A excavator has been running for over 15000 hours and is currently experiencing a malfunction, unable to turn left or right at all. Except for the rotation, all other actions are normal, indicating that the working pump should be functioning properly. We troubleshoot in order from easy to difficult. First, the pressure gauge was used to measure the pressure of the pump during rotation. The normal pressure should be 30mpa, while the highest detected pressure is 8mpa, which is significantly different. This indicates that there is a serious leakage in the oil circuit controlling the rotation.
There are four reasons for this phenomenon:
1. The pilot pressure is low and the main control valve cannot be opened;
2. The spool of the rotary main control valve is stuck;
3. The oil replenishment valve of the rotary motor is stuck or the spring is broken, losing its oil replenishment function;
4. There are scratches on the contact surface of the motor distribution plate, which makes the inlet and outlet oil lines connected.
We swapped the pilot oil pipe of the boom and the pilot oil pipe of the rotation, and then operated the rotation handle. At this time, the action of the boom was normal, indicating that the pilot pressure of the rotation was normal. Exclude the first reason.
After disassembling the main valve core that controls the rotation, no abnormal wear or jamming was found, ruling out the second reason. The fault is not on the multi way valve.
The fault lies in the rotary motor. First, check the oil replenishment valve and find that it is not stuck and the spring is not broken. The third cause has also been ruled out. Upon opening the rear cover of the motor, it was discovered that the bearings were damaged. Subsequently, the entire motor was dismantled and the current distribution plate, sliding shoes, and all components were found to be damaged. This motor is an inclined shaft quantitative motor, and the bearings are the direct cause of motor damage. Over 15000 hours have exceeded the lifespan of the bearings, so the bearings of high load operating assemblies such as hydraulic pumps or motors should be replaced regularly.
2026 September 1st Week VAFEM Product Recommendation
A linear-motion bearing or linear slide is a bearing designed to provide free motion in one direction. There are many different types of linear motion bearings. Motorized linear slides such as machine slides, X-Y tables, roller tables and some dovetail slides are bearings moved by drive mechanisms. Not all linear slides are motorized, and non-motorized dovetail slides, ball bearing slides and roller slides provide low-friction linear movement for equipment powered by inertia or by hand. All linear slides provide linear motion based on bearings, whether they are ball bearings, dovetail bearings, linear roller bearings, magnetic or fluid bearings. X-Y tables, linear stages, machine slides and other advanced slides use linear motion bearings to provide movement along both X and Y multiple axis.
2026-09-04