Many park districts maintain their vehicles. One vehicle maintenance hazard that you may not be aware of is tire explosions. Truck and tractor tires have spontaneously and violently exploded with no apparent cause or warning, while still mounted on the vehicle. The forces involved in this type of explosion are very powerful and capable of causing serious injury to anyone in the immediate vicinity, or a collision, if this occurs while the vehicle is being driven.

Even though the causes of tire explosions are difficult to determine, some explosions are thought to be caused by flammable vapors entering the tire. The temperature of the air and vapor mixture inside the tire increases due to increasing external air temperature and friction. The temperature inside the tire can reach the combustion point, resulting in an explosion.

A possible source of the problem is the introduction of flammable vapors through a compressed air system. To prevent flammable vapors from entering the compressor and becoming trapped in tires, consider these guidelines:

• Do not locate the compressor in a room that is also used for storing flammable solvents, paints, etc. The flammable vapors will be sucked into the compressor intake, and pumped into the tires.
• Do not add alcohol or other flammable solvents to the compressor tank to prevent freezing of the condensation inside of the air tank. A better solution is to drain the tank frequently, or relocate the compressor inside of the building to eliminate the freezing problem.
• Do not locate the compressor near your battery charging area. When batteries are being charged, they emit hydrogen gas that is highly flammable and can be sucked into the compressor intake.
• Do not clean the compressor air intake filter with a flammable solvent. Use a non-flammable solvent or degreaser designed for this purpose that is recommended by the filter manufacturer.

Also, tire explosions can take place when a technician is making a repair. An example is when a technician is welding a tire rim. The torch heats up the air mixture inside of the tire resulting in an explosion. The results of tire explosions can include lacerations, severe trauma to the body and even death, as rubber and metal from the tire are propelled at a technician. In some cases when a tire explodes, technicians have been physical thrown by the explosion. It is highly recommended that a clip-on air chuck or an inflation cage is used.

Technicians should receive documented training on a regular basis, to remind them of proper tire repair and the gravity of the situation. A written policy should be established along with the training program. The proper steps should be clearly communicated and followed by technicians.

Tire Repair Checklist:

• Inspect the work area before beginning the repair process.
• Make sure you have all necessary tools and equipment for the repair.
• Make sure tools and equipment are in good condition.
• Make sure safety glasses are worn.
• Remove the tire from the wheel.
• Look for wheel defects or damage.
• Make sure the tire meets manufacturer’s specifications.
• Mount the tire on the wheel.
• Insert a clip-on air chuck onto the valve stem.
• Stand away from the tire and inflate to the recommended pressure.
• Balance the wheel and tire assembly.
• Inspect the surrounding parts such as hub, nuts and brakes, before reinstalling the wheel.
• Install the wheel with a calibrated torque wrench.
• Make sure the technician complies with the manufacturer’s recommended torque pressure.
• Tighten lug nuts first, and then repeat the tightening process in a progress sequence until the proper torque pressure is applied to all lug nuts.
• The technician’s supervisor should inspect the work to ensure the lug nuts are tightened correctly.
• Proper documentation should be completed and filed.