A General Approach for Introducing Materials Handling Topics in a ...

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Proceedings of IMECE2005 2005 ASME International Mechanical Engineering Congress and Exposition November 5-11, 2005, Orlando, Florida USA

IMECE2005-82004 A GENERAL APPROACH FOR INTRODUCING MATERIALS HANDLING TOPICS IN A MECHANICAL ENGINEERING DEGREE COURSE W. John Dartnall Faculty of Engineering, University of Technology, Sydney, No. 1 Broadway, Sydney, NSW, Australia, 2007. Email: [email protected]

ABSTRACT This paper outlines the development of the teaching materials for an introductory lecture/chapter in a single semester final-year materials handling course for undergraduate and postgraduate mechanical engineers. The study of materials handling equipment and processes primarily involves the application of mechanical engineering design principles emanating from the mechanics of machine elements, structures, thermo-fluids and particle mechanics. The detail topics of our course are from two main areas: •

Bulk materials handling by screw, bucket and belt conveyors as well as pneumatic and hydraulic conveyors.



Unit (discrete) materials handling of artifacts and manufactured (packaged) products.

For undergraduate and early postgraduate students, we utilize this course to provide an opportunity for students to amalgamate and integrate their engineering knowledge and experiences, and solve complex, real world problems of the materials handling industries. Although the students are mostly fresh from their engineering sciences and hence have skills at applying basic principles, many have little or no practical experience in the materials handling industries. For this reason we start by discussing the significance of the industry and expose them to that fact that these industries have historically expanded from simple (manual) handling to large scale mechanical handling of goods and bulk solids. The particle mechanics aspect of the bulk handling component of the course is relatively unfamiliar to the students. For this reason, after giving our brief history and socio-economic perspective of the materials handling industry, we emphasize general principles related to the handling of particulate solids. We differentiate between design approaches

where designers work from basic mechanics and the common empirical design procedures often outlined by manufacturers. INTRODUCTION Since the industrial revolution, people have made increasing use of mechanical methods of handling materials. This has been to such an extent that in the western world almost everything, including food, raw minerals, building materials and finished products, has probably been mechanically handled many times before it reaches the consumer. The materials handling industry is not only economically significant, but it is fundamental to the productivity of manufacturing and distribution systems (for example, US companies invest over $90 billion annually in materials handling technology and systems). The materials handling industry is very broad, covering almost all industries, including mining, mineral processing, agricultural production, food processing, power production, chemical processing, manufacturing, packaging, pharmaceutical production and many others. Our subject covers the main systems and methods of mechanical handling of materials, both bulk solids handling and unit (discrete) handling of products and goods. Topics include: screw, belt and bucket conveyors and elevators; pneumatic and hydraulic conveying of bulk solids; storage systems; feeding, sampling and weighing of materials and systems for handling artifacts, factory products and packaged goods. We spend most of our semester course on the bulk (or solids) handling topics (retaining one or two lectures for unit handling) as we believe that the bulk handling topics are more relevant to our Australian graduates. We concentrate on bulk materials handling in this chapter whilst unit materials handling is treated later in our course. The teaching approach in this introductory lecture/chapter is to introduce bulk materials handling machines with block diagrams representing screw, bucket belt and other conveyors.

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The main elements of the block diagrams (Figure 5), (motors, mechanical transmissions, bearings, conveying systems, hoppers, chutes, control elements, etc.) are labeled and the design and operation issues surrounding these elements are expanded. The friction losses of mechanical machine elements will be well understood by students, but the internal and external friction of the particulate materials will need introduction. This frictional energy loss is sometimes high. Thus a machine such as a screw conveyor may have unusually high friction loss due to the fact that all carrying surfaces rub against the bulk solids, whereas a belt conveyor, which carries the material on a belt supported by rollers, will usually offer a considerably reduced percentage friction loss. The students are expected to be familiar with the general machine element design, engineering design processes, structural analysis, fluid mechanics and engineering thermodynamics. NOMENCLATURE: CEMA: Conveyor Equipment Manufacturer’s Association γ = bulk density of material (kg/m3) q = load per unit length of conveyor (kg/m) A = cross-sectional area of load on conveyor (m2) = mass flow of material (kg s-1) m& v = bulk mean flow velocity of material (m s-1 ) Q = volume material flow (m3 s-1 ) g = acceleration due to gravity (m s-2 ) L = conveyor length (m) H = height through which material is elevated (m) N = rotational speed (rev/min) ω = rotational speed (rad s-1 ) = theoretical power to elevate the material (kW) PH = power accelerating material loading conveyor (kW) Paccel

