An Alternative Approach

Crushing and screening plants are among the most frequently used pieces of equipment for construction and demolition recyclers. After all, without the ability to crush large pieces of concrete, asphalt, brick and other materials or the ability to separate those crushed fragments into uniformly sized piles, contractors wouldn’t have much of a demand for materials generated by their work activities.

Contractors commonly set up a stand-alone stationary or bring in a tracked crusher at job sites deemed large enough to merit it. At times, however, it may make more sense for contractors to use a crushing or screening attachment mounted to their excavators, skid steers or other material handling equipment.

"A stand-alone crusher requires significant tonnage to accommodate mobilization and demobilization expenses," says Bob Niemela, president of New Dimension Crushers, based in White Pine, Mich. "Our 2412DX crushing attachment can be delivered to the site in a pickup truck."

Beyond the transportation savings, after employing an excavator-mounted crusher or screener at a job site, contractors can realize added cost savings by eliminating a fuel source. "Crusher attachments use hydraulics off the excavator that they are attached to, to operate, rather than having a separate diesel source for power," says Bob Rossi, president of Lancaster, S.C.-based RR Equipment, which manufacturers the Crush-All crusher bucket attachment.

In most cases, as the amount of material to be processed at a construction or demolition job increases, so too does the practicality of using stand-alone crushers and screeners because of the differences in production capacity. According to their manufacturers, stand-alone crushing and screening plants are more efficient in production because they are continuously being fed, while excavator-mounted attachments must intermittently scoop or dig in order to collect the material to be processed.

"It’s all going to depend on the amount of material on a job," says Larry Giberson, president of Giberson Enterprises, which manufactures the Eco-Crusher crushing attachment. "Typically, you need more than 5,000 tons of material on a job in order for it to be worth bringing a big crusher in. Smaller jobs up to 5,000 tons are really the niche that the crusher attachments were made for."

Regarding screening attachments, they are most often used in specialized applications where contractors are not concerned with producing more than one end product and if there is no need to screen material to less than 3/8-inch in size. "The screener bucket is most often used to recycle material to be reused on the same job site," says Ed Roczey, owner of Grits Inc., the U.S. distributor for REMU Buckets.

SPECIALIZED SCREENING
While screening attachments are able to screen and produce several sizes of end products, they are hindered in that they can only screen for one-sized product at a time, in contrast to a stand-alone crusher that can separate material into several piles of uniformly sized material at one time. Thus, a screening bucket is more well-suited for prescreening or producing spec size material, either as an end product or to be reused on site.

Additionally, screening buckets may be used to prescreen materials that construction and demolition recyclers do not want entering their C&D processing systems.

"ALLU’s screener attachments can pre-sort material and screen out harmful objects such as steel and rock, prior to entering a C&D system," says Dale Mickle, national sales manager for ALLU, a screening bucket manufacturer based in Finland.

The screening bucket can be ideal for applications where the desired material may be contaminated with dirt, according to Daniel Paton, general manager of Flip Screen, an Australia-based screening attachment manufacturer. "Almost every scrap recycling yard and/or mill in the world has stock piles of steel contaminated by dirt," Paton says. "Flip screening removes the dirt from the valuable stell. Also Flip Screens are rotated in water to wash dirt off the likes of stainless steel."

Although screening attachments may only be able to produce one spec product size at a time, Paton says that its attachment is still versatile for use in a number of applications within a system. "In a concrete crushing operation, the Flip Screen can be used as a fine screen to remove the powdery, smaller fines to help crush only concrete," says Paton. "The attachment can use a large screen size to remove the larger overburden to help prevent blockages at the infeed. Or it can be used after crushing to enable sizes to quickly be sorted." Flip Screen adds that operators can change the size of the product they wish to create in five minutes, without tools.

Using a screening attachment can lead to cost savings in the amount of equipment and fuel needed for a given job. If using the screening bucket to remove potentially harmful materials before entering a C&D system, operators can screen the material directly over a stand-alone crusher or screener without having to re-handle the material with a loader or excavator. Additionally, in the case that contractors are seeking to produce a specific end product, material can be screened directly over trucks to be hauled away, ideally increasing the efficiency of transportation.

CRUSHER OPTIONS
Once construction and demolition recyclers decide that their material processing needs are best met with a crusher attachment, there are several options they can explore. First, contractors should evaluate what size product they want to crush for and then decide whether to use a jaw crusher attachment or an impact crusher attachment.

"Impactors basically work more like a roto-tiller, beating stuff around inside compared to a jaw crusher that actually crushes the material between two plates," says Giberson, whose company is a supplier for the Eco-Crusher jaw crusher. "Typically the jaw crushers in the industry are more simplistic [with] fewer moving parts. A jaw crusher runs at about 300 rpm, kind of slow and steady, compared to an impactor, which runs at about 3,000 rpm."

According to Giberson, the Eco-Crusher can reduce material to 1-inch minus in a single pass, which is smaller than the typical stand-alone jaw crusher, which he says can crush to 3-inch minus.

Rossi says RR Equipment’s Crush-All impact crusher bucket can reduce material even further, all the way down to dust. "The Crush-All is extremely versatile. It can crush everything from a complete V-8 engine all the way down to topsoil," Rossi says.

Meanwhile New Dimension’s 2412DX crusher attachment "combines the best features of the cone, jaw, and roll crushers" to create "the first new crushing technology since the development of the cone crusher in the first half of the twentieth century," according to the company’s Web site.

"Our Model 2412DX is unlike either the jaw or impact crusher and breaks rock in tension with far less horsepower and fewer fines and dust," says Niemela.

CRUSHING PROCESS
After recyclers choose the type of crushing attachment that will best meet their needs, they have several options for setting up their processing system. The most basic system would simply crush material to the desired size into one pile, but that method may not always produce the cleanest product. "If you set the crusher at 2-inch, you’ll make 2-inch minus and if there is any rebar or wire or anything in the material, it would come out in the pile," says Rossi.

In order to produce the cleanest end product, Rossi suggests employing screening equipment on the job site. "I would crush over the screening plant, so I wouldn’t have to re-handle the material," he says. "Then the screening plant would have a magnet on it and could make a variety of products depending on how the screen is laid out."

Giberson also suggests bringing a screening plant to the job site but says he would crush in a pile before screening because generally contractors can screen faster than they can crush. "I don’t want to tie up my screen or my other equipment waiting for the crusher. Let’s say the crusher can crush 300 tons per day and the screener can screen 800 tons per day. I’d rather crush for three days and then screen for one. It’s just more efficient," he says.

Whether C&D recyclers choose to employ a crushing or screening attachment, the transportation, fuel and manpower cost savings compared with larger, stand-alone equipment can be significant and increase their profits.

"People don’t realize that if you’re only crushing 300 tons in a day, how can you make any money with a bigger crusher that is [designed to crush] 1,000 tons per day?" asks Giberson. "You only have one man and one machine. He might only be crushing one-third of the work that a larger crusher can do, but you’re only crushing at one-third of the cost." C&DR