The pros and cons of the working equipment of the excavator directly endanger the working efficiency and construction progress of the equipment. A Hitachi excavator maintenance engineer now analyzes several common faults that are common in his work.
1. The speed is slow when the boom is raised and retracted
In such situations, first check whether the oil in the oil tank of the excavator is too low, resulting in insufficient oil removal or emptying of the high-pressure water pump; whether the oil filter element of the pump is blocked and the pump oil is blocked, which leads to the low oil in the car fuel tank; Keep the filter element clean and fill it with gear oil. Secondly, check whether the gear oil pump is leaking internally, so that the high-pressure water pump capacity and efficiency cannot meet the requirements; whether the sealing condition of the oil inlet and delivery pipe is good, whether there is gas entering the system software, resulting in insufficient pressure; the gear oil pump entering and exiting the oil delivery pipe Is the tipping accurate? After checking and clearing the safety hazards in the left and right positions, check whether the boom cylinder and the boom control valve, the tipping bucket cylinder and the tipping bucket control valve are internal leaks.
After analysis and practical activities, a simple method for rapid diagnosis and fault detection is found:
(1) Fully load the loading hopper and lift it to the limit position; then place the boom control rod in a negative correlation, turn off the flame, and the hydraulic oil pump will stop the oil supply interruption, which may cause accidents. Observe the boom The lowering rate of the boom; then the boom lever is placed on the raised position. If the lowering rate of the boom is significantly accelerated at this time, the internal leakage is due to the boom operating valve. In the same way, similar methods can be used for the weak condition of the bucket withdrawing bucket. The judgment is made based on the telescopic condition of the tipping bucket cylinder when the control rod is first in position and tilted backward.
(2) Check whether the piston rod sealing ring of the boom cylinder is damaged. Reduce the piston rod of the boom cylinder, and then remove the rodless cavity oil pipe, so that the rod cavity of the boom cylinder is filled with oil again. If there is a lot of working oil leaking out of the rodless cavity oil side (all normal leakage should be ≤30ml /min), indicating an error in the piston rod sealing ring, which should be removed first.
(3) If the o-shaped sealing ring of the distribution valve is embrittled, deformed or damaged, a part of the valve stem is exposed and rusted, resulting in damage to the protruding surface, which will cause leakage outside the distribution valve. At this time, the o-ring should be removed and replaced. If the rust on the edge of the valve stem is serious, a part of the rust can be ground off, and then soldering is carried out to restore it to the original straight, polished and polished. If the valve core and valve sleeve of the distribution valve are damaged seriously, it will cause internal leakage. At this time, the distribution valve should be disassembled. If the standard allows, the surface of the valve core can be plated, and then matched and ground with the valve sleeve to make it match. The gap is 0.006～0.012mm and there is no stuck condition.
(4) This type of problem also occurs when the opening pressure of the pilot safety valve is too low. At this time, do not blindly follow the trend to tighten the variable pressure screw of the main valve. The valve should be repaired to see if the pilot valve is broken, the pilot valve is well sealed, whether the main spool is stuck and the main spool damping hole Is it blocking. If there are no problems on the left or right, the opening pressure of the valve should be adjusted. The way to adjust the pressure is: first twist the oil plug on the distribution valve, connect the pressure gauge, then start the diesel engine and manipulate its speed ratio at 1800r/min, and then place the bucket electro-hydraulic directional valve to be negatively correlated , The boom is raised to the limit position to make the system software hold the pressure. At this time, adjust the variable pressure screw until the pressure gauge reads the standard value.
2. The boom lift is normal, but the tipping bucket is slow
The key reason for common failures is that the set pressure of the two load valves of the tipping bucket cylinder, the rodless cavity and the rod cavity of the tipping bucket cylinder should meet the requirements. The whole process of pressure inspection is: connect the pressure gauge at the pressure measurement place and place the tipping bucket control valve in a negative correlation to raise the boom or learn to put it down. When the crankshaft passes the dead center, the rod cavity and the rodless cavity of the tipping bucket cylinder should create pressure. The pressure shown on the pressure gauge when the piston position of the tipping bucket cylinder is the setting pressure of the load valve. If the pressure is less than the set pressure during production, the reasons will be:
(1) The common failures of internal leakage in the tipping bucket cylinder are the same as the internal leakage of the boom cylinder.
(2) The main spool of the load valve of the tipping bucket cylinder has residual particles, which jams the main spool, causing the main spool to be in a normally open condition, resulting in common failure points.
At this time, the residue should be eliminated. In addition, check the condition of the various parts in the valve. Adjust the clearance between the valve stem and the valve body. All normal clearance between the valve stem and the valve body should be 0.06～0.012mm.
3. Vibration during lifting and tipping
The actual common fault causes and clearing methods are as follows:
(1) The remaining oil is not enough, so that the pressure during work is not stable, so the gear oil should be filled.
(2) The sealing of the fuel pipe connection is not very good, and the gas enters the system software, which causes the pressure to be unstable during work. The sealing of each connection of the fuel pipe should be checked.
(3) A lot of gas bubbles infiltrate the hydraulic oil, so that the hydraulic oil with gas becomes a compressible mass. The leaky seal in the bottom pressure fuel pipe should be removed, and then the gas-stained hydraulic oil should be discharged.
(4) The locknut of the piston of the hydraulic cylinder is loose, causing the piston to shake in the hydraulic cylinder. Hydraulic cylinders and lock nuts should be disassembled.
(5) The opening pressure of the main valve is unstable, which causes the high pressure oil pressure to change, causing vibration. Check the pressure-changing spring of the valve and adjust the opening pressure.
(6) The internal leakage of the two tipping bucket cylinders and the two boom cylinders are not the same, causing the total flow to fluctuate and cause vibration. The common faults that leak in the tipping bucket cylinder and boom cylinder should be cleared. If there is no problem in the inspection and the piston has a large-scale calendering condition, it should be removed for cutting, and then plated with 0.05mm hard chrome. If the rod diameter is too small, the thickness of the guide sleeve can be appropriately increased.
