Types of bucket elevators:
Bucket
elevators are classified into three types. They classified according to
the bucket spacing and mode of discharge. They are:
1. Centrifugal Discharge elevators
2. Continuous Discharge elevators
3. Positive Discharge Elevators
Centrifugal Discharge Elevators:
In
a centrifugal discharge elevator, buckets are fixed on to belt or chain
at regular pitch to avoid interference in loading and discharge. This
type of elevators is mostly vertical in operation and can handle
practically any free flowing fine or small lumpy materials. The material
is fed into the boot of the elevator and scooped up by the buckets as
they pass round the bottom pulley or sprocket. The material is
discharged by centrifugal force as the buckets pass over the head or
sprocket.
These elevators operate at higher speeds than other types. Speed range is 70 to 125 m/min.
In
a centrifugal elevator buckets are loaded by the scooping of the
buckets at the boot. Hence such elevators are used for relatively fine
free flowing materials. Otherwise the buckets will be damaged
frequently. Usually lump size larger than 50mm are not used for these
types of elevators. On the other hand, it is also necessary to check
that the materials are not finer than 200 mesh size. (Materials finer
than 200 mesh are often aerated and cause wastage and jamming problems.
Applications:
1. Grain,
2. Coal,
3. Sand,
4. Clay,
5. Sugar and
6. Dry Chemicals.
Continuous Discharge Elevator:
In
a continuous discharge elevator, buckets are mounted without any gap on
a chain or belt. This type of elevator often used for handling larger
lumps of material that may be difficult to convey by centrifugal type.
The buckets used with this type of elevator are given such a shape that
the belt or chain passes over the head wheel, the flanged end of the
preceding bucket acts as a chute to lead the material to the discharge
spout. These elevators operate at a speed range of 30 to 50 m/min, which
is much slower than that of the centrifugal discharge type. Continuous
discharge elevators are not fed by the scooping action of the buckets
through the heap of material. A loading leg effects, feeding of
material. The slow speed and gentle method of loading and discharging
makes this type of elevator suitable for fragile, fluffy or pulverised
materials. It can operate in the vertical or inclined condition.
Application:
1. Lime,
2. Cement and
3. Dry chemicals
Positive Discharge Elevators:
This
type of elevators is similar to the centrifugal discharge elevator
except for two distinguishing features. The buckets are spaced at
regular pitch and mounted on two strands of chains, and are provided
with a snub wheel under the head sprockets to ensure inverting of the
bucket for complete discharge. The speed of the bucket is slow in the
range of 35 – 40 m/min.
This type of elevators is
used for handling light, fluffy, dusty and sticky materials. The feeding
is done by the scooping or digging by the buckets.
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