Belt conveyor system_Advanced Construction Technology (Semester-6), Civil Engineering

Prepared by
Prof. Ashish Makwana
Civil Engineering Dept. - MEFGI
1Prof. Ashish Makwana

PRESENTATION
OUTLINE…
• Belt Conveyor
• Advantages - Belt Conveyor
• Economical aspects
• Belt conveyor components
• Power required to move a belt conveyor
• Conveyor Belt take-ups

PRESENTATION
OUTLINE…
• Holdbacks
• Feeders Trippers
• Selection and design of conveyor belts
• Precautions for longer life of belt
• Belt-Capacity
• Buckets, Chutes, Buggies

BELT CONVEYOR
• One of the most common form of material
handling system used in mining industries and in
construction projects.
• Capable of conveying large quantities of
material continuously over long distances at a
fast speed.
Prof. Ashish Makwana 4

• Useful:
- in heavy industries – Fertilizer, chemical
and cement etc.
- handling materials in Asphalt plants,
Crushing and Screening plants, Aggregate mixing
plants etc.
- Coal mining industries and other industries
for handling coal and other raw materials

ADVANTAGES –
BELT CONVEYOR
• Capable of handling light or heavy, fine or
coarse, wet or dry material
• Handle, thousands of tons of material per hour
for several km.
• Handle, hot materials upto 160 degree C or so
• Lighter in weight, and consumes less power
• Operates without noise
• Gives a continuous discharge and quantity of
which can be varies by varying the speed of
conveyor belt

ADVANTAGES - BELT CONVEYOR
• Carry the material horizontally or in an
inclination
• Used for carrying the material over rough
country, where use of other means is difficult
and costly

ECONOMICAL ASPECTS
• To assess the economy of a belt conveyor to
that of trucks for hauling, it is desired to estimate
the cost of transportation by each method.
• To assess the cost of conveyor system, its
installation, maintenance, repair, electric energy,
labour, depreciation, interest on investment,
taxes, insurance must all be considered.
• Whereas to assess the cost of transporting the
materials by truck, the cost of truck, its
depreciation, maintenance, repair, interest on
investment etc. and cost of construction and
maintaining haul road be considered.

ECONOMICAL ASPECTS
• The unit cost of moving the material be
calculated and compared with that obtained for
belt conveyor system, in order to take decision
about the economy of either of the system.

BELT CONVEYOR COMPONENTS
• Belt
• Pulleys and Idlers
• Drives
• Motors and Controls
• Conveyor belt take-ups
• Hold Backs
• Feeders

Fig. Belt Conveyor System(a)

Fig. Belt Conveyor System
(b)

Fig. Belt Conveyor System(c)

Fig. Belt Conveyor System(d)

Belt
• Rubber belt – costliest single component in the
system
• Consists – carcass imbeded in rubber
• Carcass – made up of plies or layers of fabric
(cotton or synthetic) bonded together and carries
tension and absorbs impact
• Rubber compound – natural, synthetic or a
blend

Belt (cont’d)
• Steel wires stranded cables – used in place of
fabric yarn in carcass to have higher tensile
strength
• Mechanical fastners – used to make the
conveyor belts endless at the job site and also
used for quick repairs of cuts and rips in
conveyor belting in an emergency

Idlers
Fig. Troughed 3-roller idler
Fig. Single roller idler

Pulleys and Idlers
• Located at the terminals of a belt conveyors
• Conveyor belts – supported on idlers, between
the terminals
• Idlers – three roll type, with the center roll
horizontal and the two side rolls inclined to form
a trough (angle at 20 degree)
• Idler rolls - made up of steel tubing, with welded
end discs

Pulleys and Idlers (cont’d)
• Idler supporting the loaded strand of the belt –
known as upper idler and the one which is
supporting the return belt is called as lower idler
• Upper idler – 3 roller type or single roller type,
but lower idler always have single roller
• Belt runs flat on a single roller, while takes the
shape of a trough on multi roller idlers

Drives
• Nearly all belt conveyors are driven by electric
motors.
• Speed reduction – achieved by chain and
sprockets, ‘V’ belts or gearing.
• Drives are generally located at the discharge
ends or inclined conveyors.

Motors and Controls
• Squirrel-cage and wound-rotor type motors are
commonly used in conveyors.
• The motor for a conveyor belt drive must have
sufficient torque to overcome the starting friction
of the system.

Conveyor belt take-ups
• Take-ups are provided to adjust for the increase
in length of the belt due to its elongation after it
is put into operation.
• Take-ups types:
– (a) Screw take-ups
– (b) Weighted pullies

Hold Backs
• Hold backs are provided on the driving pulley to
prevent the load from causing the belt to run
backward in the event of a power failure, if the
belt is operating on an incline.
• Holdbacks are mechanical devices which allow
the driving pulley to rotate only in normal
direction and prevention it from rotating in the
opposite direction.

