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Every hydraulic system use requires a pump to supply the necessary flow and support the imposed pressure cycle. Therefore the performance of the pump in a hydraulic system is critical to the overall performance of the system. It is a well known fact that the performance of a hydraulic pump is influenced by both the speed at which it is operating and the pressure to which it is subjected. This paper evaluates the volumetric efficiency of a hydraulic pump using both the fundamental expressions which are generally accepted and actual data test data. The widely accepted equation for pump leakage is presented along with an expression that includes the parameter of speed. Results obtained using a pressure-loaded gear pump are used to compare and evaluate the analytical expressions. This comparison reveals a significant influence of speed at high pressures on the volumetric efficiency of the pump.

The Standard Multipass (Beta) Filter Method (ISO 4572) has been a highly recognized and widely accepted test throughout industry since its introduction in the early 1970's. In the past decade, the Beta Method has indeed made a major contribution in assisting users in selecting filters to meet system design requirements. However, many complaints have been voiced by users that filters normally produce a lower particle removal efficiency under field applications than they do during laboratory tests. Research results from work carried out at the Fluid Power Research Center at Oklahoma State University indicate that the degradation of the filtration (Beta) ratio in service depends mainly on the filter's retentivity characteristic. This paper highlights the theoretical basis of the Epsilon Rating Method and the concept of retentivity. Most important, the paper uses these concepts to correlate filter performance between laboratory tests and field operation.

Sievability and separability are two major criteria which have been used in the past to appraise the performance of filters. Although both criteria have significance in rating filters, it has been demonstrated in practical applications that such ratings cannot reflect the entire spectrum of filter performance. Test data obtained from more than 1200 different filters tested in the past decade at the Fluid Power Research Center at Oklahoma State University indicate that two major intrinsic filtration parameters must be addressed to appropriately and accurately assess the characteristics of a filter. They are separability (power to capture) and retentivity (power to retain). The Epsilon Rating Method was developed from the Elutivity Theory, which considers the separability (Beta Filtration Ratio), the retentivity (Delta Ratio used to express the degree of particle desorption or caking) and system operating parameters.

The Computer Aided Analysis and Simulation (CAAS) package is the result of a multiphased program aimed at developing a user oriented, computer aided design technique for the analysis, design and specification of hydraulic power transmission systems. The package is intended to eliminate the need for detailed computer programming on the part of the system designer and allows effective use of the technique by anyone familiar with the CAAS package. This study has included the development of the general system analysis and optimization techniques, the development of the Probelm Oriented Language (POL), modeling of the most commonly used hydraulic components and testing of a selected group of hydraulic system components to verify the models developed. This paper presents the rationale of the CAAS package. The theoretical basis, program structure and application examples are included.