Bucket elevator has significant advantages with a large capacity, stable and reliable operation, long service time and others, the main performance and parameters are in line with JB3926 - 85 "vertical bucket elevator" (the standard equivalent to the international standards and advanced foreign Standard), the traction ring chain is accord with MT36 - 80 "mining ring chain with high strength", the bucket elevating machine is suitable for conveying powder, granular and small non-abrasive and small abrasive materials such as: coal, cement, stones, sand, clay, ore, etc., because bucket elevator traction mechanism is a circular chain, allowing the delivery of higher temperature materials (material temperature does not exceed 250 C). The conveying height is up to 40 meters, maximum height 80 meters. The endless chain used in the continuous discharging bucket elevator is strung between the head assembly and the tail assembly and operates in the free-standing casings. Multiple buckets mounted on the chain are equally spaced for the transport of material in the vertical direction. Unlike other types of bucket hoisting equipment, continuous discharging hopper elevator is not suitable for scooping material from the feeding hopper. Instead, the material is fed directly into the bucket (for feeding) by the raised feeding chute. The gap between the charging chute and the bucket is designed to a minimum, which reducing the amount of material falling into the bottom casing of the machine. Residual material must be constantly removed to prevent buckets and materials stacked on the feed box from interfere with each other. Interference between the bucket and the material can lead to excessive wear of the buckets and in extreme cases can cause the bucket elevator to stop operating. When the bucket passes through the upper sprocket, the material is discharged due to gravity and centrifugal forces. When the bucket moves forward over the head assembly, the material slides out from the bucket and hits the front of the next bucket. The flange of the next bucket acts as a slider that guides the material to the discharge chute. When conveying powdered materials, in order to improve the discharging efficiency of the bucket lifter, the lower walls of each bucket are drilled with holes. These holes allow air to escape when the hopper is lifted; and the air can enter the buckets when the material is discharged. This design ensures that the material can be filled in the buckets and all the materials discharged from the buckets. As a professional bucket elevator equipment manufacturer, PK Machinery always provides superior product quality and considerate service to our client, further information, please browse: www.pkmachinery.com
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An aspect often overlooked with continuous bucket elevators is the need to consider how material is fed into the unit. As an equipment type, bucket elevators require a controlled infeed of material to operate effectively. Failing to consider how material will be presented to the conveyor can result in lost throughput, product degradation, and equipment damage and downtime.
Bucket elevators can receive material from a variety of upstream process equipment, including mixers, blenders, dryers, pastillators, etc. Irrespective of the equipment type, it is critical to evaluate how the flow of material will be regulated as it enters the elevator infeed. To perform effectively, bucket elevators require a uniform and consistent rate of feed.
In some installations, the need for a regulated flow of material into the elevator is overlooked entirely. For example, we have seen installations where a bucket elevator was being fed directly from a bulk bag (FIBC) discharger without the use of any control device to regulate the flow of incoming material. Feeding an elevator with an unregulated flow of material can result in the following:
To avoid these problems, it is necessary to use an appropriate control or metering device, such as a vibratory or rotary valve feeder, to ensure a regulated flow of material into the elevator. The choice of which type of control device to use depends largely upon the application which the elevator is servicing.
Vibratory feeders use vibration to feed material into the bucket elevator. The amplitude and frequency of vibration, together with the feeders angle of deflection, serve to move a regulated amount of material into the elevator.
Vibratory feeders work well for many material types, especially those that are characterized as fragile or difficult-to-handle. Unlike rotary valve feeders, the design of vibratory feeders allows for a controlled flow rate without any degradation of the material moving through the feeder. Given their ability to control the flow rate with no material degradation, vibratory feeders are a preferred choice in high-care applications where product degradation must be avoided.
A second advantage of vibratory feeders is their consistent feed rates. Due to their design, vibratory feeders avoid the pulsed feeding of material that can result from using a rotary valve feeder. Vibratory feeders are available in fully enclosed tray designs for dust containment or to protect the product from external contamination.
Rotary valve feeders consist of a housing barrel containing evenly-spaced rotating vanes which contact incoming material and move it through the feeder. In applications which use a bucket elevator, a rotary valve feeder can be used as a volumetric feeder to discharge bulk solid material from a hopper or bin directly into the elevator infeed.
As with vibratory feeders, rotary valve feeders offer a fully enclosed feeding solution. This reduces the risk of material cross-contamination that can occur with release of dust into the ambient environment. Rotary valves are also used as an air-lock, suitable for purged systems or used as an isolation device when handling potentially explosive materials.
Given the design of rotary valve feeders, where the rotating vanes of the feeder contact material and move it forward, there is an increased risk of product degradation when fragile materials are being transferred. Thus, rotary valve feeders are often best used in applications involving non-fragile materials. In addition, while rotary valve feeders can achieve consistent feed rates, the rotating vane design can result in a pulsed flow as the evenly-spaced vanes move material through the feeder into the conveyor.
