This Master Thesis has been performed at Atlas Copco Rock Drills AB, Örebro and at Linköping University, Sweden from February 2010 through August 2010.The project deals with performance improvement of hydraulic rock drill machine manufactured by Atlas Copco Rock Drills. Atlas Copco Rock Drills AB is a world leading supplier of percussive rock drilling equipment for surface and underground applications. HOPSAN, a software developed at Linkoping University, provides an integrated simulation environment for simulation of fluid power systems. During the work, a HOPSAN model of a piston accumulator has been developed and its performance with a rock drill has been studied. Furthermore, the fatigue strength calculations of a piston accumulator has been made on the basis of stress analysis performed using the ANSYS software. One of the rock drills of valveless type, developed at Atlas Copco Rocktec Division works at higher efficiency than the conventionally used rock drills. But the problem with this type of drill is that the piston swings between two large and highly pressurized oil volume which causes strength problems in the housing of the rock drill. The aim of this work is to achieve the higher efficiency of the rock drill without having any strength problems. Therefore, some study and research is proposed to replace the large oil volume by one or two piston accumulators. This thesis work involves modelling, simulation, design and fatigue strength calculations of a piston accumulator and its implementation to the rock drill. Optimization of the piston accumulator has also been conducted while working with the rock drill so that highest possible eciency could be achieved. The performance of the rockdrill with piston accumulator has been analyzed and results are studied. In the end, a short fatigue life calculations are performed and results are discussed. Prior to fatigue life calculations, a transient dynamic stress analysis has been performed and stress amplitudes are identified which contributes to the accumulated damage to piston in accumulator.

Introduction It is well established that gold mine dust is a major cause of pneumoconiosis and other lung diseases. The main sources of dust in gold mines are well documented. Rock drill operators using pneumatic percussion rock drills are at the sharp end of exposure due to the very nature of the drilling process in that rock is pulverized and liberate large amounts of dust even with the addition of copious amounts of water. Historically it has been found that the gold bearing rock formations in South Africa typically contain about 30% quartz. (1) Keeping this in mind, the potential for overexposure is obvious. The actual exposure of rock drill operators to dust and quartz is not well documented and for this reason this research focuses on this particular occupation. Objectives To measure the respirable dust and quartz exposure of Rock Drill Operators in two typical gold mines in the Free State province of South Africa in 2007. Methods This study is a descriptive, cross sectional, rapid assessment based on the findings of gravimetric sampling results taken at Rock Drill Operators working underground on two different gold mines. The actual gravimetric sampling was done in accordance with NIOSH methodology. The study population consisted of 30 Rock Drillers on one mine and another 30 on a second mine. The Rock Drill Operators was randomly selected using their company numbers and selected by the “Excel” program random number selection function. Ordinary gravimetric sampling, using Gillair pumps, was used and weighing done on the mine by a qualified and well experienced Air Quality Analyst using an appropriate methodology compatible with international best practices. Quartz analysis was done at the National Institute for Occupational Health (NIOH) in Johannesburg using a Phillips X-Ray diffraction. (Photo 2). The methodology used by the laboratory technician is conducted strictly according to the manufacturer’s specifications and in line with international best 5 practices. This laboratory participates in quality assurances programmes and is highly regarded internationally. Results The initial hypothesis that exposure underestimation in the past in terms of this particular occupation is confirmed and could be contributable to the difficulties typically experienced when using the traditional gravimetric sampling method. The average quartz percentage was determined to be 25.45% for mine 1 and 38.49% for mine 2 giving an average of 30.67% for both mines. The Total Mass means was 0.73 and 0.23 mg for mine 1 and 2 respectively with an average for the two mines being 0.49 mg. Results for Time Weighted Averages revealed values of 0.69 and 0.22 mg/m3 for mine 1 and 2 respectively with an average of 0.46 mg/m3 for both. In terms of Air Quality Index (AQI) the values were 1.4 and 0.6 for mine 1 and 2 respectively with an average for both mines therefore being 1.1. A comparison with the South African OEL for quartz showed overexposure on 32% of all rock drill operators sampled. When using the NIOSH OEL that figure is even worse at 72%. Based on these results it would thus be fair to conclude that Rock drill operators working without appropriate respiratory equipment will be overexposed and therefore potentially suffer ill health as a result. Discussion and conclusion Rock drill operators are potentially exposed to high levels of harmful dust and quartz in their normal daily work if not adequately protected using good, effective appropriate and comfortable respiratory protective equipment (RPE) and additionally having proper ventilating velocity. At an average Air Quality Index (AQI) of 1.1, it would require the mine Occupational Hygienist to immediately institute remedial action in conjunction with an investigation to determine the reasons for such overexposure. The AQI of 1.46 and 0.6 for Mine 1 and 2 respectively curiously beg the question as to why there is a difference. The answer unfortunately is not clear at first glance as both mines wetted the stope working faces equally well, ventilates the faces with similar velocities which in turn alludes to similar dilution factors but the only reasonable deduction that could be made is that high TWA respirable quartz pollutant concentrations (mg/m3) values in lots of cases corresponded with low actual quartz values. This could be co-incidental but in fact caused the TWA graph to be inversely proportional to the AQI graph. Couple this to the fact that the actual dust burden is lower in Mine 2 compared to Mine 1 as confirmed by the TWA values obtained, then the results becomes easier to interpret. However, the assumption is made that the TWA values should enjoy more preference in the analytical sense as it could be compared directly to OEL’s which serves to highlight the hypothesis very clear in that rock drill operators are over exposed to a high degree of certainty which in turn concurs with other research done in the past. The fact that the methods used to drill holes in order to be charged up with explosives has largely remained unchanged for more decades in the mining industry with no viable alternative on the horizon, emphasizes the fact that focused attention and proper risk assessment is called for to protect rock drill operator from harmful exposure. That said the normal paper dust mask cannot in all good conscience be regarded as appropriate RPE for this occupation. The aforementioned risk assessment must determine and ultimately classify which occupations would benefit from “upgrading” to better quality dust masks. To accept only one type of dust mask on a mine would be considered a travesty and contrary to the application of all good occupational hygiene principles. Failing to expedite the aforementioned risk assessment on RPE per occupation will result in failure to place effective safeguard measures in place to protect rock drill operators from harmful dust and will mean that their health will be compromised in time. The development of air line fed type hard hats incorporating a face shield, harness fitted with moisture trap, filter and a snap fit attachment to a compressed air line is likely to be the ultimate solution provided that it is light, comfortable and the introduction is done in a manner that will ensure the understanding in the benefits to be derived from using such a device in the place of ordinary dust masks by Rock 7 Drill Operators. Ultimately, using the Occupational Hygiene hierarchy of control that dictates the first consideration of such control being elimination, coupled with the horrendous ergonomic problems faced by rock drill operators, the solution seems to point inevitably towards meganisation. Using a person in the same homogeneous exposure group (HEG) as that of the rock drill operator as a forced alternative is not advisable as the exposure of a rock drill operator is very unique and certainly not comparable to that of a winch driver for example. The wet environment certainly warrants the investigation into alternative methods for sampling as normal, traditional methods proved to be inconsistent, unreliable and often unusable.

