The excavator hydraulic system is an assembly that organically connects various hydraulic components with pipelines according to the transmission requirements of the excavator's working devices and various mechanisms. It mainly includes hydraulic oil tanks, pumps, valves, various pipelines, and other components that perform various actions, such as hydraulic cylinders and hydraulic motors.
It converts the mechanical energy of the engine into hydraulic energy through the hydraulic pump, and then converts hydraulic energy back into mechanical energy through the hydraulic cylinder and hydraulic motor to realize various actions. In the whole process, the hydraulic oil is used as the working medium.
1. Main Components of Excavator Hydraulic System
1.1 Hydraulic Pump
The hydraulic pump is the core component of the excavator hydraulic system. Its main function is to draw hydraulic oil from the tank, increase the pressure of the hydraulic oil and send it to various execution parts of the hydraulic system, such as hydraulic cylinders and hydraulic motors.
1.2 Hydraulic Cylinder
The hydraulic cylinder is the energy converter of the excavator hydraulic system. It converts the hydraulic energy in the hydraulic system into mechanical energy to drive the working parts of the excavator, such as the boom, arm, and bucket.
1.3 Hydraulic Motor
The hydraulic motor is an actuator of the hydraulic system, which converts the liquid pressure energy provided by the hydraulic pump into the mechanical energy of its output shaft (torque and rotational speed).
1.4 Hydraulic Control Valve
Hydraulic control valve, also known as distribution valve, is the regulator of the excavator hydraulic system. It can control the flow and pressure of hydraulic oil to make various components in the hydraulic system to run according to the set action sequence and speed.
The excavator control valve is mainly composed of the following valve blocks: solenoid operated directional control valve, relief valve, one-way valve, and throttle valve.
The function of each valve block in the excavator control valve:
1. Directional control valve: controlling the oil in and out of the boom and arm cylinders, the oil in and out of the swing motor and travel motor, and the oil in and out of the bucket cylinder.
2. Relief valve: There are main relief valves and other relief valves. The main relief valve controls the system pressure.
3. One-way valve: controlling the hydraulic oil to make it flow in one direction.
4. Throttle valve: controlling the flow rate of hydraulic oil.
1.5 Hydraulic Tank
The hydraulic oil tank is the oil storage device of the excavator hydraulic system. It is mainly used to store and cool hydraulic oil, and send the hydraulic oil to the hydraulic system through the oil pump to maintain the normal operation of the hydraulic system.
1.6 Hydraulic Lines
The hydraulic pipeline is the delivery pipeline of the excavator hydraulic system. It conveys hydraulic oil from the hydraulic pump to hydraulic control valves, hydraulic cylinders and other execution components, and transports the return oil back to the hydraulic oil tank.
1.7 Cooler
The cooler is an important component in the hydraulic system to maintain oil stability and normal operation. It usually adopts the form of water cooling or air cooling, which can effectively reduce the temperature of the oil, thus improving the working efficiency and reliability of the system.
1.8 Common Sensors and Solenoid Valves on Excavators
Let’s talk about some solenoid valves and sensors on the excavator hydraulic system, commonly including: proportional solenoid valve, pressure sensor, rotational speed sensor, angular displacement sensor, displacement sensor, etc.
Proportional solenoid valve: It ensures that the hydraulic pump power is basically consistent with the engine speed (power) at any speed.
Rotational speed sensor: Installed at the link between the engine and the hydraulic pump, it mainly collects speed information and transmits it to the computer to check whether the engine speed matches the set speed.
Pressure sensor: Detecting the inlet and outlet pressure of the hydraulic pump, which is sent to the computer for analysis, and feeds it back to other parts, such as executing the idle mode of the excavator.
2. Excavator Hydraulic System Faults and Solutions
Failures in the excavator hydraulic system are generally caused by the hydraulic oil temperature being too high or the air entering the system.
2.1 Hydraulic Oil Temperature Too High
If you want to solve the fault, you must conduct a thorough analysis of the cause before solving it, and you must also be mentally prepared for the consequences of the fault.
If the viscosity of the hydraulic oil and the working efficiency of the system are reduced, it will seriously affect the normal operation of the machinery, and even cause the friction resistance to greatly increase, causing the hydraulic valve to become stuck. It will also cause the seal material to deteriorate, causing the hydraulic system to leak.
The reason for the above consequences may be that the fuel tank does not have good heat dissipation performance, so the temperature of the oil in the tank will rise. Faced with this situation, the fuel tank should be replaced with a larger capacity tank to achieve the purpose of cooling the oil in the tank. You can also choose to install a cooling device.
On the other hand, the cause of the failure may be that the selected hydraulic oil does not meet certain quality standards and does not meet the requirements, or the operator mixes various types of hydraulic oil, which causes the oil viscosity to be greatly increased. Therefore, when selecting hydraulic oil, we must fully consider the consequences of using substandard oil and strictly regulate the use of hydraulic oil.
Another possibility is that the environment at the construction site is harsh, so as the machine runs, the quality of oil cannot be guaranteed, and it is easy to mix with some impurities and pollutants. When contaminated, the hydraulic oil enters the clearance of the pump and the motor, which will seriously damage the smoothness of their internal surfaces, cause leakage, and increase the oil temperature. In the face of these problems, the environment should fundamentally be improved so that obstacles can be avoided.
2.2 Air Enters the Oil System
Air will also have a certain impact on the hydraulic oil of the excavator. When air enters the oil, cavitation or erosion will occur, which will damage the metal sealing material and even cause noise, destroying the stability of the hydraulic system.
The reason for the above failure may be that the joints are not fixed properly, causing a sealing problem, allowing air to enter it. Generally speaking, the hydraulic system must have good sealing, especially at the key locations of the joints. Only by fixing the joints can the oil tank be properly sealed to prevent air from entering and harming the system.
Another situation is that the suction pipeline in the hydraulic system and the pipeline connecting the system are damaged for some reason, maybe they are worn or corroded, which leads to the entry of air. This problem occurs because its pipeline layout design does not meet the specifications and actual needs. Therefore, if you want to solve this problem, you must clean and maintain the pipeline to reduce external corrosion and prevent air from entering.
The last reason why air enters the hydraulic system may be that due to time constraints, air bubbles are accidentally brought into the tank and mixed into the system when replenishing oil. In actual operation, this problem must be avoided. The operator must maintain a stable working condition when replenishing, so as to ensure the safe operation of the hydraulic system.
