Operations

Improving Ventilation in Underground Stone Mines. MSHA diesel rules are prompting operators to consider ventilation upgrades.

Success in the Field: SMC Increases Production and Improves Consistency. Tertiary cone upgrade reaps notable benefits.

Plant Sense: Getting the Most out of High Speed Cones. What new breed cone technology needs most is operator understanding.

Maintenance Matters: Cooling Systems Don’t Have to Cause Headaches. Avoiding some bad practices and knowing the importance of water quality are keys.

Tech Trends in Screen Machines and Media. Technologies to make your “money machines” (screens) more effective.

SMC Increases Production and Improves Consistency

Cedarapids Rollercone MVP 450 installed in tertiary application.

“We were looking to increase production and improve particle shape,” recalls Mark Brielmaier, former owner and current quarry manager of Southern Minnesota Construction’s (SMC) Granite Valley Quarry in Morton, Minn.
In the mid 1990s while he owned and operated the quarry, Brielmaier looked to Ruffridge-Johnson, a local dealer, to provide a cone to crush its final product. Brielmaier used a 3254 jaw and a 66-in. cone as his primary and secondary crushers for initial reduction of the quarried 27,000 psi granite and chose a Cedarapids Rollercone 54II to deliver the final product. Satisfied with the 54II’s performance, Brielmaier ran the cone crusher for a number of years, producing an average of 200 tph of a variety of products for the regional market.
After Brielmaier sold the quarry to SMC, which owns and operates four quarries and a number of sand and gravel pits throughout southern Minnesota, the operation needed to boost production to an average of 300 tph to supply asphalt plant operations in addition to local, county and state customers. So again, Brielmaier and SMC turned to dealer Ruffridge-Johnson, which specified a Cedarapids Rollercone MVP 450.
Producing more than 10 specification products from very dense granite, SMC also needed a crusher that offered quick setting changes to limit circuit downtime.
SMC installed the MVP 450 during the 2000 crushing season. Almost immediately, Brielmaier realized production increases, product quality and consistency improvements and a decrease in wear costs. Coming into its third season, the MVP 450 has processed more than 500,000 tons of granite, and the crusher has met and exceeded Brielmaier’s expectations.

Sample of product shape produced by the new cone.

The new cone helped SMC’s Granite Valley Quarry to reach its goal of increasing average production by 100 tph. With one of its primary products, a Minn DOT Spec CA-5—a 3/4-in.-minus Superpave spec product—the cone boosted production of saleable product by more than 50 tph. But more importantly, the cone crusher produced a higher quality, more consistent spec product.
The Rollercone 54II gradations, while meeting the CA-5 spec, consistently tested at the low end of the 30 to 60 percent requirement, and the percentage of flat and elongated stone produced ran very close to the 10 percent maximum allowable. After installing the MVP 450, gradation tests showed a 5-percent increase in 3/8-in. minus material and a 3.5-percent reduction of flat and elongated product. “We are getting much more consistent spec product, and it remains consistent throughout the wear life of the manganese. Now, we don’t have to run as many gradation tests as we used to,” said Brielmaier.
The cone’s remote adjustment system has given SMC an extra hour of production every day. Crushing a very dense and abrasive rock, Brielmaier must adjust the crusher’s settings a couple of times each day to compensate for bowl wear. With the older cone, the operator would shut down the circuit to make these settings modifications, which according to Brielmaier, “took about half-an-hour, twice a day.” However, the MVP 450’s settings are adjusted at the touch of a button without shutting down the circuit, giving SMC an extra 300 tons of saleable product each day.
Reducing wear costs are an added bonus. The new cone crusher produces 15 to 20 percent more 3/4-in. product than its predecessor between liner changes, decreasing wear metal costs by about 15 to 20 percent.
Last season, Cedarapids and Ruffridge-Johnson worked with SMC to install the manufacturer’s new Rollercone Super Bearing. The bearing was designed to better withstand the long-term demands of crushing dense aggregate and reinforced recycle material. Cedarapids installed the new bearing to ensure SMC’s long-term success with the MVP.
This upcoming season, SMC is looking to further increase its Granite Valley Quarry’s annual production by 100,000 tons. For the first time in 2002, the quarry will produce an A.R.E.A. #4 ballast, a spec calling for a product range between 2 in. and 3/4 in. Brielmaier is confident the operation is up to the challenge.

