What is a Bucket Elevator?
A bucket elevator, is a mechanism for transfer of
flowable bulk materials vertically.
Bucket elevators are designed to move flowing powders or
bulk solids vertically. Bucket elevators use an endless belt or chain and have
a series of buckets attached to it. Bulk material is fed into an inlet hopper.
Buckets (or cups) dig into the material and convey it up and over the head
sprocket/pulley, and then throw the material out a discharge chute or throat.
It consists of:
- Buckets to contain the material
- A belt or chain to carry the buckets and transmit the pull
- Electric Motor and Gear Box to drive the belt
- Accessories for loading the buckets or picking up the material, for receiving the discharged material, for maintaining the belt tension and for enclosing and protecting the elevator.
Bucket elevators are not self-feeding, and are fed at
a controlled rate. The buckets are usually where the chain or belt path is
vertical or steeply inclined in a single plane. The buckets are returned back
down to a tail pulley or sprocket at the bottom.
There are four broad classifications of bucket elevators:
centrifugal, continuous, positive, and internal discharge. The most
commonly used are the centrifugal and continuous discharge elevators.
Centrifugal Elevators
Centrifugal bucket elevators are most commonly used
to convey all free-flowing, powdered bulk solids such as grains, animal feed,
sand, minerals, sugar, aggregates, chemicals, etc. They operate at high speeds,
which throw the materials out the buckets into discharge throats by centrifugal
force. Centrifugal Discharge Bucket Elevator can have buckets mounted at
intervals on chain or belt. Centrifugal Discharge Bucket Elevators are
used to handle bulk materials which can be picked up by the spaced buckets as
they pass under the boot wheel and discharge by centrifugal forces as the
buckets pass over the head.
A centrifugal discharge elevator may be vertical or inclined.
Vertical elevators depend entirely on the action of centrifugal force to get
the material into the discharge chute and must be run at speeds relatively
high. Inclined elevators with buckets spaced apart or set close together may
have the discharge chute set partly under the head pulley. Since they don’t
depend entirely on the centrifugal force to put the material into the chute,
the speed may be relatively lower.
Continuous Elevators
Continuous bucket elevators are used to handle
friable, fragile materials because they minimize product damage or are used to
handle light fluffy materials where aeration of the product must be avoided.
Continuous bucket elevators may be used to handle the same kinds of material as
the centrifugal type, however they are recommended especially for handling
materials that are difficult to pick up in a boot or friable materials. Continuousbucket elevators have buckets spaced continuously on chain or belt and
operate at slower speeds. The continuous bucket placement allows the force of
gravity to discharge their load onto the inverted front of the proceeding
bucket. The bucket then guides that material into the discharge throat on the
descending side of the elevator.
