- Published: Wednesday, 01 March 2006 07:00
New Products Proliferate and Older Lines get Upgrades
The weeks and often months preceding the larger international trade shows are usually quiet periods for equipment manufacturers. Most prefer to wait to stage their new product introductions during the show itself. This year is no exception. With Intermat 2006 scheduled for the last full week in April, the early months of 2006 have seen little activity in screening product news. However, despite the lull, several new screening products have entered the market during the past year that warrant attention. These range from new, highly versatile screening media to screening machines that reach new levels of quietness with a corresponding decrease in vibration.
? Tema Isenmannís range of screening media includes its WS85 1- ◊ 4-foot polyurethane modular systems, tensioned polyurethane media for drop-in panel replacement on crown-deck screens, Flexathon polyurethane for low-blinding, fine-screening of damp material, and a wide selection of 1- ◊ 1-foot polyurethane panels in both injection-molded and open-cast versions. In the latter product line, one of the more interesting offerings is Tema's proprietary TDS medium. It is injection-molded synthetic panels with disconnected webs that provides flexibility as well as a low risk of blinding.
? One of the more innovative screening media systems to appear recently is Sandvikís modular Stepdeck line. It was initially displayed in June at Hillhead 2005 and introduced into the market in the following months. Stepdeck features a unique trapezoidal shape and screening motion, which moves material nearest to the screen surface in a zigzag pattern over the media, slowing its progress and increasing the chances of an undersize particle finding a hole.
The result, says Sandvik, is more accurate screening in which the material moves in three dimensions. The panels can be combined in different ways to suit individual screening requirements including installation both across the width as well as down the length of the screen. The standard crosswise mounting approach permits flexibile deck configurations (stepped or flat), while lengthwise mounting eliminates dependency on the location of support bars.
Stepdeck media are offered in hard- and soft-rubber compositions, as well as polyurethane (Stepdeck PU). The hard-rubber product is suitable for fine to medium-coarse dry screening applications. The flexible rubber version is intended for fine screening of troublesome materials. Stepdeck PU can be used in wet, fine-to-coarse screening applications and is lightweight for easier handling and installation.
The polyurethane panels are composed of two hardness zones: a rigid lattice at the base for strength and a softer, more flexible membrane for the upper surface to reduce blinding and pegging. The molded apertures in the panels are available in patterns ranging from square holes in line with rows staggered for normal applications, to slots configured across the material flow for wet screening or dewatering, to slots parallel to the material flow for highest capacity at lower screening accuracy. Rubber Stepdeck media features punched apertures available in square-hole, round-hole or slot configurations.
? Durex-Camlineís Dur-X-Kleen line of self-cleaning rubber screen media is designed to eliminate impact damage, plugging and blinding. The company says it is field-proven to deliver up to a 30% increase in production. Designed with molded, tapered openings and a flexible self-cleaning action, the media keeps screen openings clear so that material flows at full capacity, Durex says. The system is intended to provide accurate sizing for products with high near-mesh or high moisture content. The rubber media, reinforced with aircraft-grade steel cable, is available as Dur-X-Snapdeck modular systems that snap into place. Durex also can manufacture rubber replacement panels to fit the framework of other manufacturers' systems.
? W. S. Tylerís new Ty-Ger wire was developed and introduced recently for high-wear screening applications. Traditionally, this steel wire has only been available in larger diameters, but W. S. Tyler now provides smaller diameter wires featuring a high-carbon alloy. The company says Ty-Ger wire is produced by a drawing process that results in a high-wear, tear-resistant and extremely elastic wire with twice the tensile strength of stainless steel and up to four times the strength of basic steel ó lasting up to four times longer than both. Ty-Ger wire is available for screen replacements, including hooked screen sections, and is supported by a warranty program.
? Metso Minerals continues to offer what is quite likely the largest selection of screening media available. Under the Trellex brand, Metso's product line includes its modular step system as well as rubber panel and tensioned rubber panel media. The modular nature of the line allows users to tailor the deck makeup for specific conditions or results. For example, blank or perforated rubber panels can be installed where impact is a problem. Polyurethane panels may be installed farther down the deck to ensure higher screening accuracy.
Trellex Panelcord is a self-supporting medium offering integral steel and cord reinforcement within a hard-rubber panel. Lately, it has been gaining notice, particularly from customers processing coarsely fragmented rock or ore, because it can be ordered with rider bars on the upper surface to extend wear life in tough screening conditions. Other media in the same product category include T-Flex SS, another steel-cord reinforced, self-supporting medium; and T-Flex US, a steel-frame and cord-reinforced medium that offers versatility for those with screen decks with support frames.
? Major Wire Industriesí Flex-Mat 3, introduced at Conexpo-Con/Agg 2005, is the latest iteration of the company's Flex-Mat screen cloth design developed in the mid-1990s. Flex-Mat 3 combines polyurethane strips bonded with individual wires that eliminate the need for traditional woven wires. The polyurethane strips allow the individual wires to vibrate independently and at different frequencies to prevent material from accumulating between the wires, which can happen with conventional woven wire. Major Wire claims that Flex-Mat 3 runs cleaner and more efficient, and raises plant productivity due to its greater throughput.
