Oscillations of cylinder piston rod – comparison of amplitudes and frequencies for the transient phenomena in tap water- and oil-based PCHS

Power-control hydraulic system (PCHS), as a part of a machine or production line, provides it with all or most of the necessary movements. Most of the movements in PCHS are carried out by means of hydraulic cylinders. In this case movements are mostly generated by cylinder piston rods. More or less obvious transient phenomena occur during these movements under conditions of acceleration and deceleration. As a consequence, oscillations are induced in the system. In our work we investigate the phenomena and parameters of such PCHS for two hydraulic fluids. Most of the PCHSs still use mineral oil as hydraulic fluid but it is environmentally very harmful. Ecological awareness during natural disasters and man-made pollution is the subject of much discussion. It is everybody’s responsibility to take care of the natural environment and reduce the threats to our future existence. The preservation of drinking water and the prevention of its contamination by pollution are particularly important. Powercontrol hydraulics is one important area in which a positive step could be made to protect the resources of drinking water. The use of tap water instead of the conventional hydraulic fluids in power-control hydraulics is one of the most environmentally friendly changes that could be implemented. Therefore in this paper we show, based on dynamic-transient parameters, both the functionality and the usability of water hydraulics in comparison to the more familiar oil hydraulics. A comparison of the dynamic behavior between the conventional oil and the relatively new water hydraulics under the same conditions is described. Mineral hydraulic oil was used in the oil hydraulic test rig and distilled water was used in the water hydraulic test rig. The tests were conducted at different flow rates (11, 22 and 33 lpm) and system pressures (70, 110 and 160 bar) as well as applying different loading conditions (first, with a mass of 163 kg in the horizontal and vertical positions and, second, without the mass). The registered amplitudes of the cylinder piston rod oscillations were 20-30 % smaller in the water hydraulics with respect to the case of oil hydraulics, while the frequencies of the piston rod oscillations were 7-20 % higher.