Emeritus Professor Alan Roberts

We present measurements of the upscattering cross sections of ultracold neutrons (UCNs) from room-temperature hydrogen, deuterium, neon, argon, xenon, C4H10, CF4, and air. The values of these cross sections are important for estimating the loss rate of trapped neutrons due to residual gas and are therefore of importance for neutron lifetime measurements using UCNs. Cross sections were obtained from a combined analysis of the UCN attenuation in a gas cell and direct measurement of the neutrons upscattered in the cell. The effects of the UCN velocity and path-length distributions were accounted for using a Monte Carlo transport code. Results are compared with measurements at higher neutron energy as well as with calculations.

The results of mass-flow hopper arch geometry investigation are presented, which were conducted using a variable geometry plane-flow bin under different surcharge pressures. The influence of surcharge pressures on arching behavior was analyzed. Cohesive arches forming under different outlet openings and hopper half-angles corresponding to one specific surcharge load were measured using a two-dimensional laser rangefinder. The effectiveness of this method of arch profile measurement is demonstrated. Further mathematical characteristics used to describe arch shape are also investigated in this paper.

Train load-out bins are generally large structures that employ flood loading chutes to rapidly load material into wagons. It is often important when designing these structures to consider the dynamic loads associated with the rapid unloading of the material as these loads can often cause vibrations. Typically, calculations for the dynamic loads are based on traditional continuum calculations coupled with site data, as the unloading rate depends on factors such as gate opening time, the corresponding outlet size, train speed, and material properties. The continuum approach has been previously illustrated in the past with a case study [1]. This paper will present results using the Discrete Element Method (DEM) on the same case study and will compare results in terms of instantaneous flow rates, as well as dynamic forces and accelerations of the flowing bulk solid during discharge.

This paper examines the phenomenon of self excited dynamic loads in bins, often referred to as the 'silo quaking' problem. Mechanisms under which pulsating loads may occur in tall mass-flow and funnel-flow bins and silos and in squat funnel-flow and expanded-flow bins are investigated. Based on field observations of coal bins and laboratory studies using model mass and expanded flow bins, approximate theories are presented to described the dynamic loads that are generated during discharge. The shock load amplitude may be calculated and superimposed on the flow loads on the bin walls to predict the most critical loading condition. The combination of the cyclic shock loading with the static and flow loads permit an estimate to be made of the likely fatigue life of the bin. A brief review of the theory of wave motion in stored bulk solids is presented with a view to predicting the period and decay rate of the load pulses. The paper is illustrated by reference to four case study examples concerned with large coal bins.

The mechanics of screw feeder performance in relation to the bulk solid draw-down characteristics in the feed hopper are examined. Taking account of the changing screw geometry and volumetric efficiency along the screw at the hopper interface, a design methodology is presented which permits the determination of the required parameters of pitch, screw diameter and core or shaft diameter to meet specified draw-down objectives. Particular attention is given to the determination of volumetric efficiency, for which a new theory is presented. A theory is also presented for the determination of screw feeder torque; for design convenience, non-dimensional torque parameters are introduced. Both the volumetric efficiency and non-dimensional torque parameters take into account screw geometry and the frictional characteristics of the bulk material on the screw surface. In addition to the foregoing, the limiting condition for axial conveying and feeding to occur is investigated.

Recent developments in the technology of mechanical conveying of bulk solids are reviewed. An overview of technical and economic factors involved in conveyor design is presented. Because of their wide use in bulk solids handling operations, the paper focuses on belt conveyors indicating research developments and design trends. Attention is given to long overland conveyors where the influence of economic and technical considerations in the design methodology are indicated. Aspects of conveyor dynamics are discussed, and research and development work concerned with specific subjects including drive drum friction, rolling resistance, booster drives and bulk solid and conveyor belt interaction are highlighted. Mention is made of other types of belt conveyors notably the Cable Belt system, high lift and pipe conveyors. Other types of mechanical conveying equipment are briefly reviewed and, by way of example, some research developments into the performance of screw conveyors and bucket elevators are presented.