the bottom line...
Southern Minnesota Construction (SMC) replaced its tertiary crusher with a Cedarapids Rollercone MVP 450 to increase production by an average of 100 tph. The MVP 450 has helped SMC reach its production goals, improved final product quality and consistency, and reduced wear costs by 15 to 20 percent. The new cone’s remote-adjust system has allowed SMC to increase production. Cedarapids’ new Super Bearing has provided more assurance of uptime during long-term demand.

To submit a suggestion for a Success in the Field or for more information about any of these stories,
contact AggMan at (717) 337-0027, Fax: (717) 337-9337 or email at bill@aggman.com

Plant Sense

Getting the Most Out of High Speed Cones

New breed cone crushers do work, and work well. Understanding how they work is the key.

By Ed Hayes

Cone crusher technology has recently been advanced significantly by many crusher manufacturers through the use of various design modifications, such as increasing mantle gyrations per minute, increasing the mantle throw and improving the crushing chamber profile. When compared to previous generation cone crushers, these modifications have achieved many added benefits including the following:
• A significant reduction in the weight of, and the dynamic forces generated by, the newer models of cone crushers as compared to the older generations of cone crushers. This enables the producer to reduce the cost of the crusher’s structural support and to use a higher-capacity cone crusher in a limited-space application. It also allows the use of significantly higher capacity cone crushers in portable plant applications where highway transport weights are a limiting factor.
• By increasing the speed of gyrations and also by increasing the throw, the cone crusher not only achieves a significantly increased tons-per-hour capacity, it allows the crusher to achieve a far greater reduction-ratio from “stone-on-stone” crushing versus the older generation cone crushers in which the majority of the crushing results from the stone being compressed directly between the manganese-steel bowl and mantle liners. “Stone-on-stone” crushing accomplishes a significant reduction in the quantity of flat and elongated particles, as well as a considerably higher cubicity of the product particles to meet Superpave specification guidelines. In addition, stone-on-stone crushing substantially increases mantle and bowl-liner wear-life as compared to the “older” generation cone crushers.
To achieve the optimum cone crusher performance, it is critical that the plant operator regularly checks and maintains the proper closed-side-setting for the cone crusher. When a cone crusher is operating with a full crushing chamber, many plant operators erroneously believe that the crusher is at its full product-producing capacity. Chart 1 and Graph 1 show that significantly more tonnage of products can be made by sending less recirculating load to the crusher if the proper closed-side setting is constantly maintained. In addition to increasing the production of final products, a significant reduction in power costs and maintenance costs will result from reducing the substantial tonnage of final products that are needlessly sent back into the crushing circuit.

Chart 1
Cone Crusher Capacities
CSS—(Closed-Side Setting)
Cone Crusher Feed	3/8 in.	1/2 in.	5/8 in.	3/4 in.	7/8 in.	1 in.	1-1/4 in.
TPH Feed	205	283	345	395	423	450	495
TPH Products	205	283	342	375	368	356	287
TPH Re-circulating load	—	—	3	20	55	94	208
Cone Crusher Feed	3/8 in.	1/2 in.	5/8 in.	3/4 in.	7/8 in.	1 in.	1-1/4 in.
TPH 57's	31	88	127	174	190	207	183
TPH 8's	69	93	101	90	81	63	35
TPH #10 Screenings	105	102	114	111	97	86	69
TPH Total Products	205	283	342	375	368	356	287