In blast hole drilling, it is desirable to be able to drill as close as possible to the edge of the tunnel. The minimum distance from the edge is defined by the radial size of the rockdrill. Most of the rock drills used today have a rotation motor that rotates an axel parallel to the shank, which further rotates the shank through a gear set. Thus making the rock drill bulky. This thesis project carried out at Atlas Copco Rock Drills AB, Örebro, deals with the rotation mechanism of a rock drill. The main task of the project was to develop alternate concepts for rotation mechanism that would use the shank as a part of rotation mechanism and reduce the bulkiness of the rock drill. In order to find a suitable alternative, eight different concepts for hydraulic motor (with or without transmission) were generated and evaluated against each other. Two concepts, 1) multi-cam vane motor concept and 2) strain wave hydraulic gear motor concept, were selected for further functional design. Both concepts were designed at ideal conditions (100% efficiency) to achieve the required displacement. For the multi-cam vane motor, various design improvements were performed and the effect of different design parameters were also analyzed. Different variants of the motor were developed and analyzed. A rough design was performed for the strain wave hydraulic gear motor concept which was chosen for its novelty. CAD models for both the concepts and the related variants were developed for suggesting assembly layouts and valve mechanisms. The two concept designs would reduce the bulkiness of the rock drill. The benefits and drawbacks of the different variants have been discussed. The concepts must be further developed for implementation into a rockdrill. / Vid spränghålsborrning är det önskvärt att borra så nära tunnels periferi som möjligt. Det minsta avståndet från kanten definieras av borrmaskinens radie. Majoriteten av dagens borrmaskiner har en rotationsmotor som roterar en axel parallell till nackadaptern, vilket i sin tur roterar nackadaptern genom en drevuppsättning. Detta gör borrmaskinen otymplig. Detta examensarbete, som utfördes på Atlas Copco Rock Drills AB, Örebro, undersöker rotationsmekanismen hos en borrmaskin. Projektets huvuduppgift var att utveckla alternativa koncept till rotationsmekanismen som använder nackadaptern som en del av rotationsmekanismen och reducerar borrmaskinens otymplighet. För att hitta ett lämpligt alternativ genererades åtta olika koncept för en hydraulisk motor (med och utan transmission) som sedan utvärderades. Två koncept, 1) ”multi-kam vingmotor” och 2) ”hydrauliskt driven töjningsvåg-växel”, valdes för ytterligare funktionell konstruktion. Båda koncepten konstruerades under ideala förhållanden (100% effektivitet) för att uppnå det deplacement som krävs.För ”multi-kam vingmotor” utfördes ett flertal konstruktionsförbättringar och effekten av olika konstruktionsparametrar analyserades. Olika varianter av motorn togs fram samt analyserades. En grov design genomfördes för ”hydrauliskt driven töjningsvåg-växel”, vilken valdes på grund av att designen inte förekommit I någon litteratur. CAD-modeller för båda koncepten samt relaterade varianter togs fram för att föreslå monteringslayouter och ventilmekanismer. De två koncepten skulle reducera otympligheten hos borrmaskinen. För –och nackdelarna hos de olika varianterna har diskuterats. Koncepten måste utvecklas ytterligare för att kunna implementeras i en borrmaskin.

