Load-haul-dump Research Articles

The influence of the operating environment on manual and automated load-haul-dump machines: a fault tree analysis

The automated load-haul-dump (LHD) machines have the potential to increase productivity and improve safety, but there are many issues to be considered when optimising the operation of LHDs. Today's focus on improved equipment reliability is part of the problem, and another difficult issue is the special conditions and constraints of the operating environment. For automated LHDs, the latter issue is even more important, as humans have been removed from the production area and are not close by to solve the problems. The purpose of this paper is to find the causes of LHD idle time and to study their impact on the operation of LHDs. In this study, real-time process data and maintenance data from an underground mine in Sweden have been refined and integrated. The study takes into account the complexity of the mine environment, discusses the factors to be considered when optimising and automating the operation and uses fault tree analysis (FTA) to analyse the idle time.

Reliability estimation using a genetic algorithm-based artificial neural network: An application to a load-haul-dump machine

In this study, a neural network-based model for forecasting reliability was developed. A genetic algorithm was applied for selecting neural network parameters like learning rate (η) and momentum (μ). The input variables of the neural network model were selected by maximizing the mean entropy value. The developed model was validated by applying two benchmark data sets. A comparative study reveals that the proposed method performs better than existing methods on benchmark data sets. A case study was conducted on a load-haul-dump (LHD) machine operated at a coal mine in Alaska, USA. Past time-to-failure data for the LHD machine were collected, and cumulative time-to-failure was calculated for reliability modeling. The results demonstrate that the developed model performs well with high accuracy (R2=0.94) in the failure prediction of a LHD machine.

Influence of Driving Speed, Terrain, Seat Performance and Ride Control on Predicted Health Risk Based on ISO 263I-I and EU Directive 2002/44/EC

Operators of load-haul-dump (LHD) vehicles are commonly exposed to whole-body-vibration (WBV) levels above ISO 2631–1 and EU Directive 2002/44/EC guidelines. WBV was measured at the floor and seat while the same operator drove two LHDs on a controlled test track while driving speed, bucket load, ride control, terrain type, driving task, and seat optimization were varied. Frequency-weighted RMS acceleration was calculated and A(8) values were modeled for six driving scenarios. Vibration exposure was lowest when the LHD was driven at the lowest speed, forward, over smooth terrain, with ride control on and the bucket loaded (0.20 m/s2). The A(8) decreased from 0.84 m/s2when driving with ride control off, over mixed terrain using all gears, to 0.53 m/s2when driving with ride control on and an optimized seat. The estimated daily exposure decreased but remained just above the ISO 2631–1 and EU Directive 2002/44/EC guidelines.

Hard-rock LHD cost estimation using single and multiple regressions based on principal component analysis

In feasibility studies and mine planning, accurate and effective tools and methods facilitating cost estimation play an important role. Load–Haul–Dump (LHD) machines are a key loading and haulage equipment in most of the underground metal mines and hard rock tunnels. In this paper, a cost estimation model of these vehicles has been presented in the form of single and multivariable functions. These functions have been provided on the basis of costs types (i.e. capital and operating costs) and motor types (diesel and electric). Independent variables, in the single regression analysis is bucket capacity and in Multiple Linear Regression (MLR) analysis include bucket capacity, overall width, overall machine height and horse power (HP). The MLR is conducted in three steps. First, with the help of Principal Component Analysis (PCA), correlation between independent variables is omitted. Thereafter, significant PCs are selected and used as independent variables in the MLR functions. Finally, the cost relationships are established as functions of initial LHD variables. The mean absolute error rates are 11.59% and 6.87% for the single and multiple linear regression functions, respectively.

DESIGN FOR RELIABILITY AND MAINTAINABILITY USING FMECA: CASE STUDIES OF MOBILE UNDERGROUND MINING EQUIPMENT

Underground mining equipment must be designed to survive very demanding, and often unpredictable, operating conditions – hence reliability of equipment designs is crucial. Conversely, the underground mining environment imposes severe logistical constraints on equipment maintenance and repair – hence maintainability is also a significant design goal. This paper presents the outcomes of case studies related to the Design for Reliability and Design for Maintainability of mobile underground mining equipment. Failure Modes, Effects, and Criticality Analysis (FMECA), a well established tool for both reliability and maintainability analysis, is employed. The case studies deal with a Load-haul-Dump (LHD) vehicle and an underground truck. The specifics of the analysis methodology adopted, levels of effort, outcomes, and practical lessons learnt are discussed. The relationship between such FMECA analysis and the wider issues and implications of adoption of Related Centred Maintenance (RCM) by both mining equipment manufacturers and mining companies is also explored.

