On the move: the desired end product is a driving factor when choosing a portable crusher.
With the recent development of new highly portable crushing and screening systems with user-friendly controls and designs, many contractors can efficiently own and operate recycling systems.
Determining which recycling plant is best for an operation requires a proper review of a company's needs. Annual tonnage requirements, material type, end product and site location are all-important considerations when making an equipment investment.
A key decision that impacts most of these issues is chassis type, and recent product advancements have changed the approach many now follow. Although stationary systems led the industry early on, many contractors and recyclers are benefitting more from the flexibility offered by today's portable recycling equipment.
Configured as either wheel- or track-mount designs, portable plants can deliver the same effectiveness and productivity as their stationary counterparts, but with the added benefit of easy relocation. Even when a stationary machine is required, a moveable skid-type plant still provides some additional degree of flexibility should it be necessary to relocate the system.
Recycling plants are normally rated by tons per hour (tph). For rates of 100-400 tph, a track-mounted crusher or screen is most appropriate. Moved to a job site by low-boy trailer, the self-propelled track-mounted system can drive itself to the operating location and be ready to operate. This fast setup makes it economically feasible to move for even small jobs in the 5,000-ton to 10,000-ton range. Because of this mobility, a track-mounted system can move through a job site to the feed stockpile, rather than moving the feed material to the unit. In addition, because the unit can be controlled remotely, less labor is typically required. A small-to medium-sized wheel-mounted unit can also produce work in this volume range, but may not be able to perform with equal efficiency.
Overall, track-mounted systems provide quick setup and a low-profile, cost-effective solution for efficiently managing small and large recycling jobs profitably. The wireless controls are simple to operate and allow the worker who feeds the plant to also control and move the tracked crusher. Wireless controls allow the operator to control the feed rate, stop the system and move the plant as required from the convenience of the excavator or front-end loader cab.
For higher-volume capacity, large wheel-mounted crushers and screens might be used in lieu of a track-mounted system. Pulled to a job site by tractor truck, wheel-mounted systems must be maneuvered into place upon arrival. There is some setup time involved and, once set, they cannot always be quickly relocated around the site. Although these systems require a larger commitment and cost to operate, their production rates of 500-plus tons per hour make them very effective for large recycling projects.
CRUSHER AND SCREEN OPTIONS
After determining the most appropriate chassis configuration for the application, the crusher and screen type must then be decided. Two of the most common types of crushers used in recycling are jaw and impact crushers, although cone crushers play an important role as well. It is important to understand that a crusher crushes only and does not typically produce a spec product without the use of a vibrating screen. If volume reduction is the goal, then a lone crusher, such as a jaw or impactor, may do the job. However, if a spec product is needed, a vibrating screen must follow the crusher to create the desired screened finished product.
Jaw crushers are compression crushers designed for primary reduction of large feed materials, such as concrete chunks. A large tracked jaw crusher has a feed opening of 26 inches by 50 inches, but larger jaw crushers are available on wheel-mounted chassis. With their adjustable jaw setting, they can produce products up to 10 inches, or with a tighter adjustment, produce products down to 3 inches. Sometimes, a jaw crusher is followed by a secondary crushing unit and a vibrating screen for the production of one or more smaller final products. Jaw crushers are suitable for processing concrete, stone and demolition material, such as brick and block, and can produce larger products such as riprap. Jaw crushers are not normally well suited for crushing asphalt, as asphalt can bridge and stick inside the jaw crusher chamber.
Another popular crusher style is the horizontal shaft impact crusher (HSI). As the name implies, impact crushers process via impaction and can be employed as a primary or secondary unit in recycling applications. When compared to jaw crushers, impact crushers produce smaller product sizes and often at higher tonnage rates. They do have higher wear costs, typically ranging from 15 cents to 25 cents per ton versus 10 cents per ton for a jaw crusher. However, impact crushers provide tremendous versatility, effectively processing concrete, limestone, asphalt and most typical demolition materials; impact crushers are not designed to process harder, granite-type stone. Popular size impactor crushers are 50 inches and 40 inches wide with 42-inch diameter rotors.
HSI crushers typically have three blow bars and have two adjustable apron plates. Impact crushers typically produce a good minus 1 1/2-inch base type material but can also produce larger products, which can be screened to make some typical road materials or utility drainage materials. Impact crushers typically cannot produce larger products such as riprap, unlike a jaw crusher.
A large, track-mounted impact crusher will generally accept a feed size up to 30 inches by 30 inches with a thickness of 12 inches, depending on the crusher size, but to maximize their performance, feed material should be prepped to an average size of 20 inches by 20 inches. This guideline also applies to jaw crushers in recycling applications. Properly sized feed is one of the most important factors in demolition recycling applications. At the end of the day, an operator with properly prepared feed will put more finished product on the ground.
Where necessary, cone crushers can also be employed in a recycling system. Designed as secondary or even tertiary units, cone crushers operate by compression, and can effectively process a screened 5-inch feed to a final product of minus 1 inch. Cone crushers are suitable for crushing concrete, stone and demolition brick and block, but are not recommended for processing asphalt. As with jaw crushers, cone crushers also typically experience wear costs of 10 cents per ton.
Finally, the vibrating screen concludes the process by separating the crushed material into spec products. Available as single, double and triple-deck (and sometimes quad-deck) models, a vibrating screen is capable of producing multiple end product streams. Vibrating screens are also available in horizontal or inclined configuration. Horizontal screens provide lower head room, higher screening G-force and greater adjustability. Inclined screens tend to provide greater throughput and capacity, as gravity assists the movement of material across the surface.
