Course Content

1) Materials handling equipment: Excavator loaders,

dragline scrapers, dipper shovels and dragline cranes,
suction dredges and pipelines. Trucks, railroads,
conveyors, wire rope hoists.
2) Requirements of mining machines: Surface
Mining Machinery II requirements; underground requirements. Auxiliary
Equipment. Drainage pumps, mechanically moved
jacks. Ventilator fans, crushers, screen classifiers.
Concentrators, froth floatation and magnetic and
EMM 2409 electrostatic equipment.
3) Mining Power: Diesel-powered engines, electric-
powered engines, compressed air, underground mining
power distribution, mining ventilation equipment, mining
illumination.

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List mining material conveyance

systems.
Material Handling
machinery/ equipment: What are the principle operation
mechanisms? – The mechanics of
Conveyance Material
mining machinery.

EMM 2409 Conveyance O&M – parts and logistics

management.

Future developments– AI and

automation mechanics.

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 Applicability of conveyance Applicability of conveyance

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Applicability of Conveyance: Assignment 1 Example:

a) Select an active mining site.
b) Identify the inefficiency of
material conveyance.
c) Estimate: scalable/ measurable/
determinable ways to mechanize
and automate material
conveyance.

⛏ Groups: 2 members only.

⛏ The Report is to be handed in on
10th March 2025, and the PPT
presentation is on 11th March
2025.

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 Future Mining: Trends, challenges Future Mining: Trends, challenges
and opportunities/ solutions and opportunities/ solutions

Concepts:
v Cyclic mining: raw materials, recycling (urban mining) and re-
use of materials.
v Use of low-grade materials.
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Future Mining: Trends, challenges

and opportunities/ solutions Types of conveyors
a) Deploy some different systems to automation and control to ensure
safety and reliability. a) Belt conveyor Maneuverability:
b) Chain conveyor a) Portable
b) Occupational Health and Safety and environmental management -
safe, efficient and environmentally friendly way. c) Screw conveyor and feeder b) Fixed/ stationary
c) Flexibility to use a conveyance. d) Bucket elevator
e) Pneumatic and hydraulic
d) In-pit crushing and conveying is a way to reduce the haulage fleet
conveyor
significantly.

e) Optimize equipment efficacy and adjust maintenance for equipment

as needed.
f) Cost - transportation of the material can be more than 50% of the
total operating cost for the mine.

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 Introduction
vA belt conveyor is a rubber or textile structure with a belt shape closed
ring, with a vulcanized or metallic joint, used for material transportation.
vBelt conveyors are the most used for the transport of solid objects and
bulk materials at great speed, covering great distances (up to 30 km)

BELT CONVEYORS vA belt conveyor consists of an endless flat and flexible belt of sufficient
strength, made of fabric, rubber, plastic, leather or metal, which is laid
over two metallic flat pulleys at two ends, and driven in one direction by
driving one of the two end pulleys. Material is placed on this moving belt
for transportation.
vThe active half of the belt is supported by idler rollers or slider beds. The
return half of the belt may or may not be supported, as it generally does
not carry any additional load other than its own weight. The endless belt
is kept taught by a belt tensioning arrangement.

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Types of Belt Conveyors Cont. Types of Belt Conveyors