Virtual-Prototyping Oriented Key Research and Development System of Load Haul Dump

According to the development status of underground load-haul-dump vehicle (LHD) development, a virtual-prototyping oriented key research and development system of LHD is proposed. Based on the driven oriented and top-down design concept of virtual-prototyping, combining the overall performance design, multi-body system dynamics oriented characteristic analysis and simulation, machine assembly, main parameters verification and sub-system of LHD design, the new innovation design development system for LHD development is formed. A case study of a three cubic LHD design process is given, considering the multi-body dynamics oriented simulation of LHD overall performance ,the structure strength analysis and fatigue analysis of key components, mechanism optimization design and dynamic kinematics analysis of working device, stability, ergonomics and ROPS/FOPS (Roll-Over Protection System / Fall-Over Protection System) of driving cab, the satisfied design results is finally obtained.

Influence of Vehicle Size, Haulage Capacity and Ride Control on Vibration Exposure and Predicted Health Risks for LHD Vehicle Operators

Documented whole-body vibration (WBV) exposure levels at the operator/seat interface are limited for underground mining load-haul-dump (LHD) vehicles. Therefore, WBV exposure during the operation of eight small and nine large LHD vehicles, under loaded and empty haulage, was measured in accordance with ISO 2631–1 guidelines. Vibration exposure was also measured for a subsample of LHD vehicles equipped with a feature designed to reduce vibration exposure (ride-control). Operator health risks were predicted according to ISO 2631–1 health guidance caution zone (HGCZ) limits for daily vibration exposure. Vibration exposure was not significantly different for vehicle size or ride control but was significantly lower when driving with a loaded haulage bucket. All operators of small LHDs and one large LHD operator were exposed to vibration levels above the HGCZ.

Robotic mapping of underground mine passageways

The ability to determine the position and orientation of vehicles in real time is a key enabling technology for automation, traffic management, and to ensure safety in the presence of multiple operating vehicles. As explained in this paper, despite some misguided advertising within the mining community, a technology comparable to the satellite based global positioning system (GPS), does not yet exist for underground operations. This paper reports on the preliminary results of a study to develop a relatively low cost and robust method for obtaining globally consistent maps of underground mine environments, the purpose of which is to support the creation of a map based underground positioning technology. The described mapping technique is based on an approach from the mobile robotics research literature and is demonstrated by using data acquired with a load–haul–dump (LHD) machine at two Nordic mines.

New approach for rapid preparation of block caving mines

Block and panel caving is one of the most suitable methods for exploitation of large massive ore bodies where a high rate of extraction is required. However, many authors have studied the rate of extraction and concluded that it may be limited by the ability to prepare mines at high rates. Different approaches, to increasing the rate of extraction, tend towards the introduction of some kind of continuous drawing and materials handling on production levels, which apparently are close to reaching a practical solution. However, corresponding studies to match the rate of mine preparation to high extraction rate operations have not been discussed or published to any great depth. This paper describes some layouts and constructive techniques compatible with rapid mine preparation demand. A significant reduction of time in mine preparation, in both underground drifting and construction, is expected as a consequence of the introduction of non-blasting excavation methods and using precast concrete modules to build up underground mine construction. The main advantage of non-blasting drifting is the predictability of finishing underground drifts, such that it is possible to standardise all the components of single underground mine constructions (i.e. drawpoint and dump points). The solution requires adapting and developing both new equipment and new layouts, because neither standard full face boring machines nor current layouts for conventional block/panel caving are suitable to high speed development of caving levels. The layouts discussed focus on conventional load–haul–dump units and on mechanised continuous drawing system arrangements. In each case, the general arrangement presented has been developed by JRI Ingeniería S.A. as part of its technological innovation policy. Finally, an evaluation of the impact upon scheduling and costs is presented in comparison with conventional methods. New approaches are also mentioned about other issues such as logistics and commissioning, with new actors in the business, which may produce additional benefits for project and operation management.

