01 Noise of plunger pump or motor
(1) Vacuum phenomenon is one of the main causes of excessive noise of hydraulic pumps. 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 waves, which causes the oil to oscillate and cause cavitation noise in the system. The main reasons are:
①The oil filter of the hydraulic pump, the oil inlet pipe is 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, allowing air to penetrate.
②The oil seal of the shaft end of the hydraulic pump or the pilot pump is damaged, or the oil inlet pipe is not well sealed, causing air to enter.
②The oil level of the fuel tank is too low, so that the hydraulic pump inlet pipe is directly sucked out.
When high noise occurs during the operation of the hydraulic pump, the above-mentioned parts should be inspected first, and any problems found should be dealt with in time.
(2) Excessive wear of the internal components of the hydraulic pump, such as the wear and strain of the matching parts of the cylinder and the valve plate of the plunger pump, the plunger and the plunger hole, etc., makes the hydraulic pump leak severely. Flowing oil will generate flow pulsation, causing higher noise. At this time, the deflection angle of the variable mechanism of the pilot system can be appropriately increased to improve the effect of internal leakage on the output flow of the pump. The servo valve spool of the hydraulic pump and the piston that controls the flow will also pulsate during the movement due to local wear and tear, causing the output flow and pressure of the hydraulic pump to fluctuate, resulting in greater vibration and noise at the pump outlet . At this time, the components with serious wear and tear can be brushed, plated, matched or replaced.
(3) The hydraulic pump valve plate is also one of the important components that is easy to cause noise. Due to surface wear or sludge deposition at the opening of the unloading groove, the distribution plate will make the unloading groove shorter and change the unloading position, resulting in trapped oil, which in turn causes higher noise. In the normal repair process, the distribution plate repaired by flat grinding will also have the effect of shortening the unloading groove. At this time, if it is not properly lengthened 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 direction of rotation of the cylinder, otherwise it will also bring greater noise to the system.
02 Noise of relief valve
The relief valve is prone to 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, which forms cavitation in the front cavity of the pilot valve and causes high-frequency noise. At this time, the air should be exhausted in time to prevent the outside air from re-entering.
(2) The needle valve is excessively worn due to frequent opening during use, so that the cone surface of the needle valve and the valve seat cannot be tightly closed, resulting in unstable pilot flow and noise caused by pressure fluctuations. In this case, repair or replace it in time.
(3) The pressure regulation function of the pilot valve is unstable due to the fatigue deformation of the spring, which makes the pressure fluctuations large and causes noise. At this time, the spring should be replaced.
03 Noise of hydraulic cylinder
(1) There is air mixed in the oil or the air in the hydraulic cylinder is not completely exhausted, and cavitation occurs under the action of high pressure, which causes large noise. At this time, the air must be exhausted in time.
(2) If the oil seal of the cylinder head is too tight or the piston rod is bent, noise will also be generated due to extra strength during the movement. At this time, the oil seal or the piston rod must be replaced in time.
04 Pipeline noise
Excessive pipe bending or loosening of fixed clips can also generate vibration and noise. Therefore, dead bends should be avoided as much as possible in the piping layout, and loose clamps must be tightened in time.