In recent years there has been a steady increase in the number of self unloading ships involved in the world shipping trade. This paper focuses on unloading difficulties encountered on board the M.V. River Yarra, a vessel converted to self-unloading configuration in late 1991 which is now working around the Australian coastline. These difficulties arose when discharging cohesive materials such as gypsum, salt and slag. Due to the design of the reclaimer units a portion of the cargo within each hold was not positively reclaimed. This resulted in large unstable sections of cargo which caused damage to the reclaimer unit when they collapsed. The investigation involved the development of computer based solid models of each hold, the determination of strength and frictional characteristics of the various cargoes and a review of the slope stability of the cargo within the hold. From the solids model, the amount of cargo positively reclaimed and the capacity lost due to alterations to the holds were calculated. Measurement of the frictional and bulk strength characteristics allowed an analysis of the product stability within the hold during reclaim.

The design of screw feeders requires detailed consideration of the geometry at the interface of the screw and the feeder. This paper focuses on the determination of the required screw geometry and variable volumetric efficiency along the screw in order to predict the required parameters of pitch, screw diameter, and core or shaft diameter to meet the stated objectives. Experimental results are presented which corroborate the theoretical predictions. Specific examples are highlighted and the optimization of screw geometry to achieve a required objective such as uniform draw-down is outlined.

This paper deals with the mechanics of homogenization of bulk powders by re-circulating them in a plane symmetric silo. Several blending configurations were investigated from a simple 'hopper-in-hopper' type to a silo with several 'hopper-in-hopper' systems. It is found that the size and geometry of the silo together with the position of the insert play a vital part in determining the degree of homogenization obtained since these parameters significantly influence the velocity differential that is established during flow. Two powders have been tested and results are compared with theoretical conditions. (A)

The design of screw feeders requires detailed consideration of the geometry at the interface of the screw and the feeder. This paper focuses on the determination of the required screw geometry to achieve specified draw-down performance objectives. A theory is presented which takes into account the screw geometry and variable volumetric efficiency along the screw in order to predict the required parameters of pitch, screw diameter, and core or shaft diameter to meet the stated objectives. Experimental results are presented which corroborate the theoretical predictions. Specific examples are highlighted and the optimization of screw geometry to achieve a required objective such as uniform draw-down is outlined.

This paper presents an overview of aspects of tribology as related to the handling of bulk solid materials. The paper is primarily concerned with the evaluation of wall or boundary friction, adhesion and wear in silos, bins and chutes of bulk solid handling plant. The relevant parameters influencing wall friction, such as surface roughness and particle size, are described and the manner in which friction, adhesion and cohesion influence performance of bins and chutes is discussed. Wear in handling plant is discussed with particular attention being focused on the subject of abrasive wear. (from author's abstract)

This paper reviews recent developments in the technology of bulk solids handling. An overview of storage system design including bins and gravity reclaim stockpiles is presented and aspects of feeder performance is given. The importance of wall or boundary friction in hopper and chute design is discussed and the associated adhesion and wear characteristics are outlined in relation to the selection of appropriate lining materials. Problems due to flow instabilities during discharge from coal bins are reviewed; these flow pulsations may give rise to severe dynamic loads on the bin structure. Future directions for bulk solids handling research and development are indicated.

This paper outlines current research into the performance of conical stockpiles employing single and multiple gravity reclaim hoppers and feeders. Experimental studies are described in which the reclaim efficiency of a pilot scale coal stockpile is determined for single and multiple feeders where, for the multiple feeders, the separation distance is varied. A methodology is presented for the computation of draw-down and live capacity. The determination of feeder loads is discussed.

This paper concerns the evaluation of wall or boundary friction, adhesion and wear in bins and chutes of bulk solid handling plant. The relevant parameters influencing wall friction, such as surface roughness and particle size, are described and the manner in which friction, adhesion and cohesion influence performance of bins and chutes is discussed. Particular attention is focused on the subject of abrasive wear. The concept of a Relative Wear Number is introduced and the application of this parameter to indicate zones of wear in hoppers and chutes is outlined. The development of a linear type laboratory wear test apparatus is described and some typical results using this apparatus are presented.

This paper presents an overview of some modern developments in the field of bulk solids handling and conveying with specific reference to coal. A brief review of bin and feeder design is given and the importance of wall or boundary friction in hopper and chute design is discussed. Problems due to adhesion and wear in hoppers and chutes are outlined and indications are given as to how such problems may be minimised. A brief summary of modern developments in belt conveyor technology is included.

This paper is concerned with the performance of gravity reclaim conical stockpiles employing single, double and triple withdrawal hoppers and feeders. Tests using a pilot scale laboratory stockpile test rig are described and results are presented to indicate the reclaim efficiency for a range of hopper configurations. Records of draw-down crater geometry are presented and loads on the reclaim hoppers are shown for a range of consolidation conditions resulting from various stockpile loading and unloading strategies. Based on the model studies, together with field observations, a methodology is presented for gravity reclaim stockpile design.