Feeders
• These are used to deliver the material to a belt
at a uniform rate.
• It may deliver the material onto the belt either
directly or through a chute in order to reduce the
impact of falling material.

POWER REQUIRED TO MOVE A
BELT CONVEYOR
The total external power required to drive a
loaded belt conveyor is the Algebric sum of the
power required by each of the following:
1. To move an empty belt over the idlers.
2. To move the load horizontally.
3. To lift or lower the load vertically.
4. To turn all pulleys.
5. To compensate for drive losses.
6. To operate a tripper, if one is used.

(a) Power required to move on empty belt:
Power required to move on empty conveyor
belt over the idlers will vary with type of idler
bearings, the diameter of the idlers and length,
weight and speed of the belt.
L = Length of conveyor, m
S = Belt speed, m per minute
C = Idler friction factor
Q = weight of moving part per m of
conveyor
𝐋 =
𝑳𝑺𝑪𝑸
𝟒𝟓𝟎𝟎
𝐡. 𝐩.

(b) Power required to move a load horizontally:
L = Length of conveyor, m
C = Idler friction factor
T = Tons of material moved per hour
𝐋 =
𝐋𝐂𝐓
𝟑𝟔𝟎𝟎
𝐡. 𝐩.
(c) Power required to move a load up an inclined
belt conveyor:
When the load is moved up an inclined, the
power required may be divided into two
components; the power required to move the load
horizontally and the power required to lift the load
through the net change in elevation.
T = Tons of material moved per hour
H = net change in elevation (m)
𝐋 =
𝐓𝐇
𝟑𝟔𝟎𝟎
𝐡. 𝐩.

(d) Power required to turn pulley:
A belt conveyor includes several pulleys,
around which the belt is bent.
For the shaft of each pulley, there is a bearing
friction that requires the consumption of power.
The power required will vary with the tension
in the belt, the weight of the pulley and shaft and
the type of bearing.
For a given conveyor the friction factors for
each pulley may be determined reasonably
accurately and from this information the additional
power required to compensate for the loss due to
pulley friction may be obtained

CONVEYOR BELT TAKEUPS
• A screw take-up may be used to increase the
length of the conveyor by moving the head or
tail pulley. This adjustment may be sufficient
for a short belt but not for a long belt.
• Another take-up, which is more satisfactory,
depends on forcing the returning belt to travel
under a weighted pulley which provides a
uniform tension in the belt regardless of the
variation in length.

HOLDBACKS
• Holdback – mechanical device which
permits a driving pulley to rotate in the
normal direction but prevents it from
rotating in the opposite direction.
• The operation of a holdback – automatic
• Three types: Roller, ratchet and differential
band brake (all operate – automatically)

HOLDBACKS (continued..)
• A holdback must be strong enough to resist the
force produced by the load less the sum of the
forces required to move the empty belt, to move
the load horizontally, to turn the pulleys to drive
the tripper and to overcome drive losses.
• If a belt conveyor is operated on a decline, the
effect of the load is to move the belt forward. If
this effect exceeds the total forces of friction, it
will be necessary to install a suitable braking unit
to regulate the speed of the belt.

HOLDBACKS (continued..)
• To overcome this difficulty, an electric motor or
generator may be used as the driving unit. In
starting an empty belt, the unit will act as a
motor, but when the effect of the load is
sufficient to overcome all resistances, the unit
will act as a generator to regulate the belt speed.

FEEDERS
• The purpose of a feeder is to deliver material to
a belt at a uniform rate.
• A feeder may discharge directly onto a belt, or it
may discharge the material through a chute in
order to reduce the impact of the falling material
on the belt.
• Several types of feeders are available, each of
which has advantages and disadvantages when
compared with another type.

FEEDERS (continued..)
• Among the more popular types: Apron,
Reciprocating, Rotary vane, Rotary plow
• An apron feeder usually receives the material
from a gated hopper, which regulates the flow
onto the feeder.
• The feeder consists of a moving, flat, rubber –
covered belt or a number of flat steel plates
connected to two moving chains. This feeder
moves the material from under the hopper and
discharges it through a receiving unit onto the
conveyor belt.

• A belt feeder is suitable for handling material
consisting of relatively small pieces. If the
material contains large pieces of highly abrasive
rock or stone, a steel-plate-type feeder will
usually prove more satisfactory than a belt type.
• A reciprocating feeder consists of a steel plate
placed under a hopper. The plate is operated
through an eccentric drive to produce the
reciprocating effect, which moves the material
onto the conveyor belt.

