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All You Need to Know About: Vertical Shaft Impactor (VSI) Primers
Stedman Machine Company
All You Need to Know About: Vertical Shaft Impactor (VSI) Primers By Eric Marcotte, Inside Sales Manager, Stedman Machine Company Vertical Shaft Impactor What Is VSI? All roads, you might say, lead to the Vertical Shaft Impactor (VSI) because these crushers make it possible to create roadways and just about everything else. Francis E. Agnew of California patented one of the first Vertical Shaft Impactors in 1927. His configuration stacked three VSIs atop each other to produce sand, thus starting the VSI evolution. Today, VSI crushers – and the folks who rely on them – have produced many configurations to include everything from the addition of cascading material into the crushing chamber, to air swept separation of lighter product. One version suspends the shaft from above like a sugar centrifuge. It’s also one of the most feature-patented crushers, so some of the things mentioned here might be unique to a single manufacturer. VSIs apply a large amount of energy to crush material and that’s why it’s one of the most versatile crusher configurations today. View our VSI Machine Specifications, and get a quote today! VSI Benefits When it comes to producing materials such as aggregate for road making, VSI crushers use a high-speed rotor and anvils for impact crushing rather than compression force for the energy needed for size reduction. In a VSI, material is accelerated by centrifugal force by a rotor against the outer anvil ring, it then fractures and breaks along natural faults throughout the rock or minerals. The product is generally of a consistent cubical shape, making it excellent for modern Superpave highway asphalt applications. The rotor speed (feet per minute) controls final particle size. The VSI’s high cubical fracture percentage maximizes first-pass product yield and produces tighter particle size distribution. It has a high-throughput capacity ideal for beneficiation (elimination of soft material). Properly configured the VSI accepts highly abrasive materials. It has simple operation and maintenance. You can quickly change product size by changing rotor speed or cascade ratio. Some models have reversible wear parts to reduce downtime. The VSI typically has low operating costs even in high-moisture applications because of reduced energy costs and low wear cost per ton. VSI Disadvantages There are some feed size limitations with a VSI because of the small feed area available in the center of the rotor. Tramp material in the feed such as gloves, tools, etc. can cause problems with imbalance. The high RPM and HP require careful balance maintenance such as replacing shoes on both sides of the rotor at the same time. High wear part cost may be a problem for some hard abrasive materials, but the VSI may still be the best option. VSI Applications Major limestone applications are for Superpave asphalt aggregates, road base, gravel, sand and cement. Industrial uses include: corundum, corundite, ferro silicon, glass, refractories, silicon carbide, tungsten carbide and zeolite. Mining applications include: bauxite, burnt magnesite, iron ore, non-ferrous metal ore, perlite and trona sulfate. VSIs are excellent for everything from abrasive materials to waste and recycling applications. Verticl Shaft Crushers VSI Crushing Method The VSI is typically used after a primary or secondary crusher. This makes a VSI ideal for making sand and for making coarse and medium aggregates for concrete/asphalt production. Feed size and characteristics will affect the application of a VSI. The feed size is limited by the opening in the center of the rotor. Normally less than 5-inch material is desired, but very large VSIs can handle up to 12-inch feed. Another feature that will affect application is moisture, which can make the feed sticky. Required production capacity is the final limiting criteria. Large primary horizontal shaft impactors can output up to 1600 TPH and more. 1000 TPH is about the maximum for a VSI because of the limiting motor size and the rising G-force of a high-speed rotor, which is calculated by multiplying the radius times the square of the RPM. Shoe configurations are many: rock on rock, groups of rollers, special tip wear parts and many others. The metallurgy of the shoes is also highly varied. Rotors can have three to six shoes. The number of shoes is typically governed by the diameter of the rotor. The larger the diameter rotor, the more openings are possible. Computational Fluid Dynamics (CFD) mathematical models are utilized to simulate the flow and collision forces to reveal solutions for lower wear cost, consistent final product, and higher energy efficiency. The material to be crushed is fed into the center of an open or closed rotor. The rotor rotates at high rpm, accelerating the feed and throwing it with high energy into the crushing chamber. When the material hits the anvil ring assembly, it shatters, and then the cubical shaped product falls