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2004 Vermeer BC1000XL Portable Chipper
A chipper is a machine used to chip whole trees, branches, debris, mulch, and other types of foliage. Chippers range in size from smaller hand-fed units used in domestic and agricultural applications to mobile, whole-tree chippers used to chip slash and residue in commercial, logging, and forestry operations.

Large, stationary, industrial-sized chippers also exist as part of the overall production system in saw or pulp mill operations. The chips produced from chipping forest biomass are used as boiler fuel or to produce pulp for paper products. The two most common types of chippers include disc chippers and drum chippers.

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[edit] Features/How it Works

Chippers come in a variety of sizes and configurations and can be power-driven either with an internal combustion engine such as diesel or gasoline, by electricity, hydraulic power, or by another machine such as a tractor or skid steer loader using a power take-off (PTO) system.

Depending on the size, make, and type of chipper, the infeed system varies. Some models are self-feeding and other units require manual loading. Infeed systems may be designed with feed rollers positioned on the top and bottom or with an auger infeed-type conveyor.

2005 Jensen A430T Tracked Wood Chipper
Material is loaded into chipper in various ways. On smaller-sized chippers such as PTO-powered chippers, material is either manually fed into the machine or by a crane, loader, or on a feedable table.[1] In logging operations, a log loader or a wheel loader may be used to load and feed material into a chipper. The knives mounted on a disc or drum chipper used to chip whole trees pull the tree forward as it is being chipped. Some chippers even come equipped with a grapple to self-load material.[2]

All chippers come equipped with a type of discharge chute. The knives or blades on the chipper can be used to generate natural airflow, which is used to eject the chips out the discharge flute.[3] Other models are equipped with fans that blow the chips out of the chute.

Some of the apparent problems with chipping equipment are the production of long slivers instead of chips. This can lead to blockages inside the chipper. Therefore, the interval sharpening, cleaning, and replacement of cutting blades is important. Blades are easily dulled or damaged from dirt, stones, and other debris, particularly in high throughput operations like whole-tree chipping.[4]

[edit] Types

Bandit 65 Portable Wood Chipper
Drum chippers feature a rotary drum parallel-sided or middle-waisted with knives mounted along the length of its axis. Located behind the knives are chip breakers positioned at a right angle that work against the cutting action of knives. Drum chippers are widely used to reduce forest residue into uniform-sized chips.[5] The speed of the drum, in-feed speed, and number of blades is what determines the size and uniformity of the chip. Overall, drum chips tend to be less uniform than those produced by a disc chipper.[6]

Disc chippers operate using a type of flywheel that consists of a large-diameter steel disk usually set at a right angle or at an angle that incorporates one or more chopping blades, each with a slotted disk. As the disc rotates at a high speed, the chopping blades chip from the end of the biomass as it is fed into the machine, usually on a ridged roller system. An anvil or knife in the throat of the chipper is what provides the oppositional cutting action. These knives are either straight or curved and may be set at a radial, slightly offset position on the disc.[7]

Screw chippers were first developed in Scandinavia and built as an attachment outfitted on tractors.[8] They operate on a completely different principle than disc and drum chippers. The cutting blade in a screw chipper is a rotated, tapered, helical screw with a hard cutting edge that cuts against the inside of the housing. The rotating action is parallel to the in-feed direction. The helical motion of the screw draws material into the chipper and this is the only type of feed mechanism required.[9]

[edit] Common Manufacturers

[edit] References

  1. Sjaak Van Loo, Jaap Koppejan. The Handbook of Biomass Combustion and Co-firing. Earthscan, 2008. pg 64
  2. Terminology of Ground-Based Mechanized Logging in the Pacific Northwest. Loren D. Kellogg, Pete Bettinger and Don Studier. College of Forestry, Oregon State University. 1993. 2008-11-07.
  3. Chippers. Biomass Energy Centre. 2008-11-07.
  4. Chippers. Biomass Energy Centre. 2008-11-07.
  5. Sjaak Van Loo, Jaap Koppejan. The Handbook of Biomass Combustion and Co-firing. Earthscan, 2008. pg 64.
  6. Sjaak Van Loo, Jaap Koppejan. The Handbook of Biomass Combustion and Co-firing. Earthscan, 2008. pg 64.
  7. Chippers. Biomass Energy Centre. 2008-11-07.
  8. Facts about Chippers and Shredders. GreenMech Ltd. 2008-11-07.
  9. Chippers. Biomass Energy Centre. 2008-11-07.