February 2008

An ounce of prevention

The practical implementation of a wireless tire pressure monitoring system for mine sites

By C. Brothen and T. Lee

The introduction of new technology in mine operations has provided real opportunities for increased efficiencies and production gains that can translate into enhanced profits. This has largely been the case with the integration of computing and network technology into surface mining operations. However, embracing new technology does not guarantee positive results. The expectations and anticipated improvements should be determined well before implementation.

Wireless tire pressure and temperature monitoring systems (TPMS) are an excellent example of an existing technology that can help provide savings through lowered maintenance costs and increased productivity.

Off-the-road (OTR) tires are often out of service before their expected useful life is achieved. In many instances, this occurs because they have been operating at more than 100 per cent of some combination of the rated load, speed or distance-carrying capacity. Any movement to improve any or all of these operating parameters will positively affect tire life.

Regular checks of operating tires are mandatory and integral to any good preventative maintenance program. A wireless TPMS can provide real-time, automated performance measurements of tires operating under harsh conditions. Prompt warnings or alarms signal when a tire has exceeded operating capacities, enabling maintenance providers to proactively address condition alerts before irreparable damage occurs, thereby providing savings through lowered maintenance costs and increased productivity.

Under pressure

A tire’s ton kilometre per hour (TKPH) is a theoretical measure of the work done by a tire and is the accepted standard used today by manufacturers and tire experts. Tire manufacturers understand that tire life is dramatically affected when temperature and pressure are elevated beyond acceptable parameters and thereby exceed this value.

At Mine Expo 2000, Larry Hurst, manager of Goodyear OTR programs, stated: “The traditional TKPH/TMPH formula uses established averages, which do not account for grades, which shift weight from one end of the truck to the other, increasing tire temperature, and other variables. The key to maximizing tire life is knowing when the tires are entering the heat danger zone and taking steps to keep them out of that zone by putting the truck on a different route, performing maintenance, or some other activity.”

It follows then, that an OTR tire will experience maximum wear in the shortest period of time when the truck is in an overload condition, transporting a non-centred load, at maximum speed, over a long distance and at a high ambient temperature. Manufacturers commonly claim that a truck overloaded by 10 per cent will experience a 20 per cent reduction in tire life. An assumption can be made that under-inflation will decrease tire life by a similar percentage. We know that when either of these conditions is considered – in combination with speed and distance travelled – it will likely result in elevated internal tire temperatures, which is known to affect tire performance and shorten life.

At a recent Michelin presentation concerning the global tire crisis, it was suggested that good pressure maintenance can yield approximately 30 per cent greater tire life as compared to when pressure control is average.

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