Dr Peter Robinson

Belt conveyors offer numerous advantages for transporting granular materials over medium distances. They are known for their efficient performance, requiring minimal labor and energy input, and therefore belt conveyors are the most widely used system for bulk transportation. Understanding the causes of conveyor idler replacements is crucial since they represent the second highest maintenance cost in this transportation method, following the conveyor belt itself, which accounts for 30% to 70% of maintenance expenses. By analyzing data on the lifespan of 97,778 idler rollers provided by Vale, we have identified the primary factors leading to the replacement of impact, carrying, and return idler rollers. These causes include noise/vibration, wear, and idler seizure. Notably, noise/vibration plays a more significant role in carrying idler roller replacements (74.5%) compared to impact idler roller replacements (46.0%), which are subjected to more severe loading conditions that rapidly lead to seizure. Noise and vibration are consequences of bearing damages like pitting and spalling. In the case of return idlers, wear accounts for approximately three times more replacements than noise (62.0% and 20.6%, respectively). This discrepancy arises because these idlers do not directly bear the load of transported material; instead, abrasive wear occurs due to contact with the belt and the ore adhered to its surface. Understanding these causes of replacements enables us to gain insights into the specific operational conditions of idlers. With this knowledge, we can design more appropriate experimental plans tailored to the reality of belt conveyor idlers. This approach allows for better identification of key tests for determining idler lifespan based on their specific type.

Filtration of coal tailings and refuse has become a critical process, given a continuous push towards dry-stacking methods over conventional dam disposal. Conventionally, this process is achieved by a combination of thickening and mechanical dewatering (cyclones, filter press etc). This paper investigates the feasibility of using an open channel to passively settle coal tailings by particle size. A pilot-scale open channel was built to test coal tailings under a range of volumetric flow rates. Measurements of Particle Size Distributions (PSDs) and solids mass concentration were conducted at the open channel inlet and outlet to reflect the degree of settling. To account for the hindered settling, a modified Stokes' settling model was developed. The model was found to accurately predict observations with only a scalar multiple of Stokes' law for a single particle required, which physically reflected changes in the perceived viscosity by the settling particles. This scalar multiple was then obtained using the pilot-scale measurement data and, as it is a slurry property, this allowed for the prediction of performance under scale-up.

In belt conveying, indentation rolling resistance arises due to the viscoelastic contact between the conveyor belt and an idler roll. As a belt travels over an idler, an asymmetric pressure distribution is formed that opposes the direction of movement, therefore resulting in a drag force to the system. For conventional systems, this resistance can account for up to 60% of the total drive power [1]. Idler diameter is known to have a considerable influence on the indentation rolling resistance of belt conveying systems, by reducing the indentation and contact stress. But how big is too big? As handling equipment becomes more developed and readily available on-site to aid in conveying component installation, larger idler diameters are becoming a more viable option to install on long conveying systems due to their energy-saving potential. This paper presents indentation rolling resistance measurements with idler roll diameters of 152.4 mm, 219 mm, 316 mm and 400 mm to evaluate the influence of larger diameter rollers on energy savings and discusses the considerations for using them in long conveyor systems.

Port Waratah Coal Services has the capacity to export 140 million tonnes of thermal and coking coal annually where each ship loader transports material at a peak rate of 10,500mtph. Port Waratah are considering improvements to the life of the three Shiploader Trimmer Flap chutes as they are currently experiencing excessive wear rates, resulting in premature replacement of the Trimmer Flaps. The Trimmer Flaps are typically replaced due to the failure of the liner plate retaining bolts (welded studs) and the liner plate becoming unsecure in the Trimmer Flap shell. This is hypothesised to be related to the expansion and contraction of the liner plate due to thermally induced loads from the coal flow. This research developed a Discrete Element Model (DEM) to understand the root cause of the identified issues. An analysis has been undertaken involving field measurements and data collection utilising thermocouples, data loggers and thermal imaging cameras. It was observed the failure of the liner plate retaining studs occurred due to excessive temperature cycling as confirmed from field measurements. DEM simulations coupled with heat transfer simulations utilising accurate Shiploader geometry is also considered. Using verified material properties, a model for use in determining a design for prolonged Trimmer Flap life has been completed.

In belt conveying, pulley lagging is the source of necessary friction for power transfer. The constant need to transfer bulk materials at higher rates over longer distances has resulted in a requirement to transfer more power through the drive pulley. Despite these changes, conveyor design standards (ISO5048, DIN22101, CEMA) continue to utilise the over-simplified rope friction model (Euler's equation) to determine power transfer limits. The primary, well-known limitation of this model lies in the assumption of a constant coefficient of friction around the lagging surface that is fully developed. Recent research has demonstrated that the friction between the lagging and belt bottom cover varies with factors such as wrap pressure and speed, resulting in a misrepresentation of the behaviour in the interphase and, consequently, inadequate design of the belt conveyor system.