When using a rotary valve feeder, it is preferred to orient the feeders rotational axis to be at 90 degrees to the direction of travel of the buckets. This will ensure an even distribution of material within each bucket.
For continuous bucket elevators, it is preferred to feed material in line to the elevator infeed as opposed to, for example, feeding at right angles to the elevator infeed. Feeding material inline to the elevator infeed permits a more even distribution of material across the width of the buckets. In contrast, feeding the elevator perpendicularly can result in uneven material distribution within the buckets, as well as causing increased bucket wear that results from the more concentrated impact of material. The latter point is a particularly important consideration when moving abrasive materials or heavy products through the elevator. This can be resolved by incorporating a bias cut to either the transition chute, or vibratory feeder tray.
Minimizing the height from which material is dropped into the elevator reduces product dusting and allows for a gentler transfer of material. Ensuring a gentle transfer minimizes particle attrition and is important when handling fragile or friable materials that could degrade when dropped into elevator from too high a height. In addition, minimizing the material drop height reduces impact wear on the buckets, reducing the need for maintenance interventions and replacement parts.
To ensure that no load is present at start-up, the elevator should be started and allowed to ramp up to the desired operating speed before being fed with material. This can be accomplished by setting an appropriate time delay on the control device used to regulate the flow of material into the elevator infeed. The time delay ensures that no material enters the elevator until the operating speed is reached, avoiding any potential damage to the conveyor.
Transition chutes contain and direct material as it transfers from an upstream process into the elevator infeed. Material containment is particularly important when handling hazardous or toxic materials, which usually require fully enclosed connections. These sealed connections would be made either using a direct flanged or a flexible type. Transition chutes should be designed with a geometry and size that allows for a controlled and even flow of material through the chute and into the elevator.
When buying and installing a continuous bucket elevator, be sure to discuss with the equipment manufacturer all aspects of how the unit will be fed. Addressing the factors described above will ensure that the elevator is uniformly fed with material and help avoid performance problems that can result from improper feeding.
James Bransfield is the engineering team leader for UniTrak Corporation Ltd. UniTrak manufactures the TipTrak line of continuous bucket elevators. For more information, contact Bransfield at [emailprotected] or visit www.unitrak.com.
Whether replacing an existing bucket elevator, or building a new plant altogether, there are a few crucial decisions the purchaser should be prepared to make during the buying process. Here are some of the key design decisions that will require consideration when engaging a bucket elevator supplier.
Bucket elevators are primarily manufactured in two different discharge configurations: centrifugal and continuous. One of the first questions a bucket elevator manufacturer will ask is which elevator style the project calls for.
Continuous-style bucket elevators operate at slower speeds and lower capacities, offering gentle handling for materials that are fragile or susceptible to aeration; they are the preferred choice for applications such as potash and other fertilizers where degradation or attrition is a concern.
Continuous bucket elevators are also the best choice when handling materials that are either abrasive or inconsistent in particle size; the scooping and throwing action of the centrifugal-style elevator does not lend well to these types of materials.
Material is fed from a chute into buckets as they pass through the boot section. Buckets are designed and arranged in a way that allows the back of each bucket to serve as a discharge surface onto which the previous buckets material passes, making its way to the discharge chute via gravity.
Centrifugal-style elevators are better suited to faster, smoother handling applications where degradation or aeration of material are not a concern. This type of handling is typical of free-flowing or powdered materials and is often used for sand and ore.
The centrifugal elevator style self loads by scooping material from a hopper as it passes through the boot section. On passing over the head pulley, the buckets discharge material by throwing it into the discharge chute via centrifugal force. This elevator type operates at higher speeds and accommodates greater capacities, and as such, is the preferred choice at shipping terminals and other high-volume settings.
Centrifugal Bucket Elevator The image above illustrates the operation of a centrifugal-style bucket elevator. Note how loading is primarily a result of the buckets scooping material and discharge occurs as a result of throwing via centrifugal force.
The bucket elevator manufacturer will also want to know whether a belt- or chain-type elevator is preferred. Both belt and chain bucket elevators offer a reliable handling solution, with the decision between the two types coming down to practicality and cost.
Belt elevators offer a cost-effective solution for applications such as sand handling (a centrifugal belt-style elevator with nylon buckets offers a highly effective and economic option in such settings). They are also the preferred choice when noise is a concern, as they are much quieter than their chain counterparts.
This elevator style does, however, have some limitations. While less costly, they are not as durable as chains, making them less of a fit for especially demanding applications, such as those found at mine sites. They are also not recommended when the material to be handled is hot, or presents a risk of combustion. Further, since large particles could become wedged between where the bucket is mounted onto the belt, causing damage, the belt-style elevator is best suited for smaller particle sizes ( roughly and smaller) that avoid this risk.
