The construction, development and evaluation of a portable ferro- precipitator

Abstract

This dissertation is concerned with the construction of the locally developed Ferro-precipitator which can be utilised outside a laboratory environment. The American developed Ferrograph machine, besides being expensive (R42 000 + GST in 1984), can only be used inside a dust free, temperature controlled room. As lubricants in machinery moving parts play an important role in their performance and durability many methods of evaluating the health of machines have been devised, but none by themselves can give a complete picture of what is happening inside the machine. Various methods of oil analysis have been studied in this dissertation for comparison and/or complementary purposes, so as to establish the role of the Ferro-precipitator in the context mentioned. Spectrometric, Debris and Radio Tracer methods are based on quantitative aspects of wear particle analysis, whereas the Magnetic Plug method shows visibly large wear particles in the very high wear pattern range. A further aspect to consider is the fact that the Spectrometric analysis method, which is the most common and comprehensive method available in South Africa, is laboratory orientated. This means that an oil sample has to be taken from a machine and then sent to a laboatory for analysis. Besides being time consuming from the time the samples are taken to the time when the results are known, the Spectrometric analysis method is also very expensive. The Ferro-precipitator that has been developed, is sensitive to particle size and to the rate at which these particles are generated. This is due to the phenomenon that a varying magnetic field strength will attract different size ferrous particles accordingly. This concept was validated by manufacturing ferrous particles of various sizes, firstly by grinding and secondly by sieving. These particles, in both cases, were passed through the Ferro-precipitator in a medium of oil, and graphs of density versus distance along the slide were plotted. The graphs showed distinct variations between particle sizes. The manufactured particles were also statistically evaluated by establishing the correlation between the machined and/or the sieved particles to the optically measured particles. The sensitivity of the Ferro-precipitator was further demonstrated by comparing results obtained from an engine test carried out under controlled conditions using the Spectrometric method. If developed further, the Ferro-precipitator .could, be used in the field, which would eliminate the time lost due to samples being sent ot a laboratory. Also the cost of the machine would be a fraction of the price of the Ferrograph and/or the Spectrometer. An in-depth study of particle morphology can be carried out on the wear particles deposited on the slide, with the aid of a Scanning Electron microscope using its X-Ray attachment. The potential for such a study was demonstrated on the engine test performed for this dissertation.