In a previous paper the properties of Kevlar Aramid fibres and their applications as a reinforcing material for conveyor belting have been reviewed. The paper also included details of a series of fibre pull-out tests that determine the bond strengths at the Kevlar fibre rubber matrix interface for the belting, and further, included a design proposal for a double-lap-joint splice. This Part II paper extends the work of the previous paper with a study of the strength of Kevlar reinforced conveyor belting splices, using experimental and finite element techniques to investigate methods to increase the static strength to be at least equal to the full static strength of the belt (equivalent to 100% splice efficiency).

This paper examines the problems of cleaning conveyor belts utilizing mechanical type scraping devices. Measurements of adhesion of bulk solid particles to belt surfaces are described and the correlation of these results with belt surface roughness conditions is discussed. An indication is given of possible levels of carry-over of bulk solid particles in terms of the interrelation of the roughness conditions of belt and scraper blade surfaces. In this manner, the best likely performance limits of belt scrapers can be specified. Some results of field trials on conveyor belts handling coal in which carry-over has been measured are presented.

An apparatus has been developed for measuring a range of physical parameters of conveyor belts. Belt samples are supported on a soft elastic bed to isolate them from surrounding influences. This paper describes the application of the elastic bed apparatus for measuring the coefficients of rolling and material flexure resistances of belt conveyors. The measurement of these resistances in a laboratory environment is useful to belt conveyor analysts.

The influence of mechanical vibrations on the strength and flow properties of bulk solids is examined. A dynamic shear test is reviewed, and a theory of failure is described. A dynamic model is proposed, this model being used to examine the resonance and damping characteristics of bulk solids; the model permits the combination of Coulomb and viscous damping to be taken into account. The paper also examines the boundary friction and wall roughness characteristics under vibration condtions; a correlation between apparent RMS roughness and wall friction is indicated. The influence of applied vibrations in reducing both bulk strength and wall friction and the consequent influence on bin design and performance are examined.

The interactive roles of mass flow bins and feeders are discussed. The effect of feeder speed, gate height, clearance between the hopper outlet and the feeder surface, method of filling, rate of filling on wall pressures in mass flow bins and feeder load and power requirements of the feeders are highlighted. Measurement of wall pressures suggests that initial pressures during filling are less than hydrostatic, hence initial loads on feeders are less than theoretically predicted. The higher experimental flow loads on the feeders are due to the fact that the measured values of wall pressures toward the vicinity of the outlet of the hopper diverge from the radial stress field theory of Jenike.

This paper examines the performance characteristics of the Ross-type chain feeder used for controlled gravity feeding of rocks in mining operations. A single-block analytical model is examined, and the influence of the various parameters such as chute slope, friction factors, chain mass and chain slope angle on the performance of the feeder is investigated. The applicability of the analytical model is assessed by comparing with experimental results obtained from a small-scale chain feeder test rig.

The interactive roles of mass flow bins and feeders are discussed. The effect of feeder speed, gate height, clearance between the hopper outlet and the feeder surface, method of filling, rate of filling on wall pressures in mass flow bins and feeder load and power requirements of the feeders are highlighted. Measurement of wall pressures suggests that initial pressures during filling are less than hydrostatic, hence initial loads on feeders are less than theoretically predicted. The higher experimental flow loads on the feeders are due to the fact that the measured values of wall pressures towards the vicinity of the outlet of the hopper diverge from the radial stress field theory of Jenike.

This paper discusses the use of an anti-dynamic tube insert for the control of flow patterns and flow pressures in tall grain silos with central and eccentric discharge. The magnitude and distribution of flow pressures in tall funnel flow grain silos is somewhat unpredictable and depends on the location of an effective transition which forms within the stored grain when discharge commences. This effective transition may intersect the wall producing a dynamic overpressure. The anti-dynamic tube insert is designed to prevent an effective transition intersecting the silo wall and causing dynamic overpressure. The results of model studies are presented. Full-scale tests conducted to data show that the system operates as the model predicts and indicates a cost-effective solution for silos with distress.

