Zip on over: Material handling made easy

Dakota Aggregates LLC, which is in its second season operating a brand new processing plant, mines on 1,722 acres within the University of Minnesota Outreach, Research and Education (UMore) Park. The mine is located in Rosemount, Minn.,  within reach of the Twin Cities metro area.

The operation was designed with innovation in mind, particularly where material handling is concerned. The site spans three miles from north to south, and a mile and a half from east to west. Overland conveyor systems were chosen to efficiently transfer material from the face to the processing facility while eliminating the use of loaders and haul trucks. The conveyors are reportedly quiet while minimizing energy use and lowering operating costs per ton.

Initially, the challenge for Dakota Aggregates was finding a lower-cost overland alternative versus that of custom-engineered, conventional overland systems – and, most importantly, one that would allow the company to easily and quickly reconfigure their overland systems to accommodate changing mining requirements each season.

Dakota Aggregates has a substantial 40-year lease on the university-owned land, where melting glaciers left behind a thick blanket of sand and gravel thousands of years ago. Mining this deposit is part of the overall sustainability focus of UMore Park.

Win-win

There are major benefits of this initiative, according to stakeholders: The local region taps into the cost-efficiencies of a valuable and nearby source of aggregate products, while the university realizes an additional long-term revenue source. And, for every ton of gravel mined, a portion of the profit goes into a scholarship fund for geology and civil engineering students at the university.

Dakota Aggregates approached the site’s material handling challenges by consulting with Superior Industries, the Morris, Minn.-based manufacturer of bulk material processing and handling equipment. Superior recently launched its Zipline conveyor, a pre-engineered, modular overland conveying system designed for quick, and almost tool-free installation. Dakota Aggregates is one of the first producers in the nation to use it.

“It was refreshing to share our input on the system with the engineers at Superior and to work with them on various enhancements to this new product,” says Stacey Hannover, operations manager for the Dakota Aggregates plant, which processes more than one million tons of aggregate products annually.

The site mines from its furthest boundary and back toward the plant.

“While we are generally pulling conveyors out and shortening the distance of conveying, we can easily add on sections in other areas of the operation,” Hannover says. “We needed flexibility at the right price point. With the Zipline conveyor, we have ease of assembly and ease of onsite portability.”

The operation uses 4,900 ft. of modular conveyor sections (at lengths of 10 ft. each and belt widths of 30 to 36 in.), which is currently divided into six different overland systems of 500 to up to 1,000 ft.

“It’s easy to reconfigure any one of our modular overland systems to cost-effectively meet our changing requirements each year,” Hannover says. “As an example, during this season, we easily pulled 250 ft. out of one system.

“Also, while we generally operate on level ground, next season we will be moving a section to accommodate material transfer on an area with a 15-percent incline,” Hannover adds.

He also says installation is a breeze.

“Once we got the pattern down, three crew members marched right down the conveyor corridor and were able to assemble 1,000 ft. of overland conveyor sections in a 10-hour day,” Hannover says.

The crew used a forklift and a skid steer loader with no need for cranes or other heavy equipment.

Engineering perspective

Superior Industries started construction of the Zipline with tool-free installation requirements for the intermediate areas between the head and tail sections. Travis Thooft, a member of the Superior Industries engineering team, says the requirement meant creating a new type of fastening system that is structurally sound and reliable, yet quick and easy to use in the field.

“When you consider the typical way to put things together, the industry standard is basically weld or bolt,” Thooft says. “We took it a step further by eliminating bolts and replacing them where possible with a ‘fixed-pin’ connection. We wanted to eliminate the need to bring out a set of wrenches for most installations.”

Thooft estimates that the new design can cut installation time by up to 75 percent. “Basically, you hook in one end and then the other, with the setup for a 10-ft. section taking just about five minutes,” he says.

Thooft explains that the specification process starts by defining the overall length of the overland system, and the required horsepower. The system includes a pre-engineered head assembly and tail section, and is designed with off-the-shelf components for easy sourcing of replacement idlers and pulleys.

“Producers can customize with options such as self-aligning troughing idlers or special return trainers, idler guards and belt cleaners; or a longer or different type of gravity takeup for example,” he adds.

When compared to a spec-by-spec, highly engineered system, Thooft says the Zipline conveyor system is a lower-cost overland alternative.

“While it’s lighter in weight, it offers the structural strength of the conventional overland system,” he says. “Its big advantage is its modularity factor and unique fastening system, which allows easy structural additions in the future and easy site reconfigurations as needed.

“It also allows operations to choose between renting modular sections or purchasing a package of sections they can customize within a given set of parameters,” Thooft adds.

Driving overland solutions

What are the key drivers behind more and more operations turning to overland conveyor solutions? Certainly overland conveyors offer cost-effective material transport within a wide spectrum of capacities, and when used in place of loaders and haul trucks, operations are reducing fuel costs and expenses owing to labor, workers’ compensation, MSHA training, emissions, maintenance and engine depreciation.

Another driver is tightening regulations. While individual mobile haulage units emit and stir noise and air pollution along the entire transfer path, overland conveyor systems offer quieter, environmentally sound material transport.

Take note

For every ton of 
gravel mined, a portion of the profit goes into a scholarship fund for geology and civil engineering students at the university. It’s a win-win deal for all and an example of innovation at its best.

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