Chart 1 was produced from data published by a major crusher manufacturer for a high-capacity cone crusher. These are the crusher-discharge gradations that can be expected from “average” rock. Variations in different types of rock’s compressive strength, friability, cleavage planes, chemical composition and other characteristics will alter these percentages, some slightly and others more significantly (see Chart 1).
In addition to the previous factors, the crusher operator also has to be aware that the operational parameters for the newer-generation cone crushers are much more restrictive than the older-generation cone crushers. Operating outside of these parameters can quickly lead to mechanical and/or structural damage to the crusher, as well as a significant reduction in the crusher’s tons-per-hour capacity and a considerable loss of the cubicity of the products. Furthermore, it is critical that the crusher receives a non-segregated feed by using feed-baffles or a feed-distributor to ensure that the percentage of voids remains equal in all areas around the perimeter of the crushing chamber. A reduction of voids in any area can cause severe structural and/or mechanical problems to the crusher. It is also extremely important that the proper crushing chamber is used in relation to the top size of the feed material.
When a new plant is designed, or an existing plant is modified, it is critical that the finishing screen in the tertiary crushing circuit is sized properly. This will maximize the amount of finished products that will be screened out of the crushing circuit to go to the product stockpiles instead of being returned to the crusher as “carry-over” material. For example, 20 tons-per-hour of finished-product that is not removed from the circuit and is instead returned to the crusher may not seem like a significant amount. However, in a 2,000-hour operating year, that is 40,000 tons of product that went back to the crusher instead of being sent to the stockpile as a saleable product. In many instances, the finished-product tonnage returned to the crusher is considerably higher than the 20 ton-per-hour example. This is a significant amount of lost revenue that would be quickly recovered by the modest increase in cost to “up-size” the finishing screen to improve the screening efficiency of the crushing circuit.
Because each manufacturer has different critical operating parameters for each of its models of cone crushers, it is extremely important that every producer discuss with the manufacturer all of these factors for every new or replacement cone crusher installation. Knowing and applying all of the pertinent installation, operational and maintenance factors for each crusher will substantially reduce plant downtime, increase tons-per-hour of product production and reduce maintenance costs, resulting in a considerable increase in product quality as well as profits.

Ed Hayes is the president of H&H Solutions, Inc., in Gettysburg, Pa.

Maintenance Matters

Cooling Systems Don’t Have to Cause Headaches

Editor’s Note: This monthly column is supplied exclusively for AggMan by Association of Equipment Management Professionals (AEMP).

Diesel engine cooling systems operated without adequate coolant can suffer severe deposits as seen on the tubes of this radiator core. The result can be reduced life of the engine, transmission and hydraulic components.