Why vehicle design matters: Exploring the link between line-of-sight, driving posture and risk factors for injury

Load haul dump (LHD) vehicles have been involved in workplace accidents resulting in fatal injuries and LHD operators also report high rates of musculoskeletal injury. Poor line-of-sight (LOS) and awkward postures adopted by the LHD operator increase the risk of driving related accidents and musculoskeletal injury. The purpose of this case study was to simultaneously measure point of regard (POR), driving posture and sitting position during the operation of a LHD in an underground mining environment in order to further understand the link between these variables and the design of the LHD vehicle. A 5.35 m3 bucket LHD vehicle was used and several driving tasks were analysed. The case study results showed that despite the driving task, the operator looked to the left side of the vehicle 65% of the time. Postural implications include extreme neck rotation (> 40 degrees) for 85% of the work cycle and the average peak compression at L4/L5 was 1843N. Despite changes in driving posture the average center of pressure location for the seated operator moved very little; however changes in peak pressure were observed. The design of the LHD vehicle dictated what the operator could see, which had a direct influence on driving postures adopted by the operator and resulted in several risk factors for musculoskeletal injury.

Using visibility tools in Classic JACK to assess line-of-sight issues associated with the operation of mobile equipment

Several methods exist for measuring line-of-sight (LOS) associated with the operation of operator controlled mobile equipment but there is no consistent criteria used for all machine types or operating scenarios. Moreover, the standards that do exist are not particularly applicable for carrying out LOS analysis on mobile mining equipment. This paper describes a new method to evaluate LOS associated with the operation of mobile equipment, the LOS boxplot. The human simulation program, Classic JACK was used to analyse LOS from the operating position of five different load-haul-dump (LHD) vehicles, typically used in underground hardrock mining. The LOS boxplot method was able to demonstrate LOS associated with five LHD vehicles, and it was able to illustrate LOS improvements associated with the design modifications tested. The examples provided also show the applicability of the method for evaluating operator LOS from other types of heavy equipment.

Predicting discomfort scores reported by LHD operators using whole-body vibration exposure values and musculoskeletal pain scores

Laboratory studies have typically been used to establish a relationship between whole body vibration (WBV) magnitude, frequency, exposure duration and reported discomfort. However, the relationship between subjective reports of discomfort, and predicted comfort response according to International Standards Organization (ISO) 2631-1, predicted health risks according to ISO 2631-1 and reported musculoskeletal discomfort has not been examined. The purpose here was to compare discomfort values predicted by ISO 2631-1 with the subjective discomfort reported by nine Load-haul-dump (LHD) operators during typical operating conditions. Vibration exposure at the operator/seat interface was measured and processed, for one-hour duration, according to criteria established in ISO 2631-1. Vibration total values were determined for 1-minute exposure periods and the LHD operators provided a discomfort score associated with the same vibration exposure period. A linear regression analysis and correlation was carried out to determine the strength of the relationship between the predicted subjective reports of discomfort, ISO 2631-1 discomfort, objectively measured acceleration levels and reported musculoskeletal discomfort. Reported discomfort was poorly correlated to ISO discomfort scores (r=0.1799). Vibration exposure values and Musculo-Skeletal Disorder (MSD) variables were related to both ISO 2631-1 discomfort and to reported discomfort. The MSD scores produced stronger relationships with reported discomfort scores than did the vibration exposure values.

Maintenance and reliability analysis of a fleet of load-haul-dump vehicles in an underground hard rock mine

Equipment failures and unscheduled maintenance contribute significantly to losses in production and unnecessary capital investments for new machinery. This study investigates the mechanical breakdowns and accompanying repair hours of 13 Load-Haul-Dump (LHD) vehicles, also called scoop trams, from January 2006 to May 2007 at a typical underground hard rock mine in the Sudbury area at Ontario, Canada. The investigation was initiated to evaluate the maintenance characteristics of the machines and provide a statistical analysis of the causes for equipment failures and breakdowns. Graphical methods in conjunction with analytical and statistical methods have been applied.

