Choose what to measure to avoid information overload

Mine maintenance is different in the 21st Century.

The explosion of data technology means that technicians can monitor virtually any aspect of their equipment. Speed and engine hours came first, but now mines are measuring everything – from fuel depletion levels to individual OEM sensor data.

It’s no longer a question of tracking or not tracking. It’s a question of what to track.

Take tires, for instance. Mines pay a lot of attention to the condition of their tire stock – for good reason. Along with fuel and labour, tires are among a mine’s biggest expenses.

Technicians have long known that when tires get hot, they start to break down. Plies can separate, making them more prone to blowout. So, mines take great pains to track tire work rates in order to keep each $50,000 investment lasting as long as possible.

Different operations handle tire monitoring in different ways.

Some analyze tire data from OEM systems whenever trucks go in for maintenance. This approach may prove better than nothing, but it doesn’t give the real-time feedback necessary for technicians to intervene before tires start to break down.

More advanced operations use a tire management system, such as Wenco’s TireMax. These systems can calculate tire TKPH/TMPH (tonne kilometre or mile per hour) and let mines compare it against manufacturer’s recommendations. This method works much better, giving immediate indication should tires start to exceed their work rates. But, in the current era, even TKPH/TMPH doesn’t give the most accurate reflection of real tire condition.

Forward-thinking mines may use temperature as a key metric for tire condition. By equipping trucks with tire pressure monitoring systems (TPMS), they get a precise assessment of the environment inside each tire. Technicians can use this information to step in when those conditions could cause undue wear and tear on the tire.

But what if tracking temperature isn’t accurate enough? That’s what tire specialist Adam Gosling thinks. He represents TyreSafe Australia, a consulting firm that works to help clients maximize the value of their tire stock.

“(Temperature) is a bit vague, really,” he says. “What’s the actual temperature you’re talking about? At the tread? The sidewall? The air inside? It’s quite nebulous.” According to Gosling, internal sensors only measure the temperature and pressure inside the tire’s air chamber. Due to their large size, those measurements aren’t consistent throughout the tire.

“Some of those tires are 14 feet high,” he says. “Through convection, the air at the bottom will be cooler than the air at the top.” Gosling also notes that movement of air within a tire can cause temperature distortions. As tires travel through a mine, bumps create vortexes and eddies of air at different temperatures. Depending on the location of the TPMS sensor, it could produce inconsistent temperature readings.

Even the equations mines use for their tire work thresholds are problematic, says Gosling. Many mines rely on the ideal gas equation – a law of physics that describes the relationship between pressure and temperature in a rigid container.

“That’s not like a tire,” he says. “(Tires are) flexible, so the volume changes.” Each bump along a haul road can cause tires to deform. Different parts of each tire respond to these changes differently.

“Therefore, the calculations involved in determining that equation are horrendous,” says Gosling. His research shows that temperature measurements can prove highly inaccurate, leading a tire to exceed its approved threshold too often.

“Tire design has a safety margin built in. But when people try to use temperature as the metric, it comes undone because of the huge variances.” Rather, Gosling advocates mines use the pressure at the valve stem as their measurement for determining real tire condition.

“The temperature changes, but pressure is more consistent – especially pressure at the valve stem, where the air is trying to escape,” he says. Even though pressure also varies, he says readings from the valve stem prove much more regular than temperature readings over a significant period.

Yet, tires are simply one component of an increasingly complex set of mining equipment. Every machine part involves parameters that maintenance can check to judge performance. Should mines track oil temperature to assess engine condition? Or air temperature? Or coolant flow? Or another metric altogether?

The beauty of the data revolution is that mines can now gather information about so many elements of their operation long hidden from view. Now, the challenge lies in sorting through that information to make better decisions for better outcomes. In many cases, it starts with knowing the values that make a real difference to bottom lines and those that prove only a distraction.

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Devon Wells is the technical content writer for Wenco International Mining Systems. A subsidiary of Hitachi Construction Machinery, Wenco empowers data to make mining simpler, smarter, and safer. For more information, please visit www.wencomine.com.

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