through the opening between the rotor and the anvil and down to the conveyor below. The rotor speed (feet per minute) controls final particle size. Speeding up the rotor will produce more fines, slowing it down will produce fewer fines. Feeding Methods Center feed The typical VSI is fed, from above, into the center of its rotor. The material is then flung across an open void to the crushing chamber. It then impacts the outer anvil ring. This crushing action imparts very high energy to the material and is very effective on most types of material. It gives a very uniform and consistent grade of product. Cascade feeding V-Slam Impactors In cascade feeding, material bypasses the rotor and enters the crushing chamber from above. It’s called cascade feeding because as material fills up a large feed bowl, with an outer diameter larger than the outer diameter of the rotor, it spills over the side and falls into the crushing chamber from above, bypassing the rotor. The effect of increasing feed through cascade is similar to slowing the rotor. Cascade feeding in amounts up to 10 percent may have no effect on particle size distribution or quality. The product gradation curve and product shape will change, if an increased amount of cascade feeding is used. Vertical Shaft Impactor for Aggregates (Above: Vertical Shaft Impactor, No Cascade vs. With Cascade Feed, Particle Size Distribution Chart) Rotor and Anvil Configurations The VSI features multiple rotor/anvil configurations for various applications. From open or enclosed rotors to the tubular rotor, each machine is configured for their unique application. In many cases the rotor table, rotor assemblies, anvil ring or rock shelf are interchangeable, allowing maximum application flexibility. Crushers for Aggregate Industry Open top metal rotor shoe on metal anvil The open top metal rotor is good for large feed or medium to very hard material, but it will work best for softer materials. It can handle medium abrasive, dry or wet, but not sticky materials. High reduction ratios are common, which are excellent for sand and gravel production in closed loop systems. Shoe shape can change the production size range. A straight shoe face design produces finer product, and a curved shoe face design produces coarser material. Stedman VSI Impactor Tubular metal rotor shoe on metal anvil The tubular rotor creates higher tip-speeds, which increases first pass yield with tighter particle size distribution and also reduces the recirculation loads. One unique feature is that the rotor rotation is reversible, allowing wear on both sides of the tube. Rotating the tube itself one-quarter turn also doubles the wear. Vertical Shaft Impactor Benefits Enclosed metal rotor shoe on metal anvil The enclosed top plate on a rotor primarily prevents material from escaping from the top of the rotor, which could happen with an overfed open top rotor. Vertical Shaft Impactor Applications VSI Crushers (Above: Rock shelf when VSI at rest. In operation, the brown rock fills the chamber to the upper roof ring. Rock impacts rock in operation.) Enclosed autogenous rock rotor table on autogenous rock shelf Any time the material or rock is used as an impact wear surface the term autogenous is used. Putting a top on the rotor table and shoes allows autogenous use. During operation of the VSI, a bed of material can be designed to build up inside the rotor against each of the shoe wall segments. The bed, which is made up of material that has been fed to the rotor, extends to a wear tip. The bed protects the shoe wall segment from wear. Concerning the rock shelf anvil, it forms a near vertical wall of material upon which the accelerated material impacts. “Rock-on-rock” crushing reduces maintenance but can require up to 30 percent of material recirculation before meeting size requirements. Also, the rock shelf anvil absorbs energy that could otherwise be used for breaking, which may reduce efficiency. More RPM may be needed to achieve the same result as a solid metal anvil. Good for medium abrasive materials, rock-on-rock configurations of either or both rotor and anvil may produce consistent material with low-wear cost and can handle wet but not sticky conditions. Reduction ratios from 2:1 to 5:1 can be expected. It’s widely used for quarried materials, such as sand and gravel. Due to the many configurations of the VSI feed, rotor, anvil and open- or closed- system design; testing is the only way to ensure proper application of a VSI crusher. V-Slam Supplier Summary The VSI is one of the most versatile crushers available on the market today. Even with some limitations, like feed size and output capacity, VSI features have been and continue to be developed to maximize first-pass yields and lower operating costs. If you test your process on full-scale equipment before choosing your VSI, you won’t be disappointed. About the author: Eric Marcotte joined Stedman Machine Company and its affiliate Innovative Processing Solutions in 2010. He has a Mining Engineering Degree from the University of Kentucky.