Pempty _ conv = power overcoming empty conveyor losses (kW) Pconv _ load = additional power for load on conveyor (kW)

Pdig

= conveyor load digging power (kW)

f1

= mathematical function

Figure 1: Elevator with endless chain (1581) Figure 2 illustrates an endless chain used to haul handtrucks up an incline such as on a ship-loading ramp. Nowadays a few men operating ship-loaders will load thousands of tons in a few hours. The mechanized materials handling industry has moved apace with human progress. It includes the movement and storage of goods and materials. For this reason, the materials handling industry is primarily about its requirement for space for its handling and storage equipment, the consumption of energy for moving the materials and finally, but not least, its requirement for its own space and materials of construction.

f2

= mathematical function k1, k2 … = factors for friction, inertial and deflection losses per unit length of conveyor (kg/m or as appropriate) BRIEF HISTORICAL AND SOCIO-ECONOMIC CONTEXT Human chains were used from ancient times to move materials, for example the moving of rocks and earth to construct a mound on which to build the palace of king Sennacherib. The first illustration (Figure 1) is of an elevator with endless chain, illustrated in AD 1561. Although a similar principle had been used in ancient Egypt in the form of a chain of pots for moving water, it seems to never have occurred to anyone to use it for moving earth during many centuries. In the 1800’s, gangs of humans loaded coal on to ships or railway trucks moving about 3 to 4 tons per day per carrier. Later, wheel barrows were used and then narrow gauge lines with hand trucks; productivity increased to about 10 tons per day per carrier.

Figure 2: Endless chain used to haul hand-trucks up an incline such as on a ship loading ramp (approx. 1900)

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: Ashes, coal, wet Ashes, fly Ashes, gas producer, wet Bagasse Bark, wood, refuse Barley Barytes, powdered Bauxite, ground, dry Bauxite, mine run Bauxite, crushed, 75mm Beans : Brewers grain, spent, wet : Quartz Rice Rock, crushed : Vermiculite, expanded Vermiculite, ore Walnut shells, crushed Wheat Woodchips

Max. Rec. Conv. Slope (degrees)

Angle of Surcharge (degrees)

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Bulk Density

(t/m )

Material

Characteristics

Table 1: A portion of a large table of materials and properties relevant to belt conveyor calculations.

SOME EXAMPLES OF MODERN BULK SOLID MATERIALS HANDLING SYSTEMS AND THEIR CONTEXT Most of the manufactured solids handling equipment is supplied by manufacturers in the form of modular, fabricated products for feeding, conveying, elevating, storing and measuring of materials. The manufacturers offer catalogues containing engineering information and selection procedures. Examples of manufacturers’ catalogue information and solids handling equipment are illustrated in Table 1 and Figure 3. The performance of the equipment is usually significantly influenced by the nature and characteristics of the material interacting with it. For this reason, manufacturers and national standards organizations have developed tables such as Table 1 (for belt conveying) in which various properties and characteristics are listed such as abrasiveness, bulk density, surcharge angle, etc. The three well-known examples in Figure 3 of bulk materials transportation equipment operate on mechanical principles evident from the illustrations. In the bucket elevator, a chain or belt carries a series of evenly-spaced buckets that dig into the material at the lower entry chute/hopper and carry it over the top sprocket, where it is discharged due to a combination of gravitational and centrifugal effects. In the screw conveyor, the material partially fills the voids between flights and is transported due to the rotating screw effect. Overfilling inhibits transport due to rotation of the particulate material. The belt conveyor is primarily used for horizontal transportation with relatively small inclination.

