The article presents the results of a developed model and experimental studies of the Minimess^® hydraulic signal hose’s influence on the changes in the indications of the pressure transducer during the high dynamics of hydrostatic drives and controls. The model test results show that measuring hoses can be used as hardware low-pass filters during the digital recording of pressure waveforms. However, the cut-off frequency values of the measuring hoses obtained using the model are dramatically lower than those observed during the experiment. The experiment results show that the measuring hoses can only be used without any limitations to measure the average pressure value. In the case of measuring pressure waveforms, the user should carefully choose the measuring hose length. For this reason, the relationship between the measuring hose length and its cut-off frequency should be known.

Some users consider modern hydrostatic drives and controls to be unreliable and difficult to maintain. This view is often due to operational problems caused by issues with obtaining and then maintaining the appropriate cleanliness class of the working fluid. Recommendations on the selection of appropriate filtration system elements can be found in the literature, but there is no numerical model that could be helpful in a detailed analysis of the phenomenon. In the article, the authors tried to fill the research gap regarding the lack of a filtration model based on the filtration efficiency coefficient of filter elements used in hydraulic drives and controls. The developed model allows users to determine the influence of selected filtration system parameters on the separation of contaminants by filter elements. The model is intended to help designers and users of hydraulic drives and controls in optimizing the filtration system in order to obtain and then maintain the required cleanliness class of the hydraulic fluid. This paper also includes the results of the sensitivity analysis of selected filtration-system operating parameters in terms of the highest efficiency. In order to verify the developed model, experimental tests were also carried out, with the results presented in this paper. Based on the numerical analyses and experimental studies, recommendations that may be helpful in the selection or development of filtration systems used in hydrostatic drives and controls were developed.

This paper presents the results of the experiments related to measuring the impact of the suction space leaks in the gear pump on the pressure pulsation, resulting in the aeration of hydraulic fluid. The research authors claim that it is possible to detect leaks in the suction line, causing aeration of the hydraulic fluid, by recording and analyzing the pressure pulsation in the positive displacement pump discharge line. The measurements were performed for six leakage values, five discharge pressure settings and under constant hydraulic fluid temperature. The obtained results were analyzed in the time and frequency domains. The results of experimental research confirmed the author’s thesis.

The paper presents the results of experimental research on the impact of changes in the rotation speed of a hydraulic external gear pump on pressure pulsation in the discharge line for a constant value of pressure. The analyses were performed in the time domain (analysis of peak-to-peak pressure) and frequency domain (analysis of changes in frequency and pulsation amplitude). The results of experimental studies have shown that the change of the pump’s rotation speed influences changes in the course of pressure pulsation (peak-to-peak pressure and amplitude), in some cases significantly increasing the parameters mentioned. The obtained test results can be used to develop recommendations for designing hydraulic and hydrotronic systems equipped with a variable-speed pump drive.