Caution: Welding Wheels Is Dangerous
The heat build-up from welding a wheel can produce serious safety hazards to technicians and drivers and violates OSHA regulations. Heat from other sources as tire fires or sealants can also pose dangers.
January 2010, Work Truck - Feature
In the explosion, the body goes flying. It lands yards from where welding on a wheel was taking place. Luckily, the hurtling body isn't an actual human being. It's a dummy, used in a safety video for demonstration purposes. But it gets the point across in dramatic fashion: don't weld wheels - with or without a tire mounted on them.
The scenario the video demonstrates involves a fired-up welding torch rigged to point at a wheel rim mounted with a tire. A digital thermometer indicates the air temperature inside the tire rocketing higher and higher. The tire then blows, and the wheel rim and the dummy are blasted through the air. The sequence is part of a wheel-end safety video, produced by the Tire Industry Association and funded by Michelin North America (see sidebar).
Welding Can Cause Invisible Wheel Damage
Welding weakens a wheel, said Marvin Bozarth, a technical consultant to the Tire Industry Association. "The wheel is designed to operate at certain temperatures, and sometimes when you weld on it, the metal hardens and causes fractures that may not be visible," Bozarth said. Such damage can lead to the wheel failing.
"Don't weld them; don't hit them with a steel hammer," Bozarth said. "You've got to treat them nice and make sure they're in good condition."
Yet despite such warnings, some wheel welding does go on, Bozarth said. "I see it on some wheels," he said, surmising the practice continues to be performed by "people who are just not informed, don't listen, or they think they know better."
He added, "That's what gets people killed."
Other Sources Pose Potential Dangers
Heat from sources other than welding, such as tire fires, also can damage rims, Bozarth said. An aluminum wheel, for example, should be inspected after a tire fire. An overheated aluminum wheel might have a damaged flange. A new tire mounted on such a damaged rim can come off, he said.
Use of ether, hairspray, or other flammable substance to seal beads on a wheel is an extremely dangerous practice, both during the procedure and potentially later if someone attempts to weld the wheel, Bozarth continued.
"Sometimes residue of that material remains in the tire," he explained, "and when you weld on the wheel, it can re-ignite the residue and cause an instantaneous fire inside the tire."
Likewise, welding a painted wheel can result in a fire. As the paint heats up, combustible fumes are emitted, Bozarth said. Also, welding near the bead can heat the tire's rubber material enough to emit a gas that could ignite, causing a fire and possibly an explosion, Bozarth said.
Another tip: sealants should be evaluated carefully before use.
"I've tested a few that claim not to be flammable," Bozarth said. The claim was true with respect to some sealants, but the propellant in some of those products is flammable, Bozarth said. "So that's something you've really got to watch out for."
Regularly Inspect & Test Wheels and Components
Wheels should be inspected regularly to determine if the lug nuts are loose and to check for wheel cracks or movement. Rim inspections should be performed during tire servicing.
"If you take the tire off to fix it or replace any lug nuts, you should inspect the wheel very thoroughly," Bozarth said.
With aluminum wheels, a roll test should be performed: roll the aluminum rim on a level flat floor. "It needs to roll straight," Bozarth said. "If it rolls in a curve, that wheel needs to be disposed of."
An excellent time to inspect steel wheels is when they're being cleaned and shot-blasted in preparation for repainting.
Sam Lamerato, superintendent of the city fleet in Troy, Mich., said among the causes of wheel damage, his department pays special attention to loose studs and loose lug nuts, as they can result in oblong stud holes.
"In our city, we re-torque our wheels on all of our large trucks once a week because you don't know if they've loosened up with the stress we put on them," Lamerato said.
The Troy fleet operates approximately 30 dump trucks with GVWR of 26,000-80,000 lbs. Those trucks carry heavy loads, Lamerato noted, such as road salt. The combination of heavy loads and frequent sharp turns stresses the wheels. In addition, if a truck wheel hits or runs over a curb or parking block, the impact can loosen the wheel, Lamerato said.
"Last year we did have a few of our wheels come loose," he recalled. "They didn't come off the trucks, but the steel wheels and hubs were damaged and had to be replaced."
The city fleet is trying a new way to monitor loose wheels and lug nuts.
"To save time this year, we purchased new devices that we put on our lug nuts," Lamerato said. The plastic devices, called Wheel-Checks, are "loose lug-nut indicators." They are placed over each lug nut, all pointing the same direction. If a nut loosens, the Wheel-Check turns too, pointing in a direction visibly out of alignment with the remaining lug nuts. Lamerato said the plastic pieces are "a bright, chartreuse green, so they stand out pretty well. Even at night you can see them."
The fleet maintenance department started using the indicators a few months ago, Lamerato said. The devices run under $1 apiece and are reusable.
"They give us a better visual, so maybe we can save some time not having to re-torque the wheels every week," Lamerato said. "If we see one that has repositioned itself, then we know we have to re-torque it." WT
Video Spells Out Dangers
Kevin Rohlwing, senior vice president of training for the Tire Industry Association, wrote the narration for a safety video underwritten by Michelin North America. The overall subject of the 20-minute video, which can be seen at the Michelin Web site, is wheel end safety. The segment on wheel welding includes the following cautionary advice:
- Welding on a rim or wheel will change the properties and strength of the metal. Never apply heat or weld on a wheel, especially when the tire is still mounted on the rim.
- The temperature of a welder can reach 11,000-degrees Fahrenheit or 6,000-degrees Celsius on contact. While as much as 50 percent of the heat is lost through conduction, the surrounding metal is still heated to extremely high temperatures, which ultimately heats the air inside the tire.
- When the rubber inside the tire reacts to the heat, gases are generated that can lead to an internal fire. Eventually the rising heat and pressure becomes too great for the tire and rim to contain. While internal changes will not be apparent to the outside observer, the severe increase in temperature and pressure will cause the tire and wheel to explode catastrophically without warning.
- Remember, it is an OSHA violation to apply heat or weld on a wheel or rim. When you weld on a wheel or rim, you're placing yourself and others around you in imminent danger - especially if the tire is still mounted.