Troubleshooting Common Faults of Hydraulic Excavators

Abstract

This paper briefly analyzes the common fault phenomena such as weak operation and excessively high water temperature of the PC200-6 hydraulic excavator in engineering construction, and proposes troubleshooting measures.

Key words

Troubleshooting of Excavators

ACM

With the continuous development of high-grade highways, hydraulic excavators have played an important role in the process of earthwork construction. Our company purchased several PC200-6 hydraulic excavators at the end of 1999. During these years of use, the vehicle conditions have been basically good, but there have also been a few minor malfunctions, specifically manifested as weak engine operation and excessively high water temperature.

The following is an analysis and discussion on how to troubleshoot the problem:

The engine is working weakly

The main reason for the weak operation of the excavator engine is a problem with the fuel system. The characteristics of the fault are: the engine runs normally when idling, but when there is a load, it shows weak operation, muffled engine sound, and the engine is prone to stalling, etc. The troubleshooting is as follows First, turn on the hand oil pump. There is no air in the system and it works normally. Then, after replacing the coarse and fine fuel filters, the engine works basically normally during the small-load leveling operation, but it still does not work properly under the large-load operation. Some people believed that it was due to insufficient oil supply from the high-pressure oil pump. After analysis, they thought it was a fault in the oil circuit. So they removed the oil pipe between the filter element and the oil transfer pump for inspection and found that the rubber inside the pipe had aged. At the same time, the small filter screen inside the hollow bolt at the pipe head is clogged. This confirmed that the throttle was caused by poor fuel supply, resulting in insufficient fuel supply and thus causing the excavator to operate inefficiently. After replacing the fuel pipe and cleaning the hollow screws thoroughly, the operation returned to normal. ② The excavator operates normally when unloaded, but it emits black smoke and works weakly when digging. Inspection method: First, check the fuel supply system. If the result is normal, it indicates that there is no problem with the engine itself. After observation, it was found that there was a lot of carbon deposits at the exhaust pipe. Therefore, it was believed that the exhaust resistance was too high, causing the power to drop and black smoke to be emitted. After opening the muffler and removing the carbon deposits, the operation basically returned to normal, but there was still black smoke coming out. Later, upon careful observation, it was found that the vacuum indicator of the air filter element was red, indicating that the filter element needed to be cleaned or replaced. However, after replacing several new filter elements, the engine still emitted black smoke and the vacuum indicator of the air filter element was still red. At this point, it was found that the air intake was not smooth. So, following the air intake, I looked out and found that the coarse air filter screen had been clogged with willow catkins and other debris. After cleaning it up, the engine resumed normal operation.

When the engine water temperature is too high, the buzzer alarm will send out an alarm message

Analysis of the causes of overheating in excavator engines :① Excessive heat generation. The reason is that the engine timing is poor and the ignition is too late. Engine oil has intruded into the combustion chamber or excessive diesel has been injected. Long-term overloading operation causes the hydraulic oil temperature to be too high. After a comprehensive observation of the engine, the above causes were ruled out. The engine started running normally at first, but after working for half an hour, it overheated and gave an alarm. It seems that there are other reasons. ② Insufficient heat dissipation. The reason is insufficient water volume and water shortage operation. Poor water quality, with engine oil mixed in the water, reduces thermal conductivity. Hard water quality generates a large amount of scale, seriously affecting heat dissipation. The mixture of gas in water reduces its heat dissipation capacity. The thermostat is faulty and the large circulation opening is insufficient. Impurities such as silt, rust scales and scale clog the water tank. The grille of the water tank is clogged with branches, insects, sand and debris. The water pump is malfunctioning. The fan belt is loose, and the fan blades are deformed, resulting in insufficient forced cooling, etc. For the reasons mentioned above, we conducted a thorough inspection of the PC200-6 hydraulic excavator and consulted the manufacturer's service department. Since it has only been used for one year, it is judged that the thermostat should be normal. There is antifreeze in the water tank without rust or oil stains, etc. The possibility of the fault is ruled out. After a thorough investigation of the external causes, the fan belt was first adjusted to an appropriate tension. Then, a car wash machine was installed to thoroughly clean the water tank and the hydraulic oil radiator. After removing the oil sludge, insects and other debris on the grille, the radiator looked as good as new from the outside. After working on the construction site for a period of time, the effect changed somewhat. The overheating alarm time has been extended from half an hour to about half a day, and it can basically work continuously for about 4 hours. However, it still overheated. We then inspected the engine and later determined that it was still due to poor heat dissipation. Therefore, we analyzed the heat dissipation system. The heat dissipation system is a combination of the water tank and the hydraulic oil radiator, with a sponge completely sealed in the middle. Based on this, it was judged that there might be debris blocking between the two. So, the sponge was removed and it was found that the water tank and the hydraulic oil radiator were blocked by willow catkins. After clearing them, the operation was carried out under heavy load for a long time, and no overheating occurred again. Subsequently, an analysis was conducted on this phenomenon: As the engine is drawing air inward, the wind force is very strong. When working in an environment where willow catkins are falling, the engine's wind force sucks all the catkins onto the grille of the water tank. From the outside, only the hydraulic oil radiator can be seen, and the debris on it is removed, but it is not easily visible on the water tank inside. For this reason, we conduct cleaning and inspection between the two from time to time, and the water temperature has never been too high again.