Cat Unveils the New F Series Haul Trucks

The latest line includes an electric drive option and higher horsepower engines for the mechanical drives

By Steve Fiscor, Editor-in-Chief

Despite the many company-wide changes that Caterpillar announced last fall to realign its business, the company is still moving forward in a big way with the new large mining trucks showcased in autumn 2008. In fact, the $200 million F series haul truck program represents the company’s largest investment ever in new mining technology. Today, the Cat 793F and 797F mechanical drive trucks and the 795F AC electric drive truck are all achieving milestones.

“Our investment in the F series truck is monumental, even for Cat,” said Al Frese, product support manager, Cat Global Mining. “Never before have we updated an entire truck line in such a short period of time and brought so much value to the customers. At the same time, we have not taken our eye off of technology either. Our goal is to be the leading company in mining technology.” A great example is the new Integrated Object Detection System (See Haul Truck Safety, p. xx).

The 793F and the 797F have now accumulated more than 75,000 hours of field testing and have proven their performance capabilities and their durability. The new Cat C175 engine that powers them has racked up 130,000 hours of field testing in mining trucks and more than 120,000 hours in power systems. Because of the success of these field-follow programs, the 793F is targeted to go into full production within a few months and the 797F late this year.

Caterpillar engineers have been testing two 795F AC prototypes, including the truck shown at MINExpo, at the Tucson Proving Grounds. The development program has provided input for the construction of a new 795F AC in Decatur, Ill.. The new truck was recently shipped to a copper mine in North America where it will serve as the first field-follow 795F AC as it works at the mine. The 345-ton-capacity (313-metric-ton-capacity) 795F AC will enter a new size class for Cat, and, as a result, the primary focus of the the company’s AC electric program has been on the 795F AC. The commercial launch date will be defined as the field-follow program progresses.

“In terms of our product strategy for mining trucks, our customers asked us to make improvements on our mining trucks and we responded,” said David Rea, global marketing manager-mining trucks, Cat Global Mining. “This is a comprehensive program for every mining truck. Cat mining trucks, including the F series, have enhanced safety features and many new integrated technologies compared to what we had in the past. Our trucks are more reliable, easier to maintain and more friendly for both the operator and the environment.”

The most evident new component is the Cat C175 diesel engine, which is the power plant for each of the new trucks. The C175 meets US EPA Tier 2 emissions standards. The C175 promises longer life between rebuilds, lower sound levels, improved altitude capability and improved fuel consumption compared to the 3500 Series engines it replaces.

As a brand new platform, the 795F AC incorporates new technologies throughout. For example, four-corner blended braking and retarding—using Cat oil immersed and cooled disc brakes as well as electrical retarding—enhances safety and operator confidence. The remote-mounted generator enables servicing without removing other major components, and the wheel motors mounted inside the axle enable easy and separate servicing of the final drives. The retarding grids are radial, which promotes more uniform air flow for better reliability. And the drive system is fully integrated and fully supported by Cat.

The company believes that mechanical drive mining trucks will satisfy the needs of the vast majority of mining operations. But as the only manufacturer of 200-ton (181-mt) and larger mining trucks with both mechanical drive and electric drive systems, Cat will soon be able to offer trucks that address all mining company preferences.

Mining Truck Development Strategy

Cat has learned a lot about mining trucks over the years. Since 1975, the company has built more than 20,000 of them. “When we decided to launch this next generation of trucks four or five years ago, we visited nearly 105 customers around the world,” Rea said. “We sat down with a wide variety of customers—maintenance personnel, operations managers, production superintendents, purchasing managers–to understand their needs.”

In 2002, Cat announced the 797B series, which was Tier 1 compliant with service and braking improvements. The power on the truck was increased to 3,500 hp and the top speed increased to 42 mph. Seven years later (2009), the 797F has a new 4,000-hp 20 cylinder C175 diesel engine. Further refinements include serviceability from the ground level and added safety features.

While he freely admits he’s excited about the F series 797, Rea explained that Cat is already working on the next generation 797. “We have the 2015 target from the Environmental Protection Agency on Tier 4 Final emissions that we are working toward,” Rea said. Since the 797’s debut in 1998, Cat has sold nearly 500 units.

The D series was the last upgrade announced for the Cat 793 in 2004. Similarly, it had a Tier 1 compliant engine. The power on the truck was increased to 2,415 hp, which took the top speed up to 37 mph. The upgrade also included a power management system, extended-life wheel stations and optional extra retarding. The Cat 793F has a 16-cylinder, 2,650-hp engine and many of the same features included on the 797F. Likewise, Cat is already working on the next generation 793. Since the Cat 793 haul truck’s introduction in 1991, more than 3,000 units have been sold.

