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CHAPTER 38
MATERIAL HANDLING
William E. Biles
Mickey R. Wilhelm
Department of Industrial Engineering
University of Louisville
Louisville, Kentucky
Magd E. Zohdi
Department of Industrial and Manufacturing Engineering
Louisiana State University
Baton Rouge, Louisiana
38.1 INTRODUCTION
12 05
38.4.3 Identifying and Defining
the Problem 1220
38.4.4 Collecting Data 12 20
38.4.5 Unitizing Loads 12 23
38.2 BULK MATERIAL HANDLING 1206
38.2.1 Conveying of Bulk Solids 1206
38.2.2 Screw Conveyors 12 07
38.2.3 Belt Conveyors 12 07
38.2.4 Bucket Elevators 12 08
38.2.5 Vibrating or Oscillating
Conveyors
38.5 MATERIAL-HANDLING
EQUIPMENT
CONSIDERATIONS
AND EXAMPLES 1225
38.5.1 Developing the Plan 1225
38.5.2 Conveyors
12 08
1226
38.2.6 Continuous-Flow
Conveyors 12 08
38.2.7 Pneumatic Conveyors 12 08
38.5.3 Hoists, Cranes and
Monorails 1233
38.5.4 Industrial Trucks 1234
38.5.5 Automated Guided Vehicle
Systems 1234
38.5.6 Automated Storage and
Retrieval Systems 1234
38.5.7 Carousel Systems 1236
38.5.8 Shelving, Bin, Drawer,
and Rack Storage 1238
38.3 BULK MATERIALS STORAGE 1212
38.3.1 Storage Piles 12 12
38.3.2 Storage Bins, Silos, and
Hoppers 12 12
38.3.3 Flow-Assisting Devices
and Feeders
12 14
38.3.4 Packaging of Bulk
Materials 12 14
38.3.5 Transportation of Bulk
Materials
38.6 IMPLEMENTING THE
SOLUTION
12 18
1239
38.4 UNIT MATERIAL HANDLING 1219
38.4.1 Introduction 12 19
38.4.2 Analysis of Systems for
Material Handling 12 20
38.1 INTRODUCTION
Material handling is defined by the Materials Handling Institute (MHI) as the movement, storage,
control, and protection of materials and products throughout the process of their manufacture, dis-
tribution, consumption, and disposal. The five commonly recognized aspects of material handling
are:
Mechanical Engineers' Handbook, 2nd ed., Edited by Myer Kutz.
ISBN 0-471-13007-9 © 1998 John Wiley & Sons, Inc.
815044820.003.png 815044820.004.png
1. Motion. Parts, materials, and finished products that must be moved from one location to
another should be moved in an efficient manner and at minimum cost.
2. Time. Materials must be where they are needed at the moment they are needed.
3. Place. Materials must be in the proper location and positioned for use.
4. Quantity. The rate of demand varies between the steps of processing operations. Materials
must be continually delivered to, or removed from, operations in the correct weights, volumes,
or numbers of items required.
5. Space. Storage space, and its efficient utilization, is a key factor in the overall cost of an
operation or process.
The science and engineering of material handling is generally classified into two categories,
depending upon the form of the material handled. Bulk solids handling involves the movement and
storage of solids that are flowable, such as fine, free-flowing materials (e.g., wheat flour or sand),
pelletized materials (e.g., soybeans or soap flakes), or lumpy materials (e.g., coal or wood bark). Unit
handling refers to the movement and storage of items that have been formed into unit loads. A unit
load is a single item, a number of items, or bulk material that is arranged or restrained so that the
load can be stored, picked up, and moved between two locations as a single mass. The handling of
liquids and gases is usually considered to be in the domain of fluid mechanics, whereas the movement
and storage of containers of liquid or gaseous material properly comes within the domain of unit
material handling.
38.2 BULK MATERIAL HANDLING
The handling of bulk solids involves four main areas: (1) conveying, (2) storage, (3) packaging, and
(4) transportation.
38.2.1 Conveying of Bulk Solids
The selection of the proper equipment for conveying bulk solids depends on a number of interrelated
factors. First, alternative types of conveyors must be evaluated and the correct model and size must
be chosen. Because standardized equipment designs and complete engineering data are available for
many types of conveyors, their performance can be accurately predicted when they are used with
materials having well-known conveying characteristics. Some of the primary factors involved in
conveyor equipment selection are as follows:
1. Capacity requirement. The rate at which material must be transported (e.g., tons per hour).
For instance, belt conveyors can be manufactured in relatively large sizes, operate at high
speeds, and deliver large weights and volumes of material economically. On the other hand,
screw conveyors can become very cumbersome in large sizes, and cannot be operated at high
speeds without severe abrasion problems.
2. Length of travel. The distance material must be moved from origin to destination. For
instance, belt conveyors can span miles, whereas pneumatic and vibrating conveyors are
limited to hundreds of feet.
3. Lift. The vertical distance material must be transported. Vertical bucket elevators are com-
monly applied in those cases in which the angle of inclination exceeds 30°.
4. Material characteristics. The chemical and physical properties of the bulk solids to be
transported, particularly flowability.
