Bucket converyor

1. Bucket Conveyor

2. Bucket Elevators
Bucket elevators are one of the more commonly used
conveyors of grain between different elevations.
1. Bucket elevators are very efficient to operate because
there is little sliding of the granular material along
exposed surfaces, thus significantly reducing frictional
losses.
2. They occupy relatively little horizontal area, and can be
purchased in a wide range of capacities.
3. Bucket elevators have long lives, and are relatively free
of maintenance.
4. They require little labor to operate
5. Buckets are fixed / mounted on the belt or on the mobile
frame.
6. Operation is carried out in the enclosed /housing ,
therefore dust and fairly noise free.

3. Main parts of the bucket elevators
1) Elevator head section 2) Boot section 3) elevator legs 4) Belt for buckets 5) Buckets 6) Drive
Head Section
Shape of the head section dependent upon the 1) Bucket design 2) Pulley dia 3)
Belt speed
The discharge side of the head should be shaped in such a way that material is
thrown well, clear of the bucket in to the discharge chute, it should not fall into
down leg or creat back logging.
Back logging materials has to be than re-elevated, which affect the efficiency of
the system.
To avoid back logging , an adjustable cut-off plate is provided close to the lip of
the bucket.
Lagging on the elevator head pulley is needed in pulling heavy loads. Proper
lagging increases the coefficient of friction between the pulley and belt.
Usually lagging of head pulley is done with rubber.

5. The shaft of the drive pulley is always fixed to the pulley and bearing
outside of the casting construction.
Head shaft must be heavy enough to resist bending and to provide
required torque carrying capacity.
Shaft must be put at level, antifriction and properly lubricated bearing
should be used.
Buckets are made of steel or plastic and bolted on to the belt. Buckets
are enclosed in single housing called leg or in two legs..
Return leg may be located at some distance from the elevator leg.
Housing of the legs are also made of steel , welded or bolted together
and are made dust proof
Or tight.
The curve of the hood is designed for proper centrifugal discharge of
the grain.
The material can be loaded from the front or back or combined.

6. 1. The product flow is discharge either by means of gravity or centrifugal force.
2. The capacity is mainly dependent on bucket size, conveying speed, bucket design and
spacing , process of loading and unloading of the bucket and characteristics of the
products
3. Out of all above , belt speed is the first criteria factor and it usually kept 2.5 to 4.0 m/s.
4. The speed is dependent on the head pulley speed. If speed is too low than discharge of the
grain become more difficult and if , it is too high , than bucket will not be fed properly.
Capacity, m3.h= bucket capacity, m3 X number of buckets of the belt X speed , m/min X60
Capacity ,t/h = capacity m3/h X material density, kg/m3/1000

8. The gravitational discharge occur with non-adhesive bulk material elevated a low speed and
by means of bucket mounted closely together. In such discharge, contents of the bucket flow
over the rear side of the previous bucket.
The discharge of grains from the bucket is a combination of centrifugal and gravitational
discharge.
Part of the bucket contents is projected by the centrifugal force ( oriented towards out ward)
the rest flows by gravity (oriented down wards).
The magnitude of the centrifugal force = Cf = WV2/gr , where, W= weight of grain,
V= velocity, g= acceleration due to gravity, r= radius of the wheel + ½ of the projection of the
bucket
For optimum centrifugal discharge , and calculation of the speed of the head pulley, the
resultant force is zero; it means centrifugal force IA equal to force of gravity ----Cf=W
W = WV2/gr or V= root of gr. Since velocity v= 2πnr/60=V
Therefore,
n= 60 X root gr X root r/ 2 π root r X root r = 29.9/ root π

9. Boot Section
The boot section is separately and bolted assembly to
the leg
In this section , there is a provision of tightening of
belt as required and train the belt in such a way that
it run true to its path .
For small capacity, screw type “TAKE UP is used and
for high capacity, AUTOMETIC GRAVITY TAKE UP is
used for tightening .
In this, section loading chute is located at the point of
pick up of the product by the bucket take place above
the centre line of the return pulley.
When grain entry is done from both the side
(Combine feeding) of the boot, than additional power
is required to overcome the dredging effect while
pulling the bucket through grain in the boot.

10. Elevator Leg Section
and down moving belt containing
1. The up
buckets of the elevator are enclosed in the
elevator legs to restrict air pollution.
2. Legs are constructed as welded, bolted and
riveted unit.
3. The moving belt containing buckets up and
down could be enclosed in one unite /legs or
could be in separate legs.
4. The elevator casing near the drive and bottom
pulley should be such that when required the
whole pulleys can be dismantled and taken out.

