Machine Design

Analyze your close calls

Hazard analysis is key to the safe application of equipment in the workplace.

To be effective, however, properly trained personnel must do the analysis. Good "close-call" reporting should always be part of such efforts. Companies that deviate from these practices are sitting on a time bomb.

Here's an example. The incident described below involves a maintenance person who suffered serious injuries.

Here was the machine layout before the incident: A 10-ft-wide conveyor carries aggregate to an area where the material is to be crushed. At 50-ft intervals are vertical posts comprising the framework of the conveyor system. A walkway about 10 ft from the conveyor gives maintenance personnel access to the equipment for inspection at least once a shift.

No safety guards were in place on the sides of the conveyor, despite evidence on the ground that large pieces of aggregate hit the vertical posts and could be thrown 20 ft or more across the walkway. Sure enough, a maintenance person walking the path of the conveyor was struck by a piece of aggregate in the head and side of the face. He suffered serious injuries, though he was wearing a hard hat at the time.

Surprisingly, a hazard analysis had been performed on this machine after installation, and a number of safety-related corrections made. One item overlooked by the hazard-analysis team was the potential for falling aggregate to be thrown horizontally after striking the vertical beams, rather than falling straight down. Another potential hazard not caught by the team was that workers could get within inches of the conveyor-belt edge to check for noisy bearings. Fortunately, there were no incidents involving the latter hazard.

It turns out that lack of both a qualified lead-safety person and a human-factors person on the hazard-analysis team were cited as direct causes of the incident and resulting injury. They should have identified this reasonably foreseeable situation as dangerous and taken corrective action. Further, had a proper close-call reporting program been in place, the safety shortcomings of the equipment would have been identified and corrective action taken before anyone was injured.

After the incident, side guards were added to the conveyor system to prevent aggregate from spilling over the sides. Openings in these side guards let maintenance personnel safely reach into the area of the bearings with monitoring equipment. These small, corrective actions ensure such incidents can't happen again. The message here is, both product and workplace safety need proper attention to keep workers safe.

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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