In an industry where downtime usually makes the difference between profit and loss, proper and diligent maintenance practices should be a major part of every crushing operation. But don’t become paranoid about it and overdo in the extreme. That can actually cause you problems.
Four experienced crushing professionals offer their views on proper maintenance of horizontal impactor plants used for crushing limestone, concrete and asphalt rubble. An impact crusher requires more maintenance than a jaw crusher, but each operator believes the impactor to be more efficient for concrete and asphalt recycling, and for crushing most limestone.
Each expert emphasized the obvious importance of following the manufacturer’s maintenance schedule and procedures.
John Thompson, president, Thompson Recycle, Tecumseh, MI
Thompson Recycle crushes about 95 percent asphalt rubble. The company employs an electric-motor-powered Grasan road-portable crushing plant with a Hazemag 1515 APSE horizontal-shaft impactor. Thompson states:
We run our crushing operation from March 15 through December 15. 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.
You need two things to get that 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 no matter what. A good quality crusher will last 10 to 15 years, according to most manufacturers. I say if that’s all you’re getting, you aren’t servicing it properly. I look to get 20 to 25 years from my impactor plant.
Some crushing operators don’t want to spend the money to replace wear parts as needed, or don’t want to shut down long enough to pull proper maintenance. But without proper maintenance, you can ruin a good crusher in six weeks to six months. That’s the difference. It’s your choice, and it should be an easy one. But it’s not for some people. Wear parts are expensive. But breakdowns are much more expensive.
If you don’t replace your blow bars on time, for example, you can end up spending big bucks on a new rotor before long. Material being crushed can eat away the rotor surface if the blow bars are worn too low.
Almost all our maintenance is preventive, and it’s done daily or weekly as needed. We can’t afford breakdowns, and we have practically none. We run 24 hours a day in two 12-hour shifts, six days a week — with a seven-person 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. During our three-month winter layoff, we make any needed major repairs.
Since we move our plant a lot during the work year, we try to replace wear parts when we shut down for the move. We’re productive about 73 percent of the time. The rest is for maintenance and moving.
We use two blow bars and two dummy bars 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. We replace all other wear parts regularly, also, including side liners, rotor shoes, manganese apron, manganese blocks on the apron, impact plates, seals and so on.
Frank Azzopardi, plant manager, Stoneco Newport Quarry, Newport, MI
To improve operations at the giant limestone quarry near Detroit, a 4228 primary jaw crusher plant was replaced by a new Grasan pit-portable KRH1620 hydraulically controlled primary impactor plant in February 1998. The electric-motor-powered impact crusher increased production from 650 to 700 tph with the jaw to 800 tph with the impactor. Azzopardi says: