DEVELOPMENT OF A DIRECT PRESSURE-SENSING WATER HYDRAULIC RELIEF VALVE
Keywords:
water hydraulics, relief valve, cavitation, pressure override, hysteresis, hydrostatic bearingAbstract
A balanced-piston-type water hydraulic relief valve working at a rated pressure of 14 MPa is developed. The design focuses on preventing cavitation and improving the static characteristics and stability. To prevent cavitation, the main valve has two throttles of nearly equal dimensions in series. As static characteristics, pressure override and hysteresis are considered. To reduce the pressure override, the supply pressure is directly led to the pilot valve. To reduce the hysteresis, the main valve is supported by hydrostatic bearings, which eliminate Coulomb friction in the main valve. To improve the stability of the main valve, a viscous damper is attached to the main valve besides inserting a damping orifice between the main- and the pilot valves. Simulation of static- and dynamic characteristics are carried out to determine the valve dimensions. The experimental results for a flow rate of up to 20 litres/min showed that the measured pressure override and hysteresis are about 1 % and 0.1 % of the pre-set pressure, respectively. The developed relief valve did not radiate cavitation noise in the range (maximum pressure 14 MPa) of the experiments.
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