The gas, oil and mining sector is demanding larger tires to transport material at ever-more-challenging sites. But increased size presents greater design challenges, and closer attention to maintenance.
With the resource sector demanding the transportationof larger and larger payloads, gas, oil and mining contractors have developed an appetite for larger off-road tires. Newer large-format tires offer deeper treads and wider profiles designed to keep vehicles on the road for longer periods between tire changes.
Titan Tire Corporation, a subsidiary of Titan International Inc. with head offices in Quincy, Ill., manufactures behemoth tire-and-wheel assemblies. Through its subsidiaries, the company supplies wheels, tires and assemblies for off-road equipment, including mining, agriculture, and construction. Its 63-inch off-road tire-and-wheel assemblies measure nearly 14 feet tall, weigh more than 12,000 pounds each and are targeted for the Alberta oil sands and other similar heavy-duty applications.
Titan moved into the monster tire market in 2007 when industry reports indicated that a red-hot resource market was making it difficult for companies to field enough heavy construction vehicles for oil sands operations – not simply because of a lack of vehicles, but because tires were in short supply.
“At the time we were making steel-belted radial tires to 33 inches in diameter, but the big-haul trucks needed 49-inch through 63-inch tires that we did not make,” says Morry Taylor, Titan’s chairman and CEO.
Titan engineers would first need to choose the material to be used to manufacture the tire carcass – the network of cords that provides the tire with strength and shape.
“We knew that nylon carcass tires with steel belts were the safest tires made,” says Taylor. “The question we were asking ourselves was whether we should build a larger nylon carcass steel-belted radial tire or a steel carcass steel-belted radial. Steel has excellent tensile strength, but once tire cables are stretched to their limit an impact can destroy them and there’s no warning before the cables break. On the other hand, nylon has a 17 percent elongation capability, so you will see the tire start to come apart before it fractures.”
ADDING EXTRA BEADS
Engineering a nylon carcass tire of a larger size, however, required so many additional nylon plies that the bead of the tire would necessarily be positioned above the wheel, rather than inside, with a bead sized at three inches in diameter. Titan’s answer was to design the tire with three beads allowing it to hold air like a normal radial. The nylon was also precured using an electron beam.
Titan located its research and production facility at the Continental General Tire Inc. plant in Bryan, Ohio, after acquiring the company.
Tests of initial designs on a bull wheel tester simulating a 300,000-pound load, however, showed that the nylon carcass tire displayed superior performance characteristics. “In other words, the steel carcass tire exploded long before the nylon carcass tires,” says Taylor. “The steel belts got so hot they melted the rubber, so when that big baby broke loose, the belts cut the carcass in two. At that point we made the decision to change all of our steel carcass tires to nylon carcass. Rather than begin at the bottom sizes for the new product lineup, we got together a bunch of engineers with 40 years of experience to start building tires at 63 inches, solve the engineering challenges, then go down to 49 inches. Unfortunately, nobody had developed a large enough bull wheel machine to test a tire of that size.”
The company invested in a new 24-foot bull wheel machine constructed in Quincy. The testing facility subjects tires to loads of up to 500,000 pounds at simulated speeds of up to 45 mph to assess performance and heat characteristics and can test two tires at a time. The building was designed to withstand the explosion of 18 sticks of dynamite, the force with which a large-format tire may explode under testing. The company estimates that 10 days of testing is equivalent to about a year of field use. While some tires are tested when filled with water, Titan tests air-filled tires to more closely simulate real-life conditions.
Seven months after research began, the company produced its first 63-inch steel-belted, nylon carcass radial tire.
TREAD DESIGN CRITICAL
“Initially, we asked some of the mining operators what they wanted to see in tire tread,” says Taylor. “That turned out to be a mistake. What they wanted was a really big tread and a few bars on the side. They worked great at under 10 mph, but the rubber was so thick that they heated up like racing slicks. Instead of giving them what they wanted, we went back to the drawing board and gave them what they needed, which was an aggressive but lighter tread. We also removed the hard rubber from around the bead, which wasn’t necessary because our sidewalls were much thicker. The new designs shed about 1,500 pounds from the tire’s overall weight.”
However, just as the company’s second-generation tires hit the market, primarily the Alberta oil sands, the recent economic downturn slowed demand for the large tires, which some buyers had stockpiled.
“During the slowdown, we developed the smaller tires going all of the way down to 39 inches,” says Taylor. “Once the price of oil approached $80 to $90 a barrel, the oil sands operators (resumed heavy) digging, and the demand for tires returned. We’re now seeing renewed predictions of large-format tire shortages.”
Taylor says the biggest factors affecting tire performance in the field are load, speed, inflation, terrain and temperature. “If you have tires rated for 400,000 pounds at a speed of 15 mph and instead you’re carrying 460,000 at 35 mph, those belts are going to get hot and cut tire life by 50 to 75 percent,” he says.
“We also see tires rated for 110 psi, under-inflated to 90 psi which really eats at tire life. In the oil sands, the terrain challenges the tires because after a truck gets filled by the shovel, it has two minutes to get out of there before it starts to sink in the soil to the axles,” Taylor explains. “The truck leaves in low gear and actually pushes a wave of gummy soil ahead of it. That type of stress burns tires up in the summer and blows them out in the winter.”
ROCKS SLASH TIRES
In iron ore mining operations, the loads are even heavier per cubic yard, but the terrain provides additional challenges. “Whether it’s iron, copper, or coal, the sharp rocks on the ground at a mining operation are like ax heads and can slash a tire,” he says.
The large format tires contain tire sensors and GPS locators that transmit inflation, temperature and location data through cell phone and Bluetooth signals. For remote locations temporarily out of range, the data is downloaded from a recorder when a truck returns to the facility.
“There’s no excuse not to know the conditions under which the tire is performing,” says Taylor.
The company now also produces all-steel wheels for the tires. Each wheel undergoes X-ray testing, shot peening and stress release heat treatment. The next developments in wheels: to make them wider to increase load capacity and improve tire life.
The company is also looking at ways to replace steel belts to reduce the level of heat generated in the tires. “If we could figure out how to employ polyester or glass belts, the tire would be lighter, run cooler and perform better,” says Taylor.
The biggest technical issue for mining tires, however, is their ultimate destination as environmental concerns continue to challenge oil producers.
“If the oil producers send those tires to landfill, they really lose those carbon credits, and make a huge impact on the environment,” says Taylor. “Each 63-inch tire contains 450 gallons of oil, 4,000 pounds of carbon black, and 2,000 to 3,000 pounds of steel.”
Titan is currently selecting a site near the Alberta oil sands to locate an end-of-use facility employing pyrolysis, a thermo-chemical process that breaks down organic material at high temperatures in the absence of oxygen. It would be the first tire facility of its kind in North America. “The disposal fee would cover the cost of operating the facility, but the oil, steel and carbon black we recover would be our profit,” notes Taylor.
Taylor maintains the best way to design tires for the oil and mining industry is to actually visit the sites to see how the vehicles operate in the field. “In the oil sands, they’ve got bugs that could pick you up and fly you away,” he says. “It’s 50 below in the winter and 100 above in the summer and it makes what they do on the offshore rigs look like candy.”