5. Processing requirements. The treatment material incurs during transport, such as heating,
mixing, and drying.
6. Life expectancy. The period of performance before equipment must be replaced; typically,
the economic life of the equipment.
7. Comparative costs. The installed first cost and annual operating costs of competing conveyor
systems must be evaluated in order to select the most cost-effective configuration.
Table 38.1 lists various types of conveyor equipment for certain common industrial functions. Table
38.2 provides information on the various types of conveyor equipment used with materials having
certain characteristics.
The choice of the conveyor itself is not the only task involved in selecting a conveyor system.
Conveyor drives, motors, and auxiliary equipment must also be chosen. Conveyor drives comprise
from 10%-30% of the total cost of the conveyor system. Fixed-speed drives and adjustable speed
drives are available, depending on whether changes in conveyor speed are needed during the course
of normal operation. Motors for conveyor drives are generally three-phase, 60-cycle, 220-V units;
220/440-V units; 550-V units; or four-wire, 208-V units. Also available are 240-V and 480-V ratings.
815044820.005.png
Table 38.1 Types of Conveyor Equipment and Their Functions
Function
Conveying materials horizontally
Conveyor Type
Apron, belt, continuous flow, drag flight, screw,
vibrating, bucket, pivoted bucket, air
Apron, belt, continuous flow, flight, screw, skip
hoist, air
Bucket elevator, continuous flow, skip hoist, air
Continuous flow, gravity-discharge bucket,
pivoted bucket, air
Belt, flight, screw, continuous flow, gravity-
discharge bucket, pivoted bucket, air
Car dumper, grain-car unloader, car shaker,
power shovel, air
Conveying materials up or down an incline
Elevating materials
Handling materials over a combination
horizontal and vertical path
Distributing materials to or collecting materials
from bins, bunkers, etc.
Removing materials from railcars, trucks, etc.
Auxiliary equipment includes such items as braking or arresting devices on vertical elevators to
prevent reversal of travel, torque-limiting devices or electrical controls to limit power to the drive
motor, and cleaners on belt conveyors.
38.2.2 Screw Conveyors
A screw conveyor consists of a helical shaft mount within a pipe or trough. Power may be transmitted
through the helix, or in the case of a fully enclosed pipe conveyor through the pipe itself. Material
is forced through the channel formed between the helix and the pipe or trough. Screw conveyors are
generally limited to rates of flow of about 10,000 ft3/hr. Figure 38.1 shows a chute-fed screw con-
veyor, one of several types in common use. Table 38.3 gives capacities and loading conditions for
screw conveyors on the basis of material classifications.
38.2.3 Belt Conveyors
Belt conveyors are widely used in industry. They can traverse distances up to several miles at speeds
up to 1000 ft/min and can handle thousands of tons of material per hour. Belt conveyors are generally
placed horizontally or at slopes ranging from 10°-20°, with a maximum incline of 30°. Direction
changes can occur readily in the vertical plane of the belt path, but horizontal direction changes must
be managed through such devices as connecting chutes and slides between different sections of belt
conveyor.
Belt-conveyor design depends largely on the nature of the material to be handled. Particle-size
distribution and chemical composition of the material dictate selection of the width of the belt and
the type of belt. For instance, oily substances generally rule out the use of natural rubber belts.
Conveyor-belt capacity requirements are based on peak load rather than average load. Operating
conditions that affect belt-conveyor design include climate, surroundings, and period of continuous
service. For instance, continuous service operation will require higher-quality components than will
intermittent service, which allows more frequent maintenance. Belt width and speed depend on the
bulk density of the material and lump size. The horsepower to drive the belt is a function of the
following factors:
1. Power to drive an empty belt
Table 38.2 Material Characteristics and Feeder Type
Material Characteristics
Fine, free-flowing materials
Feeder Type
Bar flight, belt, oscillating or vibrating, rotary
vane, screw
Apron, bar flight, belt, oscillating or vibrating,
reciprocating, rotary plate, screw
Apron, bar flight, belt, oscillating or vibrating,
reciprocating
Apron, oscillating or vibrating, reciprocating
Nonabrasive and granular materials, materials
with some lumps
Materials difficult to handle because of being
hot, abrasive, lumpy, or stringy
Heavy, lumpy, or abrasive materials similar to
pit-run stone and ore
815044820.006.png
Fig. 38.1 Chute-fed screw conveyor.
2. Power to move the load against the friction of the rotating parts
3. Power to elevate and lower the load
4. Power to overcome inertia in placing material in motion
5. Power to operate a belt-driven tripper
Table 38.4 provides typical data for estimating belt-conveyor and design requirements. Figure 38.2
illustrates a typical belt-conveyor loading arrangement.
38.2.4 Bucket Elevators
Bucket elevators are used for vertical transport of bulk solid materials. They are available in a wide
range of capacities and may operate in the open or totally enclosed. They tend to be acquired in
highly standardized units, although specifically engineered equipment can be obtained for use with
special materials, unusual operating conditions, or high capacities. Figure 38.3 shows a common type
of bucket elevator, the spaced-bucket centrifugal-discharge elevator. Other types include spaced-
bucket positive-discharge elevators, V-bucket elevators, continuous-bucket elevators, and super-
capacity continuous-bucket elevators. The latter handle high tonnages and are usually operated at an
incline to improve loading and discharge conditions.