During the winter and summer months, the thoughts of heavy equipment maintenance managers fondly (or, not so fondly) turn to their diesel engine cooling systems. Certainly, all experienced equipment managers have had their share of cooling system problems.
“Over the years, cooling system problems have taken their toll on diesel engines,” said Michael Rucker, marketing manager, oil and coolant for Caterpillar, Inc. “Hard water deposits reduce an engine’s cooling capacity and can lead to short engine life. Deposits within the cooling system can also reduce the life of transmission and hydraulic components that rely on engine coolant to maintain an optimum operating temperature. Also, cavitation and erosion of engine parts can cause outright failures, not to mention increased parts replacement costs at overhaul time.”
Poor quality water has always been the primary cause of such cooling problems. Sometimes local water quality is so poor that it should not be used to either mix with coolant concentrate or to top off the radiator. It is best to use only de-ionized or distilled water. But local water may be used if it meets the criteria listed below. Water purified by the reverse osmosis process, while not as good as distilled or deionized water, may be acceptable, but should be tested.
An engine that requires frequent top off is heading for a problem. It is okay to top off cooling systems with minor amounts of water, but only if the water is of acceptable quality.
According to Rucker, when you have an engine that is “using coolant,” there are only three reasons this could be occurring:
• A leak;
• Boil over; or
• Excessive (and unnecessary) topping off.
Obviously, any leak should be detected and repaired as soon as possible. If the coolant is escaping as steam from boiling, the cooling system has a problem. The problem may be as simple as a radiator cap that is not sealing or an externally plugged radiator, or as complex and expensive as internal scale clogging the radiator core and water passages within the engine block and cylinder head.
Sometimes, inexperienced maintenance personnel add water unnecessarily. They remove the radiator cap while the engine is cool and find the water level visible, but not up to the top of the radiator top tank. They add water, perhaps daily, believing it is necessary. The coolant expands upon heating and pushes out the excess. Therefore, each day, the maintenance crew dilutes the coolant and could be introducing contaminants into the system.
In remote areas where distilled or deionized water is not available, use the following guidelines:
• Never use salt water;
• Select the best quality water available and have the water analyzed to determine its quality; and
• Never use water alone as coolant.
The use of good water is very important; however, water should never be used alone as coolant because it is very corrosive, particularly at engine operating temperatures. This is especially true of distilled or deionized water, which is sometimes called “hungry water” because of its tendency to attack any metal in which it has prolonged contact without rust inhibitors. However, because distilled or deionized water has a low ionic content, it is the easiest to inhibit and is, therefore, the best water for use in blending coolant or for top up.
Machine or engine owners in warm climates occasionally use water with Supplemental Coolant Additive (SCA) as coolant, rather than a coolant containing 50 percent ethylene or propylene glycol because they believe that the purpose of the glycol is only to protect from freezing. However, the glycol also raises the boiling point of the coolant. In warm weather, the coolant may reach the boiling point and be lost as steam resulting in the “frequent top off routine.” Proper coolant is not only “anti-freeze,” it is also “anti-boil.”
Another coolant maintenance problem can result from adding too much Supplemental Coolant Additive (SCA). “Many maintenance crews simply add SCA or change the spin-on coolant additive element at each oil change,” explained Rucker. “The better practice is to use a test kit to determine whether the coolant needs additional SCA. Such test kits are available as either paper “dip strips” or as a liquid “drop test.” Use only the test kit recommended by the coolant manufacturer because coolant additive packages vary from brand to brand.”
An overdose of silicates can result in leakage of graphite-faced water pump seals. This results from the over-concentration of silicates forming silicone dioxide and eroding the seal surface. The silicates can also precipitate out as the infamous “green goo.” Anyone who has seen this occur in an engine cooling system will remember it. Green goo can plug radiator cores and engine passages—and cause all sorts of cooling system problems.

As a comparison to photo on page 30, photo of component condition using adequate coolant.

Caterpillar Inc. decided in 1996 to reduce the impact of poor water quality and silicates in the coolant of its machines with the introduction of the company’s Extended Life Coolant (Cat ELC). When this new organic-based coolant was introduced, Caterpillar decided to sell it only as premixed coolant, and not as concentrate, in order to avoid the problems caused by poor quality water.
“During maintenance seminars five or six years ago, we used to say that over half of all engine problems or short life were caused by, or exacerbated by, poor coolant condition or cooling system trouble,” Rucker noted. “This was in the days before the introduction of Cat ELC. Since then, reports of coolant-related problems on newer Cat machines have dropped to nearly zero.”
ELC is a silicate-free coolant that does not require a periodic dose of Supplemental Coolant Additive (SCA). ELC is an organic-based coolant that Caterpillar adopted because it provides double the life of the previous coolant—from 3,000 hours to 6,000 hours. ELC does not require the addition of SCA; only one addition of ELC Extender at the coolant’s half-life, which greatly reduces maintenance costs and labor. Caterpillar has documented its requirement for this type of coolant with the Cat EC-1 specification. In addition to the Cat brand, Texaco Extended Life Coolant/Antifreeze and several other brands that meet EC-1 are available.
Rucker stated, “We are often asked if it is acceptable to top up an engine that has ELC with standard silicate-type coolant. The answer is that mixing of the two will not cause an immediate problem. That is to say, the two are not incompatible chemically, but if ELC becomes mixed with 10 percent or more conventional coolant—or with SCA, we recommend that it be maintained, from that point, as conventional coolant. That means changing it at 3,000 hours. The best practice is to always top up with the same coolant that the machine received at factory fill.”
Cooling systems of modern heavy-duty equipment are designed to be trouble-free. Problems that occur are usually the result of poor maintenance practices. If the cooling system is maintained as recommended by the OEM it should do its job of protecting the engine and all other coolant-cooled systems for the full design life of each component.

