Quarrying is an expensive business. It’s expensive in equipment, time, people and operating costs. Any advantage a quarry or contractor can get helps improve the bottom line, profits and makes the business more viable. A quarry in South Carolina has benefitted from using a specialist crushing and screening contractor, which, through the use of its expertise and a new Kleeman crushing train, has seen previously untapped resources turned into valuable aggregate.
Many quarries leave the crushing and screening at their sites to specialist contractors as they often have both the expertise and equipment to undertake tasks more efficiently and effectively. One such contractor — independent specialist crushing company Riverbend Construction Services — is using a new mobile crushing and screening train to boost aggregate processing productivity while saving money on fuel.
Riverbend Construction Services operates in the southeastern United States, primarily in Tennessee, Georgia, Alabama and South Carolina. Riverbend owns no quarries or gravel pits; instead, it provides specialist independent service to the aggregates industry including overburden removal, drilling and blasting, site development and, particularly, contract crushing and screening. For the latter operation, the company utilizes three portable crushing plants, each capable of dealing with a variety of rock and ideal for producing accurately sized aggregate even from the hardest and most demanding of materials. “Our current business model is to do contract crushing,” said Duff Boyd, president, Riverbend Construction Services, Jefferson City, TN. “We focus on mining of construction aggregates and material recycling.”
At an established quarry located in South Carolina, Riverbend has impressed one and all by taking granite production to another level in terms of productivity and efficiency. The source of the material at the quarry was untapped. The owner of the quarry was unable to process the rock using the existing work force and equipment. This is where Riverbend comes in; it has the people, the expertise, the experience and the vital equipment to deal with the granite. “Here, we are making crusher-run granite road base and a No. 4 material — which is 2 inches by 1 1/2 inches with no fines,” Boyd said. The crusher run size is 100 percent passing 1 1/2 inches, all the way down to 200 mesh size. Riverbend also does the drilling and blasting of the gray granite and loads and hauls the raw stone to the processing site located at the top of the pit.
What have proven to be essential in producing the required fractions — at a highly productive level — are Riverbend’s new Mobicat MC 110 Zi EVO primary jaw crusher, Mobiscreen MS 15 Z screen and Mobicone MCO 9i EVO secondary cone crusher, all manufactured by Kleemann and impressively all able to work “as one” via Kleemann’s Interlink technology to deliver smooth production and lower operating costs.
Through the use of the new interlinked equipment, Riverbend has averaged 305 to 335 tph, depending on the feed. Commenting on how the Kleemann equipment has boosted productivity, Boyd said, “If the feed is a good, well-blasted material, with this closed-circuit arrangement I can easily put up to 340 tph through. By well-blasted I mean a rock that’s not chunky, that’s shot well throughout with some fines in it and a variety of sizes that go into the primary. But as the rock gets coarser, productivity slows down.”
One interesting if unusual feature of the aggregate plant is that instead of a grizzly, Boyd’s new Mobicat primary jaw crusher utilizes an independent prescreen that speeds productivity. “The prescreener pulls all the fines out, and that’s where the tons per hour really pick up,” Boyd said. “But if it’s a coarse material, it all has to go through the jaw and my tons per hour will go down. The prescreen is the ticket. Currently we don’t drop any fines through the prescreen that kick out the side — instead they drop right underneath and bypass the jaw and we blend and mix them at the scalping screen.
“When we crush through the cone, those fines return back and we blend the pit fines with the crusher fines to make a more consistent crusher-run product with stable gradation. If we kicked them out at the jaw and made crusher run at the screen, we’d have two separate products; instead we send both fines products to the screen, where it blends and mixes and stays consistent.”
The feeder itself sets the feed rate for the tons per hour coming into the plant. “It runs at a higher frequency,” Boyd said. “The prescreener cleans the feed up and keeps the fines out of the crusher and that’s huge. Instead of being kicked out the side by conveyor, they go down a chute, bypassing the crusher and mix with the crushed material coming out of the jaw. It cuts down on the wear on the jaw dies and the cheek plates. It prevents wear and tear and increases throughput.”
Another appreciated benefit that has made a huge contribution to the profitability of the contract is the prescreen also equates to better fuel consumption. “These machines literally sip fuel compared to the competitors,” Boyd said. “I’ve been very, very impressed with the fuel consumption, especially the Kleemann conveyor. They use hardly any fuel at all and are very reliable.”