3. Closed Belt Conveyor: In a closed belt conveyor, the specially
1. Flat Belt Conveyor: In this conveyor, the active side fabricated belt, after being loaded with the material, can be
of belt remains flat supported by cylindrical rollers or wrapped completely around the load. It essentially forms a
flat slider bed. The conveyor is generally short in
length and suitable for conveying unit loads like crates, closed tube moving along with the material. The advantages of a
boxes, packages, bundles etc. in manufacturing, closed belt conveyor are: (i) it can handle fragile materials safely
shipping, warehousing and assembly operations. Flat and without breaking by reducing inter particle collision, (ii) it can
belts are conveniently used for conveying parts handle fine bulk materials without being swept by air (however, it
between workstations or in an assembly line in mass is not really air tight at loading and unloading points), (iii) ability
production of goods. to handle corrosive and reactive materials without contamination
2. Troughed Belt Conveyor: In this conveyor, and (iv) the tubed belt can travel around bends in more than one
comparatively wide flat belt is supported on troughed plane and hence versatile in layout.
carrying rollers or shaped supporting surface so that 4. Metallic Belt Conveyor: This is a flat belt conveyor where the
the two edges of the active side of the belt are elevated flexible belt is replaced by a cold rolled carbon or stainless steel
from the middle part to form a trough. This provides a
greater carrying capacity than a flat belt of equal width strip belt of thickness from 0.6 mm to 1.2 mm. The ends of the
for conveying bulk materials or those materials which steel strip are lap joint riveted with a single row of special wide
would slide off flat belts. These conveyors are used in flat head rivets. A steel belt runs flat on cylindrical idlers or runs
handling bulk materials of different classes. The return troughed on resilient idlers (made by suitable length of springs).
side of the belt is generally kept flat supported on Apart from all rolled strip steel belts, wire-mesh, belts of different
cylindrical rollers. designs have been used. The entire length is made up of short
length sections.
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 Cont. Types of Belt Conveyors Main Elements of Belt Conveyor
vBelt vDrive unit
5. Portable Conveyor: Short-length flat conveyors carried on a wheeled structure is
termed portable conveyor. These are particularly useful for loading and unloading of vIdlers vSupporting structure
trucks/ transport vehicles. The inclination of the conveyor can generally be adjusted to vPulleys
suit the application.
6. Chain or Rope Driven Belt Conveyor: In which the specially designed belt is driven
by a moving chain or rope, where the belt only serves as a load carrier, and motion is
by a chain or rope conveyor.
7. Submerged Belt Conveyor: In which a portion of the belt moves through a metallic
trough (casing) which is filled with free-flowing, powdered material at the loading end.
The moving belt with holes, makes the material flow to the unloading end of the trough.

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Main Elements of Belt Conveyor Aspects of Belt Conveyor Design

i. Checking/ determining the capacity of a belt conveyor,
ii. Calculating max. belt tension required to convey the load,
iii. Belt selection,
iv. Selection of driving pulley,
v. Determination of motor power,
(1) Tail pulley (9) Takeup unit vi. Selection of idlers and their spacing.
(2) Snub pulley (at head-end and (10) Carrying idlers (carrying rollers)
tail-end) (11) Pulley cleaner (pulley scraper)
(3) Internal belt cleaner (internal belt(12) External belt cleaner (external
scraper) belt scraper)
(4) Impact idlers ((impact rollers) (13) Head pulley (normally this is
(5) Return idlers (return rollers) discharge pulley and also drive
(6) Belt (continuous loop of carrying pulley)
run & return run) (14) Feed chute
(7) Bend pulleys (15) Skirt-board
(8) Takeup pulley
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 Belt Angle
a) The angle of repose of a material is the acute angle that the surface
of a normal, freely formed pile makes to the horizontal.
b) The angle of surcharge of a material is the angle to the horizontal
which the surface of the material assumes while the material is at
rest on a moving conveyor belt. This angle is usually 5 -15º less than
the angle of repose, though in some materials, it may be as much as
20º less.
c) The flowability of a material as measured by the angle of repose
and the angle of surcharge determines the cross-section of material
load that can be carried safely on a belt.

The angles of repose and surcharge depend on the roughness and

moisture content of grains, granulometric compositions, shapes and
specific gravity of rock particles.

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Limitation and Conclusion Slippage

• Belt slippage typically occurs around the drive/head pulley and happens
Limitation: when the belt and pulley do not have enough grip to adequately turn the
• The construction of a belt conveyor system requires a high capital belt around the pulley.
base. This is a major constraint that limits this work to design only • Belt slipping reduces productivity and efficiency, causing process upsets
and as such performance evaluation cannot be carried out on the or preventing the proper amount of material from being conveyed. It can
belt conveyor system. However, the research work provides design also cause belt wear and damage and put added stress on the motor,
data for the development of belt conveyor systems for industrial resulting in premature failure.
uses.
What Causes Slippage
a) Low temperatures (cold temperatures can reduce the amount of grip
Conclusion: between the pulley and belt)
• The belt conveyor system is designed with a high degree of b) Improperly installed pulley lagging
automation, loading, movement and unloading efficiency. It is also
very flexible, safe, with low initial, operational and maintenance c) Buildup on pulley
costs while eliminating repetitive short-distance movement in the d) Inadequate belt tension
manufacturing industry.
e) Worn head pulley
f) Smooth pulley surface
g) Load that is too heavy for the conveyor.
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 Slippage Slippage
How to prevent slippage: Cont. - How to prevent slippage:
a) Maintaining adequate belt tension is critical to preventing slippage. f) Remove Buildup - Excessive buildup is not only damaging to the belt
b) When there is not enough grip between the pulley and the belt, and idlers, but it can also interfere with how the belt runs.
consider installing lagging. Lagging is a material added to the surface g) Keep Belt Dry - In some cases, a wet belt could be the cause for
of the pulley for increased traction. spillage, as it can promote sticking or slipping of the material on the
c) A snub pulley may be installed. A snub pulley is simply an idler belt. This is often seen with unprotected belt conveyors operating
installed at a point which increases the arc between the belt and outdoors, as they are subject to rain and frost, which can cause the
pulley to improve friction between the two. belt to become slippery. Conveyors operating outdoors should utilize
weather covers or gallery enclosures to protect the material and the
d) Reduce Belt Load - Overloaded belt conveyors also cause spillage. belt. If the belt is operating indoors, identify the source of moisture
CEMA recommends belt loading not exceed 75%. Operations and work to resolve it.
consistently running beyond this should consider a means of either
reducing belt load, or increasing available handling capacity through h) Add a Belt Cleaner - as a preventative measure in reducing spillage
additional or replacement handling equipment. and potential buildup.
e) Increase Angle of Idlers/ Trough Depth - Idlers can be adjusted to i) Add Deck Plates & Drip Pans - Deck plates and drip pans catch
accommodate a variety of trough angles, typically 20°, 35°, and 45°. If falling material, and while they do not prevent conveyor spillage or
the trough is too shallow, material may spill over the edges. By address the root cause, they can help to keep spillage contained.
adjusting the idler angles to form a deeper trough, the material can be
better contained. EMM 2409 Lecture notes 25 EMM 2409 Lecture notes 26