The Association of Equipment Management Professionals (AEMP), formerly the Equipment Maintenance Council (EMC), is an individual membership organization comprised of equipment maintenance and management professionals. Its members are responsible for the purchase, maintenance, employee training, shop facilities and parts management of leading corporations and government entities that utilize heavy, off-road equipment. Its members also represent the major manufacturers and suppliers of the heavy equipment industry. AEMP provides end users with cutting-edge education, and it is the only organization to offer a certification program for the industry, the Certified Equipment Manager (CEM). For more information, contact Stan Orr, CAE, AEMP executive director, at (970) 384-0510, e-mail at ceo@equipment.org or visit AEMP's web site at www.equipment.org.

Tech Trends

Screen Machines and Media

By Bob Drake

Whether facing a need to make fractionated products or cleaner, drier sand and stone—or to eliminate blinding or capacity bottlenecks—some alternative screens and screen media may provide economical solutions. Installing larger traditional horizontal or inclined screens might improve screening efficiency and throughput, but newer generation multiple-slope (banana), high-speed or high-frequency screens might provide the needed improvements in a smaller footprint, with less energy consumption and with greater versatility.
Some of the alternative screens have been around for a while but warrant another look; others are relatively new to stone, sand and gravel applications even though the concepts they incorporate are well proven in the coal and metal mining and other bulk solids industries.

Multiple-Slope Screens
Multiple-slope or banana screens typically feature a steeper inclined deck section at the feed end of the screen followed by more moderately sloped to horizontal deck sections toward the discharge end. There can be single or multiple decks.
The steeper section at the feed end of the screen reduces material bed depth because gravity increases the travel speed of the material, according to Paul Smith, product manager for JCI. Reduced bed depth minimizes spillover and enables finer particles to pass more quickly through coarser particles to the screen surface, he said. Consequently, finer particles are introduced to the bottom deck faster, increasing its utilization and screening capacity. Bottom screen deck capacity often is a bottleneck to improving total plant throughput. Coarser near-size and oversize particles on the top decks slow down for efficient separation as the screen deck flattens toward the discharge end.

1. JCI Combo
JCI’s Combo screen features a top deck that varies in slope from 20° to 10° to horizontal. The second deck has sections inclined at 15°, 7.5° and 0°. The entire bottom deck is horizontal. Available in 6- x 20-ft. and 8- x 20-ft. sizes, the Combo screen has a triple-shaft design that JCI said provides an optimal oval screening motion. Stroke length, stroke angle and RPM are adjustable to suit the application. A punched-plate feedbox increases screening area and removes a high percentage of fine particles before they are introduced to the screen deck, the company said. The Combo screen design is especially well suited for accepting large-volume feed surges, for deposits containing a high percentage of fines that must be removed, for installations where screening capacity must be increased within the same structural or mounting footprint, or in closed circuit with crushers, according to JCI.

2. McLanahan Corp. Mogensen-SEL
Although the Mogensen-SEL screen does not utilize banana-type multiple slopes along the length of any single deck, the three- to five-deck machine uses different inclination angles for each deck. Built on a smaller footprint—models range from about 4.75 x 10.67 ft. to 8 x 13.5 ft.—and completely enclosed, the Mogensen-SEL is designed to separate sizes from about 0.04 to 1.2 in. It can handle feed up to about 2 in. Progressively finer screen decks mounted at increasingly steeper angles allow the use of larger screen aperatures to separate finer sizes than is possible on more horizontal decks. This helps reduce blinding, the company said.