This paper reviews the basic design methodology of belt conveyors and indicates the advantages of modern design procedures in improving both the performance and economics of belt conveyor operation. Using life-cycle economic analysis, the annual equivalent costs of conveyors, based on capital items and operating costs, are examined in relation to belt width, length and velocity. The economical viability of using narrower, faster running belts is demonstrated. In view of improved conveyor design techniques which account for belt dynamics, lower factors of safety are possible; the associated economic advantages of this improved technology are shown. The application to long distance overland transportation of bulk solids is highlighted.

The present paper examines some of the dynamic interactions that occur between the belt, the structure and the material on the belt. The system can be designed to minimize costly breakdowns due to belt wear, idler bearing failure from belt resonance, splice failure and belt breakage caused by stress waves in the belt. Guidelines are presented for solving many of the dynamic problems that would otherwise lead to increased operating costs.

Wall friction has a significant effect on the gravity flow performance of storage bins and transfer chutes. In storage bins the flow pattern, whether funnel-flow or mass-flow, is governed by the bin geometry with the wall friction characteristics of the hopper surface having a major influence. Wall pressures are also influenced by wall friction with the pressures increasing as friction decreases. Transfer chutes require lining surfaces to have low friction and wear; where the consolidation pressures are low the surface friction angle is shown to increase dramatically. This paper describes laboratory tests which can be simply conducted to examine the friction characteristics of the hopper lining.

Feeders are used extensively in bulk solid handling operations to control the gravity flow of bulk solids from bins and stockpiles. For efficient feeding a mass-flow hopper should be used, the hopper and feeder being designed as an integral unit. The design of feeders requires the loads and power for both the initial filling and flow conditions to be determined. Theories on feeder loads for both axisymmetric and plane-flow hoppers are reviewed and the interrelations with bin wall pressures are discussed. With the aid of experimental data to test the relevant theories, appropriate expressions for estimating feeder loads are recommended.

The bucket elevator is a method of lifting industrial lumpy or granular bulk material either vertically or up steep inclines. Despite their apparent simplicity, the mechanics of their operation are quite complex and often not fully understood. The design and performance of the elevator vary considerably with the flow characteristics of the material to be elevated. Factors such as bucket shape, bucket spacing, speed and feeding arrangement must be considered in the design. The article presents results of an analyses and experimental results of optimal bucket shape and speeds.

The selection of cone geometry and lining materials to ensure mass-flow and the design and construction of the hopper and its support structure are key factors in the performance and economics of the silo. Collinsville Coal Company has recently constructed a 2400 t rail loading silo at Collinsville, Queensland. This paper highlights the unique features of, and outlines the design procedures for this particular silo.

In recent years significant advances have been made in the study of the storage and flow characteristics of bulk solids. As a result there are now well-established materials testing and associated design procedures to enable storage bins to be designed for reliable and predictable flow. The purpose of this paper is to briefly outline the design philosophy of storage bins and bottom reclaim stockpiles. Particular attention is paid to the design procedures based on flow property measurements, techniques for predicting bin wall pressures, feeding of bulk solids from gravity discharge hoppers, and the prediction of flow rates of fine powders from mass-flow bins.

This paper is concerned with the economic and technical feasibility of high speed belt conveying. An economic model is presented which involves the establishment of cost or objective functions which integrate the performance characteristics with the various cost factors involved. The cost factors include energy costs and annual equivalent cost of the conveyor components. With respect to the latter, consideration is given to such factors as equipment or component life, salvage value, taxation rates and rates of return. The effects of inflation and variations in the annual differential escalation in the energy component are included in the model.

The conditions for accelerated or 'fast' flow of bulk solids through transfer chutes of variable geometry and profile are discussed. A simplified chute design theory based on a lumped parameter dynamic model is presented. This model may be applied to chutes of arbitrary geometric profile but the emphasis is given to constant curvature and straight inclined chutes. The effects of variable Coulomb frictional drag resulting from variations in the contact or 'wetted' perimeter of the flowing stream in the acceleration zones are included in the model. The solutions of the flow equations are described where the emphasis is on the determination of the stream thickness variation along the chute. The use of tapered chute sections is discussed. (A)

This paper is concerned with the determination of the effects of mechanical vibrations on the strength and flow properties of bulk solids. The influence of vibration frequency and amplitude on the yield strength, flow functions and wall frictional characteristics is examined with a view to the establishment of criteria for the design of vibrating flow promotion devices used in storage bin operation. (from author's abstract)