MA MA MA NA NA NA MA VA VA VA NA

0,75 0,70 1,20 0,13 0,24 0,60 2,10 1,10 1,36 1,30 0,70

25 30 30 30 30 10 10 20 20 20 5

25 23 28 30 27 12 15 18 17 20 7

NA

0,90

30

27

HA/S NA HA/S

1,36 0,65 2,15

10 5 20

15 8 18

MA MA NA NA NA

0,25 1,20 0,65 0,77 0,32

20 20 20 10 30

23 20 20 12 27

Characteristics Key: HA/S - Highly abrasive/sharp MA - Mildly abrasive NA - Non-abrasive VA - Very abrasive

Figure 3: Three common bulk solids handling machines: bucket elevator, screw conveyor and belt conveyor

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Figure 5 illustrates an example of a system comprising a combination of machines: a feeder, horizontal conveyor and an elevator. The feeder may control the rate of flow of the material and it discharges on to the horizontal conveyor which discharges into the feed chute of the elevator. The system designer often has to choose between varieties of operating principles for each component of the system. For example, some of the operating principles employed for horizontal conveying are: belt-on-rollers, screw, pneumatic or hydraulic transport in pipes, drag and air fluidization. Over the years, many inventions have occurred in the materials handling industry. Some of these have led to integrated manufactured products, such as the pneumatic grain drill (Figure 4), now commonly used by farmers for continuously sowing crop seeds. This implement contains the following bulk solids handling sub-systems: hopper, seed metering rotary valve, fan, and pneumatic transfer tubes.

loaded with any material. Additionally, the bulk solid will exhibit friction both internally as it moves against itself and externally as it slides against machine members. When a machine is operating 24 hours per day for the whole year (except for down-time) the friction energy can amount to a considerable cost. The machine designer needs to understand where energy is lost and how to maximize the efficiency of these machines. A simplified Conveyor Equipment Manufacturer’s Association [16] (C.E.M.A) formula for power to drive a conveyor belt is: Power (kW) = HWm ⎤ ⎡ 9.81 ⎤ ⎡ ⎢⎣1000 ⎥⎦ Lv ⎢⎣ kX + {kY (Wm + Wb ) + 0.015Wb} + L ⎥⎦

(1)

Where: L

= Horizontal distance between pulley centres (m )

H

= Vertical distance between pulley centres (m)

v

= Belt velocity (m/s)

Wm

= Mass of material per metre run (kg)

Wb

= Mass of belt per metre run (kg)

0.015

= Factor accounting for friction in return belt run

kX

= Factor from belt slip and idler rotational resistance = 0.00068(Wm + Wb) + 0.022(rotating mass of idlers per metre) (kg/m)

kY

= Resistance of belt to flexure as it moves over the idlers. (kg/m)

Table 2: Selection of the kY factor based on belt length, lift and capacity

Figure 4: Pneumatic grain drill for sowing crop seeds [2]. PRINCIPLES OF DESIGN OF BULK MATERIALS HANDLING SYSTEMS For a designer, these systems, which provide flow, storage, measurement and control of the particulate solids, are basically systems of individual machines involving motors, transmissions, friction, corrosion, wear, environmental, structural strength, control, maintenance considerations, etc. The material flow could be called “interrupted-continuous”. This is because it often ceases when emerging from one materials handling machine into the feeding hopper of another. At this point the kinetic energy (and some potential energy) in the material is lost and further energy is often required to feed the material to the next machine, as between the horizontal conveyor in the centre and elevator on the right hand side of Figure 5. The material does not necessarily flow in the familiar way that many liquids do. There is always friction in the machine elements and this is present even when the machine is not

Length m 100 200 200 400 400 800 1000

Lift kY kY kY kY m 500t/hr 1000t/hr 2000t/hr 3000t/hr 20 0.035 0.030 0.026 0.022 20 0.032 0.026 0.022 0.020 40 0.030 0.022 0.020 0.020 20 0.030 0.022 0.020 0.020 40 0.026 0.020 0.020 0.020 40 0.022 0.020 0.020 0.020 40 0.020 0.020 0.020 0.020

A number of other formulae have been used over the years and these are constantly being refined [3, 4, 13, 16]. Software has been developed that assists with design optimizations, taking costs into account [6, 9]. For each of these bulk materials handling machines there are various approaches available for energy analysis. It is worth pointing out that the energy analysis serves a double

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purpose. It enables us to look at the running cost of the machines; it also (iteratively during design) forms a basis for us to design the machine and its elements for strength to accommodate safety and reliability. FUNDAMENTALS OF ENERGY ANALYSIS FOR THESE MATERIALS HANDLING DEVICES We teach students to view the various empirical power equations as being built up from some basic elements. These equations are intended to assist understanding and not necessarily intended for direct use:

1.

