Screen media system increases quarry’s throughput

Aggregate Industries (AIUS) is one of the largest construction and building material companies in the United States. The company stresses strategic sustainability, environmental stewardship and long-term customer relationships. Its 3 million-tpy Morrison Quarry is a granite operation that illustrates that mission.

As a site within the AIUS West Central Region, the Morrison Quarry is in Jefferson County, Colorado, which is one of three counties in the six-county Denver region that offers available sources of crushed stone. As many of the potential aggregate resources in the Denver area are not accessible for extraction, the Morrison Quarry plays a key role in meeting the region’s demand for high-quality aggregate materials.

“Throughput is everything,” says Trulane Vanatta, plant manager of the Morrison Quarry. He operates “a sold-out plant.” Everything processed on a given day is sold the next.

Thus, the facility maintains a consistent focus on boosting processing efficiency and production capacity. To eliminate any bottlenecks at the screening circuits particularly, the Morrison Quarry team recently tapped into the engineering expertise at Polydeck Screen Corp. The result was the design and installation of DMax screen panels, a new ultra-high-open-area synthetic screen media system that is designed to boost throughput and allows the quarry to increase the production of its highest-value products.

Reducing recirculating loads and fines production

Prior to the DMax screen panel installation, the quarry had identified a bottleneck in the middle decks of the three screens in the tertiary circuit of the nine-screen plant. Each of the 8-ft. x 20-ft. triple-deck screens is key to the production of #57/#67 (1-in.) material.

“That’s our money maker, and we must maximize its production volume,” says Vanatta, whose team had taken belt samples that indicated a high bed depth on the middle decks.

There was a “troubling” 51 percent carryover, causing recirculating loads and the production of excessive fines. “The first thing we thought of was replacing the middle decks on two of the tertiary screens with wire cloth to achieve more open area,” Vanatta says.

However, after consulting with Sam Durnavich, regional manager of Polydeck, the operation was presented with a modular synthetic screen panel solution that would compare favorably or even exceed the open area of wire cloth – while , says the manufacturer, delivering greater wear life and ease of installation over that of traditional wire cloth.

Durnavich, before joining the Polydeck organization, had served as the assistant plant manager at the Morrison Quarry more than a decade ago. With his knowledge of the operation, he could work closely with the Polydeck engineering team to create a media solution that would more effectively address common carryover challenges. That is the background behind the design of DMax screen panels, which are intended for use where open area and throughput are the most important considerations.

Exceeding production goals

Since the installation of the first DMax screen panels on two of the middle decks in October 2015, the operation can meet – if not exceed – production goals while achieving far greater screening efficiency. According to Vanatta, they are realizing nearly 54 percent open area on their middle decks with the use of the new panels.

Compared to the 42 percent open area delivered by the previous screen deck, they have the advantage of a 28.5 percent increase in open area. DMax panels were subsequently installed on a third middle deck in mid-2016.

“That open area increase has resulted in an 11 percent increase in the production of the profitable 1-in. rock, and fines were reduced by nearly 1 percent,” Vanatta says. “The only downside to the open area is that the panels wear a little faster, but that is essentially irrelevant as the profit from the tonnage increase pays for the screen media investment more than 10 times over.”

The quarry employs standard Polydeck Rubberdex modular screen panels on the top and bottom decks of their 8-ft. x 20-ft. tertiary screens.

Engineering expertise

Durnavich says the DMax screen panel system is formulated with either rubber or polyurethane depending upon the application. “We’ve made the DMax panels with bridges that are half the width of those on our standard maxi panel,” he says. “However, the bridges are much deeper.”

He goes on to explain that reducing bridge width between apertures allows more openings in the screen panel surface, which translates to increased product pass-through.

“The increases in open area do come with a reduction in wear life. Yet when compared to standard-duty screen panels, the DMax panels are running at only 20 to 25 percent less wear life,” he says, adding wear life still exceeds that of wire cloth.

Contributing to additional open area, Durnavich says, is the fact that DMax panels are designed to fit on existing Polydeck PipeTop II stringer systems.

“This framework system features unique 1/2-in.-wide attachment rails versus the mounting styles on conventional frame systems that result in up to 3 in. of dead space where fines build up. Furthermore, our in-house tooling capabilities allow us to provide many more options in these frame systems – from varying fastening options, material options and stringer styles and types,” he says.

As is often said, if there’s a bottleneck at a plant, it’s often at the screening circuit. For the Morrison Quarry, throughput is everything. Continually increasing its screening efficiency is essential to its ongoing profitability and product quality.

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