Hazard identification for equipment-related fatal incidents in the U.S. underground coal mining

Based on the number of fatalities per year, a persistent area of concern in mine safety continues to be equipment related. Data from the period 1995 through 2007 were studied in order to identify major hazards for underground mining equipment-related fatal incidents and to perform an analysis of those that occurred over the last 13 years. Reports on equipment-related fatal incidents were obtained from the Mine Safety and Health Administration (MSHA). The results show that underground mining equipment including continuous miner, shuttle car, roof bolter, load-haul-dump (LHD), longwall and hoisting contributed to a total of 69 mining-related fatalities. The study reveals that the major hazard for continuous mining equipment-related fatal incidents is “Failure of victim to respect equipment working area”, while the highest number of fatalities for shuttle car is attributed to the hazard “Failure of mechanical components.” The study further reveals that the highest number of fatalities for roof bolter, LHD, and longwall are attributed to the hazards “Working under unsupported roof”, “Failure of management to provide safe working conditions”, and “Failure of mechanical components”, respectively. It is determined that one fatality for the hoisting system is attributed to the hazard “Failure of mechanical components” and one to the hazard “Failure to follow safe maintenance procedure”. Finally, approaches to prevention were also discussed in this paper.

Using virtual computer analysis to evaluate the potential use of a camera intervention on industrial machines with line-of-sight impairments

A medium-sized Load-Haul-Dump (LHD) mining vehicle was evaluated using visibility tools in a computer simulation environment. The line-of-sight (LOS) available to the operator of a medium-sized LHD was calculated and displayed in a boxplot. Severe LOS restrictions were observed to several areas around the vehicle. A modified LHD design, aimed at improving LOS resulted in a marginal improvement in driver LOS (20–36%). Secondary viewing systems have not been widely accepted in the mining industry but several potential locations can be easily evaluated using computer simulation. This paper tested three camera locations for their ability to increase LOS to areas around the LHD vehicle that were very difficult to see from the operator's position. All camera locations were able to significantly improve LOS to 60% or greater while combinations of forward-facing and rear-facing cameras could improve LOS by as much as 80%. Relevance to industry Several industries have successfully added closed-circuit camera systems as a driving aid for vehicles with poor LOS from the operator's compartment. The mining industry has yet to adopt a widespread camera intervention on all vehicles. This paper demonstrates the potential utility of using computer simulation to evaluate camera locations on a vehicle and discusses some outstanding issues behind the ergonomics of implementing and using camera views on industrial vehicles.

A laboratory study to quantify the biomechanical responses to whole-body vibration: The influence on balance, reflex response, muscular activity and fatigue

To determine the acute effects of whole-body vibration (WBV) on the sensorimotor system and potentially on the stability of the spine, different biomechanical responses were tested before and after 60 min of sitting, with and without vertical WBV, on four different days. Postures adopted while sitting and the simulated WBV exposure corresponded to large mining load haul dump (LHD) vehicles as measured in the field. Twelve males performed trials of standing balance on a force plate and a sudden loading perturbation test to assess back muscle reflex response, using surface electromyography (EMG). This latter test also allowed to assess if any muscle fatigue occurred as a result of the exposure. First of all, it was shown that back muscle activity while sitting with vibration was significantly higher as compared to back muscle activity while sitting with no vibration. However, WBV per se elicited very few effects on the other outcome variables and thus not supporting our hypothesis that WBV had any effect on spinal stability. Though WBV may not have elicited any effects, new findings have emerged concerning the effect of sitting on muscle fatigue and balance. It was shown that sustaining trunk sitting postures corresponding to mining vehicle operators generate back muscle fatigue. Unexpectedly, standing balance was also improved. The possible explanations and relevance of these findings are discussed. Relevance to industry Occupational groups exposed to WBV while sitting are at increased risk for low back disorders. The results of this study do not support the possible injury pathway linking WBV and back pain via sensorimotor deficits. Unexpectedly, it appears that sitting per se may affect the sensorimotor system but this may only apply to sitting postures corresponding to driving mining vehicles.

Discrete-event simulation of mine equipment systems combined with a reliability assessment model based on genetic algorithms

The combination of simulation with the maintenance analysis of mining equipment has been proven to be an effective tool to assess the impact of equipment failures on mining equipment. Genetic algorithms have been applied to multiple areas of mine design, mostly involving optimization solutions. With regard to maintenance analysis, past research in mining focused on the design of a genetic algorithm based modelling technique that is applied to the failure data of equipment to assess the reliability of a machine under study. The objective of this research is to develop, integrate and demonstrate that a methodology involving the combination of a reliability assessment model based on genetic algorithms with a discrete-event simulation model can be an effective tool for maintenance analysis of mining equipment. The reliability assessment model based on genetic algorithms provides input in the form of times between failures (TBFs) to a discrete-event simulation model. The simulation component emulates a typical mine development cycle to analyse the effect of load-haul-dump (LHD) equipment failures on production throughput, mechanical availability and equipment utilization. Furthermore, two equivalent simulation models, built in AutoMod and Simul8, are compared to evaluate the merits of employing one simulation software package over the other. This final component of the research offers the opportunity to assess two different simulation tools for the same mining problem.

