- Created: Monday, 07 March 2011 09:36
- Published: Monday, 07 March 2011 09:36
By Carol Wasson
Although synthetic screen media has been a welcome alternative for decades, many producers in the nation’s heartland have not been among the early adapters. States such as Kansas and Missouri are blessed with a non-abrasive limestone material – and as such, many operations tout the use of traditional wire cloth as the only way to go.
“But you don’t know what you don’t know,” echo brothers Warren and Jeff Harshman, who are co-managing members of Harshman Construction, LLC., a family-owned aggregate producer. The brothers recently became “true believers” in the benefits of synthetic media. Going wireless, at least on certain key decks, may have been a long time coming, they say; but now both admit that synthetic media is a proven and sensible solution toward increasing uptime and wear life, while eliminating the costly downtime caused by the blinding or pegging of traditional wire cloth.
Working the Wire
Harshman Construction is headquartered in Cedar Point, Kan. It operates 17 quarries, and runs a fleet of four portable crushing plants and one stationary plant among its locations. Like other operations in the region, the company had developed a comfort level with wire cloth. After all, it seemed to last long enough in the application, and it appeared as the lesser expensive option.
Plus, the crew had long become used to dealing with both the upside and the downside of wire cloth. In some cases, they would get adequate wear life from the wire cloth, but in high-pressure washing applications or when loading oversize material, they would have to change out screen decks at least twice per month.
But the biggest problem was the blinding over of the small openings on the bottom decks of their dry processing screens, which was brought on by moisture or heavy clay content. This resulted in considerable maintenance downtime, a loss of a percentage of saleable product, and an inability to process a higher quality aglime material. It was at this point that the Harshman brothers consulted with Polydeck Screen Corp. as to the most cost-effective solution for their particular applications.
When assisting producers in improving production rates and reaching specification requirements, Polydeck stresses screening performance first; and next, wear life versus cost. “Bottom line, performance is most important. When you can run all week without blinding regardless of the rain or moisture content, it doesn’t take long to get the payback from a new deck,” said Joe Teague, Central Plains regional sales manager for Polydeck.
Nearly two years ago, Harshman Construction’s first acquisition of synthetic media began with installations on two wash screens – a Deister 6- x 16-ft. double-deck inclined screen; and a Kolberg-Pioneer 5- x 10-ft. double-deck inclined screen.
The top decks are designed with Polydeck Urethane Maxi-Style modular screen panels with 12.5 mm x 36 mm slotted openings going with the flow on the first four feet of the feed end; and 12.5 mm square openings on the rest of the deck. The bottom decks are fitted with Urethane Maxi-Style 2.5 mm square openings; two rows of 2.5 mm square openings with 1-in. dams; and two rows of 2.5 mm x 23 mm slotted openings against the flow on the discharge end.
This screen media design for Harshman was meticulously specified by Polydeck application engineers based upon a wide range of material characteristics, specification requirements, and production goals. “One of the unique qualities of modular media is that it allows us to change a one-foot square at a time to really dial in a producer’s specification. In Harshman’s case, it ultimately allowed them to more effectively wash and rinse the material while retaining more of the bottom end that they were previously losing in their waste,” said Teague. Jeff Harshman adds that they have yet to completely change out these screen decks (other than a panel or two) since their installation.
Bottom Deck Approach
Next, Polydeck was able to alter the Harshman’s approach to the bottom decks of their dry screens after a test demonstration that Teague conducted at a nearby producer’s location. “We put in a test frame (a 2-ft. by 2-ft. area on the feed end) of the Polydeck Flexi line of rubber screen panels on a bottom deck, and we installed it on a day that followed a significant period of rainy weather. Even though the current wire cloth was supposedly designed as a non-blinding product, it was indeed blinding over significantly,” said Teague.
He goes on to explain that the test frame contained a smaller opening than what had been there.
“We ran for about 45 minutes before we shut it down to take a look. The original screen was totally blinded over and the openings on the Polydeck test frame remained entirely open,” he says.
After viewing the demonstration, Harshman ordered 7 mm Flexi rubber screen panels for the bottom decks of three new Deister 8- x 20-ft. triple-deck horizontal screens. “They have since purchased two more decks of Polydeck 1 mm x 12 mm slotted openings with flow Flexi panels to interchange on these decks as the application demands,” said Teague.
According to Polydeck engineers, the Flexi screen panel is made of a proprietary, low-durometer rubber compound that provides superior flexibility, and makes it an ideal solution in applications that deal with the effects of moisture on small particles and fines – and any resulting clumping and blinding.
The motion of the screen deck causes the surface of the Flexi panel to vibrate, which creates a trampoline effect, resulting in minimal (if any) material sticking to the screen surface. When coupled with Polydeck’s Maxi high open area screen panel design, blinding is virtually eliminated. Recently, says Polydeck, it has expanded its Flexi line to include slotted openings from 0.5mm to 50mm, and square openings from 3 mm to 50 mm.
“One of the biggest advantages to what the Flexi panels accomplish on the bottom deck is the ability to make a far higher quality aglime product. Previously, our aglime product was coarser as we had to maintain a larger screen opening size to keep from blinding the deck. This Flexi rubber deck works phenomenally well with a very small opening, and it does not blind over. It has taken our aglime samples from 50 percent to nearly 70 percent immediate availability and the farmers really like that,” said Warren Harshman.
Going from wire cloth – to being nearly wireless – has made a big difference in overall processing efficiency and as Henry Ford once said, quoted Harshman, “Most people get ahead during the time that others waste.”
But beyond that of screening solutions, Warren Harshman says his relationship with Polydeck developed over the years out of a certain synergy. Both companies are family owned and founded in 1978, and both share a like-mindedness, he says. “It’s more than crushing rock. It’s more than screening. It’s about long-term business principles and serving with integrity.” E