The Fundamentals of Bucket Elevators and How They Work
Bucket elevators equipped with Engineered Steel Chain are designed to lift enormous quantities of heavy materials to considerable heights. Thus chain selection is key to the proper functioning of bucket elevators. Chain type is broadly based on the type of bucket elevator. In most applications, straight sidebar, hardened bushed rollerless chains are applied. Offset style sidebar chains have been used for years but with chain manufacturing technology improving, offset chains are far less common for new equipment.
Centrifugal Discharge Elevators
Centrifugal discharge elevators are designed so that the buckets are fed material from the inlet feed chute at the boot section and discharge material via centrifugal force. This style of elevator typically operates at a much higher chain speed, when compared to the other elevator styles, which usually fall in the 220-330 fpm (feet per minute) range. The use of a single strand rollerless chain with a K-style attachment (every 12-18”) is very common in such elevators with attachments ranging from every 2nd pitch to every 4th pitch. Chains which have a roller in this application will become loaded with the conveyed material between the rollers and bushings. The presence of the conveyed material along with any moisture will cause the rollers to cease onto the bushings preventing them from turning.
Continuous Bucket Elevators
Continuous bucket elevators feature buckets that are spaced continuously (thus the name) and discharge material via gravity. Chain speeds in continuous style bucket elevators are typically in the 100-150 fpm range. The use of steel bushed rollerless chain with a K-style attachments are very common in this application. For elevators that use a double strand of chain will typically use an K-style (back hung) or A-style (back hung) attachment to the bucket. Typically buckets are spaced every 2nd pitch on 4”-6” pitch chains depending on bucket size.
Super Capacity Elevators
Super capacity elevators are a special kind of continuous bucket elevator designed for higher capacity requirements. Extra long buckets spaced continuously on the chain are end-hung between 2 stands of chain. Typical chain speeds are in the range of 120 fpm or less and discharge of the buckets is by virtue of gravity. The use of a steel bushed roller chain with a G-Style attachment every pitch is very common in this elevator. Buckets are typically spaced every 2nd pitch on 6”, 9” and 12” pitch chains.
Positive Discharge Elevators
Chains used in a positive discharge, or perfect discharge elevators usually run at a slower chain speed when compared to a Centrifugal style elevator. Typical chain speeds in a positive/perfect discharge elevator are 120 fpm (feet per minute) or less. Buckets used in these elevators are end-hung between two strands of Engineered Steel Chains with bucket wing attachments (common bucket spacing is 20-24”).
Elevator Chain Types
Hardened Steel Bushed elevator chains typically feature straight sidebars with heat treated pins and bushings. These types of chains are used for centrifugal discharge and continuous discharge chain bucket elevators.
Steel Bushed Roller elevator chains feature straight sidebars with a heat treated roller, pins and bushings. These chains are typically applied in super capacity, dual strand, gravity chain bucket elevators.
Chain Attachment Types
K Style attachments- Double sided attachment used on single strand and double strands of chain attached to the back of the bucket. This is the most common type of attachment primarily used for centrifugal discharge and continuous discharge bucket elevators.
A Style attachments– Single sided attachment typically used on double strand of chain back hung on the buckets. Centrifugal discharge and continuous discharge elevators will use A attachments.
G Style attachments – Are used on dual strand/double strand super capacity gravity discharge chain bucket elevators. The attachments are mounted to the side of the bucket.
Floating Attachments– This type of attachment is used primarily by European original equipment manufacturers. The attachments are bolt to the back of the bucket and then slid on to a holding pin with a retaining ring or pin. This type of attachment is primarily used for centrifugal discharge and continuous discharge bucket elevator.
For more information on Webster Industries Bucket Elevators:
Director of Sales – West & Midwest