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November 2018 www.coalage.com 27 high-hp motors continued our first order, we had a motor built with- in a year." It was precedent setting, and a mile- stone in the evolution of longwall technol- ogy in general, Steve Mohler said. "Noth- ing like that had ever been built that would meet the MSHA specs." Old Ben deployed three. "There were two on the head gate and one on the tail gate, and each of those were 450 horse- power (hp)," Scott Mohler said. The motors worked as envisioned, and word got out. Demand then rocketed. "It happened almost overnight," Steve Mohler said. "As soon as these water-cooled mo- tors were demonstrated in a mine, it didn't take long for all the manufacturers and all the other mines to want to do it be- cause the noise levels in the mines went down and the ambient temperature in the mines went down." MTI soon dominated the market it had created. "Because of the proactivity of the company, we were able to sell enough longwall motors and build relationships with the customers because we had prod- uct that no one else had," Steve Mohler said. "Any other manufacturers that have come along have never caught up with us in the U.S. in terms of sheer numbers of machines operating in the mines." One reason was the custom-built motors were designed for relatively easy upgrades. "We designed our frames to ac- cept larger hp," Scott Mohler said. "When we MSHA-certified those, we certified them on the total range that could go in- to that frame." Time would pass, longwall faces would grow, and the demand for hp would in- crease. "We were able to upgrade these to a higher hp without doing recertification or anything," Scott Mohler said. "Some of these motors went through as many as two upgrades until they reached their maxi- mum," he said. "They didn't have to build a new motor, they just had to do a redesign on the winding." Which was advantageous. As the years clicked by, the trend in hp demanded went through at least four distinct stages, from the 450 hp required in 1988 to the 2,200 hp per conveyor motor demand- ed today, Steve Mohler said. "They were pretty evenly spaced," he said. "If you do the math there you come up with, on the average, every five to seven years hp was increased." Today, "the total hp on a face conveyor now is 6,600 hp," Scott Mohler said, which is "achieved by combining three motors." Similar motors were eventually built for crushers and stage loaders, he said. "Those are two other parts of a longwall mine that converted to water-cooling not at exactly the same time but shortly after that." Over the course of three decades, MTI built more than 940 water-cooled motors. Of those, 130 were built to be upgraded. The benefits offered by MTI's wa- ter-cooled motors, which come standard on some Caterpillar solutions, read like a laundry list, but can be summed up in a word, dependability. Perhaps nothing exemplifies this as does the design of the junction boxes. Historically, junction boxes were al- most guaranteed to be destroyed when the motors were pulled and hauled to the sur- face for servicing or repair. "Most of them would get torn off before they ever reached the surface," Scott Mohler said. "When we designed our motor, we designed it with a junction box where the leads connect as part of the motor. In other words, it wasn't a bolted-on part." That means the box is "integral to the motor," Steve Mohler said. "It is welded to and is part of the frame. It is not some- thing that can be removed or torn off or damaged in transportation, or moving the motor around, or mounting it or un- mounting it." The innovation is another example of MTI applying lessons learned from its mo- tor repair business, he said. "When we saw the various modes of failure, things that were repetitively in damaged conditions or destroyed for whatever reason, logistics or what have you, all of that was taken into consideration when we made the design of our frames," Steve Mohler said. The result is an offering that rarely enters those modes of failure. Company literature reports the motors are compact, offer high-overload tolerance, are more ef- ficient, feature a lower operating cost, and are adaptable. Beyond offering a quality product, "we feel really great about our products being manufactured in the USA," Steve Mohler said. "We feel good, and our workers feel good, about contributing to the positive motion that our economy's going." MTI's water-cooled motors for mining applications can be built in the 150-hp to 2,750-hp range. Each machine is a "hand- built machine," Steve Mohler said. The only components the company doesn't build is the rotor and stator iron and the bearings. "Outside of a couple of very small auxiliary items, we build the en- tire machine," Steve Mohler said. "We have a lot of quality control for our product be- cause we are building it all here." The advent of the water-cooled explosion-proof motor for longwalls leads to quieter, cooler, and thus safer working condititions. (Photo: Mohler Technology Inc.) The junction box on a water-cooled Mohler motor is 'integral to the motor,' welded on, and can sustain the wear normal to the removal of a motor for service. (Photo: Mohler Technology Inc.)