Hydraulic liquids made from fossil fuels are a major ecological burden, despite their good corrosion and wear properties. Water seems to be the future of hydraulic fluids, but due to lack of interest and specialised equipment, it remains undervalued. We have sustainably tested a proportional directional control valve produced by threedimensional printing, using water as the hydraulic fluid. We observed the change in internal leakage as a function of the number of cycles. The measurement results are unexpected and difficult to explain. The final stage of wear on the spool was clearly visible. Corrosion erosion is the biggest problem in performing the sustainability test.
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