Some impact crushers are also designed with on-board vibrating screens, providing crushing and screening capability in closed-circuit configuration on a single chassis. Requiring far less space than a two-chassis plant, they are able to produce a final spec product from feed material in one continuous processing flow.
This closed circuit plant can provide a simple-to-use, all-in-one system, which means the contractor only has to bring one unit to the job site. A popular closed circuit track plant would include a 42-by-50-inch impactor in closed circuit with a 5-by-12-foot vibrating screen or a 42-by-40-inch impactor in closed circuit with a 4-by-12-foot vibrating screen.
An established manufacturer will have a modern factory that you can visit and they will have a substantial engineering, service, parts and field support staff that can help you with any issues. Another benefit of an established supplier is the availability of standard parts and components that can be acquired from the dealer, factory or perhaps locally in an emergency situation in order to avoid downtime.
Follow-up operator and maintenance training provided by the manufacturer is also important. Make sure that the equipment supplier provides such support.
Regardless of which recycling plant is ultimately employed, an efficient and cost-effective process can be maintained if some general guidelines are followed. Properly prepped material will ensure the most productive crushing process by eliminating bridging; numerous muncher and shear attachments are available to ensure that feed material is well prepped.
The removal of rebar and steel, as well as wood and other non-concrete material, will eliminate the potential for costly plant damage. "While a good recycling plant is designed with a higher threshold for contaminants, extra care prior to feeding will ultimately result in a more productive system. Also, because most recycled feed material contains steel contamination, it is important to have one or more good, well-placed magnets on the plant to remove scrap steel from the finished product.
Often, dust suppression systems are required on recycling plants as some materials, such as concrete, can create a great amount of airborne dust. When stockpiling the finished product, radial stacker belt conveyors are much more efficient than a front-end loader. To accurately track production, a belt scale can be mounted on the radial stacker conveyor to measure discharged material. Finally, never undersize a vibrating screen. Undersized screens will not produce a clean spec product when running close to capacity and can significantly slow down production flow. Maintaining maximum performance from a crusher requires the vibrating screen to perform at equal levels.
It is obvious that reliability and performance are critical in any equipment investment, but equally important are the service, parts availability, training and overall support provided after the equipment is installed. Thoroughly research and understand the supplier's entire manufacturing process to ensure the system maintains its investment value long after the initial delivery and installation.
Clearly, the recycling of concrete, asphalt and demolition materials has become a more mature and advanced industry. Contractors and producers have an enormous variety of systems, plants and attachments available to serve their individual application. With thorough analysis of the operation and proper due diligence in selecting a manufacturer, every facility can reap the benefits of material recycling and participate in this cost-saving and environmentally responsible practice.
The author is a regional sales manager with Kolberg-Pioneer Inc., Yankton, S.D.
RELATED ARTICLE: Smooth operators.
Volume drives the decision on when to bring a portable crusher to a job site, but a bare minimum varies between operations.
Every job is different, says Billy Mulliniks Jr., owner of Mulliniks Recycling in Jacksonville, Fla. "It depends on the job site. We try to match the size to the volume--bigger crushers for bigger jobs," he says.
Many crushers look for a bare minimum volume of material before they even consider moving their portable equipment to a job. "Even though we are highly portable, there is a minimum volume of material just simply because of the cost of moving the equipment to the site," says Randy Floyd, owner of Cox Floyd Grading in Greer, S.C. Floyd puts his minimum at about 5,000 to 10,000 tons. "Preferably 10,000 tons or higher," he adds. "That's where we really need to be."
Leonard Cherry of Cherry Demolition in Houston says that the industry has seen a shift in how much material is called for when bringing a portable crusher on the job. Overtime, technology has changed and machines have become easier to move, according to Cherry. "We've seen that the total volume needed continues to drop as the portability increases," he says.
Cherry says that back in the mid-1990s, he may have needed some 50,000 tons to justify moving a crusher. Now he says he can take it to a job for 5,000 tons.
Floyd has a jaw crusher from Komatsu and a Kolberg-Pioneer impact crusher, both track-mounted machines. He says volume tends to dictate the time frame of a job. "Once they reach their peak production, after a day or so on site, the jaw plant can turn out as much as 450 tons per hour and the impact can turn out 400 tons per hour--it doesn't take long to go through a lot of material," he says. "You've got to have something to keep you there to make it worthwhile."
Mulliniks, who uses impact and jaw crushers from Eagle Crusher Co. Inc., says a given job's timeframe differs significantly with the volume of material being processed--anywhere from one to four months, depending on the size of the job. "You're not going to do 100,000 tons in a month," he says.
One to two months is average for Floyd, although he's had jobs last as long as six months. "But that was a rock job, not concrete," he says.
However, one factor that can have a profound effect on a given job's time frame aside from material volume is the manpower behind the machine--jobs can go a lot quicker with experienced operators behind the equipment.
Crews from Cox & Floyd consist of two to three operators. To run the impactor plant, Floyd says he never sends more than two, although for some jobs three operators are required to run the jaw. He says certain situations, such as demolishing a building that's heavily laden with steel, calls for a picker along with the two regular operators to remove as much steel as possible before it reaches the chamber of the jaw.
Cherry says his portable crews vary between a minimum of three and a maximum of five. The quality of the material being processed also dictates the number of operators, in addition to the raw volume of material being handled. "If you have more trash or more steel, you'll need more pickers," he says.
But no matter how many operators go out on each job, finding and retaining good employees is key, according to Floyd, because having experienced operators on the job "makes all the difference in the world," he says.
--By Jackie Gubeno
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|Title Annotation:||OPERATIONS FOCUS|
|Publication:||Construction & Demolition Recycling|
|Date:||May 1, 2006|
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