An axisymmetric finite element solution method is developed for axial wave propagation through a series of threaded connections in rock drills. A piston impacts axially on a string of rods held together by threaded joints and the wave propagates through these joints before reaching the bit. The energy lost in the joints limits the maximum effective depth of the drill. Several computational techniques are used to efficiently model the problem. Non-reflecting boundaries are used to numerically absorb the waves as they exit a joint. The stored waves are then re-initiated into the next joint eliminating modeling of the entire assembly of rods. The preload in the threads is modeled by shrinking the threaded sleeve onto the rods. A new dynamic relaxation damping scheme is used which starts with an undamped model and then increases the damping until the solution converges. This method converges more rapidly than the standard constant damping. / Master of Science

Hand Arm Vibration Syndrome (HAVS) is a collective term for the symptoms arising from the prolonged use of vibrating hand tools. An investigation into the literature on available screening tools for HAVS was conducted. A screening tool is used for the quick identification of certain symptoms without a full medical check up, and is for use by mine medical personnel for the determination of workers with HAVS symptoms and those without. Twenty-two non-exposed volunteers were tested with the screening tools and forty-two rock drill operators. Only the rock drill operators had a medical examination and standardised tests for HAVS diagnoses, to determine their HAVS diagnosis and severity. This diagnosis was used as the standard for the evaluation, of existing screening tools and for developed screening tool, sensitivity for the detection of HAVS symptoms. The screening tools chosen were a traditional tuning fork, a similar tuning fork but mounted into a box with a set excitation unit and a two-point discriminator set a 3mm, 6mm, and 10mm apart. The results showed that a screening questionnaire that specifically focuses on the symptoms of HAVS has better sensitivity and specificity to identify cases. A two-point discriminator with variable distance points, where patients have to distinguish between one pin prick and two, was able to identify HAVS cases when the distance was set at 3mm. However, the sensitivity of the two-point discriminator was lower than the sensitivity of the questionnaire. / Dissertation (MSc)--University of Pretoria, 2007. / Industrial and Systems Engineering / Unrestricted

The world is looking for greener solutions and so is the mining industry. This quest has led to the question whether it is possible to have a completely electric rock drill. This work carries out an initial exploration of completely electrified percussion. Furthermore, it compares the preliminary performance of an electrified rock drill against a hydraulic counterpart. A mathematical model for an electromagnetic linear motor was developed and simulated as a component in the simulation software Hopsan. This component was then incorporated into a electromagnetic rock drill model which uses components from Epiroc’s in-house developed library. The electromagnetic rock drill model was then optimised and used to obtain the performance characteristics such as impact energy and frequency which were compared against one of the hydraulic rock drill models, COP 1838. The results show that it is possible to reach the same performance as the COP 1838 with enough input current. The characteristics were then studied with respect to variation of physical parameters of the electromagnetic linear motor and input current. Finally some limitations and strengths of the electromagnetic rock drill concept are discussed and some conclusions are presented.

