Common Noise Faults in Hydraulic Parts
Posted on 04/01/2024
This article takes the hydraulic system of the EC140 hydraulic excavator as an example, and introduces the possible causes and elimination methods of noise as follows.
1. Noise from the plunger pump or motor
(1) The vacuum phenomenon is one of the main causes of excessive noise in hydraulic pumps. When air is mixed into the oil, cavitation is easily formed in the high-pressure area and propagates in the form of pressure waves, causing the oil to oscillate and causing cavitation noise in the system. The main reasons are:
The oil filter and oil inlet pipe of the hydraulic pump are clogged or the oil viscosity is too high, which can cause the vacuum at the oil inlet of the pump to be too high, allowing air to penetrate.
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.
The oil level in the fuel tank is too low, causing the hydraulic pump inlet pipe to be emptied directly.
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 a timely manner.
(2) Excessive wear and tear of the internal components of the hydraulic pump, such as wear and strain on the matching parts such as the plunger pump's cylinder, valve plate, plunger and plunger hole, causing serious leakage in the hydraulic pump. When the hydraulic pump outputs high pressure or small When oil is flowing, flow pulsation will occur, causing higher noise. At this time, the deflection angle of the pilot system variable mechanism can be appropriately increased to improve the impact 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 local wear and strain, causing the piston to pulsate during movement, 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 that are severely worn or strained can be brush-plated, ground, or replaced.
(3) The hydraulic pump valve plate is also one of the important components that can easily cause noise. During use, due to surface wear of the valve plate or sludge deposited at the opening of the unloading groove, the unloading groove will be shortened and the unloading position will be changed, resulting in trapped oil, which in turn will cause higher noise. During the normal repair process, the flat-grinded and repaired valve plate will also have the unloading groove shortened. 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 the direction of its sharp angle must be opposite to the rotation direction of the cylinder, otherwise it will bring greater noise to the system.
2. Noise from 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 is caused by air vibration caused by high-frequency oscillation of pressure in the front chamber of the pilot valve. The main reasons are:
(1) Air is mixed into the oil, causing cavitation in the front chamber of the pilot valve and causing high-frequency noise. At this time, the air should be exhausted in time and prevent outside air from re-entering.
(2) The needle valve is excessively worn due to frequent opening during use, causing the needle valve cone and valve seat to be unable to seal tightly, resulting in unstable pilot flow, pressure fluctuations 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 fatigue deformation of the spring, causing large pressure fluctuations and causing noise. At this time, the spring should be replaced.
3. Hydraulic cylinder noise
(1) There is air mixed in the oil or the air in the hydraulic cylinder is not completely exhausted, causing cavitation under high pressure and causing loud noise. At this time, the air must be exhausted in time.
(2) The cylinder head oil seal is too tight or the piston rod is bent, which may also cause noise due to abnormal force during movement. At this time, the oil seal must be replaced or the piston rod must be straightened in time.
3. Pipeline noise
Too many dead bends in the pipeline or loose fixing clips can also cause vibration and noise. Therefore, dead bends should be avoided as much as possible in the pipeline layout, and loose clamps must be tightened in time.
