on the market, Riddell says. I can have a roll of polyurethane 50 feet long and 6 inches wide with the same hardness throughout the entire roll.
In addition to providing a variety of thicknesses and sizes of belt skirting, Argonics also manufactures polyurethane skirting to match an industry’s specific application. For example, the company provides a special skirting with a 20-, 35-, or 45-degree beveled leading edge so that the trough angle on the conveyor belt is better sealed. Argonics also manufactures a form called the Snap-loc Dust Seal, designed to contain particulate matter and prevent it from becoming airborne. Another product called Fold-n-Seal combines both the above-mentioned forms. It is composed of two pieces of flat skirting held together with industrial-strength cloth mesh. One piece of skirting runs right along the chute, while the other curls up and rides along the trough angle to create a dust seal.
The company likewise tailors polyurethane hardness for specific applications. If an operation is working with an elevated temperature or a belt speed that’s faster than normal, a harder polyurethane can be used that will soften up in the elevated environment.
Much of the cost savings of polyurethane comes in labor, Argonics officials note, whereby plant personnel do not have to continuously follow the line and adjust the skirting. There is also cost savings with a skirting that does not wear and allow material to escape, leading to lost manhours consumed in removing spillage.
Longevity has been the major factor, Riddell concludes. You can obviously buy a rubber product that’s lower in cost, but if you have to replace it three or four times in a quarter, [versus] polyurethane once every eight months Û you can see the difference. Û www.argonics.com; 906/226-9747, ext. 240; 906/226-9779