This paper is concerned with the determination of the effects of mechanical vibrations on the strength and flow properties of bulk solids. The influence of vibration frequency and amplitude on the yield strength, flow functions and wall frictional characteristics is examined with a view to the establishment of criteria for the design of vibrating flow promotion devices used in storage bin operation. (from author's abstract)

Many industries depend, to a considerable extent, on the need to handle materials in bulk form and it is important therefore that handling systems be designed to operate as efficiently and effectively as possible. One aspect of the handling operations of particular significance concerns the design and operation of storage bins and their associated discharge equipment. While it is usual to rely on gravity flow to discharge the contents of a bin, often there is need to promote and control the flow, particularly in those cases where the storage bin has not been designed to operate under mass flow conditions. Where flow promotion is necessary, the use of devices which impart mechanical vibratons to the bulk solid are used extensively.

Despite their tremendous range and diversity, a great many industries, such as those concerned with mining, manufacturing, agriculture and mineral, chemical and food processing, all rely heavily on a need to handle bulk materials in one form or another. In view of the substantial costs of handling operations, it is most important that these operations be performed as economically and efficiently as possible. Even small incremental gains in efficiency can yield substantial cost reductions. This paper describes a procedure by which the optimum design of continuous conveyors may be carried out. The concepts embodied in the problem formulation and solution have been established first by Roberts and Charlton and further developed by Roberts, Hayes and Scott. In essence the problem involves the minimization of a cost function which takes into account the energy consumption and the annual equivalent capital cost of the conveyor components. The generalized optimization problem is formulated and examples are given to illustrate the application of economic analysis and optimization procedures to the design of enclosed screw or auger conveyors, belt conveyors and bucket elevators.

A range of flow property data and general guidelines for bulk storage of AN Prill are presented. The data is specific to explosive grade prill produced via ICI's patented 'AN NITROPRIL' technology. Prominence is given to the apparent existence of an unusual characteristic believed not to have been previously reported for any bulk granular solid. Laboratory data suggest that under certain conditions there can be a tendency to bridging higher up in the hopper, despite a predicted absence of bridging problems nearer the outlet. This is avoided by limiting maxmum bin diameters.

This paper describes the Industrial Experience Elective Unit Scheme introduced in the Faculty of Engineering at the University of Newcastle in 1974 for part-time students in Bachelor of Engineering degree programs. The objectives and requirements of these units and the experience gained in the operation of the scheme over the past two years are discussed.

The natural responses of linear systems may be found by observation of the system's response to a known stimulus. In such tests, the observations required ore the response as a function of time when the stimulus is deterministic in form. In practical situations, the application of this method is often hampered by the presence in the response of extraneous noise and the necessity of using large-amplitude excitations. The difficulties of the method outlined may be avoided by using random stimuli and cross correlations to obtain a statistical estimate of the natural modes. This paper describes one application in which the critical speeds and relative deflection amplitudes of a machine shaft-rotor system were found with the system either stationary or running at some arbitrary speed. © 1975 Society for Experimental Mechanics, Inc.

The problem of determining the profile of a gravity flow discharge chute so that flow characteristics are to be optimum in some given sense is one of modelling the physical process and solving the resulting describing equations. The paper discusses various possible types of forces retarding the flow of granular materials and describes analytical formulations and solution methods appropriate for finding chute profiles to maximize exit velocity or minimize transit time. © 1975.

Using a single particle model and an assumed resisting force, the problem of finding the required shape of gravity flow discharge chutes to achieve minimum transit time is formulated by breaking up the path into a number of discrete segments. The method and a set of results are compared with an alternative procedure and solution obtained by use of Pontryagin¿s minimum principle. © 1975 by ASME.

One approach to the problem of finding optimum profiles for gravity flow discharge chutes is to model the system in terms of a single, representative particle moving under gravity and subject to various retarding forces. The paper discusses various possible types of forces retarding the flow of granular materials and describes analytical formulations and solution methods appropriate for finding chute profiles to maximize exit velocity or minimize transit time.

In testing some powders on a Portishead shear cell it was found that the sample sometimes becomes grossly inhomogeneous, some portions being much more compacted than others. A suggestion is made that this phenomenon may occur in other cell types without being detected, which would render interpretation of results more difficult, especially as similar inhomogeneities may occur in bulk handling plant. The Jenike shear cell was found to give values of strength of powders considerably greater than those of the Portishead cell. © 1974.

