01 noise of plunger pump or motor
(1) Suction phenomenon is one of the main reasons for high noise of hydraulic pump. When air is mixed into the oil, it is easy to form cavitation in its high-pressure area and propagate in the form of pressure wave, causing oil oscillation and cavitation noise in the system. The main reasons are:
① The oil filter and oil inlet pipe of the hydraulic pump are blocked or the oil viscosity 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.
② The oil level in the oil tank is too low, which makes the oil inlet pipe of the hydraulic pump empty directly.
In case of high noise during the operation of the hydraulic pump, the above parts shall be checked first and the problems shall be solved in time.
(2) The internal components of the hydraulic pump are excessively worn, such as the wear and strain of the cylinder body and port plate of the plunger pump, the plunger and plunger hole and other mating parts, resulting in serious leakage in the hydraulic pump. When the hydraulic pump outputs high-pressure and small flow oil, flow pulsation will occur, causing high noise. At this time, the deflection angle of the variable mechanism of the pilot system can be appropriately increased to improve the influence of internal leakage on the pump output flow. The servo valve spool of the hydraulic pump and the piston controlling the flow will also be subject to local wear and tear, which will make the piston pulsating in the moving process, causing fluctuations in the output flow and pressure of the hydraulic pump, resulting in greater vibration and noise at the pump outlet. At this time, components with serious wear and tear can be brush plated, matched or replaced.
(3) The valve plate of hydraulic pump is also one of the important components that are easy to cause noise. When the valve plate is used, the surface wear or oil sludge is deposited at the opening of the unloading groove, which will make the unloading groove shorter and change the unloading position, resulting in oil trapping, and then cause higher noise. In the normal repair process, the valve plate repaired by flat grinding will also have the consequence that the unloading groove will become shorter. At this time, if it is not properly trimmed in time, it will also produce greater noise. During the assembly process, the large unloading groove of the valve plate must be installed in the high-pressure chamber of the pump, and its sharp angle direction must be opposite to the rotation direction of the cylinder block, otherwise it will bring greater noise to the system.
02 noise of overflow valve
The overflow valve is prone to produce high-frequency noise, which is mainly caused by the unstable performance of the pilot valve, that is, the noise caused by air vibration caused by high-frequency oscillation of the pressure in the front chamber of the pilot valve. The main reasons are:
(1) Air mixed in the oil will form cavitation in the front chamber of the pilot valve and cause high-frequency noise. At this time, the air shall be exhausted in time and the outside air shall be prevented from re entering.
(2) The needle valve is excessively worn due to frequent opening during use, so that the conical surface of the needle valve and the valve seat cannot be closely closed, resulting in unstable pilot flow, pressure fluctuation and noise. At this time, it should be repaired or replaced in time.
(3) The pressure regulating function of the pilot valve is unstable due to the fatigue deformation of the spring, resulting in large pressure fluctuation and noise. At this time, the spring should be replaced.
03 noise of hydraulic cylinder
(1) Air is mixed in the oil or the air in the hydraulic cylinder is not completely exhausted, causing cavitation under high pressure and causing large noise. At this time, the air must be exhausted in time.
(2) If the cylinder head oil seal is too tight or the piston rod is bent, noise will also be generated due to other forces during movement. At this time, replace the oil seal or straighten the piston rod in time.
04 pipeline noise
Excessive dead bending of pipelines or loose fixing clips can also produce vibration and noise. Therefore, dead bending shall be avoided as far as possible in pipeline layout, and loose clamps shall be tightened in time.