Closed circuit operation
The interlinked equipment works as a crushing and screening train and as such is set up in a closed circuit. Material is primary-crushed at the jaw and both crushed material and all fines go to the mobile screen. The MS 15 Z mobile screen has two decks — the top with 2 in. panels and 1 1/2-in. panels on the bottom deck. The top deck overs go to the cone crusher to be sized down (as the jaw is set to 65mm, a 4-to 5-in. size rock goes to the cone). The cone crushes that material and sends it back to the screen for resizing.
The bottom deck overs are a 2 x 1 1/2-in. rock and the bottom deck screen-throughs are set at a 1 1/2 in. size, which is stacked as a product. Anything dropping through is crusher run, which is stockpiled and loaded on trucks.
Another direct benefit of the Kleemann plant is the use of diesel electric drives, of which Boyd said, “The jaw and the cone are diesel over electric. The crushers are run off fluid couplings but the rest of the plant is electric. The advantage is that the electrical systems are much easier to work on; any electrician who knows about three-phase electricity can troubleshoot or repair it. That’s unlike competing makes, in which all of the products are hydraulically driven. And when you have hydraulic problems, they are very difficult to troubleshoot. And Kleemann’s control panels are cushioned with springs and sealed tight. They work fabulously. Electrical over hydraulic is much easier to troubleshoot, repair and maintain.”
Synergy of operation
Boyd has found, much to his delight, how all the jaw and cone crushers are interlinked and communicate with each other, thereby boosting the performance of his plant. “Via a control wire, the cone ‘talks’ to the jaw,” Boyd said. “The cone sets the pace for the plant. If the cone starts to get too much stone, it tells the jaw to slow down a little bit until it catches up. What’s fascinating is that every 20 minutes the cone and the jaw analyze what has happened and the system gets smarter as it goes on.”
To illustrate this latter point, for example, throughout the day if the cone determines that it let the jaw slow down too much, it will adjust for that. “As the day goes on, the plant runs just fabulously,” Boyd said. “As the day progresses and we start to see a little manganese wear on the cone or die wear on the jaw — and factors change throughout the day — the plant adapts too. It takes a lot of human error out of the equation.” However, should a human interface be required and if he sees the recirculating load is rising out of the cone in the closed circuit loop, Boyd can “tighten” the cone via adjustment of its closed-side setting.
“We can go in on a daily basis and do a zero point set on the cone,” Boyd said. “The cone will screw itself down until it touches, and then back itself off. It’s a super accurate way of checking your closed-side setting. If you just go in and set it, unless you know where the zero point is, it’s not an accurate measurement. By being able to automatically zero out your cone, you don’t have to use lead weights or slugs being crushed to measure the lead to see what the setting should be. The automatic setting is fantastic; you push a couple of buttons and it’s set within five minutes.”
Keeping it efficient
Even the best equipment in a quarry needs maintenance to keep it running at its best. The Mobicat jaw crusher design also aids maintenance, Boyd found. Like the Mobicone, it features fully automatic hydraulic crushing gap adjustment, which guarantees quick setup times and on-the-fly adjustments. “The swing die on the jaw crusher is much longer than the stationary die,” he said. “That longer swing die not only protects the pitman on the jaw crusher, which is great, but secondarily it eliminates the edge or lip on a shorter swing die on competing crushers that gives an opportunity for bigger rocks to catch and hang on to. Kleemann’s taller jaw die all but eliminates stoppage due to big rocks. If you are doing 330 tph, and you have to stop for a half hour to dig the rock out, you’ve lost 165 tons of productivity.”
While Riverbend has two other mobile aggregate processing plants of other makes, Boyd chose Kleemann after doing research that included visiting Kleemann’s plant at Göppingen, Germany, outside Stuttgart. “I visited Kleemann’s factory about two years ago and was fascinated by the design, engineering and fabrication of Kleemann equipment,” Boyd said. “The engineering is fantastic. As a result I had to give them a try.” At the same time, he found support for his existing equipment was getting weak. “The support I get from Kleemann and Linder Industrial Machinery Co. has been fabulous,” he said, adding, “It’s of excellent quality.”
A dealer you can rely on
Linder Industrial Machinery’s 65-year history began in 1953 when Scott Linder Sr. and James Cox opened offices in Lakeland, FL. A culture of strong leadership that placed its customers and their needs at the forefront of the business yielded growth and expansion throughout the years. Since 1953, it has been the company’s mission to provide customers with the equipment and service they need to run successful operations. It proudly states that its customers are at the top of its organizational chart. It is a philosophy that has guided the company for 65 years, and as shown by Boyd’s experience, it is one that it remains committed to.