“We had some very aggressive targets for extending component life, better fuel efficiency, and additional productivity,” Rea said. “In 1991, when we launched the 793, the benchmark was 6,000 SMU hours per year. Today, 6,000 hours is not world class. We have customers now targeting 7,200 hours.”

Many mining companies have set a safety goal of zero incidents and Cat is committed to helping them achieve it. A number of the changes and modifications to the F series trucks resemble the list of 15 priorities set by the Earth Moving and Equipment & Safety Roundtable (EMESRT), a joint safety initiative between mining companies and equipment manufacturers, to take safety to the next levels.

When haul trucks are plotted against payload capacity (See Figure 1), an obvious gap exists between the Cat 797 and the Cat 793. “With the 797, we really took a significant step in haulage capacity of a mining truck,” Rea said. “We have filled that gap with the 795 AC electric drive truck.”

Cat is not abandoning mechanical drive haul trucks in favor of electrical drive systems. Mechanical drive still provides superior drive train efficiency, Rea explained. “Even with the new Cat AC-drive truck and all of the new advancements, mechanical drive trucks still provide the best power train efficiency, which means less power to travel at the same speed or higher speeds at the same amount of power. Better efficiency also translates into less fuel consumed.”

For the most part, the Cat mechanical- and electric-drive trucks are very similar, they have the same tires, final drives, etc., except for the large inverter box and retarding grid. These features make the 795F AC truck about 10 tons heavier than the 793F, which is 10 less tons of payload.

Electric drive components are also more expensive. “Going back 10 to 15 years, DC components actually came down in cost quite significantly,” Rea said. “With the advancement of AC drive components, they provide better power train efficiency—not as good as mechanical-drive power trains—but certainly better than DC and they are definitely more expensive.”

Electric Drive…Why Now?

When asked why Cat is developing an electric-drive truck after explaining the advantages of a mechanical-drive power train, Rea asks rhetorically, why not? “We listened to our customers and some wanted an AC-drive mining truck supported by industry’s best dealer network,” Rea said. “The new AC-drive trucks are a complement to Cat’s existing product line. We are firmly committed to mechanical-drive trucks today and will be long into the future.”

AC-drive trucks do have some specific performance advantages. As an example, the top speed on the flat is higher than a mechanical drive (40 mph vs. 35 mph). The reality, however, is that most mines have a posted speed limit that is lower than the top speed of both electrical- and mechanical-drive trucks.

An AC drive has a higher retarding speed. Fully-loaded traveling downhill for a long distance, an electric-drive truck will have an advantage over a mechanical-drive truck. “Our research shows that those downhill-loaded applications are usually in the mountains with snow, rain and poor visibility,” Rea said. “The mines are unable to take advantage of the published performance capabilities. In effect, we have actually found the opposite to be true. Because a mechanical-drive truck has four-corner braking, oil-cooled disc brakes and the traction control, the miners are more comfortable traveling at faster speeds fully loaded downhill.”

“Nevertheless, customers have asked us for an electric-drive truck and we believe there are some unique applications where it will provide a cost per ton advantage,” Rea said.

Rather than partnering with an AC-drive supplier, Cat decided to develop its own integrated AC-drive system. The Cat designed alternator is technology developed from the company’s power generation business, which has a core competency in alternators. For the power inverter, however, Cat had to reach out to Mitsubishi, which is the largest supplier of inverters. “Cat has had a relationship with Mitsubishi dating back 25 years,” Rea said. “The inverter will be painted yellow and supported by Cat.”

There are some obvious difference between the Cat system and competitive systems. What probably stands out the most is the retarding grid. The industry standard is a big box that sits opposite the cab. Cat is using a radial design (e.g., round). They found they had better efficiency. They could save weight and it runs more quietly. For those that expect to hear the squeal of the retarding grids, they will be pleasantly surprised at how Cat has modified the shroud and louvers to reduce the spectator sound.

On competitive trucks, the alternator s is connected to the engine. “That created two problems for us,” Rea said. “The forward location shifted the weight balance toward the front. The axle distribution for any truck when it’s fully loaded should have 1/3 of the weight on the front axle and the remainder on the rear axle. If the alternator is placed further forward, it’s extremely difficult to achieve that ideal load support. You end up with the front axle overloaded, which causes challenges with tires and the maneuverability. By moving it to the back we have been able to achieve that optimum weight balance.”

Also, separating the two has improved the serviceability of the truck. The standard expectation for component life is about 30,000 hours for an alternator and 20,000 hours for an engine. “It varies based on load factors, but it’s rare that the alternator would have the same component life as the engine,” Rea said. “If they are connected, you have to remove both of them to service one or the other.”

The wheel motors were designed and built to Cat specifications and integrated into the electric drive trucks. They are mounted to the rear axle, which improves serviceability. “We have an all new high speed final drive using a ring gear, which give longer life to the final drives,” Rea said.

The cooling system for the drive train is hydraulically driven. “This will be demand driven cooling,” Rea said. “In artic application or on cooler days it reduces the parasitic load, giving more speed on grade, better performance.”

To stop, an electric drive truck uses a retarding grid and most have oil cool disc brakes on the rear axle with dry disc caliper brakes on the front axle. Cat is using its four corner oil-cooled disc brakes technology on the AC drive. “It will have a few more hydraulic lines, but we firmly believe that the Cat braking system gives operators more confidence in the ability to run the truck downhill,” Rea said. 

Other F Series Improvements

In addition to the new engine, the Cat 797F and Cat 793 haul trucks offer redesigned operator stations, custom body systems; ground level service points, and 1,000-hour hydraulic filter service intervals. Safety enhancements include wider walkways, a rear access ladder and a bumper-mounted, three-way, lock-out tag-out box. There are three different techniques to lock-out the trucks, Rea explained, disconnect the battery, disconnect the starter or a transmission lockout, which is a requirement for really cold applications.

On the Cat 797F, the C175-20 ACERT engine has a single engine block and is the heart of the new truck. It displaces 5.3 liters (323 in³) per cylinder—for a total displacement of 106 liters (6,458 in³). On the Cat 793F, the C175-16 diesel engine displaces 5.3 liters (323 in³) per cylinder—for a total displacement of 85 liters (5,187 in³). The C175-16, with a 20% torque rise, allows the 793F to climb steep grades at productive speeds and to effectively negotiate poor underfoot conditions. The electronically controlled cooling system incorporates a Mesabi radiator featuring a flexible-core design that is extremely durable and easy to service.

On both trucks, a cross-flow engine design uses four turbochargers, an air-to-air aftercooler and an electronically controlled common-rail fuel system, which precisely delivers multiple injections in a single combustion event. These electronically controlled systems account for much of the high power density and low emissions and contribute to the 797F fuel efficiency and responsive performance. The engine-cooling system, also electronically controlled, uses the engine cooling fan only as needed, which conserves power and fuel.

By raising the level of the turbos on the C175, they are all above the fuel lines as well as hydraulic lines. “In the event that a hose ruptured with a hydraulic oil or fuel leak, there is no opportunity for that fluid to get inside the turbo,” Rea said.

The Vital Information Management System (VIMS) provides machine health and payload data, plus easy access to diagnostic and machine management information. “We have a common cab for the 793F, the 795F, and the 797F,” Rea said. “. By moving the VIMS to the right, Cat has increased the amount of glass in cab by 40%. We have improved visibility by 15%. Better visibility equals better safety.”

An angled, center-mounted instrument panel and a center console are the dominant features of the new operator station. “On previous generations, the operator would reach down on the left-hand side and pull a switch to raise and lower the body,” Rea said. “We now have an electronic hoist control positioned at the center console on a 45º angle. We have also put the shift lever on a 45º angle and eliminated the park brake switch.”

Levers and switches in the console are comfortably positioned just forward of the right armrest to allow easy control with minimum effort. Two fully adjustable, air-suspension seats assure comfort throughout the work shift for both the operator and trainer, and newly designed front and side windows give a commanding view of the haul road and work areas.

“In the past, when the operator parked the truck, they would have to flip a switch for the parking brake,” Rea said. “An incident could occur if the operator forgets to activate the switch. With the new F series, when the operator puts the truck in park, the parking brake is automatically activated.”

A robotically welded and ultrasonically checked frame incorporates nine mild-steel castings. The large radii castings are resilient to absorb frame flexing and ensure long life. The mild steel castings and fabrications provide flexibility, durability and resistance to impact loads, even in cold climates.

A choice of four Mine Specific Design (MSD II) body options are available for the 797F. The 793F is offered with three body options: X-Body; MSD II; and Gateless Coal Body. The X-Body uses a particularly heavy-duty design and accommodates a larger volume than previous Cat dual-slope or flat-floor bodies—but design enhancements keep the weight of the new body the same as previous bodies. The X-Body is designed primarily for new mine sites, where materials of different densities frequently must be hauled.

“On the 793F, we have moved the steering tank, air system, and batteries to provide more space opposite the operator’s station,” Rea said. “We reduce the weight of the hood. All of the computers and controls that were previously located on the backside of the cab, have now been moved around to the front.”

A 600-mm-wide (24-in-wide) stairway and walkway, assist safe entry and exit. The previous industry standard was 400 mm and Cat increased it by 50%. “The reality is that miners are getting bigger and they need more space to crawl onto the machine, especially when they are carrying coolers or backpacks,” Rea said.

The F series trucks also have several feature geared toward environmental sustainability. Aside from being Tier 2 compliant, the improved fuel efficiency of the C175 engine reduces the truck’s carbon footprint. Ecology drains on the filters improve serviceability and prevents spills. “We have doubled the filter life, reducing consumables,” Rea said. “We have extended the PM interval with oil renewal system where customer can extend the oil change intervals. Cat remanufactured components.

“Every Cat 793 and 797 that Cat builds will have the same emissions footprint regardless of where we put that truck,” Rea said. “We could have placed noncompliant engines in less-regulated regions, but that goes against our code of social responsibility. As a company, we have decided that we will produce the same 793 and 797 trucks for everybody.”

It would have been very easy for Cat to put the skids on this development program when times became tough last October, but the executive office has been very committed to this next generation of trucks. “With the introduction of the electric-drive trucks and the modifications that we have made to the mechanical drive trucks, we are very excited about being able to have a truck that will meet every customer’s need in any application around the world,” Rea said

Weathering the Storm, Preparing for the Future

For mining equipment manufacturers, 2008 was probably a high water mark. Many had some fantastic successes and they celebrated those achievements at MINExpo 2008. Reiterating the division’s new mantra, “Mining Safely, Mining More, Mining Right,” Al Frese, product support manager, Cat Global Mining, tried to frame the recent turn of events. “New orders for large trucks reached an all time high just before the end of 2008 and then plummeted during the first quarter of 2009,” Frese said. Noting that this was not the first downturn in the mining business, Frese explained that the difference this time was the rapid rate at which it occurred and the severity of going from a high level of activity to a much lower level.

The construction market had already slowed and, with mining and the global economy taking a nose dive, Cat felt it had to change how it did business. In an effort to not only position itself to survive the downturn, but to strengthen its leadership position, Cat implemented plans to weather the economic downturn, which included layoffs; salary and benefit freezes; scaled back production; inventory reductions; and enterprise re-alignment. “We had some pretty aggressive goals to reduce inventory within our operation,” Frese said. “We had taken about $1.6 billion worth of inventory out of our operation. Now we’re on par to take another $3 billion by the end of the year. We are a much more efficient company at this lower level.”

Three years ago, the company embarked on the Cat Production System (CPS), streamlining every aspect of its global footprint. CPS is an order entry through finished-goods process that allows the company to better anticipate customer needs, build in expeditious fashion, and doing so safely. “During 2008, we were producing at peak levels that we have never seen before,” Frese said. “And, we have done that in one of the safest working environments.”

As part of the more recent enterprise alignment effort, Cat created business units that are focused specifically on customer needs, similar to Cat Global Mining. “We have realigned our entire company, creating a simpler, more efficient, more customer-focused and more market-driven structure,” said Frese.

Cat Global Mining has a dedicated team that works with miners and dealers on a variety of continuous improvement projects. Continuous improvement is a term Cat uses for partnering with customers in a collaborative fashion, identifying their needs and key differences that go beyond a new piece of iron or technology to deliver the benefits that meets their objectives. The company continued to fund this vital work through the economic downturn.

“Leading up to the peak in 2008, most of our work with customers consisted of increasing production and we were determining how we could give the customer more hours of availability on the ready line,” Frese said. “The solutions varied from optimizing payloads to simply getting the trucks up the haul road more quickly.” Cat also worked with customers on haul road design and increasing cycle times.

For 2010, the mines are looking at a different scenario. Frese explained that the interest has shifted from productivity to efficiency. “Many of the projects in our $90 billion pipeline are focused on increasing efficiency,” Frese said. “The mining companies want to know how they we get the most from existing assets.”

Cat also continues to fund research and development at a very aggressive level. This year (2009) will go down in history as the second largest year ever for R&D investment, Frese explained. “If you think about the economic times, that’s a significant statement,” Frese said.

In a sense Cat has to continue its R&D efforts to sustain itself. The emissions requirements on the horizon are daunting. Basically every Cat product will have to be redesigned and developed to meet the EPA’s more stringent Tier 4 and Tier 4 Final requirements. To remain competitive in less regulated parts of the world, a lot of the engine development research deals with being able to meet emissions targets and also improve the efficiency.

Similar to the mining business, Cat is committed to safety. Cat sees protecting the people that operate its equipment far and above and beyond regulatory standards as a fiduciary responsibility, Frese explained. “We are constantly trying to identify the best solutions for mobile equipment that includes safety and sustainability for people in mining operations,” Frese said. “Cat embarked on its safety journey five years ago and the mines responded. Cat Global Mining takes safety very serious.”

Cat’s strength lies in its dealer network. “Our dealer network has the footprint, people, financial scale, and capability to support customers regardless of whether they are mining in the Democratic Republic of Congo (DRC), Chile or the western U.S.,” Frese said. “Our dealers are focused on mining. They understand the business and the have the financial wherewithal to not only sustain themselves through this cycle, but also to help miners prepare for the upturn.” The future is far from certain, but the fundamentals are starting to build in a positive direction, Frese explained, and Cat will be ready when the upturn occurs.