Power to lift the material From an ideal point of view, none of these machines needs any power unless it lifts the material, in which case the power consumed will be:

PH = m& gH (W)

(2)

2.

Power to accelerate or decelerate the material Often the machines are required to dig or accelerate a feed material. In this case, the component of power to accelerate the material to a velocity of v will be:

Paccel =

1 2 m& v (W) 2

(3a)

When material exits a conveyor it often loses all its kinetic energy and becomes stationary, in which case the power lost is as in (3).

Pdecel

1 = m& v 2 (W) 2

The power to provide the digging effect will be:

Pdig = Fdig v = Fdigω R (W)

(4)

3. Power to overcome machine friction (other than prime mover transmission losses) Machines are often tested under standard conditions with no material present such as an unloaded belt conveyor operating horizontally. A similar standard test is done with screw conveyors, of standard pitch and mounted horizontally [1, 11, 12].

Pempty _ conv = Lvgf1 (k1 , k2 , k3 ...) (W)

The parameters are like the kX, kY and Wb above and are available from various (manufacturers’) empirical tables.

4. Power to overcome both internal and conveyor/material interface friction due to the material flowing

Pconv _ load = Lvgf 2 (k4 , k5 , k6 ...) (W)

(6)

Again, parameters are like the kX and kY above and are available from various manufacturers’ empirical tables. Generally, equations (5) and (6) involve the following:

P = L × (v, N or Q ) × function (" k " factors )

(7)

(3b) Pdecel = (1 / 2) m& v 2

Vertical Elevator: Requires power to overcome material elevation, as well as frictional, inertial and digging losses in the material. Addionally, machine losses. Types: bucket, belt, aero, screw etc. P = L × (v, N .or.Q )× function.(" k" factors )

Material entering the system (possibly from a storage bin):

M

(5)

Paccel = (1 / 2) m& v 2

Horizontal Conveyor: Requires power to overcome frictional as well as inertial entry and exit losses, in the material. Addionally, machine losses. Types: belt, air slide, pneumatic, hydraulic, drag, screw etc. P = L × (v, N .or.Q )× function.(" k" factors )

Feeder: Controls volume flow rate of entering material. Types: screw, belt, apron, rotary, vibratory and reciprocating. P = L × (v, N .or.Q )× function.(" k " factors )

M

Material exiting the elevator (possibly passing to a chute and processing machine or a storage bin)

Elevated height, H PH = m& gH Pdecel = (1 / 2 ) m& v 2

Material stationary in a feed chute/hopper: Energy lost when material stops and further energy required to overcome digging friction and accererate material.

M Conveyed distance, L P dig = F dig v

Figure 5: Some essential items and principles of bulk solids handling: feeding, horizontal conveying, chute/hopper and elevating.

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EXAMPLES OF INTRODUCTORY ENERGY ANALYSIS PROBLEMS GIVEN TO STUDENTS We illustrate the estimation of power consumption in materials handling equipment with example problems that we treat in two different ways; Firstly, we propose and solve a problem using only the basic principles of the previous section of this paper. Then, we propose and solve some problems using the manufacturer’s code procedures that are commonly used in industry. The code procedures in engineering selection and design are now being replaced by software packages, and, as with the code procedures, the student is at risk of overlooking the need to understand underlying factors and principles. There is ongoing research into the flow of particulate material, and this research requires sophisticated analysis. Later in our course we introduce the students to this approach, pointing out that a clear understanding of the underlying mechanical principles is essential in this research. The outcomes of the research are useful in developing software that can enable a more detailed understanding than the two approaches that we show here. AN EXAMPLE APPLYING BASIC MECHANICAL PRINCIPLES: Our first example for students to consider requires the use of basic energy principles to estimate the power consumption of a bucket elevator.

Pdecel = (1 / 2 ) m& v 2

M Elevated height, H

PH = m& gH Material stationary in a feed chute/hopper: Energy lost when material stops and further energy required to overcome digging friction and accererate material.

