Brick & Clay Record: Enhanced Versatility through Better Screening
However, within the past few years, an increasing bottleneck in the Cleveland County plant's grinding room threatened to undermine that claim. The plant manufactures Cunningham Brick's Ad-Mix architectural line and five residential blends, and produces about 40 million brick per year. Its palette ranges from a paper white to rich browns and reds-about 22 different colors in all. While the company obtains some of its raw materials already processed, it typically grinds anywhere from 60 to 100% of the material needed for production. When demand for ground material was high, it didn't take long for the grinding room to get maxed out.
"We had two guys in the grinding plant working about 65 hours per week, and we were also bringing a couple of other guys in for an additional six hours per week. That's a lot of overtime," says Greg Grabert, technical services manager. "But even with all of that labor, we still had to shut down production occasionally because our grinding operation couldn't keep up. We were only averaging about 35-40 tons of material per hour (tph) through our grinding room."
Improved Grinding EfficiencyThe company realized that the bottleneck was occurring in its screening operation-the four single-deck, 4 x 8-ft screens simply couldn't handle a higher throughput. Cunningham Brick debated purchasing a fifth single-deck screen, but then it came across a double-deck vibrating screen* from Midwestern Industries, Inc. that promised a higher level of screening efficiency.
*The MEV, supplied by Midwestern Industries, Inc., Massillon, Ohio.
Starting at the feed end of the screen, an arc is formed by a series of flat angled surfaces between the screen panel supports. The first flat surface is slightly angled, which retains the material momentarily at the feed end. It allows the under-sized material to pass rapidly through the panel openings onto the decks below, where smaller openings retain or pass on a portion of the material. As the retained material moves over each deck, the angle increases, accelerating the particles to the discharge chute.
Grabert and Dale Russell, the Cleveland County plant manager, sent three of Cunningham Brick's materials to Midwestern's Massillon, Ohio, facility for pilot plant testing, and drove to Ohio to observe the tests in progress. They also evaluated several installations of the double-deck screen at other brick manufacturing facilities. Confident that the screen would meet its needs, Cunningham Brick decided to give it a try at its Cleveland County plant. The new screen was installed next to the four existing single-deck screens in January 2005, and the plant quickly began to see improvements.
"We've been able to save 45 hours of overtime per week-we now only have two employees in the grinding room working 48 hours per week. Additionally, we've been able to increase our throughput to 65 tph. If we had just added another single-deck screen, our throughput would have only increased to 50 tph," Grabert says.
While labor savings was Cunningham Brick's main reason for installing the new screen, Grabert has also noticed a reduction in maintenance requirements since the screen has been in operation.
"All of our screens are heated due to the amount of moisture in our material. In the past, we've had a lot of trouble with the heating systems in our screens shorting out because our material would build up on the heating mechanism," Grabert explains. "So far, we haven't had any trouble with the new screen. It's hard to gauge what the long-term performance of the system will be, but the way this screen is tensioned-from front to back, rather than from side to side like our other screens-leads me to believe we'll have fewer problems.
"Additionally, instead of sending all the material across the finish screen anywhere from fist-sized material down to our finished size of 8 mesh, the largest particles that pass across the finishing screen are now about the size of a pebble. This reduces wear on other equipment in the grinding room," he says.
The company has also noticed a reduction in loader hours, fuel consumption and electricity use due to the reduced operational hours of the grinding facility.
Enhanced VersatilityAs a result of these benefits, Cunningham brick expects to see a payback on the initial cost of the system in less than two years. But while the labor and maintenance savings have been significant, the screen's increased efficiency has also provided another important benefit-the ability to meet rapidly changing market demands.
"With all of the different colors and blends we produce, we do a lot of changeovers, and our grinding needs vary depending on the product we're running through the plant," says Grabert. "When we make white brick, we only grind about 20% of our material; however, when we're on reds, we grind 100%. With just the four single-deck screens, there were times when sales wanted us to run four weeks of reds in a row, and we couldn't do it because the grinding room just couldn't keep up. The new screen has solved that problem. We just finished a five-week run of reds, and we've also done a three-week run of reds, and we were able to avoid shutting down due to a bottleneck in the grinding facility."
Grabert admits that his job would be easier if Cunningham Brick had a much smaller product line. But he also believes that it's precisely Cunningham Brick's versatility that will enable the company to remain successful well into its next century of operation.
"By having the ability to run a higher production in our residential line with the new screen, we've positioned ourselves so that if the architectural market takes a little bit of a dip, we can supplement our bottom line with our residential products. Likewise, if the residential market takes a little bit of a dip, we can supplement with architectural. Having the ability-and versatility-to keep up with market demands is going to be important going forward," he says.
For more information about the double-deck vibrating screen, contact Midwestern Industries, Inc., P.O. Box 810, Massillon, OH 44648-0810; (330) 837-4203; fax (330) 837-4210; e-mail firstname.lastname@example.org; or visit http://www.midwesternind.com.
For more information about Cunningham Brick, visit www.cunninghambrick.com.
SIDEBAR: Trial and ErrorWhile the outcome has certainly been positive for Cunningham Brick, installing the new double-deck vibrating screen was not without challenges. Because the company decided not to remove any of its existing equipment, it had to move virtually all of the conveyors in its grinding room (except for the feed conveyor) to accommodate the new screen. The entire process took about eight days to complete. Although the project occurred during downtime that had been scheduled to handle several other maintenance issues in the plant, Grabert believes that the screen installation could have gone a bit more smoothly if he had been able to anticipate the challenges.
"When we visited the other brick plants that use this screen, they all had new grinding rooms and they designed their layouts with this particular screen in mind. They gave themselves plenty of room, so they didn't have the space constraints we did. Once we began installing the screen, we had to make some decisions on the fly. We'll probably be able to shave a day or a day and a half off the installation time with the next screen we install," he says.