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Capacity of Belt Conveyor

It mainly depends upon the cross-sectional area and speed of belt Force
The limiting ratio of tensions when Tension
tight
force
vBased on uniform feed to the conveyor, cross section area (A) is a slip is about to occur
A = 𝑘𝐵 𝐵 − 0.1 + 0.11𝐵 !tan 𝛼 !#
=e"# Force
where, !$ loose
Tail

B- Belt width, 𝛼- Surcharge angle, k- It’s a constant varies with Where, end

trough angle . P%- Bigger tension in top strand,

Force Tension
vCapacity, Q = 3600A.𝜌.V.K1 P!- Lower strand tension, tight force

where, Θ- Angle of wrap, and

Force
𝜌 −bulk density (ton/m") µ- Coefficient of grip or friction loose
Drive
K1- A reducing factor on inclined and declined conveyor. end

v – speed of the conveyor belt P1

v Value of reducing factor decreases as the inclination angle increases.

We will learn about belt tension q
P2
later in the topic.

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 o Motor o Shaft Design
Pulley Diameter Selection: Power Requirement: § Shaft design consists primarily of
§ The minimum motor power for sizing the determination of the correct
vPulley diameter depends on Total Power is summation of
of the motor is shaft diameter that will ensure
thickness of belts used or for vPower to move empty belt, satisfactory rigidity and strength
surface installation and number vPower to move load horizontally, Pmin = Pp / η when the shaft is transmitting
of plies used in belt. motion under different operating
vPower to move load vertically. Where: Pmin=Minimum motor power and loading conditions. The
Pulley dia. (Dp) = K.i (kW); Pp=Power at drive pulley (3.62 values of belt width and pulley
kW); and η: Efficiency of the reduction diameter help in selecting the size
𝑃 = [𝐾2.(L+45)B.V]+[L. Q ∗ of shaft diameter from different
gear (0.9) Pm=4.022 kW.
10&']+[28Lsin θ.Q∗ 10&'] kw conveyors handbooks.
Where, § To determine the motor horsepower o Control
Where, hp : § Compact Programmable
i- no. of plies (2-12) or thickness
in mm. K !-coefficient which depends on hpmin = Hpreq / η Controllers otherwise known as
application controllers can be
K- 120-150 for stationary surface equivalent mass of idlers & mass Where used for the control of the system.
of belt type selected for job. These controllers can be used for
conveying, 80-100 for main trunk Hpreq = Hpe + Hpm + Hpj time control and supervisory
conveying, 65-80 for gate Θ-Belt inclination. functions such as conveyor speed
conveyor, 50-65 for tail drive Where: Hpe=Horsepower required to control, speed control of individual
drive the conveyor empty, drives, speed and belt slip control,
load equilibration between two
Hpm=Horsepower required to move driving drums and speed
material horizontally, Hpj=Horsepower difference control between two
required to elevate material. motors on one driving drum.

