Machine Design

Robots Attack When Safety Measures are Lacking

A worker on a Sunday shift saw a strange movement out of the corner of his eye. When he went to investigate, he found the mechanic who’d been working on the next machine over pinned between the arm and base of an industrial robot. It took the worker and an assistant foreman several tries, including climbing down a set of stairs and around a corner, to power down the robot and manually release the mechanic.

The mechanic wasn’t breathing, so the rescuers performed CPR until the paramedics arrived. After several days in a coma, the mechanic regained consciousness. He needed extensive physical and speech therapy to recover some of the function he lost from being deprived of oxygen.

Along with two other maintenance workers, the mechanic had been repairing the malfunctioning robot. He told the other two to take a break while he continued to work. While he was alone, the robot arm moved and crushed his chest into its track.

The state occupational safety and health department (OSHD) cited the company for using generic lockout/tagout procedures that did not comply with ANSI standards for robotic equipment. It also faulted the lack of guards on the sides of the machine, an omission that let employees reach into the machine during its operation and that was directly involved in this injury.

In addition, investigators found the machinery itself unsafe. The amount of force the robot could exert was not limited by software or mechanical controls. The operators’ manual showed how to install a hand-wrist joint that breaks at a predetermined minimal pressure and triggers an alarm, but such a device hadn’t been installed. In fact, there were no alarms of any kind that would alert those working nearby of a trouble condition. Printed warnings per ANSI standards were also absent from the machine and the operators’ manual.

As part of the corrective-action plan the company worked out with OSHD, the company instituted specific lockout/tagout procedures on all its production equipment and required training for all operators and maintenance personnel. All the company’s robotic workcells are now surrounded by enclosures with interlocked access doors. Opening one of the doors shuts down the robot. Finally, an active workplace accident and injury-reduction program analyzes job hazards on an ongoing basis and ensures safe operating procedures are in place.

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

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