How Much Does It Cost To Operate a Crusher?
Stedman Machine Company
How Much Does It Cost To Operate a Crusher? By Chris Nawalaniec Crushing equipment is the heart of an industrial material-processing system. The size reduction choice you make will have a profound impact on the profitability of your business. When the right choice is made, you should expect many years of profitable operation. How do you make the right crusher choice? Crushers are not glamourous. They are brute force workhorses and what they do is simple, really. Size-reduction equipment in all forms is adding energy to a material to make big pieces smaller. Simple, right? Cost versus Value What does it cost or what is it worth? Producers need to keep that simple equation in mind. We all have to keep our eye on the ball and stay focused on profitability. What are Crushing Costs? Capital acquisition cost Base machine Structures and chutes Motors, drives, guards Energy consumption per unit produced Electricity Compressed air Wear parts cost Normal maintenance Planned downtime Lubrication costs Oil Grease Major repairs Infrequent maintenance Unplanned downtime Labor Normal maintenance Special or unique tools required When the above costs are all accounted for, they are used to quantify the production costs related to size reduction and are expressed in cost per unit of measure production. For example, $0.50 per tph. What Does Value Mean? There are always opportunities to buy a machine at a lower upfront cost. This usually translates into paying higher operating costs over the life of the equipment. Higher service labor cost. Higher wear parts costs. Higher energy costs. Often there is a justifiable case to spend additional capital dollars for the better machine. When evaluating crushing equipment suppliers, crusher manufacturers should quantify both costs: purchase price and operating costs. Before you purchase, ask for reference customers to visit. Selecting Equipment Why are there so many types of equipment? Our team brainstormed this question, and we came up with more than 50 tools or machines that are used for size reduction. What we are addressing here is industrial size reduction of dry, solid materials, which are grown, mined or chemically synthesized, and need to have a physical dimension alteration to be put to use. Customers are asked five questions to begin the equipment selection process. What is the material? What is the moisture content? What is the maximum size going into the machine? What is the size range desired after crushing? What is the desired production rate of finished product? When it’s time to dive a bit deeper to define the problem, we ask some additional questions. How long do you expect to operate the plant? Are you looking at mobile, skid-mounted or fixed installation? Are there electrical limitations or special power requirements at the plant site? Is the system open or closed circuit? Do we need to consider future expansion plans now? The variables above all affect your costs. Let’s take the first question as an example. How long do you plan to operate? There are times when mines reserves, stockpiles, permits, project contract terms affect expected life. If a project is limited by any factor, then “good enough” could be the best choice. As long as the equipment is safe and there are machine wear parts and service available, then going “cheap” may be the best choice. Another factor to consider with low-cost is limited post-sale assistance if there is some process change or major equipment problem. You don’t want to be hung out to dry. Aggregate producers typically expect to be running and profitable for many years. Always buy a crusher from an established company, develop a relationship, and expect ongoing service and personal contact. Ask before you buy about how they approach post-sale parts sales and service. Ask the company quoting how they intend to offer service for their crusher. How many field service people do they have? Are they local, regional or too far away? Not having responsive suppliers will have a significant impact on your plant profitability. Summary Investing in the best size reduction equipment for your specific needs is a big decision. The above should give you a lot to think about so equipment solutions can be objectively analyzed. Chris Nawalaniec is vice president of sales and marketing at Stedman Machine Co.