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Maintenance Procedures: Working Of Belt Conveyor System

vRubber or metal bladed wipers located on or near the head pulley of
the conveyor provide adequate cleaning and economical construction. vIdlers are used to protect and support the belt and load to be carried.
vSometimes water spray, compressed air or fixed or power driven vThe spacing of idlers on the loaded run depends on bulk weight of
revolving brushes are used. material and width of the belt.
vTramp iron can be removed from materials carried on belt conveyors (1.2m-1.5m) for < 1ton/m"
by either permanent or electromagnetic pulleys. (1.1m-1.4m) for > 1 ton/m"

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 Advantages Advantages

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Advantages Disadvantages

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 Application Belt Construction
Conveyor belts generally are
composed of three main
components:
1. Carcass
Steel cord
2. Skims
3. Covers

There are two types of belt

available:
1.Rubber belt
2.Steel Cord

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Carcass: The reinforcement Type of belt according to carcass Skims - The rubber, PVC or Covers are used in conveyor belt
usually found on the inside of a material: urethane between plies is called constructions in order to protect the
conveyor belt is normally referred a “skim.” base conveyor belt carcass and, if
to as the “carcass.” In a sense, Skims are important contributors possible, to extend its service life. In
the carcass is in the conveyor addition, covers do provide the finished
to internal belt adhesions,
belt since it must: belt with a wide variety of desirable
impact resistance, and play a
properties, including the following:
a) Provide the tensile strength significant role in determining
necessary to move the loaded belt “load support” and A. Textures: To increase friction,
belt. “troughability.” inclination and to control product
b) Absorb the impact of the • Improper or marginal “skims” B. Cleanability
impinging material being can adversely affect belt
C. A specific coefficient of friction
loaded onto the conveyor belt. performance in general and
can lead to ply separation D. A specific color
c) Provide the bulk and lateral and/or idler junction failure.
stiffness required for the load E. Cut resistance
support. F. Enhanced impact resistance, etc.
G. Hardness
H. Fire Resistance, Oil & Chemical
Resistance

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 Idlers (Rollers) Impact Idlers (Optional) Return Idlers
ü Consists of three separate rollers Types of Idlers:
to support the belt and also bend a) Carrying idlers:
it into a trough shape.
ü The two outer rollers are tilted 1) impact idlers
upwards at an angle of 25o to 30o. 2) trough idlers
b) return idlers Trainer idlers ensure the belt runs
straight and counteract mistracking.

The screw idler is constructed from a

rubber helix. It is used instead of a
scraper, e.g. on mobile belt conveyors.

Idler rollers offer support both to the

belt and its load, prevent sagging,
ensure proper alignment, and remove
carryback.
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Types of carrying idlers Types of carrying idlers

Types of Carrying Idlers 4) Impact Idlers: These are sometimes referred to as
1) In-Line Troughing Carrying Idlers: It consists of three in-line "cushion idlers". They have rolls made of resilient
rolls of equal length. It offers the best troughing shape to material. They are used at loading points to absorb the
carry maximum load. impact resulting from lumps and weight of material to
Troughing idler 2) Offset Troughing Carrying Idler: The inclined rolls are in the prevent belt from damage. This could be the troughed or
same plane offset from the horizontal plane. This type is flat type.
popular in the grain industry where light belt is used. The 35° Troughed training belt 5) Belt Training Idlers: This has the carrying roll frame
difference between this and the in-line idlers is that all three idler mounted on a central pivot perpendicular to the conveyor
Flat belt idler
rolls are longer, and the centre roll is mounted out of the belt. Means are provided to cause the carrying rolls to
line and ahead of the two trough rolls so that the roll become skewed with respect to the conveyor belt
lengths overlap; this overlap is beneficial to the belt in that centreline. As the belt traverses the skewed rolls, they
35° Troughing rubber-
the idler gap is eliminated, and belt idler ends, thereby urge the displaced belt to return to the conveyor
making it more difficult for excess idler grease to damage cushion impact idler centreline, and in so doing, the rolls are urged to realign
the belt cover. properly.
20° Troughing idler
3) Picking Belt Idler: This is also an in line troughing idler but 6) Suspended Idlers: Rolls are linked together and
it has a longer horizontal roll and two short inclined rolls. It suspended on wire rope or rigid frame stringers.
20° Flat belt rubber-cushion
is applicable where belt load must be spread for manual Normally three roll idlers are used for the carrying run
impact idler
inspection and sorting or picking. The inclined end rolls turn and five rolls at the loading point. They are used for
35° Offset troughing idler up the edges of the belt to minimize spillage. heavy-duty earth or ore-moving conveyors. They are
more tolerant to poor alignment and impact loading
because of the flexible connection between rolls.
20° Picking belt idler Suspended three-roll idler

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 Idler selection factors Types and Selection of Drives:
a) Single unsnubbed bare/ Driving Arrangement
Idler selection is governed by three known conditions; the type of service, lagged pulley drive
the characteristics of the material to be handled and the belt speed. b) Snubbed bare / lagged
pulley drive
• Type of service: This include the hours of operations per day, the
c) Tandem drive
overall life expectancy of the conveyor system and the environment in
which the idlers will operate. d) Special drives

• Type of material Handled: The weight of material governs the idler

load and spacing. Lump size increases the effect of weight because of
the impact introduced with it.