The increase of intelligent systems can be seen in every industry. Integrated sensors and processors are used with internal control systems to create better performance for mobile hydraulic applications. The report describes how an evaluation was made to see if the productivity of a drill rig could be increased. This was done by implementing a programmable hydraulic valve to control the hydraulic drilling functions. The productivity would be increased by reducing the downtime due to jamming in the drill hole. Jamming occur when the system does not compensate for changes in rock conditions. By conducting a series of tests in a controlled environment with simulated loads, the response time of the CMA system and original system could be determined and compared. The CMA system had a response time that was 60-64% faster than the original system. Two different implementations of a controller was tested. Ziegler-Nichols method was used to get the initial value of the PI parameters. The controller that was implemented onboard the valve’s CPU was considered more successfull to reduce jamming. A drill test was conducted to ensure that the programmable valve could handle a drilling procedure with the controller that was implemented onboard the valve’s CPU. The valve handled the drilling procedure well.

This thesis aims to investigate the possibility of using a mathematical model to detect several common faults in a hydraulic rock drill. To this end, a parameterized state space model of the hydraulic drill, which simulate its behavior, is created. The model parameters are divided into two categories where different estimation methods are used to determine their values. The first category consists mainly of the parameters that are assumed to be invariant and independent of the various operating conditions. Experimental data are used to estimate these parameters. The other category is the variables that change depending on the machine’s current condition and operating settings. These include the response from the rock and internal leakages in the hydraulic drill. These parameters are estimated by integrating the impact piston position measurements in the simulation algorithm. The model is simulated for different fault modes, and the resulting estimated parameters are studied. It is shown that the resulting distributions for some of the estimated parameters differ between the fault modes, which makes fault detection possible. Furthermore, a condition monitoring system based on the estimated parameters provided by the model is designed and evaluated. It is shown that the performance and the robustness of the monitoring system depend on the machine’s operating settings and condition, where the system performs best for an operating pressure of 220 bar and the internal cylinder leakages.

Text in English / This research focuses upon the killing on 16 August 2012, by the South African Police Service, of miners working in Marikana, in the North West Province, in their struggle for a just wage. This experience highlighted the ethical question of the relationship between the employee and the employer. This research investigates this question by reference to the evolution of the doctrine of the “just wage” and the “just price” in Western moral philosophy. The investigation shows that this Western doctrine is a significant basis for an ethical evaluation of the relationship between employee and the employer. However, the doctrine does require expansion by taking the woman as an indispensable factor in labour relations. Also, it requires deepening by engaging in dialogue with other philosophies of the world, in this particular case, the philosophy of Ubuntu. The dialogue with Ubuntu is justified by the fact that the majority of the miners, the actual diggers of the mineral wealth, are born into and nurtured through the philosophy of Ubuntu, even if some may have reservations about it. The dialogue reveals a specific philosophical issue, namely, a clash of the epistemological and moral paradigms. The Ubuntu epistemological-ethical maxim of feta kgomo o tshware motho (if and when one must choose between the continual accumulation of wealth and the preservation of human life then one ought to opt for the latter) is fundamentally at odds with capitalism, an economic system that elevates wealth and money to the status of a deity. A resolution of this conflict is an ethical imperative. / Philosophy, Practical and Systematic Theology / D. Litt. et Phil. (Philosophy)

Corrosion fatigue is a common failure mechanism in rock drilling components and many othermechanical parts subjected to cyclic loads in corrosive environments. A crucial part in the design ofsuch components resides in the selection of the right materials for the application, which ideallyinvolves testing and comparison of their performance under working conditions. The present work was performed with the purpose of designing a corrosion-fatigue testing methodthat would allow the designer to compare the performance of different materials exposed to corrosionfatigue, permitting also the comparison with results from dry fatigue testing. The method was designedfor rotating-bending machines. Two different steel grades were used during the work, one throughhardened and one case hardened. The effect of these heat treatments and of shot peening overcorrosion-fatigue behaviour were studied using the proposed method. It was proven that the testing speed has a strong impact on the fatigue life of steel. It was found that,at a fixed stress level, the case hardened and shot peened steel reached 3X10^6 cycles at 2300 rpm,while it failed at only 5X10^5 cycles with a testing speed of 500 rpm. A large beneficial influence of theshot peening was demonstrated. It was also observed that, at fixed testing speed, the shot peening onthe through hardened steel can increase its fatigue strength from 190 MPa to 600 MPa under corrosionfatigue. Many cracks were found at the surface of the shot peened parts, which are arrested near thesurface by the compressive stress layer from the shot peening. It was also found that, for the non-shotpeened parts, case hardening had a slightly higher corrosion-fatigue strength than the throughhardened. This might be a result of the compressive stresses from carburization, or due to the highercore toughness of this steel grade.