design of bucket elevator pdf

bucket elevator design considerations

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!