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As one of the most technologically advanced manufacturing plants in the industry, Robinson Brick continually upgrades its production operation, paying careful attention to quality. If part of the company’s system is not keeping pace with production, the company quickly addresses the issue.
About three years ago, the primary crusher and the two hammermills the company used to process its clay began slowing production and causing daily downtime. The hammermills were high-maintenance and could not handle the frequent swings in moisture content. Production was often reduced to a crawl when the hammermills encountered wet chunks of clay.
Maintenance personnel were spending over five hours each night working on the hammermills, not to mention the additional time for the crusher and associated feed belts. “We were constantly replacing the tips and shanks on the hammermills and balancing them. They had to be extremely well balanced to handle the clay,” says Tony Fabrizio, Robinson Bricks director of manufacturing and research and development. “Between the primary crusher and the two hammermills, replacement parts were costing up to $20,000 per month, and the man hours to keep the crusher and hammermills going were too high. The inefficiency was not acceptable.”
Along with Plant Manager Mike Gomez, Fabrizio began searching for an alternative.
Easy Operation and MaintenanceIn the fall of 2000, Robinson purchased a Stedman Grand Slam™ 4860 impact crusher, GS4860AR/HC-T-X, with a capacity range of 100-150 tons per hour (tph). “We chose the Stedman because it was the most straightforward,” Fabrizio says. “It was easy to use and maintain, and was also cost-effective.”
The new impactor replaced both the primary jaw crusher and the two hammermills that had functioned as secondary and tertiary crushers, as well as a little-used pan grinder. During the initial reduction or first stage, the breaker bars on the impactor impel material against the primary apron. During the second stage, the reduced material passes through to the second apron for final reduction. Both aprons allow precise gap adjustment to ensure properly sized product for the specific application.
The impactor provides up to a 30:1 material reduction ratio for more properly sized material the first time through. An open discharge on the impactor eliminates any clogging or buildup of material exiting the crushing chamber. The impactor also increases crushing capacity and throughput so that the circuit runs more efficiently. It can handle a wide variety of materials, ranging from wet and tacky to hard and abrasive.
Maintenance on the impactor is designed to be fast and easy. The rotor breaker bars can be reversed or removed quickly—typically in two hours—helping to minimize downtime. Additionally, the front and rear housing on the impactor is hinged and, when opened, provides unobstructed access to all areas of the crushing chamber and rotor. The rotor lock table allows breaker bars to be rotated or replaced by one person with a minimum of downtime.
Customized DesignAnother benefit of the new impactor was that it was built to Robinson’s specifications. One of the options Robinson chose was an air cannon with a timer. The air cannon periodically discharges a blast of air into the crushing area to dislodge dry material buildup, thereby reducing cross-color contamination and keeping buildup to a minimum. To further minimize material buildup, Robinson also had heaters installed on the aprons and nose liner of the housing.
The intake hood and the crusher support structure were also customized to simplify the mounting of the impactor. The impactor was also equipped with a proximity switch on the front-hinged housing for disengaging the crusher drive motor if the crusher should be opened while the rotor is turning.
To give the plant additional control over the product, Robinson Brick outfitted the new impactor with its own variable frequency drive for the 300-hp crusher motor. The drive allows the speed of the mill to be increased or decreased to maintain the desired end product, and also helps when the moisture content is higher than normal and greater speeds are required.
Feed hoppers meter the material into a grizzly feeder and directly into the new impactor. Feed size coming into the impactor ranges from loose dirt to grapefruit-sized clay. What emerges ranges in size from a fine powder to 1⁄2-in. particles.
The impactor processes a mixture of 100 percent clay and grog at the rate of 70 tph. With the old system, the average was 65 tph. It operates 11 to 12 hours a day and handles two feed streams—the clay feed from the grizzly and the return feed. Only about 10 to 15 percent are returns, compared to a much higher 20 to 25 percent return rate experienced on the old equipment.
As the new impactor was being delivered, an accident occurred just a mile from Robinson Brick, and the impactor was damaged so badly that it could not be installed. Robinson had prepared for the installation and was ready to shut down the plant. Stedman worked overtime to build a new impactor for Robinson. Within six weeks, another impactor was constructed and ready to be installed.
“Stedman did an excellent job for us. They took care of us, and that’s what matters,” Fabrizio says.
Increased EfficiencyRobinson is also pleased with the overall service it’s received from Stedman. “Whenever we’ve needed assistance Stedman has been right there. The Stedman guys know what they are doing, and we can get in touch with them during off hours and on the weekends,” Fabrizio says.
Overall, the company is very satisfied with its new grinding operation. “We are very pleased with the Stedman impactor. It was the right choice. It has eliminated a lot of our grinding downtime,” says Fabrizio.
“Our nightshift maintenance time was previously six to eight hours each evening—now it is typically three hours per night,” Gomez explains. “Our overall downtime on this line—a combination of nightshift maintenance and operating time lost during the day—was 10 to 12 hours daily. Now it is only three hours in a 24-hour period, which is incredible. And our monthly part replacement cost has gone from $18,000 to $20,000 [across the original pieces of equipment] to only $6,000.”
Bob Jaster, president and COO of Robinson Brick agrees. “[The new impactor] has effectively increased grinding efficiency by 20 percent. I am really happy we bought it,” he says.
For more information:For more information about Robinson Brick Co., contact the company at 1845 West Dartmouth Ave., Denver, CO 80110-1308; (800) 477-9002; e-mail firstname.lastname@example.org or visit .
For more information about the Grand Slam impactor, contact Joe Bennett or David Vest at Stedman, 129 Franklin St., P.O. Box 299, Aurora, IN 47001; (800) 262-5401 or (812) 926-0038; fax (812) 926-3482; e-mail ; or visit .