When the whole hydraulic excavator fails to operate, it is often necessary to follow the following sequence to diagnose the fault:
1. Check the amount of hydraulic oil
The hydraulic oil suction filter element is blocked, and the oil suction (including the low oil level of the hydraulic oil tank) will cause the hydraulic pump to absorb insufficient oil or even no oil, which will directly lead to the insufficient oil pressure of the hydraulic oil circuit, so that the excavator does not move. The diagnosis of this kind of fault can be eliminated by checking the liquid level of the hydraulic oil tank and the pollution degree of the hydraulic oil.
2. Check whether the hydraulic pump is faulty
Hydraulic excavators generally use two or more main pumps to provide pressure oil to the system. First of all, it can be judged whether the power of the engine output shaft can be transmitted to each hydraulic pump. If it cannot be transmitted, then the problem occurs in the power output of the engine. If it can be transmitted, it proves that the fault may occur in the hydraulic pump. In this case, an oil pressure gauge with appropriate range can be installed at the output port of each hydraulic pump to measure the output pressure of the pump, and the theoretical output pressure value of each pump can be compared to judge whether the hydraulic pump is faulty.
3. Check whether the safety locking valve is faulty
The safety lock valve is a mechanical switch in the cab, which can control the on-off of the oil circuit between the low-pressure oil circuit and the three groups of proportional pressure control valves in the cab (i.e. the left and right control handles and the walking push rod). When the safety lock valve is stuck or blocked, the oil cannot push the main control valve through the proportional pressure control valve, Thus, the whole machine has no action, and the replacement method can be used to remove the fault.
4. Check whether the main relief valve is faulty
The main relief valve is a safety valve located on the valve body of the main control valve. By adjusting the pressure regulating nut of the main relief valve, the maximum pressure of the whole hydraulic system can be set, so as to keep the pressure of the whole hydraulic system within the controllable range and avoid the occurrence of insufficient or excessive pressure. If the spring in the main relief valve is broken or the set pressure is too low, the pressure of the whole system will be too low, then the pressure of the main pump pressure oil can not overcome the resistance of the actuator to do work, resulting in the phenomenon of misoperation of the whole machine. If this kind of fault, you can start the engine, connect the safety lock valve, and operate the handle to make the machine rotate or dig. If the valve does have a fault, the excavator will not work. At the same time, because the hydraulic oil can not push the actuator to do work, the hydraulic oil will emit a lot of heat, so that the temperature of the main relief valve body will rise rapidly. To solve this kind of fault, the main relief valve can be overhauled first, and then the pressure of the main relief valve can be reset.
