Moving mountains with an overland conveyor system

An energy-generating, downhill overland conveyor system boosts safety, savings and sustainability.

Moving mountains of upper-ledge rock material to ground-level crushing and processing operations had once posed a significant transport challenge at Geneva Rock Products’ Point of the Mountain site in Draper, Utah. Today, the operation boasts a state-of-the-art material-handling solution with the installation of an innovative downhill conveyor system that meets the company’s key goals of maintaining sound, lowering operational costs and increasing worker safety.

Carl Clyde, who serves as the company’s vice president of gravel and asphalt, says that within Utah’s sand-and-gravel industry, this particular downhill conveyor system is unique. The system is particularly unique because it’s designed to generate electricity – enough to ultimately provide power to much of the 50-acre site.

“Geneva Rock Products is committed to sustainability, and we find this system to be the most efficient, safe and sustainable way to move aggregate materials,” says Clyde, who adds that the $11 million overland system will pay for itself in two years or less.

In the fall of 2012, Geneva Rock began cutting the grade in preparation for installation, which would begin in December 2013. Startup was initiated in May 2014, and the following fall marked the final phase of the project, which included getting the power contained and interconnected on the property.

The overland system was designed, engineered, and manufactured by Superior Industries, a manufacturer of bulk-handling systems, as well as components such as idlers and pulleys. Throughout the entire process, the team at Geneva Rock worked closely with Superior’s engineering and service teams, as well as with the veterans at Salt Lake City-based Kimball Equipment, a dealer for Superior Industries.

Clyde says the entire team has done a tremendous engineering job in designing the system and each of its components, ultimately allowing the operation to lower operating costs while maximizing uptime and meeting production goals. Meeting production goals is especially important to the Point of the Mountain operation.

“It is imperative that we operate as efficiently as possible, as this site alone provides more than 75 percent of the material that our company requires,” says Ed Clayson, aggregate production manager at Geneva Rock. “We mine a unique quartzite material that is highly sought after in our area.”

Described as a quartzite that is pre-split by natural seismic forces, Clayson says the 100 percent fractured face of the material leads to the concrete and asphalt products that their customers expect.

System overview

Clayson explains how the new overland conveyor system is a great fit for the operation. “First, it allows us to efficiently feed two of the largest crushing circuits in the state of Utah,” he says.

Material is transported at up to 3,500 tph from the ledge to the crushing plants, he adds. Summing up the system, Clayson describes the operation’s capabilities as being able to move material from the mountain and deliver it to a jobsite in the same day.

Transport begins with loaders feeding the material into vibrating grizzly feeders, where it’s sized to 7-in. minus and discharged to a hopper, which feeds three downhill conveyors of varying lengths (700, 800, and 1,050 ft.).

Conveyed on 60-in. belts, the material is transported 400 ft. per minute. As a gravity-fed system, the steepest point of the downhill incline is at an 18.66 percent grade. After traveling 2,550 ft., the material is fed to a 100-ft. transfer conveyor, and then onto a 150-ft. radial stacker, which feeds two tunnel feeders – one going to the wash plant and the other to the dry plant.

“With the radial stacker, we’re able to create two surge piles ahead of the tunnel feeders if we need to,” Clayson says. “Should we ever have to shut the overland system down, having the surge piles will reduce or eliminate any processing downtime.”

Sustainability and sound environmental practices

Clayson also outlines the basics of how the overland conveyor system generates electricity.

“The conveyor system is controlled by PLC (programmable logic controller) controls, and a variable frequency drive acts as a braking system to control the energy,” he says. “Essentially, the system takes the excess power generated from the belt and feeds it to a central distribution center to be used for plant operations,” Clayson adds that more energy is produced the more material is on the belt.

“That is sustainability at its best,” he says.

According to Superior engineers, another major driver behind the investment in an overland conveyor system is the reduction of particulate matter in the air. Highly scrutinized due to tightening environmental regulations, individual wheeled haulage units, such as dozers, loaders and haul trucks, emit and stir pollution along the entire transfer path. Superior engineers argue that overland conveyor systems offer quiet and almost dust-free operation – and when designed properly, they can blend in with the environment.

Operating costs and safety

Clayson says that prior to installing the conveyor system, Geneva Rock was faced with the concern of how to safely get material from upper levels to the processing level. As its material source continued to get higher and further away from the processing plants, dozers were used to push material for long distances.

“It took considerable time to get the bench down to a safe level and work underneath it,” he says. “That is a tremendous amount of dozer use, wear and tear on equipment, and labor costs. Now we have minimal material handling at the top, and the material is easily and safely conveyed down.”

Clayson adds that if not for the new conveyor system, the operation would have required an additional nine pieces of mobile haulage equipment to meet current production capacity levels.

Also, Clayson stresses the importance of another key safety feature: the emergency braking system. Superior outfitted the conveyor system with a Svendborg hydraulic brake system. Unlike overland conveyor systems that move material uphill or along a flat ground surface, the downhill conveyor poses additional hazards due to gravity, terrain and profile. It’s imperative to have an intelligent braking system to address the starting and stopping requirements under various load conditions, Clayton says.

“With the tonnages and the grade involved, these conveyors require a highly effective braking system, and this one works flawlessly,” he adds.

Take note

Geneva Rock’s Point of the Mountain quarry provides more than 75 percent of the material that the company requires.

Carol Wasson is a veteran freelance writer for the aggregates and construction equipment industries.