Six points analysis of hydraulic system failure of

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Six point analysis of excavator hydraulic system fault

now take the domestic yw-100b hydraulic excavator, which is widely used in engineering construction, as an example, to analyze the common fault phenomena, causes and troubleshooting methods of its hydraulic system

1. Two main oil pipes of the travel motor burst. The main reason why the two main oil pipes (A and b) of the walking motor of the hydraulic excavator often burst is that the spool of the two speed valve fails to return in time after the speed change, resulting in the failure of the coupling between the oil inlet and the oil return port, resulting in the instantaneous high oil pressure. At this time:

(1) appropriately increase the spring force of the two speed valve spring. After the control pressure is released, the valve core can be reset smoothly under the action of spring force. However, it should be noted that the method of adding shims at the growth rate cannot be simply used to increase the spring force, but must be tested with the spring force

(2) grind the two speed valve, remove burrs, and make the valve core move freely in the valve body without jamming

(3) the popularity of operation will also be further expanded and standardized. For example, the correct operation of shifting gears during the walking process of the excavator is: no matter changing any speed, the excavator must be stopped first, and then shift gears before walking

2. Walking deviation. When the excavator deviates from the running direction, under the condition that it is determined that the technical condition of the walking motor is normal and the tightness of the crawler is adjusted correctly, the following sectional inspection can be carried out:

(1) check the hydraulic circuit of the walking until the hardness value obtained for two consecutive times is the same. First check the side with slow travel speed, start with the combination valve, remove the two oil pipes on the pressure limiting valve, and block the oil outlet with plugs. Then remove the two walking oil pipes on the other combined valve, start the engine, pull the walking joystick of the combined valve with plug, observe whether the oil pressure meets the requirements, and then observe whether there is oil flowing out of holes a and B of the other combined valve (pressure limiting valve). If the oil pressure is normal, and no oil flows out of holes a and B of the other combined valve, it can be considered that the fault is not in the combined valve; If the oil pressure does not reach the normal value, it indicates that the internal leakage is serious; If oil flows out of holes a and B of another combined valve, it indicates that the two combined valves have been in collusion. The only way to make it collude is the shuttle valve. Check the tightness of the shuttle valve or replace the shuttle valve

(2) if the combined valve works normally, check the central swivel 3 experimental equipment in sequence. There are many oil passages at the central swivel joint, which are easy to collude with each other. The inspection method is: remove the A and B oil pipes of two walking motors, and then block the A and B oil pipes of one hydraulic motor; Start the engine, pull the reversing valve of the hydraulic motor blocking the oil pipe, and check whether the oil pressure is normal (confirm that the working performance of the two oil makeup valves is intact); Then observe whether there is oil from the A and B oil holes of the hydraulic motor that is not blocked. If the oil pressure is abnormal and oil comes out of the A and B oil holes that are not blocked, it is considered that the oil passages of the central swivel are not well sealed, and the oil passages have been colluded with each other, so it is necessary to repair or replace the seals of the central swivel. The second and fourth oil grooves of the central swivel are connected to the A and B oil holes of the left travel motor, while the stroke of the third and fifth oil grooves 1 General electro-hydraulic servo testing machine is not large, which is connected to the A and B oil holes of the right travel motor. If the second and third oil grooves are in collusion or the fourth and fifth oil grooves are in collusion, the excavator moves abnormally

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