Common Faults of Bulldozers and The Solutions

- Dec 10, 2019-

Bulldozers, as equipment for promoting ground road construction, can save a lot of material and human resources, speed up the road construction and reduce the progress of the project. However, in daily work, the bulldozers often fail due to improper maintenance of the equipment or long time lost. Specific analysis of these failure causes:


  1. The bulldozer cannot be started: After it is stopped in normal use, it cannot be started again, and there is no smoke. The starter can work normally, and the fault is preliminarily judged to be on the oil circuit. When the manual pump was used to pump oil, it was found that the amount of oil pumped was sufficient, and there was no air in the oil flow, and the manual pump could work quickly. It means that the oil supply is normal, there is no blockage of the oil circuit, and there is no air leakage. If the machine is newly purchased, the fuel injection pump (lead seal is not removed) is less likely to fail. Finally, observe the flameout lever, and find that it is not in the normal position, and then start normally after turning it by hand. It is determined that the fault is on the solenoid valve. After replacing the solenoid valve, the engine works normally, and the fault is eliminated.


  2. Bulldozer electrical failure: After the night shift is completed, the machine cannot start and the starter motor fails to rotate.

    ① The battery is faulty. If the starter motor fails to rotate, there may be a problem with the battery. The measured battery terminal voltage is less than 20V (24V battery). It is determined that the battery is faulty and the battery returns to normal after desulfurization.

    ② The line is loose. After using it for a while, the fault remains. After the battery is sent for repair, it returns to normal. At this point, the author thought about it. The battery is new, so it is less likely to lose electricity. So I started the engine and found that the ammeter was shaking from side to side. There was no stable voltage output when the generator was detected. At this time, there are two possibilities: The circuit is faulty. Second, the generator itself cannot work normally. Check the line and find that there are several lines loose. After tightening, the generator returns to normal.

    ③ The load is too large. After a period of use, there was a battery loss. The same fault occurred so many times. The reason is that the construction machinery generally uses a single wire system (negative ground). Advantages: the line is simple and easy to maintain. The disadvantage is that it is easy to burn electrical equipment.


  3. Bulldozer's steering is not sensitive: Right steering is not sensitive. After the joystick is actuated, sometimes it can turn and sometimes the response is slow. The steering hydraulic system is mainly composed of a coarse filter 1, a steering pump 2, a fine steering filter 3, a steering control valve 7, a brake booster 9, a safety valve and an oil cooler 5. The hydraulic oil in the steering clutch case passes through the primary magnetic filter 1 and is sucked in by the steering pump 2 and then pumped into the fine steering filter 3, into the steering control valve 4, brake booster and safety valve. 2MPa), the released hydraulic oil flows into the oil cooler bypass valve. If the oil pressure of the oil cooler bypass valve exceeds the set pressure of 1.2 MPa due to blockage of the oil cooler 5 or the lubrication system, etc., the hydraulic oil is drained into the steering clutch case. When the steering rod is pulled halfway, the hydraulic oil flowing to the steering control valve 7 flows into the steering clutch. When the steering rod is pulled to the end, the hydraulic oil continues to flow into the steering clutch to disengage the steering clutch, and at the same time flows into the brake booster, so that The brake acts as a brake. After analysis, it is presumed that the failure occurred: ① the steering clutch cannot be completely disengaged or slipped; ② the steering brake does not work. For 1, the reason that the clutch cannot be completely disengaged or slipped is: the external cause is insufficient oil pressure for steering the clutch. The measured pressures at the B and C ports are not much different, because the machine is only sensitive to the right steering, and the left steering is normal, indicating that the oil pressure is sufficient, and the fault cannot occur here. The internal cause was a malfunction in the internal structure of the clutch. For internal causes, we need to perform disintegration inspection, which is more complicated and will not be inspected for the time being. For 2, there are three reasons why the steering brake does not work: ① The brake oil pressure is insufficient. The measured pressures at ports D and E are the same, which may be ruled out. ② The friction plate slips, because the machine is not used for a long time, the possibility of friction plate wear is relatively small. ③ The braking stroke is too large, tighten it with a torque of 90N · m, and screw back 11/6 turns. After the test, the insensitivity of the right steering was resolved. At the same time, the possibility of failure of the internal structure of the clutch is also ruled out, and the failure is caused by the braking stroke being too large.

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