After severe wear hydraulic excavator according to the following three points we find the cause of the malfunction, and system improvements:
(1) Check the boom cylinder internal leakage situation. The easiest way is to raise the boom, to see if a significant free fall. If the whereabouts of the obvious would be demolished cylinder inspection, seals should be replaced if worn.
(2) Check the control valve. First rinse valve, check valve for wear, such as wear and tear should be replaced. Valve remained unchanged after the installation, and then check the control valve spool wear, the gap is generally use limit 0.06mm, badly worn should be replaced.
(3) measuring the pressure of hydraulic excavators. If the pressure is low, then make adjustments, plus the pressure is still not be set up, then pump heavy wear.
In general, the resulting load can not raise the boom was mainly due to:
a. Hydraulic Pump severe wear. At low speed pump serious leak; high-speed operation, the pump pressure has increased slightly, but due to pump wear and internal leaks, volumetric efficiency decreased significantly, it is difficult to reach the rated pressure. Exacerbated by long working pump wear, temperature rise, and the resulting hydraulic components wear and aging seals, damage, loss of sealing capability, hydraulic oil deterioration, leading to malfunction.
b. hydraulic component selection is unreasonable. Specification of the boom cylinders 70/40 Non-standard series, the seal is also standard parts, manufacturing cost and inconvenience of replacing the seal. Boom cylinder bore small, is bound to make the system set pressure is high.
c. Hydraulic system design is unreasonable. Control valves and hydraulic steering pump for a single series, the safety valve set pressure points 16mpa, while the rated working pressure of hydraulic excavators for 16mpa. Pump always at full load or prolonged overload (high) case work, and the system has Hydraulic shock, for long periods of oil, hydraulic oil contamination, increased wear of the hydraulic pump, the hydraulic pump so that the pump casing burst (after he found such failure).
And the effect of improving
(L) improvement of the hydraulic system design. After much argument, and finally the use of advanced priority valve with load sensing hydraulic steering gear form. The new system in accordance with steering requirements to assign priority traffic, regardless of load size, low speed steering wheel can ensure adequate supply, all the rest can be used to supply the working unit circuit, thereby eliminating the shift caused by excessive power supply circuit losses, improve system efficiency and reduce the work pressure hydraulic excavator.
(2) optimization of the boom cylinders and hydraulic modeling, reduce system operating pressure. By optimizing the calculation, the boom cylinder standard series 80/4. Pump displacement by a 10ml / r increased to 14ml / r, the system set pressure 14mpa, meet the boom cylinder lifting force and speed requirements.
(3) It should also be noted in the course of the proper use and maintenance of loaders regularly add or replace hydraulic oil, hydraulic oil to maintain the cleanliness and strengthen routine inspection and maintenance.