Pdig = Fdig v

Figure 6: Diagram illustrating energy requirements for the bucket elevator

Pdig + Paccel + Pelev =

Bucket elevator problem to demonstrate basic principles Estimate the power required to lift wheat grain using a bucket elevator (Figure 6), given the following data: H = 12 m ; N = 160 rpm ; Material flow = 22 tonne/hr Mean chain sprocket diameter = 400 mm Digging force at mean bucket centerline radius of 300 mm, (Although this force fluctuates, a mean value is taken) = 50 N Mechanical (shaft) efficiency of bucket elevator = 85 % Solution, using a fundamental approach & = 22/3.6 = 6.11 kg/sec Mass flow of material = m

Power required for digging the material from the hopper:

Pdig = Fdig v = Fdigω r = Fdig r 2π 50 × 0.3 × π ×

N = 60

160 30

= 251.3 W (8)

Power required to accelerate the material:

Material exiting the elevator (possibly passing to a chute and processing machine or a storage bin)

251.3 + 77.2 + 719.3

= 1,047.8 W (11)

Net shaft power required to drive bucket elevator =

1047.8 ×

100 85

= 1233 W

(12)

EXAMPLES APPLYING SELECTION DESIGN CODES INVOLVING EMPIRICAL PROCEDURES: The examples below illustrate the use of codes, such as the CEMA codes, in selecting bulk solids handling equipment and estimating the power requirement. The code power formulae are constructed along the empirical lines of the previous section. NOTE: In the examples below all references are to the procedures, formulae and tables of the relevant CEMA codes. These codes are published on the websites of several manufacturers [7, 10, 11].

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Paccel =

1 2 1 6.11 ⎛ 160 ⎞ m& v = m& ω r 2 = ⎜ 0.3 × π × ⎟ = 2 2 2 ⎝ 30 ⎠

6.11 × 5.032 2

= 77.2 W

(9)

Power required to elevate the material:

Pelev = m& gH = 6.11 × 9.81 × 12

1. Screw conveyor example: We provide a screw conveyor problem as our first example because it demonstrates rather important issues for students: the influence of friction on system efficiency. Another important issue is that the materials handling industry frequently uses empirical procedures rather than fundamentally derived procedures.

= 719.3 W (10)

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Example: 18 tonnes per hour of brewer’s grain (wet) is to be moved to an elevation of 3 m. Allow sufficient floor space for effective performance of the screw conveyor.

calculate the required horsepower to convey 853 ft3/hr for 38 feet in a 12” conveyor. Using the known factors find that: (16)

Solution 1: using CEMA procedure [1, 4, 7, 10, 11]:

L = 38´ C = 853 ft3/hr N = 67 RPM from step 2 above

Preliminary calculations and conversions to Imperial units.

W = 58 lb/ ft3 from step 1A

Data for brewer’s grain: γ = 55-60 lb/ft3 , CEMA code: 58 C1 / 2 45T, Try an inclination of 150 :

Fd = 55 see Table 1-12, for 12” Fm = 0.8

Fb = 2.0 see Table 1-13 for L

L

Ff = 1 see Table 1-14, standard 30% 150

Fp = 1 see Table 1-15

H=3m

Figure 7: Estimate length of conveyor L = 3/sin(150) = 11.6 m, = 11.6/0.305 = 38 ft (~ 12 m) CEMA Fig 7.1, derating due to 150 inclination ~ 80% & ) = 18 tonne/hr = 18,000/3,600 = 5 kg/sec Flow ( m = 5*60/0.455 = 659 lb/min. Flow (Q) = 659/58 = 11.4 ft3/min = 659x60/58 = 682 ft3/hr Allowing for derating due to inclination, (13) Flow (Q) = 682/0.8 = 853 ft3/hr (1.) Refer to material characteristic table 1-2 for Brewers grain, spent, wet and find: (14) A. γ: 55 – 60 lb/ft3 (use 58 lb/ft3 ) B. material code: C½ - 45T Refer to table 1-1, material classification code chart where: C½ = Fine ½” and under 4 = Sluggish 5 = Mildly abrasive T = Mildly corrosive C. Intermediate bearing selection: L or S Refer to table 1-11 Bearing Selection, Find: L = Bronze S = Nylatron, Nylon, Teflon, Hi-density, Polyethylene, Graphite Bronze, Oil-impreg. Bronze, and oil-impreg. D. Material Factor: Fm = 0.8 E. Trough Loading: 30%A (horizontal standard pitch,) Refer to Table 1-6 capacity table and find 30%A which shows the various capacities per RPM of the standard size screw conveyors and the maximum RPM’s for those sizes. (2.) From Table 1-6, Capacity table under 30%A note that a 12” screw will convey 1,160 cubic feet per hour at 90 RPM maximum, therefore at 1 RPM a 12” screw will convey 12.9 cubic feet. For 853 ft3/hr capacity at 12.9 ft3/hr per RPM, the conveyor must therefore run at 67 RPM (853 ÷ 12.9 = 66.1). (15)

e = .88 see Table 1-17

(4.) Solve the following horsepower equations:

