Thesis (MBA)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Manufacturing plants should strive towards achieving and maintaining good safety records. It is however difficult for plants to identify specific safety problem areas that can be improved on. One way to identify specific safety areas that needs improvement is by conducting a safety culture survey. A manufacturing plant within South Africa realised the need to improve on its safety performance. However, it was not clear which aspects of its work and safety related practices were at risk. Management therefore decided to obtain an assessment of the safety culture profile of the plant. The assessment was done by way of a plant-wide safety culture survey. The safety culture questionnaire was developed, as part of this research, through an in-house consultation process. This process resulted in identifying 16 different safety-related themes. With the help of literature, these themes were further explored to design the questionnaire. The identified safety themes were measured during the survey and results obtained for each of the plant’s identified safety practices. The survey also provided an overall mean score of the plant’s safety culture, providing management with a better understanding of where they stand in their safety improvement journey. The plant’s equipment, materials and tools; overall rules and regulations; environment, health and safety suggestions; rewards and reinforcement; and management involvement practices was identified as practices that require an immediate response. The plant’s incident reporting and investigation, discipline and training safety practices were identified as less urgent risks.

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

This thesis reports upon a second phase of research into the effects of free-stream turbulence quantities on heat transfer to impermeable gas turbine blading. It describes the development of a novel form of turbulence generator, to control separately the turbulence quantities intensity and frequency upstream of a cascade of blades at levels typical of the gas turbine. The turbulence generator was calibrated for these individual quantities, with a hotfilament anemometer system combined with on-line analog and digital signal processing. Blade heat transfer coefficients measured by two independent techniques are compared. A large quantity of data is presented, taken from a first stage high pressure rotor blade and a nozzle guide vane. These were subjected to steady flow and turbulent streams induced by both the novel turbulence generator and by more conventional turbulence grids. Surface pressure measurements have also been made, to predict the heat transfer rates by applying formulae derived from simple geometries. Much of the boundary layer over the two blades was apparently laminar. For the laminar regions, the simple formulae for heat transfer (flat plate for example) multiplied by a turbulence term, will provide as good a correlation as any. The intensity Tu is the most important turbulence quantity, but there is some evidence that the frequency of the perturbations can effect heat transfer. Other evidence presented would s'uggest that profile geometry is an overriding factor, which dictates the development of the turbulence, whatever its origin, as well as controlling its interaction with the boundary layer. None of the correlations available for the prediction of boundary layer transition are applicable. On both blade suction surfaces separation seems to have occurred, and the analysis indicates that transition on the pressure surfaces of modern blades will be inhibited by the high free-stream accelerations. Beyond transition, heat transfer is little affected by turbulence. It is now clear, that measurements of the turbulence as it develops through the cascade must be performed before a successful prediction procedure for all of the boundary layer regions can emerge.

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