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Tyre mounting: Safety risks

By Louis Rumao

Inflated tyres, especially the large truck and bus tyres, contain a tremendous amount of potential energy. Tyre blast during servicing can cause severe injury and death. Blast injuries of large tyres are similar to those resulting from landmine explosions, except there is no thermal or chemical damage.Louis_Rumao

Little has been reported about the destructive nature of these blasts. One study conducted in Quebec, Canada, listed 360 accidents over a period of 10 years, including ten fatal ones, directly attributable to heavy vehicle tyre blowout or explosion. Another study at two middle-east hospitals reported seven tyre-related injuries between March 2003 and September 2009, which needed hospitalisation. Four of the seven cases involved injuries caused by explosion while tyres were being inflated.

A search of the English literature, through MEDLINE, on tyre blast injuries listed 763 cases wherein most of the patients were young-aged male mechanics and the explosions usually occurred during tyre servicing, especially during inflation. Injury was caused by the pressure impact of the explosion or by direct hit of the rim. Head and face were the most commonly affected regions (48 per cent) followed by the upper limbs (20 per cent). About 25 per cent of patients had multi-trauma and the overall mortality was high (19 per cent), mainly caused by head injuries.

Even small tyres can cause severe injury patterns in the case of an explosion. High inflating pressures and low safety distances are the main factors responsible for this occurrence. However, injury data from exploded small tyres is not readily available.

Prevention can only be achieved through broad safety information and the use of suitable filling devices. Tyres should be considered as compressed air tanks. However, substantial safety regulations set up for the operation of pressure tanks are not applied to tyres.

Occupational safety devices like a protection cage with an automatic inflating gadget will help minimise the risk of injury from tyre inflation. A safety distance of 2.5 metres from the inflating tyre is recommended. If the wheel is not fixed, its components including the wheel rim could act as missiles. Big, exploding tires can produce blast waves. These risks are mainly unknown to the general public, so safety instructions are often ignored. Besides the underestimation of such a potential hazard in tyre inflation, other factors involve damaged tyres and wheel rims, overpressure for tyre bead setting, and short inflating hoses.

­­­Safety precautions

The Rubber Manufacturers’ Association (RMA) recommends the following warnings and safety precautions:

• Serious injury or death may result from: Explosion of tyre/rim/wheel assembly due to improper mounting.   – – Never ever exceed 35PSI(240kpa) air pressure when seating beads.

Always use safety cage or other restraining device and clip-on extension hose.

Only specially trained people should mount tyres.

• Tyre failure due to misapplication/inflation/overloading/exceeding maximum speed: Follow tyre manufacturers’ instructions

Check inflation pressure frequently with gauge

• Explosion of the tyre/rim/wheel assembly due to welding the rim: Never rework weld, heat or braze the rim of a tyre/wheel/rim assembly without first removing the tyre.

Must match tyre and rim/wheel size

There is a danger of serious injury or death if a tyre of one bead diameter is installed on a rim or wheel of a different diameter. Rims of different diameters and tapers cannot be inter-changed. Always replace a tyre with another tyre of exactly the same bead diameter designation and suffix letters. While it is possible to pass a 16” diameter tyre over the lip or flange of a 16.1” or 16.5”size diameter rim, it cannot be inflated enough to position itself against the rim flange. If an attempt is made to seat the tyre bead by inflating, the tyre bead will break with explosive force and could cause serious injury or death.

.Lubricate components correctly before assembly

Use only lubricants recommended by rim and tyre makers, such as vegetable oil and animal soap solutions. If a lubricant is water-based, it should contain a rust inhibitor. When dry, the lubricant should not remain slippery. Do not use petroleum, silicone, or solvent-based lubricants as these may damage the tyre rubber or cause rust buildup or tyre-to-rim slippage. Apply an approved tyre lubricant to rim bead seat area, tyre beads, tyre flap, and other rim to tyre contact surfaces just before mounting tyre.

(Photo courtesy: http://www.bendpak.com)

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