Machine Design

Machine without e-stops, interlocks injures worker

A worker at a poultry plant was injured when she got too close to a mechanism for stapling turkey bags. There were no interlocked safety gates or emergency-stop (e-stop) buttons on the machine when the accident happened.

The machine involved in the accident carried up to 16 plastic-bagged turkeys at a time around a central hub while sucking the air out of each bag, stapling the bags closed, and delivering each bag to a conveyor moving it to the next station. Each of the 16 stations had a two-sided clamping mechanism to secure the bag on the suction port. When the clamp halves opened, each nearly touched the clamp half of the adjacent station.

It wasn’t uncommon for the staples feeding the machine to jam, setting off an alarm that called for operator intervention. Operators climbed a step to unjam the stapling mechanism. They also had to reach between the stapler and the clamp apparatus to disable the jammed-stapler alarm.

The accident happened after the worker unjammed the stapler. Her hand caught between the open clamp halves of two adjacent stations as she climbed down from the step. Seconds later, her arm was pulled under the stapler which jammed into her arm, severely injuring her.

Investigators quickly identified several problems with the machine’s design. There was no convenient way to perform lockout/tagout on the machine before unjamming the stapler. Consequently, workers performed this frequent, minor maintenance job with the machine running, placing themselves in a hazardous situation.

Turning off the jammed-stapler alarm meant reaching into a hazardous area between moving parts of the machine when the reset button could easily have been mounted in a safer spot. Another oversight was the lack of e-stop provisions that would let a trapped worker stop the machine.

In addition to these design flaws, safety documentation associated with the machine was scant. A few stickers warned users of pinch points, but there was nothing legible from a safe distance to warn workers of risks from moving parts, pinch points, or maintenance procedures.

Soon after the accident, the processing plant added two important safety upgrades: an e-stop button within reach of the workers’ station and a small interlocked gate that keeps workers away from the stapling mechanism and stops the machine if opened. MD

This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to [email protected].

Edited by Jessica Shapiro

© 2011 Penton Media, Inc.

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