NON-INTRUSIVE ANALYSIS OF CONTAMINANT WEAR IN GEAR PUMPS THROUGH FERROGRAPHY

Scope and Method of Study. The proposition examined in this thesis is that Ferrographic wear debris analysis provides a non-intrusive method which exhibits finer resolution and requires less acceleration than previous methods for evaluating the contaminant wear of gear pumps. The study proposes that the damage to such a pump due to particulate contamination entrained in the fluid medium results in an enlargement of the inherent leakage paths which is reflected in both degradation in output flow and generation of wear debris. Specific objectives of the research were the investigation, both theoretically and experimentally, of the correlation between flow degradation and Ferrographic wear debris data. In addition, the influence of the pump operating speed and output pressure upon the contaminant wear were examined along with the effect of contaminant concentration and particle size range.; The theoretical considerations involve the formulation of a general flow degradation model for the gear pumps and the development of an expression for Ferrographic density data from a contaminant wear test. A Ferrographic Contaminant Wear Model based upon both the flow degradation and Ferrographic density relationships was proposed to permit the transformation of wear debris generation into flow loss through proper consideration of clearance changes within the pump.; The experimental phase of the study included a set of statistically planned experiments. These tests were designed to evaluate the influence of test sequence, pump speed and output pressure upon the flow degradation and wear debris generation of a gear pump. The relationships and interactions between the operating parameters of the pump and the concentration and particle size range of the particulate contaminant were experimentally evaluated. The total testing phase of this effort included numerous appraisals of the Ferrographic technique to evaluate its capabilities and limitations, complete performance tests on five of the test pumps and twenty-four contaminant wear tests.; Test results were used to determine the initial performance characteristics before subjecting the pumps to a controlled contaminant environment. A flow degradation model was formulated based upon the expressions which describe the performance of the gear pumps used in the contaminant wear tests. Also, standard statistical analysis methods were applied to the experimental results to assess the variables which have a significant influence upon the contaminant wear of gear pumps. Finally the experimental data were used to develop an emperical Ferrographic Contaminant Wear Model.; Findings and Conclusions. The use of Ferrographic analysis technique has been shown to be a repeatable and viable method with a high degree of resolution in the study of the contaminant wear of gear pumps. From the results of this study, it can be concluded that both the wear debris generation and the flow degradation characteristics are related to the clearance changes within the gear pump due to contaminant wear.; It has been shown that the operating speed of a pump is not a significant parameter in the contaminant wear process and that the testing sequence does not significantly bias the test results. The Ferrographic density data closely followed a power law function of the particle size range of contaminant exposed to the pump. The coefficient of the power function relating Ferrographic density to particle size range was shown to be a function of the contaminant concentration while the exponent was related to the pump operating pressure.