Bucket elevator horsepower requirements can be calculated for space-bucket elevators by multi-
plying the desired capacity (tons per hour) by the lift and dividing by 500. Table 38.5 gives bucket
elevator specifications for spaced-bucket, centrifugal-discharge elevators.
38.2.5 Vibrating or Oscillating Conveyors
Vibrating conveyors are usually directional-throw devices that consist of a spring-supported horizontal
pan or trough vibrated by an attached arm or rotating weight. The motion imparted to the material
particles abruptly tosses them upward and forward so that the material travels in the desired direction.
The conveyor returns to a reference position, which gives rise to the term oscillating conveyor. The
capacity of the vibrating conveyor is determined by the magnitude and frequency of trough displace-
ment, angle of throw, and slope of the trough, and the ability of the material to receive and transmit
through its mass the directional "throw" of the trough. Classifications of vibrating conveyors include
(1) mechanical, (2) electrical, and (3) pneumatic and hydraulic vibrating conveyors. Capacities of
vibrating conveyors are very broad, ranging from a few ounces or grams for laboratory-scale equip-
ment to thousands of tons for heavy industrial applications. Figure 38.4 depicts a leaf-spring me-
chanical vibrating conveyor, and provides a selection chart for this conveyor.
38.2.6 Continuous-Flow Conveyors
The continuous-flow conveyor is a totally enclosed unit that operates on the principle of pulling a
surface transversely through a mass of bulk solids material, such that it pulls along with it a cross
section of material that is greater than the surface of the material itself. Figure 38.5 illustrates a
typical configuration for a continuous-flow conveyor. Three common types of continuous flow con-
veyors are (1) closed-belt conveyors, (2) flight conveyors, and (3) apron conveyors. These conveyors
employ a chain-supported transport device, which drags through a totally enclosed boxlike tunnel.
38.2.7 Pneumatic Conveyors
Pneumatic conveyors operate on the principle of transporting bulk solids suspended in a stream of
air over vertical and horizontal distances ranging from a few inches or centimeters to hundreds of
feet or meters. Materials in the form of fine powders are especially suited to this means of conveyance,
although particle sizes up to a centimeter in diameter can be effectively transported pneumatically.
Materials with bulk densities from one to more than 100 lb/ft3 can be transported through pneumatic
conveyors.
The capacity of a pneumatic conveying system depends on such factors as the bulk density of
the product, energy within the conveying system, and the length and diameter of the conveyor.
815044820.001.png
Table 38.3 Capacity and Loading Conditions for Screw Conveyors
Max. Size Lumps
Lumps
10%
All Lumps or
Lumps 20-25% Less
Max.
Hp.
Capacity
at Speed
Listed
Hp at Motor
30 ft 45 ft 60 ft
Max. Max. Max.
Length Length Length
Diam.
of
Flights
(in.)
Diam.
of
Pipe
(in.)
Diam.
of
Shafts
(in.)
Max.
Torque
Capacity
(in.-lb)
Feed
Section
Diam.
(in.)
Hanger
Centers
(ft)
15ft
Max.
Length
75ft
Max.
Length
Capacity
tons/hr ft3/hr
Speed
(rpm)
5 200
10 400
15 600
9
10
10
12
12
12
2l/2
2l/2
2l/2
2l/2
3l/2
2l/2
3l/2
2l/2
3l/2
3l/2
3l/2
3l/2
3l/2
2
2
2
2
3
2
3
2
3
3
3
3
3
10
10
10
12
3/4
3/4
3/4
1
P/2
IV2
ll/2
2
21/4
2V2
2l/2
3
40
55
80
45
7,600
7,600
7,600
7,600
16,400
7,600
16,400
7,600
16,400
16,400
16,400
16,400
16,400
6
9
9
10
0.43
0.85
1.27
1.27
1.27
1.69
1.69
2.12
2.12
2.12
2.25
2.62
3.00
0.85
1.69
2.25
2.25
2.25
3.00
3.00
3.75
3.75
3.75
3.94
4.58
4.50
1.27
2.25
3.38
3.38
3.38
3.94
3.94
4.93
4.93
4.93
5.05
5.90
6.75
1.69
3.00
3.94
3.94
3.94
4.87
4.87
5.63
5.63
5.63
6.75
7.00
8.00
2.11
3.75
4.93
4.93
4.93
5.63
5.63
6.55
6.55
6.55
7.50
8.75
10.00
4.8
6.6
9.6
5.4
11.7
7.2
15.6
9.0
19.5
11.7
14.3
16.9
13.0
20 800
12
1
2
3
60
10
25 1000
12
12
1
2
3
75
10
14
14
14
16
2l/2
2l/2
2V2
3
3l/2
3l/2
3V2
4
45
55
65
50
12
12
12
14
VA
ll/4
ll/4
ll/2
30 1200
35 1400
40 1600
12
12
12
815044820.002.png

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