Shredding Equipment Focus--On the Horizon

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Horizontal grinders are a popular choice for scrap wood and C&D recycling.

August 16, 2006

Whether reducing the volume of material for landfill or recycling debris into a usable end product, horizontal grinders are gaining in popularity among C&D recyclers. The ability to work in confined spaces and a general reputation for safe operation are just two of the features giving horizontal grinders a leg-up over other secondary grinding equipment like tub grinders.

With horizontal grinders, recyclers can process a variety of material, including mixed C&D debris, clean wood debris, pallets, green waste and municipal solid waste (MSW). In addition, they can be used to make an equally varied amount of end products. With C&D-related material, recyclers can use horizontal grinders to do everything from volume reduction to making products like mulch and boiler fuel.

Land clearing may remain one of the biggest applications likely for horizontal grinders, but their versatility is helping the equipment to gain access to a number of different markets.

SAFETY FIRST. Safety is a high priority on any jobsite, and the horizontal grinder’s reputation for safety is helping it to gain favor among operators. It’s a particularly important issue for Chuck Tomlinson, manager of Amerigrow Recycling in Delray Beach, Fla., who says his horizontal grinder—a CBI 6000—is well matched to his specific operation.

"We’re open to a lot of traffic here and we take in a lot of trucks everyday," says Tomlinson. Horizontal grinders tend to have the edge when it comes to safety—they don’t have the reputation for discharge that tub grinders do, says Tomlinson, which is why he opted for a horizontal model at his heavily trafficked facility.

Morbark Redesigns Wood Hog

Morbark Inc., Winn, Mich., has introduced a redesigned version of its 4600XL Wood Hog.

The hammermill is 14 percent larger than its predecessor, increasing the tip swing up to 36 inches, and the infeed opening has been expanded to 60 inches.

The grinder, which features 18 hammers, has power options of up to 860 hp. The increased screening area provides users with added grinding capabilities.

The machine is programmed with Morbark’s Iquan System, which has a tool that allows the operator to quickly adjust feed systems from the control panel to obtain maximum production rates while keeping the engine load constant. The system is available with an optional satellite modem that provides a wireless link between the factory and the machine and allows a factory service technician to access machine functions and to diagnose problems.

The redesigned 4600XL also comes standard with an adjustable fifth wheel pin, which allows weight transfers to accommodate state and highway road restrictions.

The WDH 120 infeed chain is designed for longevity, according to Morbark, with the rail size on the chain measuring ½ inch. The machine also has a reversing radiator fan to maintain a clean radiator screen, which saves on horsepower.

The redesigned 4600XL Wood Hog is also available as a track-mounted unit.

More information is available at

At Amerigrow, Tomlinson says the company mainly processes landscape debris for mulch and compost soil. He says he tried using a tub grinder, but the constant discharge of large materials—including big logs—made it too dangerous, so he invested in a horizontal grinder. "The horizontal grinder has material coming into an enclosed grinding chamber, but with tubs, there’s nothing to stop the discharge," he says.

This aspect makes horizontal grinders ideal for work in urban areas, according to Gary Davis of grinder manufacturer Recycling & Processing Equipment of Peru, Ind. "You can work in confined areas with the horizontal—right downtown," Davis says, a factor that is becoming more important in an industry where urban work and jobsites in and around populated areas are becoming more common.

Larry Doose, president of Silva Corp., Burnsville, Minn., says that horizontal grinders are also less restrictive in the size of material they can handle. "If you’re constricted to a 10- or 12-foot tub, introducing the material into it presents a challenge," says Doose, who uses a horizontal grinder manufactured by Vermeer Manufacturing of Pella, Iowa.

While horizontal grinders may offer a number of advantages over tub grinders, they are still subject to contaminants that can cause problems for operators in any market, from the strictest content requirements for mulch to the less-stringent standards of boiler fuel.

KEEPING IT CLEAN. Contaminants are a fact of the business that operators have to contend with no matter what material they are handling.

Contaminants come in two varieties: those that pose a threat to the equipment and those that could diminish the quality of the end product.

Steel is chief among those contaminants that are dangerous to the grinder, says Charley Duffy, owner of Bull’s Eye Demolition in Cape Coral, Fla., which operates a 6700 Peterson grinder to process wood debris for the mulch market. "Obviously, it’s bad for the mill," he says.

In addition to metal, rock and concrete must also be kept out of the grinders, first to avoid damage to the machine itself and secondly to keep such contaminants out of the final product, says Recycling & Processing Equipment’s Davis.

The grinder operator is key to keeping these contaminants out of the machine, particularly with C&D debris, which is more likely to contain ungrindable material.

Gibson says proper preparation on the jobsite is the best defense against contaminants. He adds that usually, C&D debris is run across a picking line where the wood is sorted out for grinding.

Although Amerigrow does not accept C&D wood, Tomlinson says his facility does do a visual sort of material before it is loaded into the grinder with either excavators or backhoe loaders, extracting visible pieces of metal.

For the high-end mulch market, Doose says Silva Corp. has to be particularly vigilant. "We constantly have to be looking at our material and pulling out contaminants that will degrade the quality of our product," he says. Doose points out treated wood, plastic and garbage as potential threats. He recommends trying to reduce contaminants at the source by training suppliers to provide contaminant-free material. For anything that does get by the suppliers, "our operators are constantly on the watch," Doose says.

On the downstream side, Davis also recommends running the material under a magnet to pull out any stray steel that may have gotten through.

Paying close attention to the infeed material can also help operators extend the lives of their horizontal grinding equipment, particularly wear parts.

THE LONG RUN. According to Gibson, another advantage of horizontal grinders is that their construction makes the grinding process a little easier on the machine’s wear parts compared to a tub grinder. He says that because horizontal grinders are chain-fed machines, a good deal of sand and dirt tends to shake down and exit through the bottom onto the belt, bypassing the hammermill altogether, resulting in more even wear.

However, Gibson still advises operators to run material that is as clean as possible to get the longest life out of their wear parts. He boils it down to a basic principle: "The cleaner the wood, the longer the life. The dirtier the wood, the shorter the life," Gibson says.

Duffy also says that keeping abrasives out of the feed material is the first step toward saving wear costs. He likens letting too much dirt into the machine to "putting sandpaper on the wear parts."

Davis recommends checking a horizontal grinder’s tips morning, noon and night and adds that operators should be sure to adjust the rotor speed to match the grinding application. For instance, Duffy says a slower speed should be used with C&D debris, while a faster speed should be used for clean wood.

To optimize wear part strength, Tomlinson suggests that operators can also add more carbide to the ginder’s teeth to lengthen their lifespan.

"Maintenance is your biggest concern," says Duffy. "You have to check your tips and open your mill up every day." He adds that keeping the equipment properly greased goes a long way in extending the life of wear parts.

Gibson also recommends that operators make sure their horizontal grinders come with proper tramp metal or steel systems that disengage the hammermill if it hits a large foreign object. This feature, which protects the machine as well as its operators, comes standard on most equipment, though not all, Gibson says.

An increasing need for equipment that can work in confined spaces has driven the market for horizontal grinders. As markets expand, operators and manufacturers expect the trend favoring horizontal grinders to continue, as well.

The author is associate editor of Recycling Today and can be contacted at