Shredders play an indispensable role in many applications including manufacturing, recycling, solid waste reduction, security, wastewater treatment, oil and gas production, the transportation and production of biosolids, and more. Shredding offers a multitude of benefits in addition to the most obvious – size reduction. Shredders are used for processing materials used for producing a product or fuel, protecting business intelligence by destroying confidential product or documents, recycling of product or waste and shredding solids to ensure that other equipment or processes run smoothly. Corporations, government agencies and municipalities all employ shredders.
Some industrial applications for reducing solids include the destruction of foods, pharmaceuticals, rubber, pallets, steel and plastic drums, furniture, construction debris, tires, containers, corrugated boxes, packaging, labels, and other bulky materials. Industrial shredders are also used for the destruction of documents, x-rays, media such as hard drives and other electronics to protect the privacy of individuals and corporate information.
Municipal applications include recycling centers and smaller shredders with multiple cutting teeth for finer reduction for use in wastewater treatment plants. The recycling industry has found many uses for shredders such as shredding tires for the recovery of rubber. This recycled rubber is found in many applications and products including hot melt asphalt, basketball courts, playgrounds, and shoe products. The rubber is also used in civil engineering practices for the sub-grade insulation of roads, backfilling, and for fuel as “Tire Derived Fuel”. Scrap wood is shredded for recycling and used for the manufacture of many types of wood products such as particle board and paper. Plastic bottles are recycled into PET (polyethylene terephthalate) plastic chips for the production of new bottles. Recycling or reusing all of these products through shredding reduces waste in the environment, increases corporate profitability, and reduces carbon emissions.
SELECTING THE RIGHT SHREDDER
Type of Material to be Processed
Different types of shredders excel at processing specific materials. Tree branches are typically shredded using a high-speed chipper. Plastics are most often processed in a granulator (rotary knife cutter) however; bulky plastic shapes are often put into a shredder as a first stage before granulating. When planning to shred cars, this type of application is typically accomplished using a hammermill. Although, processing a variety of waste materials may require versatility with a minimal amount of noise and dust, then a twin shaft shredder can be the optimal solution.
Understanding the output size requirement will help in determining the type of equipment to install. Some facilities require the material to be separated, whereas others may need re-shredding and grinding. A single-pass shredder will cost less but if the material needs to be reduced to a very small size and compressed then compaction equipment may be required.
Choosing a shredder to handle the correct capacity is important to the success of any installation. Capacity is typically expressed in pounds per hour and is determined by the physical size, weight (bulk density), and the amount of material to be shredded. The capacity may be limited by the cutting chamber size. Check the capacity rating carefully before purchasing the machine and allow for some excess capacity. Using a shredder with a maximum capacity too close to the desired capacity can lead to a shortened service life. However, over-sizing a shredder by a wide margin can lead to excessive power use and take up too much floor space.
Two basic feed types are common: manual and automatic. Manually fed shredders usually have a hopper and work by either hand feeding the material or using a fork lift to drop the material in. Automatic feeders or conveyors help optimize shredder performance by giving a constant and regular supply of materials to the shredder.
Portability, safety, and noise are concerns when selecting a shredder. Select the proper location for the shredder because it is not easy to move a machine weighing a half ton or more. Depending on the material, dust and other airborne particles can be an environmental hazard. Noise is another factor to consider as some shredders (such as hammermills) create more noise than others.
Shredders endure a great deal of stress and maintenance is necessary to keep them running efficiently. Cutters, blades, or hammers will wear under normal use and require sharpening, adjusting, or eventually replacing. Consider maintenance, repairs, and ease of obtaining replacement parts when choosing a manufacturer. Always evaluate the access location for maintenance when determining where to locate any equipment including your shredder.
TWIN SHAFT SHREDDER
One of the most versatile types of shredders is the twin shaft shredder, such as the Franklin Miller TASKMASTER Shredder. These devices employ two parallel counter rotating stacks of cutters that intermesh at low speed under extremely high torque. As the cam shaped cutters intermesh at close clearance, they cut, shear, tear, slice, and rip apart a variety of materials into smaller pieces typically in a strip or chip-like output shape. The geometry of this dual shaft cutter also makes it very good at feeding in irregular shaped solids. This type of shredder generally employs no sizing screen so the output particle is determined by the cutter shape. Twin shaft shredders may be designed for specific solids such as tires, medical waste, documents, bottles with liquids and more. The specifics of the application determine the configuration of the unit although some shredders have a specific design for only one application and are not versatile by any means. The shredder’s model numbers usually describes the unit’s cutting chamber length and width. The complete unit is typically comprised of the main cutting mechanism with shafts, cutters, bearings, drive and housings, stand, hopper (a funnel like feeding chute), and a controller either mounted on the unit or elsewhere.
In operation, the material is fed into the top hopper of the unit and is discharged out the bottom. Some shredder designs can be set up vertically as well as horizontal. Specific designs are fitted with advanced shaft seals and sealed housings suitable for handling liquids.
As there are varying degrees of quality, precision, engineering and care from different sources of shredders, the choice of a manufacturer as well as type of shredder can greatly influence the success of the installation.
CRITERIA FOR SELECTING THE RIGHT SHREDDER:
• Is the shredder rated for the capacity to meet your requirement?
• Is the shredder made by a manufacturer with long-term experience and a reputation for customer service?
• Can the shredder handle your material as well as achieve the desired output particle size and consistency you desire?
• Is the shredder rated for liquids as well as solids, if necessary?
• Does the shredder have a design and cutter chamber size suitable for your materials?
• Do you have the electrical service to meet its power requirement?
• Is the shredder available with the options or materials you require?
• What are the maintenance requirements?
• Is the shredder of a robust design for long-term dependable operation?
• Does the manufacturer offer the support and guidance to help you in the selection, installation and support of the equipment?
As you can see there are many considerations before selecting a suitable shredder. Gathering all the necessary information to match against the shredders specifications will help shorten the process of matching the equipment to your requirement. If you are considering recycling, check that you have the necessary permits. Seeking expertise and advice from a reputable company is a good start and requesting a demonstration using a sample will confirm the shredder’s effectiveness. Visit the manufacturer’s website to review the company’s history and read some case studies to learn how other businesses have used shredders to solve operational difficulties. The last part of the equation is determining your budget. Keep in mind some units, although initially are less expensive may be inferior quality and in actuality cost more long-term to operate and maintain.