Kilfoil, Arthur Mark2018-11-292018-11-291997https://hdl.handle.net/10539/26151A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering.The flushing flow rate required to maximise penetration rate of holes drilled by rotary percussion is dependant on drilling parameters and chip size. Experimental work to determine the optimal flushing water flow rate for two common drilling situations was undertaken. It consisted of drilling, analysis of chip samples and flow visualization. A computer modal to predict flow rate was developed. Its output and the experimental results Were combined to explain the relationship between penetration rate and flow rate. All chips should be fiushed from the gap between the bit and the end of the hole in the time between hammer blows (ie. - within the duration of a percussion cycle). As flow rate increases, flushing improves and therefore penetration rate increases. Once flushing is adequate there is no mechanism for further increases in penetration rate, thus it remains constant and independent of further increases in flow.enRotary drilling.Rock drills.Thesis