Hydraulic system fault judgment method
Power source----Noise of hydraulic pump or motor (1) Suction is one of the main causes of excessive noise of hydraulic pump. When air is mixed into the oil, it is easy to form cavitation in its high pressure zone and propagate in the form of pressure waves, causing oil to oscillate, resulting in cavitation noise. The main reasons are as follows: 1 The 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 pump inlet to be too high, so that the air penetrates. 2 The hydraulic piston pump or the charge pump shaft end oil seal or O-ring is damaged, resulting in poor oil pipe sealing, causing the air to enter the o 2 oil tank too little oil, the oil level is too low, so that the hydraulic pump inlet pipe directly sucks. When there is high noise in the working of the hydraulic pump, the above parts should be inspected first, and the problem 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 piston pump's cylinder block and the distribution plate, the plunger and the plunger hole, etc., causing serious leakage in the hydraulic pump. When the hydraulic pump outputs high pressure and small Flow pulsation occurs when the fluid is flowing, causing higher noise. At this time, the deflection angle of the pilot system variable mechanism 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 that controls the flow will also cause the piston to pulsate during the movement due to local wear and strain, causing fluctuations in the output flow and pressure of the hydraulic pump, resulting in large vibration and noise at the pump outlet. . At this time, the components that are severely worn or strained can be subjected to brush plating or replacement treatment. (3) The hydraulic pump distribution plate is also one of the important components that cause noise. In the use of the distribution plate, due to surface wear or sludge deposition on the opening of the unloading groove, the unloading groove will be shortened and the unloading position will be changed, resulting in a trapped oil phenomenon, which in turn causes high noise. In the normal repair process, the flat-repaired distribution plate will also have the effect of shortening the unloading groove. If it is not properly trimmed in time, it will generate more noise. During the assembly process, the large unloading groove of the distribution 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 block, otherwise it will bring greater noise to the system. 2. Noise of the relief valve The relief valve is prone to high-frequency noise, mainly due to the unstable performance of the pilot valve, which is the noise generated by the high-frequency oscillation of the front chamber pressure of the pilot valve. The main reasons are as follows: (1) Air is mixed into the oil to form a cavitation in the front cavity of the pilot valve to cause high frequency noise. At this time, the air should be exhausted in time and the outside air should be prevented from re-entering. (2) The needle valve is excessively worn due to frequent opening during use, so that the tapered surface of the needle valve and the valve seat cannot be tightly combined, resulting in unstable pilot flow and pressure fluctuations, which may cause timely repair or replacement. (3) The pilot valve is unstable due to the fatigue deformation of the spring, which causes the pressure fluctuation to be large and causes noise. At this time, the spring should be replaced. 3. Noise of hydraulic cylinders (1) Air is mixed in the oil or the air in the hydraulic cylinder is not completely exhausted, and cavitation occurs under the action of high pressure, causing large noise. In this case, the air must be drained in time. (2) The cylinder head oil seal is too tight or the piston rod is bent, and noise will be generated due to the difficulty during the movement. In this case, the oil seal or alignment piston rod must be replaced in time. 4. Pipeline noise (1) There are too many dead bends in the pipeline. When inspecting and installing the pipeline, be careful not to use too many right-angled joints, or the joints are not large enough to generate noise. Therefore, blind bends should be avoided as far as possible in the piping arrangement. (2) Loose externally used pipe clamps allow the vibration of the hydraulic system to transmit to the outside of the pipeline, which can also generate vibration and noise.