(17)

A. HPf = LNFd Fb = 38 × 67 × 55 × 2.0 = 0.280 1000 1000 B. HPm =

CLWF f Fm Fp 1,000,000

=

853 × 38 × 58 × 1 × 0.8 × 1 = 1.50 1,000,000

Find the Fo factor from 1-16; by adding HPf and HPm and matching this sum to the values on the chart. ( HPf + HPm ) Fo 1.78 × 1.65 C. HPt = = = 3.34 e 0.88 Total power to convey the material horizontally: = 3.34x 0.746 = 2.5 kW (this is all frictional)

(18)

Solution 2: Theoretical power to lift the material:

PH = m& gH = 5 × 9.8 × 3 = 147 W = 0.15 kW

(19)

An approximate total power obtainable from the CEMA procedure for both conveying and elevating the material requires the addition of (18) and (19), giving: Total power to elevate material 2.65 kW (20) Machine efficiency = (0.15/2.65) x 100 = 5.6 %

(21)

Check this problem by the methods of companies such as [9, 11, 12], all of whom use the CEMA procedure. 2. Bucket Elevator example: The bucket elevator requires a smaller floor area than the inclined screw conveyor, and we show it to be a more efficient machine in our second example by applying it to the same problem of elevating18 tonnes per hour of wet brewer’s grain by 3 m.

(3.) With the above information and factors from Tables 1-12 through 1-17 refer to the horsepower formulas on H-22 and

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Solution: using CEMA procedure [10, 11]:

kX = 0.00068(Wm + Wb) + 0.022(rotating mass of idlers per metre) (kg/m) = 0.00068(46.3+60) + 0.022(30) = 0.732

Data: Flow (Q) = 682 ft3/hr as calculated in (13)

kY = 0.035 from Table 1

Material: Brewers grain, spent, wet

(27)

Power (kW) as (1) = Weight per cubic foot: 58 pounds HWm ⎤ (28) ⎡ 9.81 ⎤ ⎡ ⎢⎣1000 ⎥⎦ Lv ⎢⎣kX + {kY (Wm + Wb ) + 0.015Wb} + L ⎥⎦

Capacity:18 tonnes per hour or 682 cubic feet per hour Lump size: small, < ¼ inch

3 × 46.3 ⎤ ⎡ 9.81 ⎤ ⎡ ⎢⎣1000 ⎥⎦100 × 3⎢⎣0.732 + {0.035(106.3) + 0.015 × 60} + 100 ⎥⎦

Percentage of lumps: as above Shaft centres: 10 feet Service: 8 hours per day

= (22)

Referring to Table 1, note that the material is non-abrasive, non-corrosive, but sluggish (angle of repose beyond 45 degrees). Type 100 is recommended. Turning to Table 2, it is found that Type 100 will meet the capacity and lump size requirements. However, since the material is sluggish, the Type 700 continuous elevator is selected as that best suited to handle the material. Referring to the capacity table for Type 700 elevators, it is found that a No. 705 elevator will adequately handle the capacity and lump size of the material. (23) Horsepower is then calculated as follows: SHP = (0.136 + 0.036 x 10) x 58/50 = 0.472 x 58/50 SHP = 0.548

(24)

Assuming a drive efficiency of 85 %, actual required power is then calculated as follows: P = 0.548/0.85 = 0.65 hp = 0.65 x 0.746 = 0.48 kW (25) Efficiency = (0.15/0.48) x 100 = 31 %

(26)

3. Belt conveyor example: The belt conveyor is often used for conveying materials considerably larger distances than the screw or bucket machines, with possible vertical undulation.

