The reason for the strong and short-term vibration of spring safety valve during the normal shutdown of oil pump is that during the shutdown of oil pump, the oil hammer is produced by the chronic movement of pressure oil in the pipeline. Its vibration intensity is the strength of shock wave, and its vibration frequency is the frequency of shock wave. Its vibration property is attenuation amplitude, the whole process of vibration, until the shock wave force of the oil hammer is less than the opening preset force of the spring safety valve.

The vibration process of the spring safety valve is: when the working pressure of the spring safety valve is adjusted according to the design requirements, that is, when the upper limit value of the working oil pressure of the oil pressure equipment is 3-4kg / cm2, the oil drain hole is fully open. The upper limit (rated oil pressure) of working oil pressure of ys-2.5 oil pressure equipment is 25kg / cm2. The working pressure of spring safety valve is adjusted to 28-29kg / cm2, and the oil drain hole is fully opened. When the oil pressure of the oil pump in the pressure oil tank rises to the rated oil pressure (25kg / cm2), the oil pump stops, that is, the power supply is cut off. At this time, the pressure of the oil inlet pipe is slightly greater than 25kg / cm2.

Because of the shutdown of the oil pump and the inlet of the oil inlet pipeline, a low-pressure area is formed near the oil pump, the pressure oil in the pipeline flows back to the low-pressure area, and the low-pressure area transfers to the center of the oil inlet pipeline at a very fast speed. At this time, although the power supply of the oil pump has been cut off, it is still rotating at a large decreasing speed due to inertia, and the pressure peak formed by the driving oil also lags behind the low-pressure area to transfer to the center of the oil inlet pipeline. At the same time, the pressure oil in the pipeline near the outlet of the oil inlet pipe continues to flow into the pressure tank under the action of inertia force. When the inertia force is exhausted, the pressure of the pressure oil tank is higher than the oil pressure of the pipeline, the check valve returns, and the check valve does not return to its place. The pressure peak formed by the backflow of part of the oil and the pressure peak formed by the oil pump are still in the reverse direction, which is transmitted to the center of the oil inlet pipeline, and will inevitably collide somewhere in the center of the oil inlet pipeline. The pressure of the two-way oil hammer formed must be far greater than the spring type safety The working pressure of the valve (the place where the two pressure peaks collide is not necessarily at the spring safety valve, the distance between the spring safety valve and the two pressure peaks is the reason why the vibration of the spring safety valve is different). The huge pressure formed by the two-way oil hammer is a wave peak, which makes the oil drain piston (Fig. 2) compress the spring (Fig. 1) at a large speed to open all the oil drain holes. Since the pressure peak is followed by the pressure trough, and the spring is greatly compressed by the pressure peak, the spring force formed is also large. The piston in the oil discharge chamber impacts the valve body rapidly under the condition of great downforce (3 in the figure). From the beginning to the end, this is the whole process of spring safety valve vibration. The anti vibration strength is the strength of shock wave, and its vibration frequency is the frequency of shock wave.

After the oil pump is shut down, the resistance to be overcome by inertia is very large, the rotating speed is greatly reduced, the ability to form the pressure peak of the driving oil is becoming smaller and smaller, and the pressure peak formed by the opening and closing of the check valve of the reverse pressure oil tank is becoming smaller and smaller gradually, so the vibration property is attenuation amplitude, in fact, the whole vibration process is only a few seconds.