3. Metso Minerals DS, TS and Multi-Slope Series
Multiple-slope screens available from Metso Minerals include Nordberg’s DS series, TS series and banana-type Multi-Slope series. The DS series has a conventional inclined top deck and dual-sloped second and third decks consisting of an initial steep section and shallower final-screening section. The compact units are available in 5 x 10 ft. and 5 x 8 ft. sizes. Nordberg TS series triple-deck screens, available in five sizes from 5 x 16 ft. to 10 x 27 ft., have three sections on each deck, varying in slope from steep (feed end) to shallow (discharge end). Nordberg’s Multi-Slope series have concave upward, true banana-type decks with progressively flattening slope toward the discharge end. They are available in single- and double-deck configurations in 10 sizes ranging from 6 x 18 ft. to 12 x 27 ft. Metso said its Multi-Slope screens eliminate blinding and caking and require less space than conventional screens of comparable capacity.

4. Midwestern Industries Multi-Vib and MEV
Midwestern Industries offers two screens suitable for dry screening 2-in. to 165-mesh material. The Multi-Vib is available in three models: 3 x 5 ft., 4 x 6 ft. and 5 x 7 ft. It uses five screen decks to vertically stratify the feed material and reduce the load on any single deck. Several decks can be used as “reliever” decks to minimize the bed depth on the finest product screen, Midwestern said. Lineal-motion vibration is provided by twin, 7.5-hp motors. The MEV screen uses elliptical motion created by adjustable counter weights. It is driven by 3-hp, 5-hp and 10-hp motors on the 3- x 5-ft., 4- x 8-ft. and 5- x 10-ft. models, respectively. One to five decks provide separation down to 165 mesh.
Both screens utilize what the manufacturer calls parallel-arc configuration of the screen decks. Screen inclination is lower at the feed end of each deck to momentarily retain material, which allows undersize to rapidly pass to lower decks, according to Midwestern. Inclination increases toward the screen discharge end. The Multi-Vib and MEV use end-tensioned screens that can be changed from the back (feed end) in about 10 minutes, the company said. The compact units require up to 50 percent less structural support compared to conventional rectangular screens of similar capacity.

5. Sizetec Vertical Sizer
Designed for size separations ranging from 1 in. to 50 mesh, Sizetec’s Vertical Sizer uses triple decks, each with two-deck sections at different angles. The first, steeply inclined, end-tensioned deck makes a rapid “roughing” separation, according to the company. Material then flows to a horizontal polyurethane knock-in deck or side-tensioned deck for final separation and cleaning. The Vertical Sizer Model 4423H has a compact 5.6- x 8.9-ft. footprint and uses two 5.3-hp motors to develop vibration frequencies up to 1,200 cpm. Sizetec also has recently developed a line of larger multi-slope deck screens. Each deck has three variably sloping sections with a short vertical step between each section.

6. Tabor Machine Company TMS Multiple Slope
Tabor’s TMS screen uses a multiple-slope deck system comprising five deck sections separated by replaceable polyurethane wear liners. The slope of each deck section varies from feed end to discharge: 30°, 22.5°, 15°, 7.5° and 0°, respectively. Varying deck slopes help maintain a thin bed of material the entire length of the screen, which improves screening efficiencies at high tonnage rates compared to conventional horizontal screens, according to Tabor. The overhead-mounted vibrating unit, utilizing Tabor’s TH drive mechanism, produces linear motion, developing high G forces, the company said.

7. Tema Systems Inc. Type BHG Banana
As a result of a partnership with Linatex Africa Ltd., Cincinnati-based Tema Systems is marketing Siebtechnik-designed banana screens in North America. TEMA Systems is a member of the European-based Siebtechnik/TEMA group of companies. The Type BHG Banana screen is generally a single-deck unit with three variably inclined sections: 25° to 40° in the steep feed end, 15° to 25° in the middle, and 0° to 15° at the discharge end. Traditionally used in applications for coal and other minerals, the units are available in unusually large sizes, up to about 16 ft. wide and 36 ft. long.