Example: 500 tonnes/hour of bituminous coal, 50 mesh and under, to be transported at a velocity of 3 ms-1 100 m and elevated 3 m. The belt used has a mass/unit length of 60 kg/m. Rotating mass equivalent of idlers = 30 kg/m. Solution: using CEMA procedure as in (1) above [1, 6]:

(29)

Theoretical power to elevate material:

PH = m& gH = 139 x 9.8 x 3/1000 = 4.09 kW

(30)

Efficiency = (4.09/19.8) x 100 = 21 %

(31)

DISCUSSION In this introductory lecture we provide a general overview of the bulk materials handling industry. We consider the evolution of this economically and sociologically significant industry from the days when materials were manually handled to current times when almost everything, including food, raw minerals, building materials and finished products has been mechanically handled many times by the time it reaches the consumer of the developed countries. We describe some of the main elements of a mechanical handling systems employed in the movement and storage of particulate materials. We generalize the principles involved in the construction of power estimation formulae and demonstrate some of the code procedures that are employed by the industry. The total design of equipment and systems is to be covered in the remaining modules of the course. The specialised areas include: •

Screw, bucket and belt conveyors (movers).



Hydraulic transport of bulk solids.



Pneumatic transport of bulk solids.



Bins, chutes and hoppers.



Measuring and weighing of bulk solids.



Design tools for the materials handling industry: mathematical modelling, finite element modelling, discrete element modelling and custom software.



System design for materials handling. This is treated by having several real case study projects spread throughout the course. The complexity of the materials handling systems progressively increases with the students’ familiarity with the subject.



Introduction to unit handling principles.

Wb = 60 kg/m

m& = 500 tonnes/hr = 500/3.6 kgs-1 = 139 kgs-1

19.8 kW

& /v = 139/3 = 46.3 kg/m Wm = q = m 8

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CONCLUSIONS Our introductory lecture/chapter provides the students with an overview of the materials handling industry, its economic and sociological context and an introduction to the type of equipment and systems that are commonly used in the bulk handling of materials. We feel that this is important for many Australian mechanical engineers, who are all likely to spend at least part of their working career in dealing with materials handling systems. The systems that our graduates will encounter are most likely to involve particulate materials from the mining and food industries. Having set the above scene, we show in a summary way how a few general mechanical principles underlie the various empirical codes of practice used in the selection of equipment and the design of materials handling systems. We point out that the few general principles are, in effect, preliminary to more advanced analyses that result from research efforts that are constructing a science about the movement and storage of particulate solids. These advanced analyses are likely to become available to practicing engineers in the form of design software. We also point out to the students that the trend towards sophisticated design software is similar to the trend to finite element modelling software used in mechanics, electrical engineering and thermo-fluids that they have already experienced in their undergraduate courses. REFERENCES

[5] http://www.cemanet.org/ [6] http://overlandconveyor.com/ [7] http://www.conveyoreng.com/ [8] http://www.goodmanconveyor.com/ [9] http://www.helixtech.com.au/ [10] http://www.martinsprocket.com/SecH_TOC.htm [11] http://www.screw-conveyors.com/ [12] Lodewijks, Ir. G., 1995; “The Two-Dimensional Dynamic Behavior of Conveyor Belts”, Beltcon conference.* [13] Müller, K. P., 1991; “Do Belt Conveyor Standards Replace Fundamental Principles ?” Beltcon conference.* [14] Nordell, L. K., 1997; “Particle Flow Modeling: Transfer Chutes & Other Applications”, Beltcon conference.* [15] Roberts A. W., 2001; “Design Considerations and Performance Evaluation of Screw Conveyors”. Beltcon conference.* [16] Staples, P., 1981; “Conveyor Design and Design Standards, (Belt Conveyors - Design, Operation and Optimization)”. Beltcon conference.* [17] * Beltcon conferences are on the following website: http://www.saimh.co.za/beltcon/belt_main_index1.html

[1] ANSI/CEMA 350-1988, 1988; “Screw Conveyors”, Conveyor Equipment Manufacturers Association. [2] Bell, Brian, 1996; “Farm machinery”, Farming press books and Videos, Miller Freeman Professional Ltd, UK [3] CEMA, 1997; “Belt Conveyors for Bulk Materials 5th Ed”, Conveyor Equipment Manufacturers Association. [4] Colijn, Von H., 1985; “Mechanical Conveyors for Bulk Solids (Studies in Mechanical Engineering 4)”, Elsevier Science Publishers, Amsterdam.

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