Teamwork Helps Integrate Design, Manufacture and Installation of Size- Reduction Systems
Stedman Machine Company
Teamwork Helps Integrate Design, Manufacture and Installation of Size- Reduction Systems By Eric Marcotte, Inside Sales Manager, Stedman Machine Company Designing and deploying size-reduction systems takes experience. Many people can collect and install some of the pieces they feel are needed to create a working system, but experience with the interrelationships between components is harder to find. And to ensure safety and performance, crushing, screening, storage and handling systems need to be professionally engineered. A system is always more than just a collection of parts; they must work together whether it’s a properly designed chute or an elaborate processing plant. Retrofitting new crushers, conveyors, screens or other pieces of equipment is also not always an easy process. Even if drawings and specifications no longer exist, plant designers need to make sense of what is there and know what it takes to make new pieces fit in an existing puzzle. If continuing production during the upgrade is required, system bottlenecks will need to be prevented. For example, raw material or finished product stockpiles may be required to keep downtime to a minimum. Also, access and space requirements need to be confirmed and double-checked. First - Assemble a Team Engineering and expertise in a variety of areas are required to develop size reduction systems, including: crushing, screening, structures, conveyors, chutes, hoppers, dust collection and storage, whether for a small equipment retrofit or a large turnkey facility. CAD and process design software applications are must have. Limit multiple layers of personnel. Work directly with the engineers and personnel to select the equipment and design the system. Project management, installation, scheduling and tracking experience will be needed. Be sure supervisors and installers are MSHA trained and have experience in fieldwork. Second - Process Design While most projects present new challenges, a widely experienced team will bring in ideas from other industries. Typical projects involve the following processes and types of equipment. industrial crusher Load out and material receiving This can be a feed hopper with an apron feeder, belt feeder, vibratory or screw feeder, truck dump or railcar unloading system. Bulk material transportation Designing, building or procuring belt conveyors, stackers, apron conveyors, screw conveyors, and pneumatic handling conveyors. Crushing Crushing is the basic building block of a size-reduction system. Experience with a large range of crushing equipment offers many solutions. Properly feeding material into the crusher greatly increases its efficiency, contributes to even wear and maximizes wear metal costs. Bulk material storage Specifying, providing and installing a range of silos, hoppers or other bulk storage solutions. aggregate crusher Screening Experience with many screening manufacturers to include the right screening solution into the system. Dust Collection Including the proper dust collector and dust collection system is a key component to allow a crushing system to work properly. Experience with many dust collection vendors will facilitate properly sizing, connecting and installing the best dust-collection system solution. Controls and Electrical Components To make sure that all components of a system work together, work with control system engineers, panel builders and electrical contractors to create a working, integrated system. Buildings, Foundations and Structure Design, procurement and specifications for buildings, foundations and structures for the equipment supplied on any system. Third - How to Do It Every project has a different set of circumstances that are unique to it. Try to follow a simple checklist to ensure the best possible solutions to the problems. Initial project team meeting. Crusher and screening testing as required. Define required scope for the system. Create preliminary concepts and drawings. Review with operators and supervisors. After receiving feedback, fine-tune the drawings, concepts and put forth a detailed proposal. Set up kick off meetings as required. Proceed with the purchase of major components. Proceed with a detailed system arrangement. Detail major assemblies. Assemblies put out for detail drawing creation. Drawings are self-checked and then crosschecked for accuracy. Assemblies are re-entered into system layout from detail assemblies to verify fit. Approval drawings sent out as required. Vendor drawings checked and approved. Items checked as they are received. Work with vendors and shipping to verify shipment accuracy. Pictures are taken of all shipments for record purposes. Installation supervisor works with install crew to identify, locate and erect items as needed. As installation finish date nears, begin check of motor rotations, sensors etc. Final customer acceptance – formal reviews to finalize “punch list,” follow up items and document the system is performing as specified. Example - Typical Quarry Expansion A limestone quarry running since the 1950s and producing 500,000 tons per year wanted to increase yearly production capacity up to 1.5 million tons with