The polyurethane strips are centered on the screen deck's crown bars to provide a secure wear surface and ensure proper tensioning. Polyurethane overlaps on side-tensioned cloth ó standard on cloth with an opening of ?-inch or smaller and optional with larger openings ó prevent material leakage through the spaces between cloths. Flex-Mat 3 is available in screen opening sizes from 40 mesh to 4-inch and in various wire diameters.
Series D media has diamond openings and is for use on vibrating screens with a longitudinal or lateral tensioning system. These screens are made of crimped wires laid flat and held together by molded polyurethane bands. Series S screens have wave-shaped openings and are recommended where serious blinding problems occur due to moisture. They are for applications requiring small openings. Series T screens are recommended where heavy loads or impacts may occur; for example, when 25% of the material screened is four times larger than the opening of the screen. Series T screens have triangular openings and are designed for use on vibrating screens with a longitudinal or lateral tensioning system. They are composed of alternating crimped and straight wires.
? At the mechanical end of the screening spectrum, Metso Mineralsí Nordberg FS series of vibrating screens received a major upgrade. The new models feature all-welded deck frames; top decks that can be equipped with selectable types of urethane, rubber, wire cloth, and punch plate media; and middle and bottom decks with standard side-tension cloth. These models employ Metso's MV modular vibrators to generate a 3:1 elliptical motion. A new internal pipe spacer and full-height side plate reinforcement provide enhanced structural integrity. The pipe spacer also serves as protection for the internal vibrator components. The MV modulators also are available on the company's IS and TS series screens.
There are four sizes of vibrator cartridge: MV1, MV2, MV3, and MV4. Each cartridge consists of a short shaft, mounted in two screen-duty bearings with counterweights at each end. Grease lubrication of the bearings makes the vibrator compact. Counterweights are adjustable to provide easy stroke adjustment and to fine-tune the screening action. A shaft line is made up of two MV vibrator cartridges linked by a connection shaft. One, two or three shaft lines are used to achieve the desired screen motion.
Modular design means less downtime when maintenance is required. Only the affected module has to be replaced. Depending on the machine design, a new MV vibrator can be installed in as much as three hours (compared with 12 to 24 hours for other screens). Because the vibrator cartridge does not require service, there is no chance of contaminating or damaging new bearings, no press needed, and the task requires much less expertise. MV cartridges are interchangeable and available as a new replacement or a factory-remanufactured unit that comes with a warranty.
The revamped FS screens are targeted at the replacement market. Their standard sub-base facilitates installation by having the motor base, drive guards, and snubbers pre-located. Knockouts for live-mounted spray pipe holes can be included with the machine, making the screen series applicable for wet or dry operations. Four standard models of the FS screen are available: a 6- ◊ 16-foot double-deck scalping version, and 6- ◊ 20-foot triple-deck, 7- ◊ 20-foot triple-deck, and 8- ◊ 20-foot triple-deck sizing models. Other sizes and configurations can be requested.
? Rotex, which manufacturers the Minerals Separator and Rotex and Megatex screeners, introduced a service in late 2005 for replacing wood screen frames with all-metal automatic tensioning screen frames. The metal frames are designed for attaching screen cloth with spring tension clips. This allows the cloth to be quickly removed and replaced and ensures uniform tension across the entire screen surface. The screen frames and top covers can be constructed of 14-gauge mild steel, 304 stainless steel or 0.125-inch aluminum. The bottom pans are made of mild or 304 stainless steel. With the new frames, a one-time adjustment of the roller and bumper system ensures proper location of the screen frame ó even after repeated screen frame changes. No sieve jacks or additional adjustments are required, and no tools are needed to remove or reinstall the screen frame.
? A relative newcomer to the screening equipment sector is Smart Screen Systems. This company developed a high-frequency, low deck-angle screening machine that has been used in specialized mining applications and may have potential for aggregate production. Although high-frequency screens have been available for many years, the company's S3i-102 model offers some interesting features. In order to cause the screen panels to vibrate, conventional vibrating screening equipment employs energy-intensive force in the form of powerful electric motors that drive an eccentric shaft. The eccentric motion of the shaft causes the screen panel and the entire chassis and support structure to shake.
Typically, conventional vibrating screens consume substantial amounts of energy and often require frequent motor and bearing maintenance as they shake thousands of pounds of steel to cause a screen panel to vibrate and process a given amount of mineral slurry. This application of brute force also produces excess noise and vibration, which endangers worker health and safety, and increases the wear rates of other structures and machinery in the vicinity.
The S3i-102 uses energy-saving smart electromagnetic motors and specially designed resonators to amplify motion and cause only the screen panel assembly (not the entire machine) to vibrate at resonance. A controller and accelerometer are used to keep the screen panel assembly at desired frequency and stroke even as the material load to the screen varies over time. While under load, the S3i-102 is claimed to consume substantially less energy. Since it has no rotating electric motor, no eccentric shaft and no bearings, it requires very little maintenance and significantly reduces noise levels and vibration effects.
Because of the specialized nature of the design ó a low deck angle of 25 degrees and performance tailored for dewatering or very precise particle separations ó Smart Screen units have been used mainly in hard-rock operations such as iron ore and other kinds of ore processing. However, the company is looking closely at applying the screen's design elements to a version suitable for aggregate handling.