1、 Noise of plunger pump or motor

1. Air suction is one of the main reasons for high noise of hydraulic pump. It is easy to form cavitation in its high pressure area and propagate in the form of pressure wave, causing oil vibration and cavitation noise of the system. The main reasons are:

(1) The oil filter and oil inlet pipe of the hydraulic pump are blocked or the viscosity of the oil is too high, which can cause the vacuum at the oil inlet of the pump to be too high and air to penetrate.

(2) The oil seal at the shaft end of the hydraulic pump and pilot pump is damaged, or the oil inlet pipe is poorly sealed, causing air to enter.

(3) The oil level in the oil tank is too low, so that the oil inlet pipe of the hydraulic pump is directly sucked empty.

When high noise occurs in the operation of the hydraulic pump, the above parts shall be checked first, and problems found shall be handled in time.

2. The internal components of the hydraulic pump are excessively worn, such as the wear and tear of the matching parts between the cylinder body and the port plate, the plunger and the column plug hole of the plunger pump, which causes serious leakage in the hydraulic pump. When the hydraulic pump outputs high pressure and small flow oil, flow pulsation will occur, resulting in high noise. At this time, the deflection angle of the variable mechanism of the pilot system can be appropriately increased to change the impact of internal leakage on the pump output flow. The servo valve spool of the hydraulic pump and the piston controlling the flow will also pulse during the movement of the piston due to their resistance to wear and strain, causing fluctuations in the output flow and pressure of the hydraulic pump, which will produce large vibration and noise at the pump outlet. At this time, the worn and strained components can be brush plated and matched or replaced.

3. The valve plate of hydraulic pump is also one of the important components that are easy to cause noise. During the use of the port plate, due to surface wear or oil sludge deposition at the opening of the unloading groove, the unloading groove will become shorter and change the position of the unloading groove, resulting in oil trapping, which will then cause higher noise. In the normal repair process, the large unloading groove of the port plate must be installed in the high-pressure cavity area of the pump, and its sharp angle direction must be opposite to the rotation direction of the cylinder block, otherwise it will also bring greater noise to the system.

2、 Noise of overflow valve

The overflow valve is prone to generate high-frequency noise, which is mainly caused by the unstable performance of the pilot valve, that is, the noise generated by the air vibration caused by the high-frequency oscillation of the pressure in the front chamber of the pilot valve. The main reasons are:

(1) Air is mixed in the oil to form cavitation in the front chamber of the pilot valve, which causes high-frequency noise. At this time, the air shall be discharged in time to prevent the outside air from entering again.

(2) The needle valve is excessively worn due to frequent opening during use, which makes the cone surface of the needle valve and the valve seat unable to fit, resulting in unstable pilot flow, pressure fluctuation and noise. At this time, it should be repaired or replaced.

(3) The pressure regulating function of the pilot valve is unstable due to the fatigue deformation of the spring, which makes the pressure fluctuate greatly and causes noise. At this time, the spring should be replaced.

III Hydraulic cylinder Noise of

(4) Air is mixed in the oil or the air in the hydraulic cylinder is not completely discharged, which causes cavitation under high pressure and causes large noise. At this time, exhaust the air in time.

(2) If the cylinder head oil seal is too tight or the piston rod is bent, the noise will also be caused by different forces during the movement. At this time, the oil seal or straight piston rod must be replaced in time.

4、 Pipeline noise

Vibration and noise can also be caused by excessive dead bending of pipelines or loosening of fixing clips. Therefore, dead bending shall be avoided as far as possible in pipeline layout, and loose clips shall be tightened in time.