AKRON-Goodyear has issued a product service advisory listing recommended safety procedures to protect workers from the dangers of zipper ruptures in all-steel radial truck tires. Zipper breaks, so named because the exposed ends of the broken steel cord surrounding the ruptured area resemble an opened zipper, have erupted with a force that has hurled victims several feet.
Unless these precautions are followed carefully and completely, Goodyear warned, such failures can cause ``serious personal injury or death.'' For this reason, the company advised dealers to review the following recommendations with their tire service personnel.
Since permanent damage to the tire due to underinflation cannot always be detected, any tire known or suspected to have run at 80 percent or less of normal operating inflation pressure could have permanent structural damage and should be treated as underinflated, the company advised.
As such, the tire should be demounted using proper precautions and not be reinflated until after it has been carefully inspected by a trained technician and the cause of its underinflation determined.
In the bulletin, Goodyear strongly recommended:
Visually inspecting truck tires daily for cuts, snags, penetrations or puncturing objects;
Checking the inflation of highway truck tires at least weekly, or more frequently if operating conditions dictate, using an accurate, calibrated air gauge;
Marking and segregating any tires suspected of having been operated underinflated in order to prevent their accidental use prior to a thorough inspection by a trained tire technician.
Scrapping any tires that show discoloration and wrinkling of the innerliner and/or weakness and distortion of the upper sidewall (all of which are indications of damage due to underinflation);
Inflating tires-after being serviced-to 20 psi over their recommended operating pressures in an approved safety cage using an extension hose with clip-on air chuck and a pressure regulator (Goodyear's emphasis).
Following this, the tires should be allowed to remain overinflated for 20 minutes before being deflated to their recommended operating pressures and then removed from the safety cage.
Use of an OSHA-approved inflation safety cage and an extension air hose with a clip-on air chuck has been a long-standing Goodyear policy and is one of the requirements of federal Occupational Safety and Health Administration (OSHA) Standard 1910.177, the bulletin said.
However, Goodyear said it also strongly recommends the use of an approved safety cage when servicing any light truck or larger truck tire.
In describing zipper-type failures, the Goodyear service bulletin said, ``Underinflated truck tires can be subject to cord fatigue in the upper sidewall area caused by overflexing of the tire. This cord fatigue leads to a loss of strength of the ply cords. When a tire loses air and is continued in service without remedial action, it may sustain internal damage that could lead to failure upon reinflation or subsequent service.
``Since tire damage due to underinflation is beyond Goodyear's control as a manufacturer, it is not covered by the Goodyear adjustment policy. This applies whether or not the reason for the original air loss is evident in the tire,'' the bulletin stated.