11. Elevator Belt
• In normal operation of the bucket elevator, the load exerted by the elevator
height, product weight, weight of the belt, and idle tension and the digging
resistance are taken by the belt.
• It is to be noted that bucket elevator belt has no support between the drive
and return pulle, therefore cross stiffness of belt is very important.
• Total stretch of the belt under maximum load should not exceed 1-2% of the
belt length.
• Four type of belt are used for both belt conveying and bucket elevator.
• 1) Duck 2) Batala 3) Stitched canvas 4) solid woven cotton.
• The belt are covered with natural or synthetic rubber to overcome wear during
operation.
• Majority of belt are made of folded –ply construction .
• The pull resistance of the belt depend upon the applied fiber and no. of ply.

12. • To increase the tensile strength of belt , several
layers of fibers are put together to built a carcass
which could withstand very high tensile force with
maximum of stretch.
• The belt strong but could have weakest point of belt
joining . Several types splicing are possible.
• The type of belt splicing depends on the thickness
of the belt and the severity of the operation.
• The belt of five ply thickness or less , the bolted
clamp joint, the lap joints or butt –strap joints.
• The belt width should be 25 mm wider than the
bucket width.
• Pully width should be 80-100mm wider than the the
belt
• Inside casing should be 150-200mm wider than the
belt.

13. BUCKET
1. Three types of buckets are generally used for elevating the bulk materials
are Deep 2) Shallow ,3) – shaped with guiding side wall .
2. Speed of Deep bucket is maintained (2-3.3 m/s) and centrifugal loading is
done .
3. The main feature of bucket are their geometrical dimension; Width
(B),Length (L) and Hight (H).
4. The selection of bucket is done on the basis of loading and unloading and
properties of materials to be conveyed
5. The side edge of deep bucket , a small angle of inclination with horizontal
could provide good depth and useful for conveying granular, SMALL
LUMPY AND POWDERY material.
6. Shallow bucket have steeply inclined top side edge and low depth for
quick Emptying during unloading and hence is used for conveying wet
and poorly
7. Flowing pulverized and fine lumpy materials.
8. Both deep and shallow bucket has rounded bottom for better and
complete Emptying and used in the elevator with widely spaced bucket.

15. • As per the requirement , buckets are made of different materials and
come in various shape and size.
• The shape of the bucket is very iportant for filling and discharge
• Digging of buckets in the boot section and centrifugal discharge at the
head section which influences the shape of the bucket
• For centrifugal discharge , the resultant of product weight and the
centrifugal force should preferably be directed towards the lip of the
bucket.
• Bucket should have wide open mouth for digging and discharging the
product and at the same time lip of the bucket must not be too low and
bottom angle should not be too big, otherwise it would cause spillage
of the product, so there has to be compromise in between above two
points.
• Generally top angle taken as 800 while the bottom angle is kept 20-300
• Small buckets have fairly large capacity , high side walls which prevent
spilling.
• Space between two bucket is kept in general 2.0-3.0 times of the

17. • It is located near to the elevator head.
• Belt is turned around the drive pulley
• Drive motor with gear box and coupling are
mounted on a rigid and separated frame.
• At elevator head, a working platform is provided
and a ladder is provided for access to this
platform
• Theoretical Hp = QHF/4562 where, Q= capacity
of bucket , kg/min, H= lift of elevator, m
• F= factor, 1.5 for elevator loaded as on the up
side and 1.2 for elevator loaded on the bottom
side.
• A provision of 10-15% should be added to above
theoretical Hp to compensate the losses due to
friction, power requirement for loading and
power transmission and drive loss.
DRIVE MECHANISM

18. 1. The primary disadvantage of bucket elevators is the comparatively high
purchase and installation costs.
2. Other considerations relate to maintenance and repair coast.
3. The motor for a bucket elevator is located high above ground in the head of the
conveyor.
4. Similarly, chutes are suspended high above the ground.
5. The bases of most bucket elevators are located in pits in order to be fed by
gravity from a receiving pit.
6. This can increase problems associated with clean-out of the conveyor, especially
if water collects around the elevator boot.
7. Bucket elevators are not portable, although additional downspouts may be
added to serve other locations.
8. There is potential for mixing of material as a result of accidentally directing
material to the wrong location because the operator often cannot directly see
where the material is being transferred.