With recent advancements in conveying technologies, conveyors are required to achieve greater lifts, longer conveying distances and higher throughputs. As such, drive stations continue to increase in size, with gearless drive stations in excess of 10 MW in existence. A significant amount of research has been conducted into the design and optimization of these systems, however, the use of standard methodologies to quantify drive friction is a known limitation that remains. Currently, design standards use Euler's classical 'rope friction' equation to determine drive limitations, with this method failing to account for a variable friction coefficient around the drive pulley. Due to this, the calculated drive is conservative and reaches the limit of efficacy with high-capacity conveyors, due to the high belt tensions required, and the necessary overdesign in structure. This paper investigates the frictional behaviour between a belt conveyor and pulley lagging materials and presents test results demonstrating how the friction coefficient varies with changing load and slip velocity. This improved understanding of the frictional behaviour between the conveyor and drive pulley lagging will further the design capabilities of high-capacity conveyor systems.

It is common practice to analyse the flow properties of a bulk material sample for a range of Moisture Contents (MC). It can also be quite common that the material supplied requires 'drying' to analyse moisture contents at lower values than what may be supplied by the client. This paper investigates the influence of thermal drying techniques on the flow properties of bulk materials. The chosen drying techniques are Air-Drying (AD), drying at ambient temperature and Oven-Drying (OD), drying using an oven at 105 °C. The flow properties of three bulk material samples are considered with each sample compared at the same MC after the drying technique has been undertaken. Each bulk material sample also has baseline testing undertaken at the As-Supplied (AS) condition. To analyse the effects of thermal drying on bulk material flow properties, a case study is also presented to consider the anticipated changes to outlet dimensions for a funnel flow bin design.

A wedged plane-flow hopper and horizontal belt feeder is employed to investigate the flow patterns and stress field redistribution at the hopper and feeder interface. The flow patterns are recorded by a high speed camera in conjunction with coloured material layers. The three-dimensional stress field in the feed zone and its influence on the feeder operation are discussed. The vertical stresses acting on the feeder for initial filling and flow conditions are measured along with longitudinal shear feeder loads. The experimental results are compared with theoretical values derived using relevant feeder load theories. The influences of different filling heights and clearance between the hopper bottom and feeder surface on feeder loads are presented. Numerical simulations using the Discrete Element Method (DEM) are carried out additionally to analyse feeder loads at the hopper and feeder interface, with the results being compared with those obtained experimentally.

Investigation and uptake of filtered tailings continues to grow throughout the globe. This is driven by a wide range of site-specific considerations, which include such factors as tailings characteristics (e.g., amenability to filtration), production rates, climate, water availability, cost drivers, environmental requirements, and social factors. Despite the aforementioned technological growth, the currently available filtration technology is not able to meet the needs of many operations and projects that would otherwise adopt the technology. Experience with large-scale industrial filtration shows that vacuum belt filter systems meet the needs of many modern users, exceptions being the inability to effectively dewater tailings at altitude and/or with a fine particle size distribution: a potential fatal flaw. This paper presents a case study on the utilization of the patented Viper Filtration technology on gold tailings to overcome this challenge and shares the resultant full-scale plant design, highlighting the features designed to overcome cost and scalability deterrents. This technology is a novel mechanical process which complements the vacuum pressure in dewatering the filter cake as it travels along the belt filter. This project commenced with a pilot testing program, which successfully met the objective to rigorously test, measure and record any performance improvements achieved when engaging the Viper technology. Of the two tailings products tested, gross improvements of 4.2%w/w and 5.7%w/w were achieved when compared to the conventional vacuum belt filter operation. This pilot testing facilitated measurement of operating and design data, which forms the basis of the full-scale system design and resultant equipment supply of three vibration roller assemblies for retro-fitting on the existing vacuum belt filter.

The throughput of a belt conveyor system is the primary design parameter when considering a new installation, determined by the cross-section of the material on the belt, coupled with the belt speed. Optimizing this area not only improves efficiency, but also minimizes capital costs through the optimal selection of equipment. Whilst speed-related optimization has seen considerable attention, the cross-sectional area has largely been neglected due to existing design constraints of the system. Conventional belt conveyors typically utilize a 3-idler troughing configuration, which forms a trapezoidal cross-section with a parabolic surcharge. The rigidity of this support directly limits the geometry of the cross-section that may be considered. A new conveyor system developed at the University of Newcastle supports the conveyor belt by a rail-based carriage, with no relative movement between the belt and carriage. This configuration allows the cross-section of the belt to be freely optimized in order to maximize the material throughput for a given belt width, or alternatively to minimize the belt width for a given throughput. This article utilizes the calculus of variations to optimize the form of this cross section, and demonstrates that an increase in throughput of up to 30% is possible, compared to troughed installations.

The energy loss due to indentation rolling resistance in a conveyor belt system can account for up to 60% of the total power usage. It arises due to an asymmetric pressure distribution as a viscoelastic belt cover is indented by a rigid idler roll. This causes a retarding moment on the idler roll, dependent on the load, speed, idler diameter and the properties of the conveyor belt cover. As pouch conveyor systems become more prevalent in industry, the supporting structure, and thus the indentation rolling resistance of such systems is of importance. These designs typically employ curved belt profiles, or spherical idlers in order to aid belt tracking and closing. From this, a spherical indentation into a generalised Maxwell backing is modelled, and compared with experimental values. In addition to this, the strain dependency across the contact is investigated.