Machine Design

Poor Tire Inflation Safety Leads to Injury

A worker had just finished repairing and reinflating a heavy-duty trailer tire and was standing 1 to 2 ft away when it exploded. 100-psi air released by the sidewall blowout knocked him to the ground. His work pants were torn to shreds, but more seriously, doctors had to rebuild his tibia plateau, just below the knee, with bone from his hip, plates, and screws.

The worker had removed the Goodyear Unisteel radial tubeless truck tire from its rim to repair a puncture in the tread area. Although machinery is available for demounting and remounting tires like these, its cost was prohibitive for the small shop the worker owned. So he did all the work with hand tools, following procedures he had used many times in the past.

After he inflated the remounted tire, the worker heard a popping sound coming from where the tire was leaning against a wall. However, he did not have time to react before a gash about 15-in. long opened parallel to the tire’s circumference, releasing the highpressure air that injured him.

The tire belonged to a truck driver whose dual-axle trailer had been running the tire in question. Two weeks before this incident, the driver reported that another tire on the trailer had blown out on the road, resulting in a gash of similar length and location to the one that caused the worker’s injury.

Because the failure modes were so similar, the worker questioned whether Goodyear had noted any quality defects during the time the two tires were manufactured. Although the tires appeared well maintained on visual inspection, investigators surmised the sidewalls of both tires had been weakened in service. Overloading or underinflation can damage the steel ply cords in tire sidewalls, leading to blowouts like the ones in this case.

Because inflated tires are effectively pressure vessels, workers should take precautions when working around them, especially if the tire has been run underinflated or its condition is unknown. These precautions include keeping hands and body parts out of the volume projected by the disk of the tire, inflating the tire in a safety cage or other restraining device, and using an extension air hose that keeps the worker out of harm’s way.

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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