• Speed of belt: the effect of various forces are generally enhanced with
the increase in the speed of belt.

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Single unsnubbed bare/ lagged Snubbed bare / lagged Tandem drive: Special Drive:
pulley drive: pulley drive:
Single Unsnubbed Bare / Lagged Pulley Drive: This is the simplest drive Tandem drive: Here belt tension estimated to be high; the angle of wrap is
arrangement consisting of a steel pulley connected to a motor and the belt increased by adopting tandem drives. Both of tandem pulleys are driven. The
wrapped round it on an arc of 180°. This can be used for low capacity short center tandem drive with arc of contact from 300° to 480° or more can operate with one or
conveyors handling non-abrasive material. The pulley may be lagged to increase two motors. The location of such drive is usually determined by the physical
the coefficient of friction. requirements of the plant and structural constraints.

Snubbed Bare / Lagged Pulley Drive: Here the angle of wrap is increased from Special drive: Special drives with snub pulleys and pressure belts used in heavy
180° to 210° or even up to 230°, by providing a snub pulley to the driving pulley. In and long conveyors.
majority of medium to large capacity belt conveyors, handling mild abrasive to
fairly abrasive materials, 210° snub pulley drive with load pulley lagged with hard
rubber is adopted.

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 Tensioning Arrangement
Types of All belt conveyors require the use of some form of take up device
pulleys (Tensioning Arrangement) for the following reasons:
1) To ensure adequate tension of the belt leaving the drive pulley so us
to avoid any slippage of the belt.
2) To ensure proper belt tension at the loading and other points along
the conveyor.
3) To compensate for changes in belt length due to elongation.
4) To provide extra length of belt when necessary for splicing purpose.

Usually there are two types of take up arrangements.

a) Fixed take up device that may be adjusted periodically by manual
operation
b) Automatic take up devices for constant load type

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Manual Screw Take Up: Automatic Take-Up:

• The most commonly used manual take-up is the screw take-up. In a
• In an automatic take-up arrangement, the take-up pulley is mounted
screw take-up system, the take-up pulley rotates in two bearing blocks
on slides or on a trolley which is pulled backwards by means of a steel
which may slide on stationery guideways with the help of two screws.
rope and deflecting pulleys. The carriage travels on guideways
The tension is created by the two screws which are tightened and
periodically adjusted with a spanner. mounted parallel to the longitudinal axis of the conveyor, i.e.,
horizontally in horizontal conveyors (e.g. gravity type automatic take-
up arrangement) and at an incline in inclined conveyors. Hydraulic,
Disadvantage: Pneumatic and electrical take-up devices are also used
The main problem with the use
of manual take-up is that it
Tail pulley take-up
requires a vigilant and careful
operator to observe when take-
up adjustment is required.
Perfect tension adjustment with
this system is also not possible. Vertical take-up
For this reason, these devices
are used only in case of short
conveyors of up to 60m in length
and light duty.
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 Take-Up: Hold Back
• Inclined conveyors require an anti-runback device to prevent reverse
movement of the belts. Such a device is referred to as a backstop, or
holdback. They are also employed on flat, overland conveyors to avoid
the unusually severe shock loading on start-up where the loaded belt
sags between idlers.
• A loaded inclined belt conveyor of sufficient slope tends to move
backwards, when forward motion is stopped by a cessation or
interruption of power or mechanical failure in the driving machinery. The
consequence of this could result in serious belt damage, safety hazard,
and spillage. A backstop is used to prevent this reversal of motion. It is
a mechanical device that allows conveyor to operate in only one
direction (the desired). It permits free rotation of drive pulley in the
forward direction and automatically prevents it in the opposite direction.
Three main designs are used: ratchet and pawl, differential band
brakes and over-running clutch.
vBackstops can be classified either for :
i) low-speed ii) high-speed use.

