Proper maintenance practices should be a major part of every crushing operation. But don't become paranoid and overdo it. Excessive maintenance can actually create more problems than it solves.
Experienced crushing professionals offer their views on maintenance of horizontal impactor plants.
Invest in quality, then maintain it
Thompson Recycle, Tecumseh, MI, crushes about 95% asphalt rubble using an electric motor-powered Grasan road-portable crushing plant with a Hazemag 1515 APSE horizontal-shaft impactor.
"We run our crushing operations from March 15 through December 15," says John Thompson, president. "We've been in business for about nine and a half years and have moved from one site to another more than 500 times. We've crushed about 14 million tons of asphalt rubble, and our plant is still solid, efficient, dependable and runs like a top."
Thompson believes two elements are crucial to achieving this kind of performance. "First, get a top-quality crushing plant designed for your specific needs. Second, establish a sensible maintenance and repair schedule and stick to it," he advises.
According to most manufacturers, a quality crusher will last 10 to 15 years. But if properly maintained, Thompson believes you can expect a lot longer life. "I look to get 20 to 25 years from my impactor plant," he says.
Investing in wear items and pulling the equipment down for periodic service is critical. "Without proper maintenance, you can ruin a good crusher in six weeks to six months," says Thompson.
Consider blow bar replacement. "If you don't replace your blow bars on time, you can end up spending big bucks on a new rotor before long," Thompson points out. "Material being crushed can eat away the rotor surface if the blow bars are worn too low."
Daily and weekly preventive maintenance allows Thompson Recycle to keep plants running continually. "We can't afford breakdowns, and we have practically none," says Thompson. "We run 24 hours a day in two 12-hour shifts, six days a week, with a seven-man crew, including me. At the start of each shift, we check over the entire plant, make any adjustments and make note of the condition of major wear parts."
Because plants are moved frequently throughout the work year, the company tries to replace wear parts when it shuts down for a move. "We're productive about 73% of the time," Thompson notes. "The rest is for maintenance and moving."
Two blow bars and two dummy bars are used for balance and to protect the rotor. "We turn the blow bars about every 20,000 to 25,000 tons. So we get about 80,000 to 100,000 tons before blow bar replacement. We get about 700,000 tons per turn on the mono-block apron, and about 200,000 tons on the apron rear impact plates before the edge is worn off," says Thompson. "We also replace all other wear parts regularly, including side liners, rotor shoes, manganese apron and apron blocks, impact plates, seals and so on."
A three-pronged approach
Complete Resources, Columbus, OH, is a contract crushing company that processes concrete and asphalt rubble and aggregates with several diesel-powered Grasan road-portable and pit-portable impactor plants.
"We have a three-pronged approach to maintenance and downtime prevention," says Butch Cherrington, vice president. "First, we make the plant operator responsible for regular equipment maintenance. In our case, that person is the foreman. Second, we employ several full-time mechanic-welders who take care of heavy and non-scheduled repairs. Third, we try to perform maintenance as much as possible when moving equipment from one crushing site to another."
According to Cherrington, a balance needs to be struck between running the plants until they break and maintaining them as good as new, neither of which is profitable. "If left up to production people, plants would be run into the ground in short order," he notes. "If my maintenance people had the say, I would have plants in 'as new' condition, but I could not afford to operate them."