Cat® 793 mining truck fleet achieves 100,000 hours and beyond (Shown: Cat® 793B Mining Haul Truck)

100,000 Hours Hauling... And Beyond

793 Mining Trucks

Sierrita Mine Gets Extended Life from Cat® 793 Trucks

People and Processes are Key

Freeport-McMoRan’s Sierrita open-pit mine is a low-grade copper operation located in southern Arizona, USA, some 48 kilometers (30 miles) north of the Mexican border. While known for its copper and molybdenum production, the mine site is also recognized for the performance of its fleet of high-hour Cat® 793 trucks — and the people, processes and service excellence that have led to this achievement.

2008 article in "Viewpoint: Perspectives on Moden Mining"  highlighted the mine's success with the 793, and the factors its management saw as key contributors. A modified version with a link to the original article is presented here.


Caterpillar’s first 793A-series truck was put into service at Sierrita in 1991, and is one of five 793s on site that have worked in excess of 100,000 hours. By 2008, it had already undergone more than 200 preventive maintenance services, consumed more than 17 million liters (4.5 million gallons) of fuel, and had 132 tire changes.

“No one really expected this truck to do the hours that it has already achieved,” said mine manager Derek Cooke at the time. “It has already passed even the most optimistic of expectations and is performing well. Indeed, it is Sierrita’s intention that this haul truck will run another 50,000 hours. I think I can safely say there are several more years left in this truck.”

While these factors were significant in themselves, it was the condition of the truck that was most impressive. Despite its age and long hours of service, truck availability remained high at 90.4 percent.

“It’s not the hours run by this machine as well as others in the fleet that is unique, but their condition and the availability that these trucks have enjoyed that is so impressive,” noted Steve Maracigan, account manager at Cat dealer Empire Machinery. “The remarkable availability has been achieved through hard work, pride in workmanship, and an adherence to a structured maintenance process.”

Sierrita’s Connie Puckett, Remote Asset Monitoring Project fleet coordinator, attributed the high hours to the basic maintenance philosophy of her department. “It goes right back to the basics,” she says. “Have a good, thorough Preventive Maintenance (PM) program, do your fluid changes when they need to be done, monitor equipment condition and application, and respond to keep the equipment in the best condition that it can be.”


Being Proactive

As mining equipment gets older, its availability tends to decrease. However, that wasn't the case for the haul truck fleet operating at Sierrita — due in large part to the fact that the mine had a world-class PM program, with processes and procedures in place to support its equipment fleet.

“The truck fleet was new, the maintenance philosophy was not,” says Puckett. “We were fortunate enough to start with a good piece of equipment, then with Empire and Caterpillar supporting our maintenance philosophy, we’ve kept it that way, and in some cases we’ve actually been able to improve the performance of those trucks.”

One part of Sierrita’s maintenance program is a pre-PM inspection, which involves a thorough inspection of the truck about five days before it is due to arrive at the maintenance shop. This ensures that any replacement parts, specialized equipment and appropriately skilled mechanics are available the minute the truck enters the PM bay.

“The biggest challenge to getting a truck to operate at over 90 percent availability is the sustainability of a robust maintenance program,“ said Larry Kitto, Empire Machinery’s director of mining. “Maintaining this high degree of professionalism does not happen by chance; it is an attitude that starts at the top and filters down — without dilution — to every part of the organization.”

Economic analysis illustrates that it is better to rebuild a well-maintained haul truck that is in good condition, than it is to retire it in order to buy a new one. “Every piece of equipment has a life expectancy,” said Maracigan, “But even after this time, it is still worth maintaining it as replacement costs are so high, and even new trucks still need to be maintained.” Those who set in place a comprehensive program to keep their machines in good condition with high availability reap the rewards which they justly deserve, said Maracigan.




Finding the right people

The pride and diligence shared by the maintenance team at Sierrita in maintaining equipment is illustrated by the high availability of the machinery. The team has developed and maintained highly consistent processes for maintaining equipment to world-class standards — and has rightly earned the respect of the mine. In fact, an audit of the maintenance program, performed by Empire, Caterpillar and Sierrita, found excellent and effective processes already in place.

Cooke was clear that ensuring that the right things happen comes down to good people. “I would like to say that it’s a complex collection of systems and procedures alone that is the key to our success here at Sierrita, but in the end it is the people who execute it all that make the difference,” he sais. “We have excellent people throughout the team. Larry Buhlke, Sierrita’s maintenance superintendent, has high expectations, holds his people accountable and is always looking to correct even the smallest of details. We have a great group of supervisors, and a fantastic work force. They all take pride in their contributions in support of this haul truck fleet — which operates at a level of availability that some mining operations can only dream of.”

The partnership with Empire is key. “Unforeseen breakdowns are a major issue at any mine,” said Tony Sharpe, Empire’s project manager at Sierrita. “Empire and Sierrita’s maintenance and operations staffs work together, doing everything they can to ensure that breakdowns do not occur.” A great relationship between the mechanics and the operational side of the mine also contributes to the overall health of the haulage fleet. Each understands the work and responsibilities of the other, said Sharpe, and they all have a mutual respect for each other’s work.

Much of the maintenance work requires a high level of technical expertise and involves many man-hours. Sierrita’s maintenance crews include some of the mine’s most dedicated performers — people who are bright, enthusiastic and experienced. These teams have an emotional buy-in for the machines for which they are responsible, explained Maracigan, as well as an immense sense of pride in keeping them in excellent condition and running at high levels of performance.

Learn more about the Sierrita 793 Success Story

A longer version of this article originally appeared in "Viewpoint: Perspectives on Modern Mining." Read the original article and and subscribe to receive Viewpoint directly in your inbox:



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A longer version of this article originally appeared in "Viewpoint: Perspectives on Modern Mining." Read the original article and and subscribe to receive Viewpoint directly in your inbox:


Going Beyond 100,000 Hours

Take a closer look at the fleet of high-hour Cat 793s currently at work on Freeport-McMoRan’s Sierrita copper mine in Arizona.

The success of the five Cat® 793 trucks at Sierrita continues. Here’s a quick look at the fleet that Freeport now aims to keep hauling for 300,000 hours before retiring.

Follow the Sierrita 793 Story