• A rotary-vane feeder consists of a number of
vanes mounted on horizontal shaft. As the
material flows down an inclined plane, the
rotating vanes deliver measured amounts to the
conveyor. The rate of feeding may be regulated
by varying the speed of the rotating vanes.
• A rotary-plow feeder consists of a number of
plows, or vanes, mounted on a vertical shaft.
The plows rotate over a horizontal table onto
which the material is allowed to flow. The rate of
feeding may be regulated by varying the speed
of the plows.

TRIPPERS
• When it is necessary to remove material from a
belt conveyor before the material reaches the
end of the belt, a tripper should be installed on
the conveyor.
• A tripper consists of a pair of pulleys which are
so located that the loaded belt must pass over
one pulley and under the other.
• As the belt passes over the top pulley, the load
will be discharged from the belt into an auxiliary
hopper or chute.

TRIPPERS (continued..)
• A tripper may be stationary or a travelling type.
The latter type may be propelled by a hand-
operated crank, a separate motor, or the
conveyor belt. If tripper is installed on a
conveyor, additional power should be provided
to operate it.

SELECTION AND DESIGN OF
CONVEYOR BELTS
• Sufficient width
• Sufficient strength
• Sufficient thickness and correct grade
• Sufficient Lateral Flexibility
• Sufficient Impact Resistance
• Sufficient Lateral Stiffness
• Sufficient Longitudinal Flexibility
• Angle of Inclination

PRECAUTIONS FOR LONGER
LIFE OF BELT
• Edges may not be damaged during storage,
installation and working.
• The belts should be stored in cool, covered and
dry places.
• These should be protected from oily substances.
• In case of any cut is noticed, it should
immediately be sealed with conveyor belt
solution to prevent entry of moisture.
• Frequent starting and stopping of belt under load
should be avoided.

PRECAUTIONS FOR LONGER LIFE OF BELT (continued..)
• Absorption of oxygen by rubber belt reduces the
tensile strength and elasticity and fine cracks are
developed on the belt surface. Since absorption
of oxygen is faster in sunlight or heat, it should
be stored in cool and dark places.
• For longer life it should run flat, while for
maximum output it should have deep toughing
and more speed, which is responsible for
reduced life.

BELT-CAPACITY
• "Carrying capacity of a belt (tons per hr.) =
Cross-sectional area of material on the belt ("
m^2) x Speed of the belt (metres/(per hour) x
Unit weight of the material (tons per m^3)
• Cross sectional area of the material depends
on the width of the belt, depth of troughing.
As a thumb rule the material should be
loaded on the belt so as avoid spillage in
such a way that 25 + ½ width of the belt, in
cms, from sides are not loaded.

BUCKETS
• Buckets: Buckets are used for conveying
materials (especially concrete) in horizontal and
inclined direction. For inclined conveyor the
angle of inclination should not be more than 70.
• Normally V-shaped buckets are used. Properly
designed bottom dump buckets enable concrete
placement at the lowest practical slump. Care
should be taken to prevent the concrete from
segregating as a result of discharging from too
high above the surface.

BUCKETS (continued..)
• Gates should be designed so that they can be
opened and closed at any time during the
discharge of concrete.
• There are two types of feeding: Point feeding
and drag feeding. When material is filled in the
bucket at one place, it is called point feeding.
When bucket is dragged in the heap of material
it is called drag feeding. In case of point feeding
the speed is 20 m per minute while in drag
feeding the speed is 10 m per minute.

CHUTES
• Chutes: Chutes are often used to transfer concrete
from higher elevation to a lower elevation. They
should have a round bottom and the slope should
be steep enough for the concrete to flow
continuously without segregation.
• Truck mixers are normally equipped with inbuilt
swing chutes. These chutes are hydraulically
operated for direct placing of the mix. when the
concreting location is within chute reach.
• Drop pipes are used to transfer the concrete
vertically down.

BUGGIES
• Hand buggies and wheelbarrows are usually
capable of carrying from 4 to 9 cft. of concrete,
and thus are suitable on many projects, either as
the sole or main concrete placing equipment for
small works. When considering the use of
buggies and wheelbarrows, the expense of
building ramps, runways, etc. should be taken
into account as they can operate on smooth and
rigid surface. Hand buggies are safer than
wheelbarrows because they have two wheels
rather than one.

BUGGIES (continued..)
• Hand buggies and wheelbarrows are
recommended for distances less than 60 m,
whereas motor propelled buggies (power
buggies) can traverse up to 300 m. The bucket
is made of either steel or polyethylene steel is
preferred only if the buggy is also to be used for
hauling hot material, such as hot asphalt.

THANK YOU

Belt conveyor system_Advanced Construction Technology (Semester-6), Civil Engineering

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