a new automated plant. The new design needed to have the capability to stockpile hundreds of thousands of tons of finished product. The focus was on creating a state-of-the-art plant with designed-in flexibility to do different product sizing. The automated plant needed to have the ability to run production all day as well as to be able to change the product sizes within 10 minutes. The design and fabrication of a new plant may take up to two years to complete as each idea is considered and "wish lists" are sorted out. You don’t want to come back and say we should have done this or done that. Get the very best of everything you can get into the plant for longevity. The project will include numerous conveyors, sensors, controls, vibrating screens, feeders and other equipment. size reduction machine Installed electronics and control systems feed a programmable logic controller. Each conveyor at the plant is equipped with terminal strips that are all wired to communicate information to one main processor, bringing all of the information together in one place to make it easy to operate. All of the feeders and conveyors are monitored to collect all of the information required to operate the plant. With the ability to monitor the speed of the conveyors and feeders, the quarry can keep an eye on production and troubleshoot maintenance issues. The reason for having an automated control system is that if something goes wrong on one of the conveyors, you’ll see it fast enough to prevent a catastrophe that might require digging out a conveyor. If something does go wrong, the computer can take over and begin dropping conveyors, discharging material and shut the feeder down. Since the quarry can now monitor the conveyors moving, the speeds and the tons per hour, limitations can be set to help catch problems before they become too serious. If something is going wrong, say conveyor 2A is slowing down, you can put limits on how much you want to allow it to slow down before the feeder is paused and then limit how long that feeder stays paused. In the end, the quarry was able to more than double their production capacity with the help of the automated plant. The plant was built, delivered and installed as planned with no problems. This is an ideal situation if a quarry is sitting on huge reserves of limestone and plans to operate the crushing plant well into the future. Projects such as this are successful when the customer’s needs are defined and understood, and the project team – including the customer and all supplier partners work to accomplish the project goals.
Expect More from your Horizontal Shaft Impactor
Stedman Machine Company
By Eric Marcotte The mineral processing industry usually evolves rather than revolutionizes, but the Horizontal Shaft Impactor (HSI) has revolutionized the crushing process in numerous industries.32 IMPACTOR 400 There are several varieties of the HSI, and their similarities are more numerous than their differences. All varieties feature externally fed horizontal rotors with breaker bars, which propel material into a series of apron-mounted breaker plates that crush or pulverize many different types of materials to specified degrees of fineness. In 1946, Dr. Erhard Andreas of Muenster, Germany, patented the “Andreas Impact Crusher System.” His design utilized old torpedo tubes and steel from decommissioned tanks. Since then, there have been many unique features of the design patented, but they all operate similarly. This article reviews current techniques employed to get the most from this versatile design. Versatility Reduction ratios of up to 30:1 are achievable in a single stage. The simple design offers low capital and operating cost. Low headroom requirements make it easy to install. Product sizes may be varied by changing rotor speed and the clearances between rotor breaker bars (also called blow bars or hammers) and apron breaker plates. HSI applications have gone beyond soft and nonabrasive materials such as limestone, phosphate, gypsum and weathered shales, to harder minerals thanks to the introduction of alloy steel rotor breaker bars. Typical alloy steels contain manganese and/or high or medium chromium content. There are many different crushing chamber designs on the market, and proper selection will depend on the knowledge of the application for proper feed, crushing chamber configuration, metallurgy of the crushing chamber components, gap setting and rotational speed. Finally, computer controls can automatically adjust HSI settings on the fly to adjust for wear or changing specs. Operation HSIs have a lined crushing chamber with rotating breaker bar rotor on a horizontal axis. The size reduction takes place quickly along short fracture lines, producing a more cubical product to meet aggregate specifications. This fast impact fracture is different from the slow compression breaking in cone or jaw crushers that produce more slabby or flat material (5:1 length to height ratio). 