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April 2, 2009 By: Darren Constantino, North Coast MediaEstablished in 1954, Geneva Rock Products Inc. is an aggregate producer and contractor based in Utah. The company began to experience excessive equipment downtime owing to metal contamination, so personnel sought a supplier capable of resolving the issue.
The problem was found to be on a conveyor feeding shot rock into a vertical impact crusher. Ed Clayson, Geneva Rock aggregate superintendent, said, “We found that tramp metal contamination was mixed with product flows moving into the expensive crushers. We were regularly repairing wear parts within the rotor assembly. The downtime on the crusher for maintenance — not to mention the replacement parts — resulted in unnecessary expenses,” Clayson said.
Hoping to find a magnet supplier that could offer a solution to this costly problem, personnel from Geneva Rock attended the ConExpo-Con/Agg trade show in Las Vegas. There, they were introduced to Eriez Magnetics, an Erie, Pa.-based company.
Eriez officials determined the Geneva Rock application called for its Series 7000 suspended electromagnet. This powerful magnet effectively removes damaging tramp metal from thick, solid flows such as coal, limestone, sand and gravel. Eriez sales representative John Johnson conducted an audit of the line in question.
“The most important factors in the selection of the proper suspended electromagnets are burden depth, belt width, suspension position and tramp iron size,” Johnson explained. “Other considerations relate to the size and density of the aggregate material and functional issues that relate to the line itself, including belt speed and belt incline.”
For this specific application there was another fundamental consideration — altitude.
Located in Utah, the Geneva Rock electromagnet would sit 5,500 ft. above sea level. Since heat dissipates more slowly at higher elevations, the installation at Geneva Rock required a special electromagnet coil assembly to ensure proper heat dissipation and provide long coil life.
According to Eriez, the Series 7000 suspended electromagnet design is the product of a unique computer program developed by the company. For special requirements, the most efficient and economical adaptations of standard models can be computer-designed in minutes, resulting in no long deliveries or spiraling costs for tailor-made magnets.
Coil considerations
The coil is one of the most important design characteristics of an electromagnet. Cutting coils cuts overall costs, and that’s how other manufacturers of magnetic equipment reduce their costs, according to Eriez. However, this can also create an opportunity for problems.
Johnson said, “Eriez uses conservative coil design techniques to ensure longer and more productive magnet life. We offer the warranty to demonstrate our confidence.”
Shortly after installation, a problem was found where the pulleys on the self-cleaning gear failed. Eriez repaired them at no cost and in a timely fashion,” Clayson said.
Immediately following the installation of the new suspended electromagnet, significant improvements were noted. Clayson said the magnet was extremely successful in reducing wear-part replacement in the crusher rotor.
“We knew we needed the equipment and I knew Eriez had the Cadillac. We didn’t wait for the results. We bought three units — two for Geneva and one for a sister company.”
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