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Low-speed Backstop Design Types

There are three basic backstop designs that are or have been used to
prevent anti-runback throughout the many years of conveying materials;
a) Rachet and pawl
b) Differential handbrake and
c) The overrunning clutch design

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 Material Density (t/m 3)
Factors selection affecting of belt conveyors Coal 0.8
Solid coal 1.35
1. Material characteristics. Gravel 1.4 – 1.7
2. The length and speed of a conveyor. Dry ashes 0.55 – 0.65
Wet ashes 0.7 – 0.8
3. Required belt tension. Broken sandstone 1.35
4. Troughability of the belt Solid sandstone 2.4
5. Pulleys: The diameter and face width of the pulley affect the Broken limestone 1.45
selection of the belt conveyor. Slag 1.35
Dry sand 1.6
6. Loading and unloading of the material.
7. Cost – the most economical suitable belt to move material as per The belt strength affects the maximum force which can be taken by the belt, and
job requirements should be selected. the value of the maximum force depends on the power required and the drive
head frictional grip. The power required by a belt conveyor can be divided into
three components.
i. power for the empty belt, We
ii. Power to convey the material, W m
iii. Power to raise the material, Wr
The total power required by a belt is then W T = We + Wm ± Wr
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Belt tension calculations criteria: Definition of terms Belt tension calculations criteria: Definition of terms
𝑇) -effective tension required at drive B – Belt weight (kg/m) 𝑇) = 𝑇+ + 𝑇0 + 𝑇5 + 𝑇89 + 𝑇8:
pulley (N) 𝑇+ = 𝑔𝐶𝑄(𝐿 + 𝐿* ) – tension due to 𝑇89 - tension due to force to accelerate material
C – composite friction factor for belt total friction of empty conveyor. It continuously as it is fed onto belt conveyor.
conveyor. compirses of carrying side friction
, 𝑇8: - tension required to overcome friction due to
𝐿* - is the length factor associated with 𝑔𝐶𝑄(! + 𝐿* ) and return side friction accessories e.g. skirt board, tripppers, plows etc. 𝑇% − 𝑇! = 𝑇) ;
C. -./, 𝑇% = (1 + 𝐾)𝑇)
! The minimum recommended belt tension to
L- horizontal length of the belt 1 prevent a sag, 𝑇* is given by;
conveyor 𝑇0 = 𝑔𝐶(𝐿 + 𝐿* )
- tension due to
".34 !
- ;<".$% =& '
load required to move belt horizonatlly. 𝑇* =
Q – weight factor (kg/m) >(@8-)
1
T – the tonnage load on belt (t/hr) 𝑇5 = 𝑔 - tension required to lift For 𝑇* for sag is given as 2%;
".34
load up an inclined belt.
S – speed of the belt (m/s) 𝑇* = 61.25 𝐵 +
1
𝑙*
".34
H – net change in elevation between
loading and discharge points 𝑇) = 𝑇+ + 𝑇0 + 𝑇5 𝑙* = is the normal carrying side idler spacing at
(excluding tripper height). low tension, m.
1 16
𝑇) = 𝑔 𝐶 𝐿 + 𝐿* 𝑄+ ± Sag – belt sag between idlers, m
K – drive factor ".34 ".34
Belt power = T7S, in watts
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 Analysis of belt tension B. Belt tension calculations
Depending on the profile of the conveyor belt and the location of the
3. Horizontal conveyor belt with
2. Horizontal conveyor belt the drive at any point on the
drive and the maximum belt tensions have different magnitudes and with drive near or at the tail
locations, as illustrated in the cases below:
return side

Belt tension calculations

1. Horizontal conveyor
belt with a drive at or
near the head 4. Elevating conveyor
belt with a drive at the
head.

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B. Belt tension calculations C. Belt tension calculations

7. Decline conveyor belt
with tail-end drive (hold
5. Elevating conveyor back)
belt with drive near or 𝑇$ = 𝑔𝐶𝑄(𝐿 + 𝐿% )
at the tail

6. Elevating conveyor
belt with a drive at any 8. Decline conveyor
point on the return side. belt with tail-end
drive (no hold back)
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 D. Belt tension calculations Example

9. Decline conveyor
belt with head-end
drive (hold back)

10. Decline conveyor

belt with head-end Assignment 2: if the location was changed to the tail-end,
drive (no hold back) determine the maximum and the slack side tension.

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Exercise: attempt the

above question of an
elevated belt conveyor
using data values of
the previous example.
Choose either to be
driven at the head or
tail end.

