What are the hydraulic system noises of CAT 320D excavator

Pipeline noise

Excessive dead bends in pipelines or loose fixing clips can also generate vibration and noise. Therefore, in pipeline layout, dead bends should be avoided as much as possible, and loose clips should be tightened in a timely manner.

Noise of overflow valve

Overflow valves are prone to generating high-frequency noise, mainly due to the unstable performance of the pilot valve, which is caused by the high-frequency oscillation of the pressure in the front chamber of the pilot valve leading to air vibration. The main reasons are:

(1) Air is mixed into the oil, forming air pockets in the front chamber of the pilot valve and causing high-frequency noise. At this point, it is necessary to promptly exhaust the air and prevent external air from re entering.

(2) The needle valve is excessively worn due to frequent opening during use, causing the conical surface of the needle valve to not fit tightly with the valve seat, resulting in unstable pilot flow, pressure fluctuations, and noise. At this time, it should be repaired or replaced in a timely manner.

(3) The pressure regulating function of the pilot valve is unstable due to spring fatigue deformation, causing large pressure fluctuations and noise. At this time, the spring should be replaced.

Noise of hydraulic cylinder in Carter 320D excavator

(1) Air is mixed in the oil or the air in the hydraulic cylinder is not completely discharged, resulting in cavitation under high pressure and causing significant noise. At this point, it is necessary to promptly exhaust the air.

(2) If the cylinder head oil seal is too tight or the piston rod is bent, noise may also be generated during movement due to friction. At this point, it is necessary to replace the oil seal or straighten the piston rod in a timely manner.

Noise of CAT 320D excavator plunger pump or motor

(1) The phenomenon of suction is one of the main reasons for the high noise of hydraulic pumps. 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 oscillation and resulting in cavitation noise in the system. The main reasons are:

① The blockage of the oil filter and inlet pipe of the hydraulic pump, or the high viscosity of the oil, can all cause the vacuum degree at the pump inlet to be too high, allowing air to infiltrate.

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

The oil level in the tank is too low, causing the hydraulic pump's inlet pipe to be directly emptied.

When there is high noise in the hydraulic pump of the Caterpillar 320D excavator during operation, the above parts should be inspected first, and any problems should be promptly dealt with.

(2) Excessive wear of internal components of hydraulic pumps, such as the wear and tear of the cylinder body and distribution plate, plunger and plunger hole of plunger pumps, can cause serious leakage inside the hydraulic pump. When the hydraulic pump outputs high-pressure and low flow oil, flow pulsation will occur, causing high noise. At this point, the deflection angle of the variable mechanism in the pilot system can be appropriately increased to improve the impact of internal leakage on the pump output flow rate. The servo valve core of the hydraulic pump and the piston that controls the flow rate may also experience local wear and tear, causing pulsation of the piston during movement, resulting in fluctuations in the output flow rate and pressure of the hydraulic pump, thereby generating significant vibration and noise at the pump outlet. At this point, components with severe wear and tear can be brushed, plated, matched, or replaced.

(3) The distribution plate of a hydraulic pump is also one of the important components that can easily cause noise. Due to surface wear or oil sludge deposition at the opening of the unloading groove during use, the distribution plate will shorten the unloading groove and change the unloading position, resulting in trapped oil and causing high noise. During the normal repair process, the distribution plate repaired by flat grinding may also have the consequence of the unloading groove becoming shorter. If it is not appropriately elongated in a timely manner, it will also produce significant 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 rotation direction of the cylinder body, otherwise it will also bring significant noise to the system.