While smaller belt elevators can handle capacities comparable to that of a chain elevator, this is only true up to a point; in addition to a lower tensile strength, their capacity is limited by practicality; beyond a certain capacity, the size of the casing and components required would be impractical.
Chain elevators are also the best option for handling higher-temperature (greater than 400F) or potentially combustible materials, as well as materials of a larger particle size that could otherwise become lodged between a bucket and belt.
A well-chosen bucket style often means the difference between seamless production and constant downtime for bucket repair or replacement. Elevator buckets are available in a wide range of styles and materials depending on whether the chosen elevator is of the continuous or centrifugal design.
Since centrifugal elevators will require the buckets to scoop up material, buckets in this category are equipped with a reinforced lip on the leading edge in order to discourage any distortion during digging.
AC Buckets are chosen for especially heavy-duty applications, or when the material being conveyed is hot or highly abrasive. This bucket style also accommodates a much higher capacity than the AA bucket style.
Close-centered, or CC buckets are an increasingly popular bucket style for centrifugal elevators. The buckets unique shape, along with a design that allows buckets to be spaced closer together, offers additional capacity over what AC buckets can handle.
Inspection doors are important for troubleshooting or routinely examining elevator performance and the overall condition of the equipment. Further, some operations may require access doors that allow for easy access to the units internals for changing or cleaning buckets, shoveling or washing out the boot section, or other routine maintenance procedures.
Bucket elevators typically come with access doors at the boot section and inspection doors at the head section, but additional access or inspection doors may be helpful at the intermediate sections as well, depending on the applications. Depending on where the bucket elevator is located in the plant, and the surrounding infrastructure, ladders and safety cages, as well as platforms may also be necessary.
The purchase of a new bucket elevator requires several design decisions on the part of the purchaser. For those new to bucket elevators, FEECO can walk you through the process and provide guidance on critical decisions based on your handling requirements and goals.
FEECO has been providing reliable bucket elevators to a range of industries since 1951. Our diverse material experience, combined with our flexible design process and high quality standards, ensures you get the best handling system for the job. For more information on our bucket elevators, contact us today!
An important factor for the successful operation of any bucket elevator is how material is fed into the unit. To ensureconsistent throughput rates, material should be fed in at a steady rate that results in optimal filling of the buckets. Underfilling or overfilling of the buckets is a symptom of poor feeding of the conveyor.
When supplying a bucket elevator, UniTrak always considers how the unit will be fed. Many applications will not require the use of a feeder as the product is coming to the elevator from an upstream process. For example, product may be fed into an elevator from a mixer, or a pastillator. In these cases, the supply of product to the bucket elevator is controlled and regulated. However, if product is not being fed to the elevator by this method, then it is necessary to control the supply of product to the elevator inlet with the use of a feeder.
Vibratory feedersuse both vibration and gravity to feed material into the bucket elevator. Gravity determines the direction of flow through the feeder, while a precisely regulated amount vibration is used to move the material.
Vibratory feeders work well for many material types, including those that are characterized as difficult-to-handle. A major advantage of vibratory feeders is that do not damage or degrade the material or product moving through the feeder. Given their propensity for no product damage, these types of feeders are a great match for the gentle handling characteristics ofTipTrakTMbucket elevators.
A second advantage of vibratory feeders is their consistent feeding rates. Vibratory feeders avoid the pulsing or rhythmic feeding of material that is sometimes encountered with other feeder technologies.
Rotary valve feedersconsist of a housing barrel containing rotating vanes that move material through the feeder. In applications using a bucket elevator, a rotary valve feeder can be used as a volumetric feeder to discharge bulk solid material from a hopper or bin directly into the conveyor.
Rotary valve feeders are available with round or square inlet and outlet flanges. For feeding TipTrakTMbucket elevators, UniTrak often recommends the use of a round flange, because it is often better to use a flexible connection between the feeder and the TipTrakTM. An advantage of rotary valve feeders is the wide range of service types available standard and heavy duty models are available, as well as those designed for sanitary service and easy cleaning.
Due to the nature of their design, where rotating vanes contact material and move it through the feeder, rotary valve feeders may damage or degrade fragile materials. Thus, these types of feeders are best used in applications involving non-fragile materials and products. In addition, while rotary valve feeders can achieve consistent feed rates, the rotating vane design can result in some pulsing as material is fed through the feeder into the conveyor.
Selecting and recommending feeders for bucket elevators is an important aspect of the application review process at UniTrak. In every case, we want to ensure that the bucket elevator is consistently and reliably fed, with no damage to the product, the environment, or operator health and safety. If you would like to know more about feeders for bucket elevators,please contact our sales department.