Five tips to maintain suspended electromagnets

Proper care and routine maintenance checks go a long way toward saving money and the headaches that come with downtime, especially when it is preventable.

Routine checks are critical for all types of equipment, especially in quarry plants, cement plants, mines and recycling operations.

Suspended electromagnets (SE), which are available in both self-cleaning and manual cleaning models, have an average lifespan of 20 years. But to reach or even exceed that length, plant operators must schedule preventive maintenance checks to minimize costly downtime.

For manual-clean SEs, maintenance is straightforward. Plant operators should check SEs once a shift or daily for tramp iron that may have built up during operation. When removing tramp iron from the SE, timing is based largely on how much tramp is attracted to the magnet. Don’t let too much tramp iron build up on the magnet before turning it off to clean it. A cleaner magnet is a stronger magnet.

At minimum, product buildup and dirt should be cleared from the top of an SE once a month. Limestone dust, for example, can collect on top of the magnet box and act like an insulated blanket, which can weaken the magnet’s strength by heating it beyond its operating temperature. A cooler magnet is a stronger magnet.

Here are five tips to keep equipment – specifically SEs – in operating condition regardless of application or environment:

Check the rubber belt daily

Conveyor belts around SEs are available in a variety of widths based on the size of the magnet, but the same maintenance protocol applies because the equipment has its core functionality: The heavy-duty rubber belt and pulley are set up to discharge tramp iron from the magnet.

Put safety first when checking the belt on a self-cleaning SE. Stop the belt before troubleshooting or performing checks and maintenance. Routine inspections are required to increase the life of an SE belt. Plant operators can inspect a belt in the morning, only to discover a hole in it that afternoon.

On average, a rubber belt can last anywhere from six to 12 months. But lifespan really depends on the sizes and shapes of the tramp iron traveling on a conveyor that are attracted up to the SE. One large piece of tramp iron can destroy the belt on a self-cleaning SE, but the cost of a replacement belt pales in comparison to the damage and downtime that could be caused by this tramp metal destroying a long conveyor belt, crusher or other equipment downstream from the SE.

It is important to keep the belt around an SE running when it is energized. When running, it acts like a fan, helping to cool the magnet. Remember, a cooler electromagnet is a stronger magnet.

Because you cannot predict tramp iron and belt damage, it is critical to keep a spare belt on hand, as well as a belt repair kit. The kit includes rubber patches and epoxy compounds to repair small holes in the belt.

Check belt tension monthly

Efficient SE belt operation can be achieved without applying excessive tension on the pulleys.

If the tension is too tight, it can cause premature failure of the rubber belt, pulley shafts or bearings. If the tension is too loose, excessive sag could result in interference from the belt onto the conveyor the aggregates are traveling on.

The belt should only be tightened enough to prevent slipping when conveying tramp iron off the magnet. For best performance, have 1 to 2 in. of sag at the ends of the magnet corner. At the center, 3 in. is acceptable unless it interferes with material flow.

Grease SE bearings monthly

Lubricate bearings on a schedule consistent with other equipment in the same environment. An NGL1 No. 2 lithium-based grease is recommended.

A simple pump from a grease gun every month makes a noticeable difference. Limestone and cement dust will destroy bearings in short order if not lubricated on schedule. A destroyed bearing will lead to a costlier repair if the pulley shaft gets damaged. After 250 hours of running, check pulley hubs and tighten the screws to 17 lb. ft. of torque.

Check oil yearly

Make sure to check the oil level on all SEs – manual or self-cleaning – once a year. If low, fill it to the proper level and find the source of the leak.

The transformer oil within the SE should be changed every five years. In between, filter press the oil. An SE is strongest with fresh oil having a higher kilovolt value.

Contact a technician or service center

Routine checks and scheduled maintenance – procedures many plant operators already have incorporated into their production schedule – can go a long way to extend the life of an SE and avoid costly downtime.

Remember, while the lifetime of an SE is fairly predictable, the life of a rubber belt can vary, so it’s highly recommended to have a spare belt and belt kit on hand and at the ready.

Plant operators should also consider contacting a technician or service center to help keep production moving.

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John Klinge is the director of strategic sales-aftermarket at Eriez.