32 IMPACTOR2 400Feed enters the primary crushing chamber and meets the rotor breaker bars, which impel the feed against the first apron lined with breaker plates. Impact with the rotor, the breaker plate, and inter-particulate collision all contribute to comminution. Material is reduced in the primary chamber and passes by the front apron breaker plate gap, entering the secondary and, in some configurations, tertiary chambers, for final reduction. A high percentage of the initial size reduction comes from the first impact with the rotor breaker bar. Aprons are shaft suspended at the front and from a spindle in the rear, allowing for continuous gap adjustment as wear progresses. Unlike hammer mills, the open discharge impactor has no screens or grates holding material inside the crusher; material is efficiently processed at high rates for low costs. The rotor breaker bars operate best at specific speed ranges for maximum results. As the total processing capacity and rotors get larger, the number of breaker bar rows increases. On smaller sizes, there are only two rows; on larger rotors, there are four or more rows of rotor breaker bars. The optimum configuration has material delivered to each row of rotor breaker bars in a continuous bed over the width of the rotor for optimum performance and consistent wear part utilization. Some rotor interiors are open, and some are closed depending on feed conditions. For example, concrete recycling requires a closed rotor so rebar doesn’t get entangled. Application The HSI is used for all types of material with compressive strength less than about 20,000 lb. per sq. in. It’s widely used for sand and rock for roads, railways, reservoirs, electrical grid isolation, building materials and many industrial applications such as metal reclamation and recycling.34 IMPACTOR3 400 Wear part metallurgy is critical to proper applications and performance. It’s a good idea to keep a log of these items to determine the best wear part selection and maintenance schedule: feed and discharge information, throughput rates, change out records and measurements of worn parts. Proper selection of wear part metallurgy will result in optimum production rates; longer maintenance cycles and fewer changeouts, which reduce costs in labor, increase the wear part’s life as well as reduce downtime. Materials with high moisture content can be successfully handled by using heaters and air cannons to reduce and dislodge material adhering to the crushing components and chamber. Size Control The spacing between rotor breaker bars and breaker plate aprons can be adjusted to produce different products within one crusher. It is possible to crush soft raw material limestone or high-grade harder limestone for cement or asphalt applications with one crusher by externally adjusting the breaker bar and plate settings. Gap adjustment between the rotor breaker bars and breaker plates by manual or computer controlled systems adjusts the crushing gap so that product particle size distribution remains constant. Maintenance HSIs have multi-turn breaker bars for extended life before changeout. Design simplicity offers safe and easy access for breaker bar replacement and access to all areas of the crushing chamber. Front-opening models eliminate the need for a crane in some cases. Rear-opening models can allow unique installation applications. Summary 34 IMPACTOR 400 HSIs have evolved from humble beginnings through improved crushing chamber design and metallurgy advancements to automation controls. HSIs have proven they are capable of size reduction of all types of material sizes and hardness with minimal maintenance and excellent cubical particle size distribution control. Stedman Machine Co., www.stedman-machine.com Eric Marcotte is inside sales manager for Stedman Machine Company
Part 4 - Information Systems and Maintenance Work Control
PAUL D TOMLINGSON
Part 4 – Information Systems and Maintenance Work Control - Parts 1, 2 and 3 of this series established that many existing fully-integrated information systems do not provide adequate support of supervisor’s maintenance work control needs. Work order elements are too complex and time consuming for use in the ‘pressure-cooker’ working environment of maintenance supervisors. As a result many supervisors are using ineffective work control procedures that neither control work nor provide field data for required information. In turn, maintenance planners are compelled to prepare ‘official’ work order documents to capture missing data. Many planners are simply ‘work order administrators’ with no time left to plan. When management requires information, these planners may be ‘creating’ bogus information misleading management decision-makers. Since not all work requires planning, a simpler work order element for supervisors can meet their work control needs and also allow them to control all non-planned work. Information system problems are acknowledged by system developers but without being corrected. However, many maintenance organizations have contributed by not developing a well-defined maintenance programs and specifying their information needs. Instead, they have accepted and tried to use the generic information output of overly complex package systems. This ‘log jam’ requires corrective actions. An outstanding PC-based system that satisfies the supervisors work control requirements, returns planners to their full time planning tasks and creates essential information has been identified. The system developer’s introductory presentation was obtained and is attached.