Dynamics of pilot operated pressure relief valves subjected to fast hydraulic transient

Pressure relief valves are the components which take on the important role of protecting the hydraulic systems from over-pressure. The basic working principle of the pilot relief valve is quite well-known, the main stage will open as soon as the pressure on pilot stage exceeds the spring setting. However, the main stage of a pilot relief valve can open in case of sharp dynamic transients even if the pressure setting of the pilot stage is not met. This feature is worth of investigation because on the one hand it could cause an unwanted pressure unloading of the circuit, while on the other hand it could be beneficial against harmful pressure transients. A lumped parameter dynamic system will be presented in the paper including the wave equations in the pipes and highlighting the dynamic behavior of the pilot operated pressure relief valve with particular emphasis on the damping effect against the pressure wave propagation.