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www.rockproducts.com ROCK products • May 2016 • 19 extensive research and development center at this facility (the other is in Germany) to meet the needs of the iron and steel industry. Costly Downtime with Crusher Repairs According to Dixon, the process to ap- proach the Eriez team began in 2013 when expensive crushers were being damaged by undetected tramp metal. "The trigger for this project was the fact we spent nearly $750,000 on three crusher repairs for several years and had to find a way to prevent that from happening in the future," he said. "We called Eriez and Kemper and asked for a solution." The first phase was choosing and in- stalling the proper metal detector. Magnesita established several bench- marks and provided metal test cubes to ensure that the Eriez Model 1250 E-1 Metal Detector with 10-in. open- ing, would perform to specifications. The test cubes included 5/8-in. fer- rous, 1.25-in. stainless steel and 1.25- in. manganese. A "performance guar- antee" was included in the contract, meaning if the metal detector did not perform at the quarry as specified during a one-month commissioning phase, then Eriez and Kemper would remove the detector with a full refund. Once in-house testing at Eriez was complete, the metal detector was in- stalled in March 2014 and passed all performance tests the following month, according to Dixon. "Our old metal de- tector was outside the tunnel of the quarry, so we were getting false trips due to CB radios and handheld walkie talkies," he said. "Even when we moved the old detector inside the tunnel, we were still getting interference. Eriez made a lot of recommendations to stop the false trips with the new unit." The new metal detector – located in- side the tunnel – is on the 30-in. wide #5 conveyor belt at an incline of 30 de- grees with a feed rate of 380 tph. The belt travels at 540 ft. per minute. Eriez recommended a flag marker system where a flag drops onto the belt within 24-in. of either side of the tramp metal detected. After the flag drops, the con- veyor coasts to a stop for quick metal removal. Greater Efficiency with Eriez SE Magnet Once officials at Magnesita were satis- fied with the metal detector, the next phase was based on another Eriez recommendation, which involved the company's Model SE-7520 Self-Clean- ing Suspended Electromagnet. The unit is located above ground on the 36- in. wide Q7 conveyor belt, about 100 yd. from the metal detector, according to Dixon. The Eriez electromagnet unit was installed in October 2014. Magnesita was using an older manual cleaning style, permanent suspended magnet. The newer Eriez electromag- netic unit operates at a much higher efficiency. This self-cleaning electro- magnet has field strength 2.5 times stronger than the older permanent magnet at the same cross-belt 10-in. suspension height. "Our older permanent magnet had enough strength to pull ferrous off the top of the burden surface, but it could not pull up the imbedded mate- rial," Dixon recalled. "Also, it was not a self-cleaning model, so material would accumulate on the magnet and require manual cleaning. We really needed a more powerful magnet to prevent any kind of tramp metal from going into our two crushers." "The Eriez SE magnet has the ability to pull out metal with greater force than Suspended Magnets • Metal Detectors Heavy Duty Feeders Double-Team Dangerous Tramp Metals! Eriez' Suspended Magnets and Metal Detectors remove tramp metals before they reach your valuable crushers and down- stream equipment. Download Catalogs & Product Selection Guides SUSPENDED MAGNET & 1200 SERIES METAL DETECTOR Call 888-300-3743 or visit www.eriez.com Call 888-300-3743 or visit www.eriez.com