Shredding Equipment Focus--Avoiding Garbage In

DAMAGE CONTROL. Shredding and post-shredder sorting equipment is increasingly designed to be more automated and require the use of fewer human hands and labor hours.

Human eyeballs, however, still play an important part in determining how well a metals shredding plant functions, affecting everything from product quality, profitability, machinery damage control and avoiding the introduction of hazardous materials.

Much of this human touch must come up front at the scale house and inspection area, while the operator in the shredder tower also can play an important role in boosting product quality and avoiding equipment downtime.

In terms of profitability, initial inspectors and scale house personnel are critical to ensure that the shredder feedstock being purchased by weight consists of a higher percentage of ferrous and nonferrous metals and a lower percentage of contaminants such as dirt, tree limbs, concrete and asphalt. As Baumgartner observed dryly at his Operations Forum presentation, such materials do not represent "a high-profit part of your business."

Another critical part of the pre-inspection involves finding materials that can damage the shredder or otherwise cause operational downtime.

Even though reject doors are designed into shredding plants, large, heavy unshreddable objects, such as hunks of hardened steel are still better off never reaching the hammers and walls of a shredding chamber. Operational efficiency takes a hit whether downtime ensues or whether some wear parts are damaged before they reach their maximum lifespans.

Sealed containers (such as propane tanks) are another item to look for in the inspection process. While many shredder operators report that the sound of a propane tank blowing up inside the shredder chamber is a case of a bark that is worse than the bite, there are still many good reasons to monitor incoming scrap for tanks and other sealed units.

Shredding plants that become blasé about propane tanks may be prone to eventually letting a more harmful—perhaps hazardous or more powerfully explosive—pressurized container into their shredder. The consequences can be damaging financially, environmentally and possibly to the safety of employees.

Less dramatic but still important is to be on the lookout for wiry and stringy materials that can wrap themselves around the rotor of a shredder. While such materials may not cause catastrophic damage, they can reduce the performance of a shredder and lead to intermittent periods of downtime when the mill is stopped so the unwanted material can be extricated from the chamber.

Perhaps the most difficult part of putting in place a thorough inspection process, however, is designing it so that it can still be done quickly, before a dozen or more trucks are backed up and waiting to get to the scale.

CHECKING IT TWICE. When it comes to profitability, a shredding plant’s best friends can be experienced, sharp-eyed personnel at the scale house and in the shredder control room.

But whether breaking in new employees at these important positions or simply refreshing the memories of experienced personnel, Baumgartner recommends that employers maintain a checklist of materials that should be pulled out of the shredder feedstock stream.

A checklist can be designed so that certain hazards are aligned with the type of purchased scrap in which they are most likely to be found: