With increased attention to safety and productivity, truck makers look at ways to engage the operator and eliminate downtime
By Steve Fiscor, Editor-in-Chief
Hauling ore is an important aspect of the underground mining process that is often taken for granted until something goes wrong. Similar to any piece of mining equipment, the more consistently underground mine trucks run, the more they produce. When availability diminishes or they go down unexpectedly, which seems to happen at the worst possible time and location, mine production takes a big hit.
Underground mine trucks have improved steadily with the times. Technology affords the operators conveniences that were not available before and sophisticated electronics allow maintenance technicians to effectively diagnose problems. Today’s machines are designed with safety and service in mind. Even though they have made great strides, there is still room for improvement.
Truck makers are already thinking about the next generation and how those fleets will be serviced and maintained. Anticipating future situations, such as those created by Tier 4 engines or the need for drivers to operate more hours and drive longer routes, they are already considering what tools the mines will need. They are also looking at ways to increase uptime and maximize future productivity.
While the role of the ore truck remains the same, the settings in which it operates are starting to change. More underground mines are looking at long hauls from the face to the surface. In some cases, that means leaving a rather warm, humid face area and entering a dry, much cooler atmosphere on the surface in a matter of minutes. As more mature open-pit mines transition to underground operations, a miner with a different background will sit at the controls and expect more.
Ore Truck Evolution
Many of the recent changes that have been incorporated into mine trucks would be considered more evolutionary than revolutionary. Describing the market for underground mine trucks, Mike Sheffield, product line manager, Sandvik Mining and Construction, says that, except for a slight dip two years ago with the global financial crisis, the demand for trucks has steadily grown during the last 10 years and it could soon be reaching its highest levels. “The trend seems to be toward larger trucks and bigger fleets,” Sheffield said. “We are receiving more requests for quotes for the bigger trucks and more of them. A typical quote used to be three of four trucks, but now we’re seeing five to eight trucks at a time.” With prices for metals at high levels, mines are once again investing in production.
Mines are wisely looking more deeply at the longer term operating costs of the equipment as much as the upfront capital costs. “They are thinking more about long-term economics and that’s the right way to look at costs,” Sheffield said. “They are also frequently considering service agreements. They want our expertise and experience to help them keep their equipment in tip-top shape and do what they were designed to do, moving rock from point A to point B.” The days of having a couple of spare trucks on standby are long gone.
While the mining companies are showing more interest in automation and electric drive trucks, safety seems to be at the top of everyone’s list, Sheffield explained. “Customers are focused on higher levels of safety, followed by increased productivity and reduced operating costs,” Sheffield said. “The roots of many of today’s safety-based initiatives with underground hardrock mining equipment can be traced to Australia and, as those mine engineers and managers migrate into other mining regions that reasoning travels with them.”
Today, safety is engineered into the trucks rather than added on after the fact. “There’s a big difference,” Sheffield said. “Consider the access to the top of the equipment. Today, we have clearly marked steps and handrails in contrasting colors so that people climbing on the machine have a clear path. From the service side, we want to perform maintenance from the ground level safely and quickly—a feet on the ground approach.” It’s a safer way to work and it gets the truck back into operation quickly.
One of the biggest safety concerns with underground haulage is fire safety. “When a mobile piece of equipment catches fire, it’s probably going to be about as far away from fire extinguishing systems as possible,” Sheffield said. “That’s important because the chances of extinguishing the fire are greatly diminished the farther it is from a firefighting system.” Because the vehicles have a high fire load with fuel, hydraulic oil and tires, the onboard fire suppression system is critically important. Sandvik trucks employ either a Sandvik FS1000 water-based fire suppression system or a powder-based system from Ansul.
If fire safety is the primary concern, then braking ranks a close second. Trucks tend to be some of the largest underground vehicles, and they are loaded with rock and usually traversing a steady grade to a dump point. Some of the underground ramps in Australia are 8- to 10-km long and the miners fear runaway trucks. Many of the truck’s safety features apply the brakes if there is a system failure on the vehicle, such as low engine oil pressure, loss of clutch pressure in the transmission circuit, etc. “All of the brakes are spring applied,” Sheffield said. “If there is a failure, the truck is parked on springs rather than air or hydraulic pressure—failsafe braking.”
Sandvik trucks use fully-enclosed, wet disc brakes, where the braking surface is enclosed in oil. “Brake life on our trucks is now approaching 8,000 to 10,0000 hours, compared to 1,000 hours as little as 15-20 years ago,” Sheffield said.
On some of the longer hauls, operator fatigue is also a concern. “Going up ramp for 10 km at the speeds we travel could take as long as an hour,” Sheffield said. “An operator could fall asleep in this situation. We are evaluating warning systems that alert the driver when the machine has not received input in a certain time period. The system would monitor regular activities, such as steering or accelerating. After five minutes of inactivity, a light flashes or a horn sounds.”
What if the truck blew a tire while climbing the ramp fully-loaded? The mine is faced with a disabled vehicle sitting in the middle of the main haulage. Changing a tire on a fully loaded mine truck on a 15% grade with 1-m of clearance around the machine requires skill. Mines in Australia have taken two or three days to complete a risk assessment on how to change the tire in this situation, Sheffield explained. “There is no denying it’s a hazardous situation,” Sheffield said. “Right or wrong, miners usually use a loader to lift the truck and then find a way to safely support the frame.”
The blind spot on the center articulated trucks also poses a concern. “On a lot of the larger trucks, the operator can’t see that area from his station,” Sheffield said. “If someone were to walk into that area unnoticed, it could be a bad situation.” Sandvik is looking at ways to effectively warn miners of the dangers and alert the drivers.
Improving a Popular Piece of Equipment
For Sandvik, the Toro 50 has been an outstanding success story. Obviously productivity improved 25% over the 40-ton truck, but it has become the paradigm of reliability, Sheffield explained. The other Sandvik trucks are measured against the Toro 50 as far as reliability. “We know lots of cases where the Toro 50 has more than 30,000 hours,” Sheffield said. “It’s been the most successful of the big underground trucks to date. More tons have been hauled by the 50’s than any other underground truck in the world.” To put the market into perspective, Sandvik made 250 50-ton trucks. The company has sold 67 40-ton and 35 60-ton mine trucks.
In its prime, the Toro 50 was the leader. Today, Sandvik has upgraded the T50D with better diesel engines, improved hydraulics and electronic controls to create the TH550, a modern day version of an extremely reliable predecessor. The truck relies on the VCM electronic control system. “The new trucks all use a much higher level of componentry,” Sheffield said. “All of the electrical connections are well sealed. It is a lot easier for technicians to troubleshoot faults with the VCM system; most can be discovered from the operator’s seat. Before VCM it could take longer to troubleshoot a problem than to fix it. In the past, mechanics could spend four or five hours isolating a problem that takes 15 minutes to repair.” The VCM system directs maintenance technicians to the root causes, eliminating hours of trial and error.
This reduction in repair time is a big deal. A truck makes its money when it’s moving, Sheffield explained. “A truck does not earn anything while it’s sitting still,” Sheffield said. “The more hours per year the truck operates, the much higher the productivity and value to the mine owner.”
The new trucks will soon be available with tire pressure monitoring systems. “Tires are a big cost item on a truck,” Sheffield said. “Early warning signs can help eliminate catastrophic failure. Running at high or low pressure is not good for tire life. If the mining company can monitor the tires while the machine is running, they can minimize tire costs.”
In addition to these maintenance enhancements, the trucks also have automatic lubrications systems, and centralized hydraulic pressure points. Safety devices are easier to install.
Looking toward the future, Sheffield said mining companies will see changes with engines and improvements to suspension systems. He also believes truck makers will improve how the trucks are engineered and constructed. “It’s only a matter of time until the Tier 4 cleaner burning engines are introduced to and extensively used in underground mining environments because that will be the primary type of engine the mines and the OEMs can purchase from the engine manufacturers,” Sheffield said. “Because the engines will require higher quality fuels and engine oils, Tier 4 engines will have a big impact on maintenance programs underground.” With diesel fuel prices on the rise again, mining companies are also considering electric and diesel-electric hybrid drives as alternatives.
With drivers running at higher speeds and longer hours, mining companies can expect to see more advancements in the area of truck’s suspension system—the vehicle and not just the operator’s seat. “Some of these operators spend the better part of 10 to 12 hours driving these trucks,” Sheffield said.“We are looking at the interaction between the tires, seat suspension, struts, shock absorbers, etc., to give the smoothest ride over the roughest terrain. Whole Body Vibration (WBV) is on the ‘A’ list of more and more mining companies who are looking at employee health and safety.”
Back to that truck blocking the main haulage, Sheffield believes that someday truck makers might be able to integrate systems for emergency breakdown repairs into the trucks. “We are looking at different ideas for integrating emergency repairs—something to jack a tire off the ground or a way to steer the truck temporarily to a more suitable spot for repair,” Sheffield said.
Sheffield also believes that, by using a more modular construction technique, Sandvik might be able to reduce the time it takes to replace an engine or an axle. “Instead of week to change an engine, maybe it becomes a shift or an hour,” Sheffield said.
Seeing some of the large open-pit mines make the transition to underground mining will be interesting. “Open-pit miners are mass miners in the biggest sense of the word,” Sheffield said. “To get the same production levels by underground means will require a lot more work. Demand will also increase for production and vehicle monitoring systems because that’s what these miners were accustomed to on the surface.”
The operating environment will change as well. If the situation is one where a high-altitude operation in the Andes is hauling from the face underground to a crusher installation in the pit on the surface, the truck will encounter several radical climate changes throughout the cycle.
Trucks normally remain underground in a constant environment. The truck would enter the pit from a portal fully loaded seeing a drastic change in its environment in a matter of minutes. “As more pits go underground, we will likely see more challenges develop,” Sheffield said.
From a truck haulage point of view, however, truck makers will continue to focus on increased safety and productivity. In its simplest term, the dimensions of the drift will not change, so the only way to increase production is to move a higher payload safely through the hole faster, for more hours in a month due to increased uptime.