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Steep Nevada mine challenges dump trucks

CARSON CITY (NV)/USA, May 28, 2015 – The gypsum mine in Western Nevada outputs more than 5 million tons per year. This translates to more than 150 dump truck loads a day, which need to take the steep lane to the top of the pit. There, they meet their ultimate challenge.

Family-run mining business, Art Wilson Companyhe company, has been producing limestone for cement rock, and gypsum for the agriculture and turf markets, for almost 50 years. The anhydride produced from the Adams Claim Mine is a form of gypsum that is of a higher purity than most gypsum produced in the region, and is in high demand.

Customers from far afield use the produce from the mine as a fertiliser for fields, golf courses and lawns. Art Wilson Company is set up for high volume distribution for the 5.4 million tonnes of gypsum produced annually. Up to 166 trucks are loaded per day, each hauling on average 21.8 tonnes.
“Sales of our gypsum produce have grown from around 250,000 tons (226,796 tonnes) in 2008, to almost twice that today,” said Paul Wilson, mine manager for Art Wilson Company. “With growing demand, and plans for opening a new mine, it was necessary for us to evaluate our trucking strategy.”

Terex TA400 delivering its load

The Terex TA400 replaced a fleet of rigid trucks in Nevada. | photo: Terex

Steep ascent from bottom to top

The trucks operating at the mine are required to make a 0.75-mile (1.2-km) haul cycle from the bottom of the pit and haul material up the 10% grade. Art Wilson Company has historically operated 45 tonne (50 US ton) capacity rigid dump trucks at the Adams Claim Mine before the need for a change of strategy was identified.
 
Nevada-based Terex Trucks dealer, Shafer Equipment Co., provided Art Wilson Company with a TA400 articulated dump truck for a thorough evaluation. “There were a number of elements that had to be considered in the selection of new trucks, including the limited road size, the incline of the haul roads, and ability to handle bad weather in winter,” explained Paul Wilson. “The Terex Trucks TA400 passed all the tests. We went with the 38 tonne-capacity truck as it is close to the capacity of the rigid trucks we were using.”

Slippery slope

The original rigid trucks required substantial roads and struggled to pull on the high grade in the slippery underfoot conditions experienced during bad weather.
“During winter, even a light layer of snow in the mine would make it difficult for the previous trucks to navigate the slope,” said Jay Shafer, president of Shafer Equipment.
The TA400’s ability to climb and – more importantly – descend the 10% grade proved to be one of the critical factors in the decision-making.

White Terex articulated dump truck with white load in Nevada

A local Terex dealer let the mine operator test the machine
on site before purchasing it. | photo: Terex

Retarder system beats traditional breakes

“The retarder system in the TA400 really stood out to us,” said Paul Wilson. “We also tested a truck with a single retarder system and wet disc brakes, which overheated on the downhill when trying to keep up with the TA400.”

Truck operator, Ty Vanroy, was most impressed by the TA400’s ability to handle the downhill slope smoothly. “I loved the exhaust brake in the TA400,” he said. “I didn’t need to use the brakes when going down even steep hills, which makes the brakes last longer.” The TA400 has a dual retarder system, where a modulating transmission retarder is coupled with an efficient exhaust brake and fully-enclosed oil-cooled multidisc brake.

Having proved its worth in all performance tests, four Terex Trucks TA400s were purchased, and are currently operating at the Adams Claim Mine. The TA400s have two primary responsibilities at the mine: hauling material from the pit to the crushing circuit, and removing overburden from areas being prepared for blasting. The company blasts 22,680 tonnes of material two to three times per month in order to maintain supply.

We don’t run fast; we run steady”

Steady and consistent is the motto at the Adams Claim Mine, according to Paul. “We don’t run fast; we run steady,” he said. “We run at about 10 mph (16.1 kmph) and are more concerned about getting material out of the pit consistently, rather than speedily.”

“You could say that dump trucks are the heart and soul of the operation,” said Robert Franklin, regional sales manager for Terex Trucks. “Carrying overburden and the muckpile to the crushing circuit is vital in order to keep the operation moving.”

Driving up the steep slope

Steep drive up- and down. When snow falls on these lanes, the previous trucks struggled to pull up. | photo: Terex

Swedish engine

The TA400’s 443 hp (330 kW) Scania turbocharged diesel engine develops 1,663 ft/lb (2,255 Nm) torque, allowing fully loaded trucks to easily pull the 10% grades. The three axles are locked in permanent all-wheel (6 x 6) drive to maintain traction when facing slick roads.
"I typically keep the truck in low range on the grade, but I can easily switch between low and high gear with the toggle switch inside the cab," explained VanRoy.

Paul Wilson is also expecting a significant cost saving with the new fleet of Terex Trucks, thanks to increased fuel efficiency, as the TA400 will, on average, reduce fuel consumed by an incredible 50% in comparison to the previous trucks.
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