While grinders with less horsepower can certainly grind shingles effectively, they have an increased chance of plugging from slugs of shingles, so operators must exercise extra care in maintaining proper feed rates.
Grinders with too much horsepower will not proportionally increase production rates because shingle grinders usually use screens with small holes, which limit the rate at which material may flow out of the grinding chamber.
“The production rate of a 1,000-hp grinder might not be much higher than a 700-hp grinder — although the wear rates and fuel consumption could be measurably higher,” says McIntyre.
Magnetic systems. If the grinder will be processing tear-off shingles, it should be equipped with one or more magnetic systems, such as a magnetic cross-belt magnet or magnetic head roller on the discharge conveyor for removing roofing nails and other ferrous metal. “Asphalt plants that incorporate RAS may have redundant metal removal systems, yet most of the steel should be removed on the grinder side of the process,” says McIntyre.
In some ways, selecting a shingle grinder is a process of identifying the features you don’t want in a machine that will be processing a highly abrasive waste material. “You don’t want the additional and unnecessary expense of augers, drive chains and drive sprockets operating in highly abrasive fines,” says McIntyre. “You don’t want a messy machine that spills a percentage of everything loaded into the infeed back out the front end. You don’t want non-replaceable structural surfaces exposed to the high-speed shingle grinding process. Screens and teeth should be your primary maintenance items, not any permanent surface of the machine.”
What wear items are crucial to keeping your machine producing?
The rotor teeth and sizing screens do the most work processing asphalt shingles and need to be replaced as they wear.
“Wear-related maintenance depends on where the abrasive grinding process is focused,” says McIntyre. “Any surface that is exposed to abrasive fines moving at high speeds will require replacement, rotation, hardfacing or other maintenance at some point.”
When selecting a shingle grinder, parts support from the manufacturer is critical, because downtime in any business is lost profit. “We get paid by the ton,” says Lambert. “Our crews are out to do a job and get the job done right the first time so we have a repeat customer.
“Customers don’t want us working on our machines when we should be making a product for them,” he continues. “They want us to be up and running. They want us to come in, do our job and get out.”
McIntyre concurs. “The flow of incoming shingle waste doesn’t stop if you have downtime,” he says. “Paving projects don’t stop for downtime. Shingle recyclers need grinding equipment that will reliably produce RAS according to their schedules.”
When selecting an asphalt shingle grinder for your equipment fleet, one thing is certain. The more you know, the more you research, the better your decision will be.
“Companies that want to start recycling shingles should make sure to talk to others who have considerable experience in the shingle recycling market,” says McIntyre. “Time spent on education will have immeasurable payoffs.”