High-Speed/High-Frequency Screens

8. Deister Machine Company BHST/BHSM
Optimum separation of fine materials is the benefit claimed by Deister for its BHST and BHSM high-speed vibrating screens. Steeper screen inclination (30°) increases particle travel rate, reducing bed depth; and higher G-forces developed by higher speed and stroke quickly stratify material for effective screening, the company said. The screens are available in single- and double-deck models in sizes up to 6 x 18 ft. All single-deck units and the bottom deck of double-deck models use end-tensioned screen cloth or modular urethane panels. This provides a uniform depth of bed across the full width of the screen by eliminating channeling of fines caused by the crown in side-tensioned cloth, Deister said. BHST units have the vibrating mechanism mounted on top of the frame; BHSM units, which are all double deck, have the vibrating mechanism located between the decks. Double-deck screens, 6 x 14 and larger, have dual vibrating mechanisms. Ball tray decks and screen enclosures also are available.

9. Metso Minerals TY HM Series
Designed for fine, dry screening, Nordberg’s TY brand HM series high-speed screens operate at up to 3,600 rpm. Gravitational and vibration forces separate coarser particles away from the screen surface, allowing finer particles to pass through, the company said. The narrow units are available with single, double or triple decks in seven sizes from 3 x 5 ft. to 4 x 20 ft.

10. Production Engineered Products (PEP) Vari-Vibe and Duo-Vibe
At 3,000 to 5,000 rpm, PEP’s Vari-Vibe and Duo-Vibe screens provide high-frequency separation for chip sizing and fines or sand removal. A steep inclination angle allows gravity to move material across the screen panel, and vibration, induced to the screen cloth only—instead of to the entire screen box—applies force directly to the material, the company said. High frequency and low amplitude lifts larger particles higher and keeps fines closer to the screen surface, increasing the probability of separation, according to PEP. Vari-Vibe screens are available with single or double decks in sizes from 6 x 6 ft. to 6 x 24 ft. and screen vibration frequency up to 5,000 rpm. Duo-Vibe screens have a 5- x 10-ft. top deck driven at 1,200 rpm and a 6- x 12-ft., directly induced variable high-frequency bottom deck.

Alternative Screens

11. Aggregate Equipment Inc. (AEI) bivi-TEC
Finding application in dry screening fine product, such as chips, manufactured sand and ag-lime, AEI’s bivi-TEC screen uses a dual-vibratory process to eliminate clogging and blinding, according to the company. Two weights moving relative to each other alternately tension and relax the 13-in.-wide urethane screen mats. The screen box is accelerated approximately 2 Gs; the screen mat can receive up to 50 Gs, AEI said. The bivi-TEC screen is designed to separate material from 35 mesh to 2 in. They are available in sizes ranging from 3 x 10 ft. to 8 x 24 ft. in single- and double-deck configurations and as portable or stationary units.

12. Allmineral Liwell
allmineral is the U.S. distributor of the Liwell “flip-flow” screen manufactured by Hein, Lehmann in Germany. The screen uses polyurethane panels that are alternately tensioned and relaxed up to 600 times per minute. In the tension phase, the screen panels are stretched up to 10 mm, which slightly changes the shape of the openings and causes pegging and adhering particles to break away, the company said. Screen surfaces receive up to 50 Gs of acceleration; the machine structure receives only 2 to 3 Gs.

Self-Cleaning Wire Cloth
Dry screening of finer grained products has traditionally been a problem, even at very low moisture contents, because of the tendency for the material to clog and blind screens. In addition to low separation efficiency, stopping production several times a day to manually clean screen cloth—often on the bottom deck—can severely hamper production rates and drive up costs per ton.
Heated wire cloth, ball tray decks and chains are sometimes used to reduce blinding. Specially designed urethane panels also can be effective; however, they generally result in loss of screen capacity because of significantly lower percentage of open area compared to wire cloth. For these reasons, self-cleaning wire cloth is gaining in popularity with aggregate producers.