State Estimation Based Model Predictive Control for LHD Vehicles

LHD (load-haul-dump) vehicles are used extensively in underground mining operations for ore transporting, primarily in tunnels where access is difficult or dangerous. To ensure underground efficient and safe LHD's performance, a robust feedback control strategy is needed. A state estimation based MPC scheme was designed for control purposes, and evaluated by simulation. The state estimator was developed by testing four approaches, in order to select the optimal one: the extended Kalman Filter, Particle Filter, Moving Horizon Estimator and a genetic algorithm based Moving Horizon Estimatior. The simulation shows that non-linear MPC performs better than linear MPC for path tracking.

Predictions of health risks associated with the operation of load-haul-dump mining vehicles: Part 2—Evaluation of operator driving postures and associated postural loading

Driving posture and whole-body vibration (WBV) (reported in Part 1) were measured during the operation of seven load-haul-dump (LHD) mining vehicles. Simultaneous exposure to WBV and non-neutral postures could increase an LHD operator's risk of developing a musculoskeletal injury. The percentage of work time spent in neutral, moderate and severe neck rotation, trunk rotation, trunk flexion and trunk lateral bend postures was determined via a 3DMatch analysis of 1 h of videotaped driving for each LHD operator. Peak and cumulative spinal loads at the L4/L5 level also were estimated using 3DMatch. Operators averaged 89% of the time with their necks rotated more than 40°, 3% of the time with the trunk rotated more than 30°, 24% of the time with the trunk in forward flexion between 20° and 45°, and 16% of the time with the trunk in lateral bend between 15° and 30°. The average maximal compressive force (based on static measure estimations associated with posture only) at the L4/L5 level of the spine was 2176 N, and the cumulative compressive load for an 8-h work shift was 34 MN. A total injury risk score, which considered vibration exposure, working postures and spinal loading, was correlated with LHD operator musculoskeletal injury reports. Therefore, exposure to vibration and non-neutral working postures appears to increase musculoskeletal injury risk amongst LHD operators. Relevance to industry Equipment operators have the potential to be exposed to several factors that can contribute to the onset of adverse health effects. This study illustrates the importance of considering the combined impact of vibration exposure and non-neutral working postures in order to reduce injury risk associated with LHD vehicle operation.

Predictions of health risks associated with the operation of load-haul-dump mining vehicles: Part 1—Analysis of whole-body vibration exposure using ISO 2631-1 and ISO-2631-5 standards

Predicted health risks, associated with the operation of load-haul-dump (LHD) vehicles, based on ISO 2631-1 criteria are limited and have not yet been determined according to ISO 2631-5 criteria. Therefore, health risks predicted by ISO 2631-1 and 2631-5 criteria are reported and compared in this paper. Whole-body vibration (WBV) exposure was measured according to procedures established in ISO 2631-1. A tri-axial seat pad accelerometer was used to measure vibration exposure at the operator/seat interface. According to ISO 2631-1 criteria, calculated 8-h equivalent vibration dose values placed three of the seven LHD operators above the health guidance caution zone (HGCZ) boundaries and four LHD operators within the HGCZ. However, health risks predicted by the ISO 2631-5 criteria were always lower than the risks predicted by ISO 2631-1 criteria. Relevance to industry In 2004, ISO released a new standard for the evaluation of WBV, ISO-2631-5. The boundaries for probable health effects were established using the best guidance at the time; however, they have not been epidemiologically validated and very few studies have reported health risks based on ISO 2631-5 criteria. This study provides a comparison of predicted health risks based on ISO 2631-1 and ISO 2631-5 and provides data that could suggest the ISO 2631-5 boundaries for probable health effects may be set too high. Alternatively, the data presented in this paper suggests more dialogue is required to identify the appropriate application of ISO 2631-1 and 2631-5 given the different health risks predicted for a data set with high shock content.