The slow turning and weakness of the excavator is one of the common hydraulic faults. It is believed that many of the main friends of the excavator have been encountered, mainly in the slow speed, incoherence, and sometimes abnormal sound.
In the work, when the operating handle is placed in a rotating position, the control oil reaches the control valve and drives the rotary valve rod to make the high pressure oil supplied by the rear working oil pump into the rotary motor; at the same time, the oil circuit of the oil tank is cut off, the pressure of the brake loosening valve is increased, and the valve rod is pushed to the other auxiliary pressure oil to enter the brake piston and turn on the rotary piston and turn on the rotation. The braking device makes the rotary motor act; the rotary motor outputs power through the pinion of the transmission, and the pinion is engaged with the rotary gear ring to generate a rotary motion.
Cause of failure
According to the working principle of the slewing mechanism, there are three main reasons for the failure, namely, the main working oil path failure, the mechanical transmission failure, and the control of the oil circuit fault.
1. Main working oil inspection
When the pressure of the main oil road is low, the excavator will not be able to turn. Measuring the pressure of the main working oil system, there is a six angle oil plug at the outlet of the post working oil pump, and the pressure gauge is installed after dismantling. The rotating handle is operated, the engine is accelerated and the pressure is reached to 23.5MPa, indicating the working pressure of the system, the main working oil way and the liquid. The pressure components are normal, and if they are below, they indicate that the main oil path is leaking.
2, mechanical part check
The power transmission of the rotary motor mainly depends on the meshing and rotation of the gear gear and the rotary gear ring. In this process, if the gear is stuck between the gears, the rotation will not move.
3. Check the inspection of the oil road
Due to the residual of the pollutants in the hydraulic system of the excavator (the excavator enters the sand grains and debris of the hydraulic system in the process of production, work and maintenance), the hydraulic control elements will be lost after a long period of work, and the control of the oil pressure in the system will fail, and the specific reasons are the following.
(1) the failure of the safety valve on the rotary motor
(2) the pressure of the rotary overflow valve, the pressure of the P1 pump (the front pump) and the servo pressure are below the normal value (normal 27-30MPa).
(3) the failure of the unidirectional valve with the bucket load
(4) the valve spool failure of the rotary valve
Failure case
A Hitachi excavator has a slow starting speed and a weak turning load.
fault analysis
1. Wear of overload safety valve of rotary motor of excavator
2. The pressure of the P1 pump and the servo pressure are lower than the calibration value when the rotary overflow pressure, no-load and load are applied.
3, the wear of one way valve seat on the bucket of the excavator
Troubleshooting
1, start the test, turn slow and weak
2, check whether the two sides of the excavator are slow, if only one direction is slow, indicating that there is a problem with the overload safety valve of the rotary motor.
3. The pressure meter is used to test the rotary overflow pressure of the excavator, the maintenance pressure of the P1 pump and the servo pressure when the load is loaded. The left and right revolving overflow pressure is 14MPa (normal 27-30MPa), and the P1 pump pressure is 2.5MPa normal.
Failure result
The above test shows that there is leak point in the high idle speed of the excavator engine.
