Sand Processing

Making your off-the-road tyres go the distance

If you use off-road tyres in your operation, you are well aware that there is a gap between the demand for tyres and available supply. Two questions arise when that statement is posed: Why? How long will the shortage last?

The simple answer to ‘Why?’ is that demand for basic commodities is at record levels. It is not surprising that companies mining these products are trying their best to raise production to all-time highs. These companies are doing everything to make more money while product prices are high, consuming more tyres.

This situation puts pressure on all sizes of tyres because of support equipment demands. The worst shortage is in large off-road tyres, but aggregate operations will have difficulty finding smaller sizes as well in the coming years.

On the off-road-tyre production side, additional off-road tyres will become available as new production begins and ramps up to full capacity. Unfortunately, it appears there will not be enough supply to meet demand for at least five years. So, what should happen in the meantime?

The best thing to do is to maintain the tyres you have. Simply put, determine how to make those tyres last. This requires proper maintenance and a reassessment of operating conditions to better use those tyres. By following this strategy, you will not only make tyres last longer and reduce tyre costs, you also will see an improvement in overall productivity.

An effective tyre maintenance program must include: in-service inspection, out-of-service inspection, repair/retread and continuous review of operating conditions.

Maintaining a tyre starts with an air-pressure maintenance program. Running an off-road tyre with inadequate air pressure can damage the tyre.

It is the air within the air chamber of a tyre that actually supports the load of the vehicle and its payload. When a tyre does not have enough air pressure, it does not have the correct shape in which the tyre was designed to operate. When ‘out of shape’, the tyre doesn?t provide maximum traction, braking and cornering ability nor does it flex where it was designed to flex, which causes heat and fatigue.

If your intention is to make your tyres last as long as possible (and achieve the maximum production possible from the machine it carries), you need to ensure the tyre is being used at its designed shape.

How do you determine the configuration of a tyre’s designed shape? Determine the maximum load on the tyre (using your heaviest material, maximum load and maximum vehicle speed) and consult the tyre manufacturer’s load and inflation table. This table will tell you how much air pressure is needed to support that tyre load. While consulting this chart, notice how much carrying capacity is lost for just 4 to 5 psi. This range, which may seem minimal, is significant to performance.

Once you have determined how much air pressure the tyre needs to provide maximum traction and cornering, you have to take into account the fact that this air pressure is based on a ‘cold’ tyre.

How do you compensate for all those times when someone has to check ‘hot’ tyre pressures? Add 10 per cent to 15 per cent to the cold pressure and make that your expected hot pressure. If you find that you normally build up more or less pressure during the work day, make that your target hot pressure.

Once you have determined how much air pressure you really need, simply stencil both cold and hot pressure levels on the hub or fender near each wheel position? That way, each operator will know what the target pressures should be and adjust the air pressures accordingly.

However, do not deflate the tyre too much until you have eliminated all possible causes of extra pressure. Check for other possible causes, such as an air chuck left on too long.

Once you have set your cold and hot pressure targets, how often should you check air pressures? It is important to understand that every tyre will lose some air pressure just because manufacturers cannot make the inner liner of the tyre impervious to air migration.

To ensure that off-road tyres operate at the designed shape, check and correct air pressure at least once a week. By checking air pressure less often, such as every few weeks, you risk reducing a tyre’s life substantially, while also hindering the performance of the machine it rides on. Can you afford to take the chance that a tyre may be ruined because air pressure was not checked? Not in today’s shortage market.

Be sure that air-pressure checks result in air-pressure corrections. It does no good to check air pressures with merely the intent of correcting them later, since the correction may not happen.

Also, make sure that your ‘tyre boss’ gets a copy of the inspection report, which shows what the air pressure was and what it was corrected to. Your tyre boss should compare the current week’s air pressures to those recorded the previous week. This is when you can determine which tyres are constantly losing pressure and take corrective action.

Get everyone involved
It is critical to your operation’s success that you manage your tyres. You must know the condition of all off-road tyres and do something about the tyres that need attention. The first step in this process is to get all operators, mechanics and supervisors actively looking at the tyres used in the operation. If anyone finds new damage/injury that is growing, it must be reported to the tyre boss to determine a course of action. The decision may be to leave the tyre alone or remove it for repair, or perhaps move it to another position.

Every damage/injury to a tyre must be considered for repair. Remember, tyres and rims are pressure vessels. Any weakness in either component can cause that assembly to come apart, often explosively. Just like the untreated human body, a tyre does not heal, it only gets worse over time. If you do not bandage an injury or perform surgery, the human body will get infected and will not perform as desired. The same holds true for tyres.

Repairing off-road tyres is something that should be considered in every case, even if (at first glance) spending the money does not appear to be economical. If the tyre can be repaired and still provide a safe pressure vessel, consider spending the money for the repair and keeping the tyre off to the side only for emergency use. That way, in the future, if you cannot obtain a replacement tyre, you at least have an emergency spare to keep you rolling until you get a replacement. So your investment in that repair will be repaid many times over.

Establish a committee
It is a good idea to establish a tyre committee ? made up of production supervisors, maintenance supervisors and operators ? for each of your sites. The group should meet regularly to spot check tyres in service in the fleet. The committee also should inspect all out-of-service tyres (looking for things that can be corrected) to prevent losing another tyre to the same circumstances. Meeting with your supplier and factory representative can go a long way toward bolstering tyre performance.

It is also important to review past decisions and how they have influenced your aggregate operation. On a regular basis, the tyre committee should tour the operation – looking at curves, grades and loading and dumping areas to determine what variables are putting undue stress on your tyres. Remember, variables that affect a tyre also affect machine durability and production. Watch out for road crown in corners that produce a negative super-elevation. Watch out for excessive water on the road caused by water trucks. You will be surprised at what you find when thinking about off-road tyres as you tour the operation.

An effective system of record-keeping also is important. The biggest challenge is forecasting off-road-tyre needs. Without accurate records detailing what kind of performance has been achieved and at what level your current tyres are at, it is difficult to manage this asset. Our company, as well as several others, offers tyre record-keeping software. Whatever system you decide to use, you owe it to yourself to keep detailed records.

Before you purchase an off-road tyre that is different from what you normally use, get some advice on how this tyre may affect your operation. You may find that the new tyre has a pattern with a high possibility for tread cut. You may discover that the bias tyre you are installing in place of a radial will slow down the vehicle. Understand the potential ramifications of your decision. This is where your supplier can help. Pick up the phone and ask questions. You are not alone in your quest to get the most out of off-road tyres.

Jack Dutcher is manager, off-road training and development, for Bridgestone North America.

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