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Assignment 3: decline the conveyor with the drive at the tail-end Types of feeders
a) Screw Feeders - A conveyor screw feeder
can be located at the bottom of storage bin
to control and regulate flow of most
materials uniformly and continuously,
except those materials containing large
lumps or highly aerated fines, or those that
tend to pack.
b) Belt Feeders - A very short conveyor is
installed under a storage facility. Generally,
the belt is flat and is supported on closely
spaced idlers or on smooth slide pates. The
Screw Feeder Belt Feeder feed is controlled by varying belt speed and
by the size of the opening through which
the belt feeder drags its load. Belt feeders
are used for handling fine, free flowing,
abrasive and friable material.

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Cont. Types Discharging or

of feeders unloading of Stationary trippers Movable trippers

material from
Apron Feeder
Drag-scraper Vibrating belt conveyor
Feeder Feeder

c) Drag Scraper Feeders - consist of plates or bars mounted between two strands of
conveyor chain. The plates or bars drag along the bottom of a trough. Drag scraper Two typical movable Movable trippers with
feeders are used for fine or small-lump material. trippers reversible cross-belt.
d) Vibrating Feeders - consist of a pan or trough to which is imparted a vibrating motion so
that the material is impelled in a definite controlled flow. It is normally positioned under
the opening in the bottom of a bin or a hole under a storage pile. Vibrating feeders
handle a wide range of materials but are not good for material that tends to stick and
build up on the surface of a pan or trough.
e) Apron Feeders - are made up of metal plates mounted on or between strands of
conveyor chain. The chains are fitted with rollers that ride on metal tracks. Apron feeders Typical tripper with two Typical movable tripper with
are used for handling abrasive, heavy and lumpy materials. transverse stacker belts. reversible shuttle belts.
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 Screw Conveyor
Trippers
Trippers are devices used to discharge materials from a belt conveyor at points upstream from the head
pulley. A tripper consists of a frame supporting two idling pulleys, one above and forward of the other. The
belt passes over and around the upper pulley and around and under the lower pulley. The material on the
belt is discharged to a chute as the belt wraps around the upper pulley. The chute can be arranged,
augmented by movable gates, to discharge the material to either or both sides of belt conveyor, or onto the
conveyor belt beyond the tripper.
There are two main types of trippers; stationary or movable trippers.
1) Stationary Trippers - This is used where the discharge of material is to occur at a specific location. One
or more stationary trippers can be used on a belt conveyor.
2) Movable trippers - The tripper frames are mounted on flange wheels which engage parallel rails
supported on either side of the belt. The tripper can be moved by a cable winch, by the belt itself, or by
an electric motor mounted on the tripper. Trippers move in both forward or reverse direction to fill a bin
from end to end or to make a long pile on each or one side of belt conveyor. The tripper can be located
in any number of places for spot discharge.

Three auxiliary tripper arrangements are described:

a) Tripper with reversible belt: A movable tripper carries a horizontal cross belt. By means of a gate in the
bifurcated tripper chute, and a corresponding travel direction of the cross belt, material discharged from
belt conveyor can be placed in long piles or windrows on either side of the tripper. Individual piles of
various materials or different grades of the same material can be stockpiled on either side of the tripper.
b) Tripper with two transverse stacker belts: This is used to form higher piles than is possible to form with
a horizontal cross belt. The tripper is outfitted with two inclined stacker conveyors. Continuous high
piles can be built on either side of the
c) Tripper with movable shuttle belt: This also uses a cross belt, which is a shuttle, or movable belt and is
reversible in direction. Flat-topped piles with a large top area can be built with this arrangement.

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Bucket Elevator Design/ fabrication

The capacity of a bucket elevator

mainly depends on the following
factors:
a) Bucket Volume
b) Bucket Spacing
A – Length
c) Belt Speed
B – Width
d) Bulk Density of the Product C – Back height
e) Filling Factor of the Bucket D – Front lid
T – Thickness of
𝐿 × 𝑁× 𝑆 × 𝜌 × 𝐹 the bucket.
𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦, 𝑘𝑔/ℎ𝑟 =
3600
L = Bucket Volume in litres When measuring dimensions B, C and D
N = Number of Buckets per meter make sure the bucket is on a flat surface
and the back is positioned vertically.
S = Belt speed in m/s
T: using a micrometer/ ruler, measure
ρ = Density of product in ton/m3 the thickness of the bucket.
F = Filling Factor is without unit
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 Example:
Given the following data, determine the bucket capacity.
Capacity in Kg/hr = 12000
N = Number of Buckets per meter = 3 (assumed)
S = Belt speed in m/s = 0.8 m/s – standard speed
ρ = Density of product in ton/m3 = 1.6 ton/m3
F = Filling Factor is without unit = 0.6 (assumed)
3600 is seconds per hour
L = Bucket Volume = Unknown

