The death of a worker who suffocated when both his hands were caught in a conveyor’s tail pulley was one of the six to 10 conveyor accidents I investigate yearly. Although conveyors have long been recognized as having hazards, their dangers seem to go unrecognized when they are part of a larger system.
Anyone designing or operating a system with a conveyor should take a look at three accidents typical of the conveyor mishaps I’ve seen and take steps to avoid the missteps that lead to the accidents.
One accident involved a rock-crusher system. A worker replacing a zerk fitting at the tail-pulley bearing had both hands caught between the tail pulley and the conveyor belt. The movement of the belt squeezed him against the tail pulley so he could breathe out but couldn’t breathe in. He died of suffocation.
The conveyor carrying crushed rock to a pile had been set up improperly by the rock-crushing-machine company and was constantly mistracking. Maintenance personnel from the machine company had to remove a 200-lb guard from the tail pulley each time they adjusted the conveyor-belt tracking system, something they were called upon to do many times. As you can imagine, it wasn’t long before workers took off the guard and left it off. This was misstep one.
Each time they adjusted the belt, workers performed a proper lockout/tagout. Electrical switches for lockout/tagout were in a trailer 25-30 yards from the conveyor. There was only one lockout/tagout lock in the trailer; if it was in use, other switches could not be properly locked out. Misstep two.
The supervisor had locked out the conveyor switch in the trailer before the accident. Prior to unlocking the switch for the conveyor and turning the switch on, he visually checked the conveyor. However, he did not have a clear line-of-sight from the trailer to the entire conveyor, and he could not see the tail pulley. Misstep three.
Nobody working on the rock crusher on a daily basis had proper lockout/tagout training. Misstep four.
To keep this accident from happening again, the company should have made sure everyone working on the rock-crusher team was properly trained in lockout/tagout and that they were following procedure. This isn’t just common sense, it’s an OSHA requirement.
The tail pulley should have had a guard in place. To ensure the guard is used as intended, it should be made of a strong material so it’s light enough for one person to move. It should be attached to the conveyor frame with hinges so it cannot be removed, and its position should be monitored by an interlock.
Moving lubrication fittings to a safer area, for instance on the safe side of a guard, would also protect workers. A single lubrication tube with a zerk fitting on its end could serve all pulley bearings that need lubrication.
Having a switch at the conveyor that could lockout its operation would make workers more likely to perform proper lockout/tagout procedures than if they have to walk a distance to the trailer.
Finally, although there were warnings and instructions on the conveyor framework, they were poorly worded, and, in some critical cases, not visible to the workers.
Next month, we’ll discuss another conveyor accident.
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 firstname.lastname@example.org.