Effect of the balanced piston on the stability of hydraulic pilot-operated relief valve

The stability of a pilot-operated relief valve is investigated through mathematical modeling and experimental measurement. A comprehensive mathematical model of a cartridge-type pilot-operated relief valve is developed, which is designed with a balanced piston at the front of the pilot poppet. The dynamic behavior of such a valve was then investigated using a frequency-domain analysis method. The balanced piston was found to have a marked effect on the stability of the relief valve. The local stability of the valve under various annular clearances was further discussed by the normalization method. The results indicate that an appropriately sized balanced piston can improve the stability of the relief valve's subsystem. However, when the annular clearance is large, the subsystem's dynamic characteristics do not change obviously, although it does raise the pilot poppet damping ratio to some extent. Furthermore, numerical simulations and experimental studies were produced to validate the above conclusions, and excellent agreement between the measurement and the model was obtained.