Using a single particle model and an assumed resisting force, the problem of finding the required shape of gravity flow discharge chutes to achieve minimum transit time is formulated by breaking up the path into a number of discrete segments. The method and a set of results are compared with an alternative procedure and solution obtained by use of Pontryagin's minimum principle.

A BRIEF OUTLINE OF THE RESEARCH PROGRAMME OF THE MECHANICAL ENGINEERING DEPARTMENT OF WOLLONGONG UNIVERSITY COLLEGE, N.S.W., AUSTRALIA WHICH ENCOMPASSES CONVEYOR PERFORMANCE STUDIES, GRAIN DAMAGEINVESTIGATIONS, ONE AND TWO PHASE FORCED FLOW OF GRANULAR MATERIALS IN ELEVATED CONDUITS, THE DESIGN OF DISCHARGE CHUTES FOR GRAVITY FLOW INSTALLATIONS AND THE DETERMINATION OF FLOW PROPERTIES OF BULK SOLIDS.(SKH)

Two aspects concerned with the flow control of granulated bulk solids being transported under gravity through discharge chutes are discussed. The first deals with the optimization of chute profile under steady-state operation to achieve specified extremum conditions such as minimum transit time or maximum exit velocity. Three methods of analysis are presented; namely, Pontryagin's Minimum Principle, discrete segment and polynomial approximations, the later is shown to be the most effective. The second aspect involves the application of the pseudo-random binary signals (p. r. b. s. ) and cross correlation techniques to the identification of flow transients in chuts. A pilot study is described and the feasibility of this technique to continuous flow control in mixing and blending operations is discussed.

Using a single particle model and an assumed resisting force, the problem of finding the required shape of gravity flow discharge chutes to achieve minimum transit time is formulated by breaking up the path into a number of discrete segments. The method and a set of results are compared with an alternative procedure and solution obtained by use of Pontryagin's minimum principle.

An analysis of the required profile shape of gravity flow discharge chutes to achieve minimum transit time. The authors develop dynamic equations for a grain element in the flowing stream. They employ energy considerations to derive a functional for transit time and use the Euler-Lagrange equations to derive differential equations for approximate minimum transit time curves. They solve the differential equation, numerically with the aid of a digital computer, to obtain chute profiles for various values of the friction coeffcient and then compare the profiles of minimum time under Coulomb frictional drag with the cycloidal chute profiles that apply when the frictional drag is zero.

An analysis of the required profile shape of gravity flow discharge chutes to achieve maximum exit velocity is presented. The dynamic equations for a grain element in the flowing stream are developed and utilizing energy considerations, an expression for exit velocity is obtained. Maximizing exit velocity involves minimizing losses; on this basis conclusions concerning required chute curvature are drawn. © 1970.

Presented in this paper is a method which allows the determination of stress fields within complex shapes such as are found with agricultural materials; for the purposes of demonstration the loaded wheat grain has been chosen for detailed analysis. By employing photo-elastic and numerical techniques it is possible to obtain quantitative results which show the distribution of stress within a cross-section of a loaded grain. © 1969.

The flow of granular materials through curved or straight discharge chutes is classified as either ¿fast¿ or ¿slow." Fast flow is the more efficient and occurs when the material flows in contact with the chute bottom and side walls, but does not make contact with the top. On the other hand, slow flow occurs when the material is in contact with all four faces of the chute. Under fast flow conditions, the grain stream thickness varies along the chute with the minimum thickness occurring near the point where the mean stream velocity is a maximum. The paper investigates the conditions governing fast flow and presents an approximate analysis to account for the grain stream thickness variation. The analysis, based on the assumption of steady flow, involves the solution of nonlinear differential equations. An equivalent friction coefficient is introduced to account for the frictional drag on the chute bottom and side walls; this friction coefficient is not constant but is found to vary with the changing stream thickness. Results of experimental investigations performed on chutes of known geometric shape are correlated with the analytical solutions. High-speed cine photography is used to determine the actual velocities and paths of individual grains in the moving stream, thus enabling the velocity profiles to be determined at different points along the stream. The paper presents data and recommendations for optimum chute design. These data include suggestions relating to the best chute shape to meet a given set of conditions and information concerning the optimum chute cutoff angles to avoid flow obstructions. © 1969 by ASME.

