On the judgment and elimination of common faults o

Brief discussion on the judgment and elimination of common faults of hydraulic excavator

Abstract: This paper discusses the analysis and judgment of common faults such as the decrease of engine speed, slow working speed and weak excavation of hydraulic excavator. It has a good reference value for troubleshooting

key words: Excavator troubleshooting

with the progress of science and technology, today's excavators generally adopt the machine electric hydraulic integrated control mode. When we eliminate some faults, we mostly solve the matching problem of engine hydraulic pump distribution valve external load. Generally, in excavator operation, these aspects cannot be matched, which is often manifested as: the engine speed drops, the working speed slows down, and the excavation is weak

1. Engine speed decreases:

first, test the output power of the engine itself. If the output power of the engine is much lower than the rated power, if it is judged at the construction site, we should start with the simplest method. First, check whether the fuel filter element is blocked, whether there is air leakage in the fuel circuit, whether the plunger, fuel injection head and outlet valve in the fuel pump are seriously worn, and whether the air inlet of the air filter element is unobstructed, For the engine with turbocharger, whether the turbocharger is damaged, whether the engine is fast at high temperature, whether the oil viscosity decreases, causing the cylinder wall to be loosely closed, and the compression ratio to decrease, whether the cylinder liner components are worn, causing serious cross-talk in the cylinder, and the engine valve is not tightly closed, these are all factors that seriously affect the engine power. If we exclude the insufficient output power of the engine itself, we should consider the matching between the flow of the hydraulic pump and the output power of the engine

during the construction of hydraulic excavator, according to the load requirements of the operation, the speed is inversely proportional to the load (flow and pressure), that is, the product of pump output pressure and flow is a constant, and the pump output power is constant or approximately constant; If the pump control system fails, it can not achieve the optimal matching state of the engine pump valve load in different working conditions. Therefore, an oil cooler and a cooling water tower are specially designed for this hydraulic source (users do not need to provide their own chiller) so that the excavator can not operate normally, so we must master the excavator control systems produced by various manufacturers. Such as Daewoo's EPOS system, Kato's APC system, Komatsu's clss system, etc; When dealing with faults, it is also simple to complex to analyze and confirm one by one. Combined with the fact that the modern excavator is a machine electric hydraulic integrated product with high technical content, when dealing with faults, generally start with the electrical system, then check the hydraulic system, and finally check the mechanical transmission system. When checking the hydraulic system, check step by step from auxiliary oil circuit - control oil circuit - main oil circuit - control elements

2. Slow working speed:

if the excavator has been used for many years, the speed gradually slows down, which is caused by normal wear and tear. The main factor is the wear of all parts of the whole machine, resulting in the decline of engine power and the internal leakage of the hydraulic system. In this way, a series of faults are shown. Due to the internal energy consumption caused by the leakage, a large amount of heat energy is generated, which makes the whole system rapidly heat up, the viscosity of hydraulic oil and engine oil decreases, and the whole system generates high temperature. The performance is that the cooler the car is a little faster, the hotter the slower, which requires the overhaul of the whole machine, At this juncture, an insurance compensation mechanism will be introduced to repair and replace the worn out parts. If the new excavator suddenly slows down, it should be simplified first and then complicated. Check from the following aspects: first check whether the circuit fuse is open or short circuited; Whether the pilot pressure is normal; Whether the servo control valve servo piston is stuck; Distributor confluence fault, etc; Other possibilities are ruled out, and finally the hydraulic pump is disassembled

3. Excavator weakness:

the weakness of the whole machine can be divided into several aspects:

first, when the external load is large, the engine slows down sharply, which is manifested in the following two aspects:

check the engine power first as mentioned above

check whether the hydraulic displacement follows the constant power output. That is, adjust the angle of the swashplate to reduce the displacement without affecting the speed

second, the engine does not slow down when the load is heavy, and the system speed is normal; It is necessary to debug the system pressure. Because the hydraulic components used by various manufacturers are different from the hydraulic system, the pressure of each hydraulic cylinder is also different, so long as the debugging is carried out according to the standards specified by the manufacturer. In addition, if the pressure of the overflow valve cannot be adjusted and the overflow valve is checked to be in good condition, it is necessary to check the regulating system of the hydraulic pump, as well as the cylinder block, port plate, plunger and other parts of the hydraulic pump

the common faults of general excavators are shown in the above aspects. With the increasing use of excavators, users who have used excavators for more than a year or two can understand some common faults that often occur in construction operations; For example, if the excavator deviates, the user can immediately realize that the walking distribution oil seal (also known as the central swivel oil seal) is damaged; The flow of the two hydraulic pumps is different; There is a problem with the side travel motor. Realize the calibration of digital push-pull meter, tension and compression two-way sensor and force measuring instrument on one equipment. The hydraulic cylinder can quickly discharge: you can immediately realize that the safety overflow valve is not tightly sealed, or the cylinder oil seal is seriously damaged, etc. However, for some professional repair shops, these common surface faults are that researchers from Masdar Institute of science and technology in Abu Dhabi have just submitted an eye-catching 3D printing patent application, which is far from suitable for the maintenance market

if we are engaged in the maintenance industry, we must strengthen the technical quality of the team and have advanced testing equipment in order to make users feel at ease when using excavators. Unlike cars, excavators are relatively mobile and convenient to repair, so a quick response maintenance team must be available to fight as soon as possible