If the diesel engine is running normally and the corresponding actuator movement is weak when the pilot handle is operated, the inspection, analysis and maintenance can be carried out in the following order from easy to difficult.
1. The pilot pressure is abnormal
(1) The indication value of the pilot pressure gauge is very low or zero.
① Loosen the pilot relief valve and cap, use a wrench to make a small angle adjustment in a clockwise direction, and at the same time observe whether the indicated value of the pilot pressure gauge changes.
A. If there is a change, the pressure can be adjusted to 2.7-3. 3 MPa.
B. If there is no change, the following faults may exist:
a. The hydraulic oil level is too low, and the pilot pump is emptied. In this regard, hydraulic oil should be added to the specified height.
b. The pilot relief valve is loose. Therefore, the pilot valve should be further tightened on the valve seat.
c. The pilot relief valve spring yields or breaks. Therefore, the spring should be replaced.
d. The spool of the pilot relief valve is severely worn, and the seal between the spool and the seat is poor, and the spool needs to be replaced.
②The leakage in the pilot pump is serious and needs to be removed for repair or replacement.
(2) The indication value of the pilot pressure gauge is higher than 3.3 MPa. At this time, the pilot relief valve should be adjusted so that the pilot pressure is 2. 7~3. 3 Mpa 0
2. The pilot pressure is normal
If the pilot pressure is normal or normal after adjustment, but the motion of each actuator is still weak, the inspection should be continued in the following order:
(1) Operate the pilot valve, make each actuator work and hit the limit block, and observe whether the speed of the diesel engine is significantly reduced. If the engine speed is significantly reduced, it may be caused by the following faults:
① If the air filter is blocked, the air filter should be inspected and maintained according to the diesel engine instruction manual;
② If the diesel filter is blocked or partially blocked, the diesel filter should be inspected and maintained according to the diesel engine instruction manual;
③The fuel flow is not smooth, and the problem of insufficient fuel supply needs to be eliminated;
④ There is air in the fuel system, so exhaust the air in the fuel system.
(2) Respectively check whether the overflow pressure value of the main safety valve of the two sets of multi-way reversing valves meets the overflow pressure value specified in the operation manual of the excavator. If the overflow pressure of one or two main safety valves is too low, you can loosen the main safety valve with lower overflow pressure and cap, operate the corresponding actuator controlled by the main safety valve, make small angle adjustments while observing the pressure The table indicates the value.
If the pressure value changes with the adjustment angle, the pressure can be adjusted to the specified value. If the main safety valve is adjusted, the overflow pressure value does not change, which is generally caused by the following reasons:
① The tightening torque of the main safety valve installed on the valve body is not enough, and the main safety valve needs to be tightened further;
②The foreign matter is stuck on the contact surface of the valve core and the valve sleeve, so that the valve core cannot return to the original position, the foreign matter should be removed;
③If the spool orifice is blocked, the foreign matter in the orifice should be removed;
④The main safety valve spool and valve sleeve are severely worn, and can be paired and ground to make the contact surface tightly sealed.
(3) Check the flow rate of the variable pump. At this time, there may be the following three situations:
① There is no flow output, at this time, you can check and eliminate the fault according to "1" in this subsection.
②Insufficient flow can be checked in the following order:
A. Whether the oil level of the hydraulic oil tank is low.
B. Whether the viscosity of hydraulic oil is too large or too small. If the viscosity is too high, it should be preheated to a certain temperature before operation. If the viscosity is low, check whether the hydraulic oil used meets the requirements, and replace the hydraulic oil that is not poisonous to the brand specified in the machine's instruction manual.
C. The internal leakage of the main hydraulic pump is too large and the volumetric efficiency is reduced. At this time, the following inspections and repairs should be made.
a. The clearance between the plunger and the plunger hole of the copper cylinder is too large, and the plunger or the copper cylinder can be used alone to make the clearance meet the specified size;
b. The fitting clearance between the spherical surface of the copper cylinder body and the spherical surface of the valve plate is too large, an adjustment gasket of appropriate thickness can be added at the center rod to make the fitting clearance meet the requirements;
c. The disc spring gasket is severely worn and should be replaced;
d. Re-check the fit clearance of the regulator guide rail surface, valve plate, copper cylinder, disc spring washer, etc., and add an adjustment shim of appropriate thickness to the center rod.
③If the flow meets the requirements, the inspection should be continued in the following order:
A. Whether the machine has been left unused for a long time. If it is, it may be that after the air is separated from the oil, it floats in the control pipes and hydraulic cylinders and other actuators, causing the actuators to act weakly. Therefore, the oil should be chemically analyzed, and sometimes the hydraulic oil needs to be replaced according to the specified brand.
B. Air mixed in the oil will also cause weak movement of the various actuators. The main oil pump or the gear pilot pump sucks air, the casing of the pump has sand holes, the welding pores of the oil inlet pipe, and the installation of the oil inlet pipe is not sealed, etc., will cause the hydraulic system to enter air, sometimes due to the replacement of hydraulic oil, pumps, valves, etc. Into the air. If the oil pump is emptied, add hydraulic oil; if you change the hydraulic oil, valve, and pump to mix the air into the oil, you can operate the machine for half an hour to run at a small load, and work with the load after the air in the oil is exhausted. If the shell sand hole, the oil inlet pipe or the unsealed location are difficult to find, the hydraulic oil tank can be sealed first, and then 0.2-0. 4MPa air pressure is applied to the oil tank, so that the leak can be easily found, which is a malfunction. point.
If after all the above faults are eliminated, the movement of each actuator is still weak, the clearance between the valve stem and the valve hole of the multi-way valve should be carefully measured. If the multi-way valve has been used for a long time, after frequent reversing, severe wear and large internal leakage, it will also cause the motion of each actuator to be weak. At this time, replace those multi-way valves with a large gap between the valve stem and the valve body. The valve can also be equipped with a stem or body alone to reduce the matching clearance.
Summary: During construction, there are still many failures and maintenance of excavators. In order to reduce the frequency of failures, it is also very important to strengthen the daily maintenance of excavators. In short, correct analysis of the causes of excavator failures and timely treatment, strengthening the maintenance of excavators are the prerequisites for ensuring the efficient and safe work of excavators, and full attention should be paid in actual work.