For the purposes of understanding the way in which wheat grains are able to withstand the loads to which they are subjected during mechanical handling by conveying and processing equipment, it is necessary to have some knowledge of the stress distributions throughout the grain. For light load conditions it is shown that the grain stresses can be analyzed on the basis of elasticity theory employing the Hertz stress analysis. As the loads are increased up to the point of failure the stress distribution is rather complex and difficult to analyze theoretically. It is shown that with the aid of photo-elastic model studies in conjunction with microscopic deformation investigations on actual grains a qualitative analysis is possible. By means of this technique a better understanding of the mechanism of failure is obtained. © 1966, The British Society for Research in Agricultural Engineering. All rights reserved.

The low flexural rigidity of auger conveyors often results in the critical speed for transverse vibrations occurring well within the working speed range of the conveyor. Operation at or near the critical speed should be avoided, not only for the safeguard of the conveying machinery itself, but also because of the increased damage which is inflicted upon the material being conveyed. It is shown that the computation of critical auger speeds can be carried out, with sufficient accuracy for practical purposes, by neglecting the stiffening effect of the helical auger blade. An approximate theoretical analysis of the blade stiffness is presented which serves to explain why the stiffness is negligible in certain cases. An experimental study was performed to correlate the theory and to obtain critical speed measurements of a 6 in auger for comparison with values computed from a theoretical equation. © 1965.

The paper presents a theory, combined with design equations, to compute the loads on structural elements, in particular those of trestle legs of tubular construction supporting load-out belt conveyors, where the trestle legs are substantially buried in gravity reclaim stockpiles. The stress conditions, both active and passive, that arise during filling and reclaim are examined taking into account the position of the trestle supports with respect to the load out conveyor discharge during filling, and reclaim hoppers during draw-down. The theory examines the various loading conditions due to the stored bulk solids focusing on the determination of the lateral or bending load distribution on the trestle support legs. The compressive, in-plane shear traction loads which may influence the buckling effect in the buried legs are also examined.

Rotary plough feeders are widely used in many industries, notably the power generation industry for feeding bulk solids from storage stockpiles and bins to conveyors. They are used in either the fixed configuration in the case of ploughs located under mass-flow storage bins, or in the travelling configuration as in gravity reclaim stockpiles and long plane-flow bunkers. A programme of research at The University of Newcastle has been examining the mechanics of rotary plough operation, both in the fixed and travelling configurations. This paper describes the test rig used for this research and presents results indicating the performance characteristics. The mechanics of operation is investigated and equations for predicting the performance of plough feeders are presented.

This paper presents an overview of the basic principles of blending and mixing in bins. The problems of segregation during filling and discharge are briefly discussed and the salient characteristics of mass-flow as they relate to mixing and blending are indicated. The mechanics of mixing and blending in mass-flow bins using a re-cycling process are described, with an indication being given to the geometrical parameters of the bin that are required in order to achieve good performance. A review of the use of inserts to correct flow problems and to achieve mass-flow is given, with particular mention being made of the cone-in-cone insert developed by Johanson. The application of a hopper-in-hopper plane-flow bin with screw feeder to prevent segregation is described by reference to experiments performed on a pilot scale test rig. Criteria for the correct design of the bin and feeder are given.

This paper presents an overview of aspects of tribology as related to the handling of bulk solid materials. The paper is primarily concerned with the evaluation of wall or boundary friction, adhension and wear in silos, bins and chutes of bulk solid handling plant. The relevant parameters influencing wall friction, such as surface roughness and particle size, are described and the manner in which friction, adhesion and cohesion influence performance of bins and chutes is discussed. Wear in handling plant is discussed with particular attention being focused on the subject of abrasive wear. The concept of a Relative Wear Number is introduced and the application of this parameter to indicate zones of wear in hoppers and chutes is outlined. The development of a linear type laboratory wear test apparatus is described and some typical results using this apparatus are presented.

Conventional troughed belt conveyors have been used extensively in bulk solids handling in industry over a long period of time. While their usage is largely associated with in-plant movement of materials, their application to long distance overland transportation is gaining considerable interest. This paper outlines the objectives to be achieved in increasing the belt width, length and velocity. The use of narrower, faster running belts is shown to be economically viable for long distance overland transportation.

This paper reviews the basic design methodology of belt conveyors and indicates the advantages of modern design procedures in improving both the performance and economics of belt conveyor operation. Using life-cycle economic analysis, the annual equivalent cost of conveyors based on capital items and operating costs will be examined in relation to belt width, length and velocity.

