New plant, automation system double operation’s production capacity

By |  November 10, 2017

Four generations of the Duff family have overseen quarry operations for the past 67 years at Duff Quarry Inc. in Huntsville, Ohio.

Among the reasons for their long-term success is a focus on high-quality, economic throughput.

“That’s one of our focal points,” says Ross Duff, vice president. “For the past 10 years, automation has allowed us to maximize safety, improve ease of maintenance and have direct oversight of material quality.”

Photo courtesy of Duff Quarry

Duff Quarry was bare farm ground when the late C.E. Duff purchased it in 1950. Its abundant limestone deposit runs about 400 ft. deep and covers around 400 acres.

Today, with three locations, Duff Quarry includes Ohio Ready Mix and Mr. Concrete Builders Supply, employing more than 60 people in Huntsville, Russells Point and Bellefontaine. Customers come from within a 25-mile radius of Huntsville.

New era

The Huntsville quarry contains bluish-gray dolomitic limestone, which is ideal for construction materials like concrete and asphalt production, the company says. Upper layers of the quarry’s limestone deposit have a high magnesium content, giving the stone a reddish hue. Lower limestone layers, in laminated sheets, are dark gray.

The quarry’s limestone is crushed and used in a number of construction projects, including private and business drives in the area. Duff Quarry customers also purchase a variety of crushed limestone products, riprap, concrete sand, mason sand and gravel.

In 2005, when Duff Quarry was responding to increased product demand, it purchased a new limestone crushing plant from Stedman Machine Co. At the time, Duff was updating the plant it had used since 1956, seeking equipment that would offer flexibility with product size.

The Duff family first learned about Stedman around 1956, when it purchased a Stedman 48-in. four-row cage mill to process agricultural lime at its old quarry. In 1994, Duff purchased a Stedman Mega-Slam crusher for a different location because the company believed it was a superior crusher with its portable plant.

Over two and a half years, a Stedman affiliate, Innovative Processing Solutions, designed and fabricated the new automated system, which utilized Stedman’s 5460 Mega-Slam and 6460 Grand-Slam size reduction impact crushers. Innovative Processing Solutions specializes in custom solutions for bulk material handling systems, using equipment from Stedman and other manufacturers to create a variety of systems.

The extended system design timeframe gave the Duff family the opportunity to develop a system that can serve them for many years.

“We bought the plant in 2005, installed it ourselves and completed construction in 2007,” Ross says. “It was more than 95 truckloads of steel. Apex Engineering set up our automation. The plant uses twin Stedman impact crushers, a Deister grizzly feeder, scalping screen and twin finish screens.”

Twelve employees kept the old plant running while the new plant was designed and installed. Prior to installing the new system, the quarry’s annual processing average was about 600,000 tons of limestone. With the new system, production averages 1.5 million tpy when running at full capacity.

Customized crushing

From left: Plant Operator Jason Beecraft, Mine Foreman Bill Page, President J David Duff and Vice President Ross Duff. Photos courtesy of Duff Quarry

The quarry’s automated system includes a fiber linked A. B. Rockwell PLC system run by redundant Windows-based computer control rooms. Quarry operators manage the automation by utilizing an application that runs through two iPads. The system is set up so only one iPad can make system changes at any one time. The plant operator can access the automation system from anywhere on the mine site.

“When we designed our plant, we wanted to avoid having our plant operator watch quarry activities from a remote control room,” Ross says. “Using the iPad allows the plant operator to have direct oversight of material quality and make immediate changes as necessary.

“It also eliminated the need to contact the person in the main control center,” Ross continues. “A delayed response is not always the safest way to operate. If the plant operator is right there they can stop or start the plant and inspect any equipment to identify maintenance needs.”

The iPad used to control the system uses a WiFi signal generated by a router installed in the quarry. Signal strength can vary but is always strong enough to make iPad use viable, Ross says.

“You could even control our plant from an iPhone,” he adds. “Because of the phone’s screen size, that isn’t realistic. But in an emergency I could shut the plant down with my phone.”
Initial concerns about dust affecting iPad operation were allayed because the iPad has no vent holes or keyboards that could collect dust from the quarry.

