Machine Design

For lack of a guard, a severed hand

Recently, I was an expert witness for a person who was injured while using a dust collector in a cabinet shop.

The dust-collector manufacturer will remain nameless, but all two-inlet dust collectors look and function much the same.

These dust collectors are designed to attach to woodworking machines such as saws and planers. But manufacturers know (or should know) that people will also use the dust collectors as vacuum sweepers. The 4-in.-diameter inlets are fitted with flexible hoses. If only one inlet is being used, a rubber cap covers the second inlet, which is held on by friction.

In this particular case, a person was cleaning up the woodworking shop at the end of the workday. He was using the flexible hose as a vacuum sweeper when he sucked up a soft-drink cup. The cup perfectly plugged the inlet. He tried to dislodge the cup but could not.

Finally, he decided to turn off the dust collector and disconnect the flexible hose. He spent the next 20 sec or so looking for a screwdriver to remove the hose but could not find one. He then decided that the fan inside the dust collector had stopped because there was no noise coming from it. So he removed the rubber cap and reached into the machine to remove the cup. As he did his hand was severed by the rotor, which was still rotating with sufficient energy to do this dastardly deed.

What was missing from the dust collector that would have prevented this terrible accident?

  • A proper guard would have stopped this young man from reaching in the inlet. The manufacturer stated that any guard would interfere with the proper operation of the machine. I demonstrated to the jury a guard of my own design that, in fact, did not interfere with the proper operation of the machine, but made the machine more efficient than when it was used without the guard in place.
  • Proper warnings. There was nothing on the machine or in the owner's manual that would have alerted anyone that the fan, after being powered down, could continue to rotate for over 1 min with enough energy to cause serious injury.
  • The manufacturer never did a safety or hazard analysis of the machine to determine what aspects of its operation could seriously injure users and those performing service and maintenance.

The jury came back with an award to the young man for $1.8 million. This, by the way, was in a very conservative county in northern Minnesota.

Lanny Berke is a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a question about safety? You can reach Lanny at [email protected]

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