This paper discusses the use of an anti-dynamic tube insert for the control of flow patterns and flow pressures in tall grain silos with central and eccentric discharge. The magnitude and distribution of flow pressures in tall funnel flow grain silos is somewhat unpredictable and depends on the location of an effective transition which forms within the stored grain when discharge commences. This effective transition may intersect the wall producing a dynamic overpressure. The anti-dynamic tube insert is designed to prevent an effective transition intersecting the silo wall and causing dynamic overpressure. The results of model studies and full scale testing in a wheat silo are presented.

This paper examines the surface friction and wear characteristics for bulk solids in motion against hopper, chute and feeder walls in bulk handling operations. In hopper design, wall friction has a significant influence on the flow patterns generated and gravity flow performance. While reliable gravity flow in hoppers requires low wall friction, it is inevitable that wear will take place. Procedures are presented for determining specific wear in bins indicating zones of high potential wear and where hopper linings may need to be made thicker. A method to predict the wear characteristics of chutes and feeders is also presented.

Recent research has concentrated on the analysis of transverse and longitudinal vibrations of conveyor belts. In the case of transverse vibrations, belt tension, troughing configuration and idler spacing are of significance. For the longitudinal mode the starting and stopping characteristics are important from the point of view of dynamic stresses induced. Based on this research, a general approach to conveyor design will be discussed which includes much of the known dynamic behaviour observed in operation. Computer flow charts are used to describe the method for including dynamic analysis into conveyor design.

This paper examines the performance characteristics of the Ross-type chain feeder used for the controlled gravity feeding of rocks in mining operations. A single block analytical model is examined and the influence of the various parameters such as chute slope, friction factors, chain and chain slope angle on the performance of the feeder are investigated. Of particular interest is the range of chute slope angles defined by the limits for braking and feeding. The applicability of the analytical model is assessed.

Many industries throughout the world depend to a considerable extent on bulk materials handling operations. The cost of handling bulk materials is very substantial and in many instances constitutes a major portion of the final product cost. For this reason, it is important that bulk materials handling plant be designed and operated with a view to obtaining high efficiency and reliability coupled with maximum economy. As a part of this goal it is necessary that as much information as possible be collected on the bulk solids handled and on the operating conditions under which handling and storage is expected to occur.

Conventional troughed belt conveyors have been used extensively in bulk solids handling in industry over a long period of time. While their usage is largely associated with in-plant movement of materials, their application to long distance overland transportation is gaining considerable interest. This is made possible with the development of steel cord reinforced belts, with considerable potential being seen in the new belt reinforcing materials which offer significant reduced weight advantages. This paper reviews the basic design methodology and outlines the objectives to be achieved in increasing the length of belt conveyors. Using life-cycle economic analysis, the annual equivalent cost of conveyors based on capital items and operating costs, is examined in relation to belt width, length and velocity.

At present belt conveyor systems are designed according to belt manufacturer's handbooks or standards such as 1S05048 and DIN22101. These designs are based on static analysis methods and do not contain guidelines for incorporating the dynamic behaviour of the moving belt. Large factors of safety are traditionally employed to accommodate most dynamic stresses in the belt. A general approach to conveyor design is discussed which includes much of the known dynamic behaviour observed in operation. Computer flowcharts are used to describe the method for including dynamic analysis into conveyor design.

This paper examines the surface friction and wear characteristics for bulk solids in motion against hopper, chute and feeder walls in bulk handling operations. Procedures are presented for determining specific wear in bins indicating zones of high potential wear, and where hopper linings may need to be made thicker. Wall friction is examined, the influence of such factors as particle size distribution, wall roughness, moisture content and contact time of bulk solid on the wall being described.

The influence of mechanical vibrations on the strength and flow properties of bulk solids is examined. A dynamic model is proposed and the fundamental characteristics of bulk solid vibrations are investigated with a view to the establishment of a dynamic shear failure criterion. The influence on storage bin design and performance is examined.

An analysis of the required profile shape of gravity flow discharge chutes to achieve minimum transit time. The authors develop dynamic equations for a grain element in the flowing stream. They employ energy considerations to derive a functional for transit time and use the Euler-Lagrange equations to derive differential equations for approximate minimum transit time curves. They solve the differential equation, numerically with the aid of a digital computer, to obtain chute profiles for various values of the friction coeffcient and then compare the profiles of minimum time under Coulomb frictional drag with the cycloidal chute profiles that apply when the frictional drag is zero.