Solution:
12000 = L x 3 x 0.8 x 1.6 x 0.6/ 3600
12000 = L x 0.00064
L = 12000 x 0.00064 In the Gross Volume Column, we have to look for a bucket of 7.6 ltrs.
L = 7.68 Ltrs The bucket No. 25 of 400 mm in length is 8.7 litres. This means that
we will have to select a bucket of 400 mm length and that will give us a
capacity above 12000 kg of sand.
It implies that if you use a bucket of 7.68ltrs then your Bucket Elevator will
give a capacity of 12000 kg/hr.
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Chain conveyor Chain conveyor

The major components of a chain conveyor are :
• The term chain conveyor means a group of different types of conveyors
used in diverse applications, characterised by one or multiple strands of (i) Pulling chain - Different types of chains are used in chain conveyors
endless chains that travel the entire conveyor path, driven by one or a such as round-link, combinations and Link-plate chains
set of sprockets at one end and supported by one or a set of sprockets (ii) Sprocket to drive - The sprockets are made of good grade cast iron
on the other end. with chilled hardened teeth or from cast steel or plate steel. The teeth
are machined to suit type of chain used.
• Materials to be conveyed are carried directly on the links of the chain or
on specially designed elements attached to the chain. The load-carrying (iii) Take-up arrangement The most common type is adjusting screw type
chain is generally supported on idle sprockets or guideways. for positioning the bearing blocks supporting the take-up sprocket
shaft. The range of adjustment should be sufficient to permit initial
• The endless chains are kept taught by a suitable chain tensioning device slack-off of the conveyor chains for joining of two links to make them
at the non-driven end. endless and ample adjustment for initial stretch and subsequent wear/
elongation. The alternative design is counterweighted-type, providing
automatic constant tension in chain. This type provides constant chain
tension under variable temperature conditions also.
(iv) Drive arrangement - Drive for a conveyor generally consists of an
electric motor coupled to a speed reduction gear unit which in turn is
coupled to the driving sprocket.
(v) Various other components specific to various type of chain conveyors.
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 Parts of a chain conveyor Types of chain conveyor
a) Apron or pan conveyor: This is the most common type of chain conveyor. It consists of one or
more strands of endless chain, usually link plate roller type, running in steel guides. Rollers
ensure minimum pulling effort in the chain, while roller guides supported on the superstructure of
the conveyor, carry the entire load of the materials and chains. The carrying surface of the
conveyor is composed of a series of plates or shapes called apron, which are attached to the
links of the chains through cleats. The bed created by the aprons is used for carrying bulk
materials as well as unit loads. When the conveyor aprons have vertical flanges on all sides to
form a pan like shape, if is specifically called a pan conveyor. Materials carried by the apron is
discharged over the sprockets at the driven end, and the conveyor chain with aprons comes
back empty on its return Journey. These are generally slow speed conveyors with a speed range
of 20 to 35 rpm.
b) Cross-bar or Arm conveyor: This type of conveyor consists of a single or two strands of
endless chain, to which are attached spaced, removable or fixed arms (or cross members) from
which materials are hung or festooned. The arms may be replaced by shelves/trays to support
packages or objects to carry them in a vertical or an inclined path. Types include: (i) pendent
conveyor, (ii) pocket conveyor (iii) wire mesh deck conveyor, (iv) removable-crossbar conveyor,
(v) fixed cross-bar (or arm) conveyor, (vi) swing tray conveyor.

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Cont. Types of chain conveyor

c) Car-type conveyor: It consists of a series of small platform cars, propelled by
an endless chain, running on a closed track. Car-type conveyors may have
vertical runarounds over sprockets having horizontal axis. However, more often
they are designed with horizontal runarounds (carousels) over sprockets (or
sheaves for rope drive) with vertical axis. This type of conveyor is also called a
carousel conveyor or a pallet-type conveyor.
d) Carrier chain & flat-top chain conveyor: Carrier chain conveyor consists of
one or more number of endless chains to which may be attached one of the
many different attachments for the purpose of carrying unit materials or objects.
In many cases, the materials are conveyed while being directly in contact with
the chain/chains.
e) Trolley conveyor: These conveyors consist of a series of trolleys supported
from an overhead endless track and propelled by an endless chain or cable,
with the loads usually suspended from the trolleys. This is one of the most
versatile type of chain conveyors which can work in horizontal and inclined
paths, vertical curves and horizontal turns to follow complicated routes.

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