The wheel may well be the single most important feature to consider when selecting a refuse compactor. The key to understanding the wheel’s importance is to understand the difference between compression and compaction. Compression is accomplished by loading a pre-determined amount of material into a space designed to withstand high pressure. The material is then squeezed together by a force that collapses the volume into a smaller space. By removing the air voids from the original mass, compression allows the material’s original volume to be reduced.

Compression requires retention of the mass by some outside force, such as ropes or bands, in order to maintain its reduced volume. If released, the mass will most likely expand, depending on the type of material that makes up the mass. Cans and bottles, for example, will retain their compressed size. However, most material is resistant to this type of force and will “spring” back to near original size when released.

Compaction requires material to be broken down and manipulated into a configuration where it becomes compactible without being held in place. Compaction cannot be achieved by simply repeatedly running over material. An aggressive action must take place in order to break the material down, make it fit together and, finally, be placed with a minimal amount of air voids.

The idea of compaction is best illustrated by a bag of potato chips. Have you ever bought a bag of potato chips and noticed how full the bag is? It’s full because of air voids. If you crush the contents of the bag, you’ll see how much product you actually have - probably about 10 percent of the original volume.