13. Buffalo Wire Works CleanSlot
Buffalo Wire Works’ CleanSlot screens have alternating pairs of crimped and straight wires held in position by crimped cross wires. This “three-dimensional” weave causes material to tumble over the wire, which enhances cleaning and stratification, according to the company. The crimped wires vibrate rapidly to help keep the screen clean. Buffalo Wire Works recommends CleanSlot screens for de-sanding material and eliminating fines from asphalt chip production. They have also been used in production of manufactured sand, slag, ag-lime and lightweight aggregate.

14. Durex Products Dur-x-Accuslot and Dur-x-Vibraspan
With alternating straight and crimped wires, Dur-x-Accuslot screens have roughly triangular openings, from 3/32 to 1/2 in. The screens are available woven from oil-tempered steel, Dur-x-cel XL-25 premium grade steel, or stainless steel wire of various diameters in side- or end-tension design. Panels are available in any width up to 84 in. long. Dur-x-Vibraspan screens are custom woven to match cross wire location to a machine’s support bars in order to maximize screen life and open area. Slot length, hook configuration and overall size also are customized.

15. Hoyt Wire Cloth Veno, V-2, Serpa and Polyflexx
Veno screen media by Hoyt Wire Cloth features alternating straight and crimped wires in oil-tempered, high-tensile or stainless steel. The crimped wires help in sizing control and “pick up” the throw of the vibrator to provide cleaning action, according to the company. Serpa screens are similar to the Veno design but without the straight wires. Hoyt’s V-2 is a loosely woven longslot screen made from stainless steel. Veno, V-2 and Serpa screens are available with cross (cluster) wires designed to correspond to the screen’s support bars to maximize open area and with polyurethane-coated cross wires to improve wear.
Hoyt’s new Polyflexx screens incorporate abrasion-resistent material internally reinforced with wire cable and woven fiber. Because of its elasticity, Polyflexx reduces blinding and plugging of near-size particles, the company said. The media is lightweight and provides more open area than modular urethane systems.

16. Major Wire Flex-Mat
Boasting sales of more than 20,000 in five years, Major Wire said its Flex-Mat self-cleaning screen cloth lasts an average of five times longer than woven wire cloth. The flat profile wire is available in three patterns with openings from 30 mesh to 2 in.:
• Series D—opposing crimped wires forming diamond-shaped openings.
• Series S—parallel crimped wires forming long, wave-shaped slots.
• Series T—alternating crimped and straight wires forming triangular openings.
Different than most self-cleaning screens, Flex-Mat uses polyurethane strips bonded to individual high-carbon, tempered or stainless steel wires instead of using cross wires or cross wires encased in urethane. The polyurethane strips allow the wires to vibrate independently and at different frequencies to prevent buildup of material, Major Wire said. Cross wires can inhibit vibration, according to the company. The polyurethane strips are centered on each screen deck crown bar. Major Wire also developed a software program that, based on current production figures, calculates percentage increases in production and profits that the company said are obtainable by switching to Flex-Mat screens.

17. Metso Minerals/W.S. Tyler Cobra Vibe
Designed for screen-blinding applications, W.S. Tyler’s Cobra Vibe is a “flex-type” wire screen manufactured in three opening designs. The designs provide screening accuracy close to traditional wire mesh square openings, according to the company. The screens have polyurethane reinforcement strips and W.S. Tyler’s traditional hook strips. No deck modification is required.

18. Midwestern Industries Klear Screen
Three wire diameters and nine straight-wire/crimped-wire combinations help Midwestern Industries’ Klear Screen fight blinding and clogging. The company said its crimping process, where both straight wire and crimped wire are woven side by side, enables the screen panels to resist blinding.