“No proprietary software is loaded on the iPad,” Ross says. “It’s basically a touchscreen remote for the main control computer that runs Windows.”

Although Duff Quarry’s automated system can be connected to the Internet for updates and other resources, it’s only connected for short periods of time to address a specific need.
“Our primary network is an intranet,” Ross says. “We avoid Internet connections as much as possible to reduce hacking potential. Programmers can access our system remotely to adjust it, but we’re very cautious with that.”

Precise products

Stedman’s Mega-Slam is a primary impact horizontal shaft impactor that effectively handles large feed sizes. The machine is built to handle thousands of materials, ores and chemicals in wet and dry applications.

Mega-Slam’s design offers safe and easy access for breaker bar replacement and access to all other areas of the crushing chamber, according to the company. The machine’s front opening feature eliminates the need for a crane.

The Grand-Slam secondary impact crusher, meanwhile, is built to handle the same type of materials as the Mega-Slam. Through design simplicity, employees have safe and easy access to breaker bars and all other crushing chamber areas.

The twin impact crushers give Duff Quarry the cube-shaped rock that provides greater psi strength when used in concrete mixes, which represents a significant portion of their business.

Integrated with an automated variable frequency system, the grizzly feeder provides the variable speeds that allow for maximum throughput without overloading the crushing plant.

“Our plant has amperage and motion sensors on every conveyor,” Ross says. “Belt scales directly control throughput on the feeder so production runs at maximum speed without overloading belts. We also use tramp metal detection and pneumatically controlled discharge gates to dump material. In the event that metal makes its way into the plant, our automation system empties all belts to protect the crushers.”

Quarry-wide benefits

Photo courtesy of Duff Quarry

The dolomitic limestone at Duff Quarry is desirable for construction materials like asphalt and concrete.

With its automated system, Duff Quarry can also manage electricity meter spikes because the system will automatically cut feed rate if production exceeds 840 tons for more than five seconds.

Each crushing plant conveyor is equipped with terminal strips wired to communicate production information to one main processor, allowing one staff member to monitor conveyor performance. All feeders and conveyor operations data are also recorded for use in evaluating the system’s overall performance.

The new plant system allows Duff Quarry to crush rock in a variety of weather conditions, including heavy rain. Pumps and drain lines under the plant ensure that flooding cannot occur.

The Duff family expected to reduce maintenance issues by at least 50 percent with the new plant because automated data management provides evidence of equipment issues well ahead of a breakdown. Since the plant can now be operated with just two staff members, the company no longer shuts production down for lunch hours.

Adjusting product size takes just minutes, and the same conveyor can be used to handle different product sizes.

Doubling output

Overall, Duff Quarry more than doubled production capacity with its automated system and new plant.

“We also have brilliant staff operating the plant,” Ross says. “Bill Page, a foreman here for more than 40 years, is a great example of that.”

Over the years, Page tried different methods to prevent screen media clogging. He never found an effective product or method, so Page developed his own: the Blinding Buster.

“We wanted to ensure our material quality on the finish end was automated, too,” Ross says. “Bill patented an invention to eliminate screen blinding. Every screen media, by nature, will blind, given the right conditions. The Blinding Buster continuously sweeps blinding off finish screens while we’re in production.”

The Blinding Buster consists of two major components: the control assembly and motor assembly. The control assembly wires are designed to connect to the normally open auxiliary contact of a screen’s magnetic starter. The screen can be set up to start manually if the motor start isn’t available.

The motor assembly includes a standard 20-ft., 3/8-in. chain that can be cut to any length or extended to accommodate all screen sizes.

Installing the Blinding Buster takes a 2-in. black steel pipe mounted level approximately 6 in. above the screen opening. The pipe has to be affixed so it doesn’t vibrate with the screen.
“The Blinding Buster allows us to screen in subpar conditions when we normally wouldn’t be able to,” Ross says. “We are also able to dry screen finish products without washing. We’re so happy with this product that we’ve made it available to other quarry producers.”

Loretta Sorensen is a freelance writer in Yankton, South Dakota. She produces material on a variety of topics, serves as a ghostwriter and has authored her own books.

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