CONTAMINANT SERVICE LIFE AND COST OF HYDRAULIC SYSTEM.

摘要

Scope and Method of Study. This study is concerned with the contaminant service life and cost of a hydraulic system. The object is to derive the life equation of a hydraulic pump and to develop a technique to minimize the cost of a hydraulic system consisting of a pump and a filter.;Findings and Conclusion. (1) The particle size distribution of ACFTD currently used deviates considerably from the correct value in the small particle size range. (2) The leakage flow ratio representing the flow degradation characteristics of pumps due to contamination is expressed with a straight line on Log-Log paper. Therefore, the values of the leakage flow ratio at any two data points can be a pump performance indicator. (3) The Beta rating which is currently used to evaluate the filter performance is affected by the particle size distribution upstream of the filter. Therefore, the filtration ratio, (beta), does not represent the inherent transmission property of the filter medium. (4) The flow distribution developed in this paper can present the inherent transmission property. The mean value of the flow distribution or the median of the original variable can be used as a performance indicator of the filter media. (5) The life equation of a hydraulic pump can be expressed in terms of only four parameters, the contaminant concentration ingressed in the hydraulic fluid, the median pore size of the flow distribution, and two leakage flow ratios derived from the tests with a 10 micrometer and a 30 micrometer classified dust. (6) Although the life of a pump is influenced seriously by the above four parameters, the combination of a poor quality filter and a poor quality pump should not be used from the standpoint not only of the life of the pump, but also from the economy of the hydraulic system. (7) A method which minimizes the maintenance cost of a hydraulic system was developed. By using this method, the most economical filter can be chosen for a given pump and a contaminant condition.;In order to predict the pump life accurately from the laboratory tests, conducted by ISO standard, the particle distribution of ACFTD is investigated precisely and new methods to evaluate the performance of filters and the leakage flow characteristics of pumps are developed. By using these results, the pump life equation is established, then the method to minimize the maintenance cost of the hydraulic system is developed.