Abstract: The bucket wheel machine has a wide range of applications in many fields, and the hydraulic system is an important component of the bucket wheel machine, which has a significant impact on its normal operation. However, the hydraulic system of the bucket wheel machine may also experience some failures. Therefore, this article focuses on the causes and treatment measures of the hydraulic system failures of the DQ1500/1000.45 bucket wheel machine manufactured by Changchun Electric Power Equipment General Factory.
Keywords: bucket wheel machine; Hydraulic system; fault
Foreword
The hydraulic system of the bucket wheel machine has a crucial impact on its normal operation, but it is also prone to problems such as high hydraulic oil temperature and leakage at the connections of hydraulic components. Therefore, studying the causes and treatment measures of hydraulic system failures in bucket wheel machines is of great significance for their normal operation.
1. Overview of bucket wheel hydraulic system
1.1 Introduction to Hydraulic System
Hydraulic system is essentially a technology for achieving mechanical transmission and control. Compared with other transmission technologies, hydraulic systems have a more compact structure, more sensitive response, and are easier to achieve operational automation. Therefore, hydraulic systems have been widely used in many fields. In hydraulic systems, oil works in a regulated and controlled state, so hydraulic transmission and hydraulic control have a very close relationship, which also has a very important impact on the normal operation of the entire hydraulic system. The hydraulic system must meet the requirements of its executing components in terms of force and speed. During the operation of the hydraulic system, the magnitude of the system pressure depends on the external load. The larger the external load, the greater the required hydraulic pressure, and the smaller the external load, the smaller the required hydraulic pressure. The speed of piston or working machine movement depends on the flow rate of oil entering the hydraulic cylinder through the throttle valve per unit time. If the flow rate is larger, the speed of the hydraulic system will be faster. The hydraulic system is mainly used to achieve hydraulic transmission, and the pressure of the hydraulic system is closely related to the load and flow rate.
1.2 Bucket Wheel Hydraulic System
In bucket wheel machines, the hydraulic system is a very important component, and the hydraulic system of bucket wheel machines mainly includes two parts, namely the cantilever pitch hydraulic system and the tail car amplitude hydraulic system. The structures of the two hydraulic systems are roughly the same, so this article takes the cantilever pitch hydraulic system as an example to explain the hydraulic system of bucket wheel machines. The working principle of the hydraulic system for the cantilever pitch of the bucket wheel machine is as follows: the direction of oil supply is changed through an electro-hydraulic directional valve, causing the cantilever pitch amplitude cylinder to extend or retract, thereby achieving the cantilever pitch of the bucket wheel machine. In its working process, in order to effectively prevent the upper pitch amplitude component from causing severe impact and vibration due to changes in the center of gravity causing the pitch cylinder to rise and fall at excessive speed and change amplitude, balance valves are often installed on the oil circuits entering and exiting the cylinder to ensure that the cylinder moves up and down at a stable speed. When the oil cylinder stops working, it can lock the forearm or bucket wheel machine in the desired working position after the amplitude change, without automatic descent. In order to ensure that the electro-hydraulic directional valve can change direction in a timely manner, an internal control and internal manifold type electro-hydraulic directional valve is also used in the boom hydraulic system of the bucket wheel machine. The hydraulic cylinder of the cantilever pitch hydraulic system of the bucket wheel machine is a differential type. In order to ensure that the piston rod chamber of the cylinder can smoothly lower the bucket wheel at the required speed during operation, it is necessary to adjust the opening amount of the one-way throttle valve accordingly.
2. Hydraulic system failure and cause analysis of bucket wheel machine
2.1 Common faults of bucket wheel hydraulic system
For the hydraulic system of bucket wheel machines, damage to the lifting system oil pump and oil tank may occur during its operation. There are many control valves in the hydraulic system, which are also extremely prone to malfunction. In addition, joint oil leakage, oil cylinder oil leakage, and unstable oil tank pressure are common faults in the hydraulic system of bucket wheel machines. The existence of these faults has a very important impact on the normal operation of the bucket wheel machine and must be given sufficient attention.
2.2 Contaminants in Hydraulic Oil
In the hydraulic system of bucket wheel machines, common hydraulic components mainly include solenoid valves, relief valves, hydraulic control check valves, directional valves, pressure reducing valves, throttle valves, and flow control valves. Once these hydraulic components fail or malfunction, it will have a significant impact on the normal use of bucket wheel machines. The main reason for its failure or malfunction is the presence of pollutants in the hydraulic oil. The sources of pollutants in hydraulic oil mainly come from three aspects: the failure to clean them in a timely manner during the manufacturing and installation of hydraulic components, the leakage of oil returned to the oil tank in the surrounding environment, and the pollutants generated gradually in the working system. The presence of pollutants in hydraulic oil is an important factor affecting the normal operation of hydraulic components.
2.3 Leakage of hydraulic components
Leakage of hydraulic components is also an important cause of hydraulic system failure in bucket wheel machines, and the main locations of leakage in bucket wheel machines are the joint surfaces of hydraulic components, pipe joints, and cylinder seals. The main reasons for hydraulic component leakage include the following aspects. Firstly, the hydraulic system experienced abnormal operation, causing an increase in oil temperature and accelerating the aging of the oil. This also shortened the service life of seals and hoses, leading to oil leakage at the joint surfaces. Secondly, the prolonged use of hydraulic components can result in uneven or overly rough mating surfaces, ultimately leading to hydraulic component leakage. Again, if the compatibility between the oil and the sealing material is poor, it can also lead to leakage problems.
2.4 Hydraulic pump processing quality is unqualified
In the process of machining and production of hydraulic pumps, if their machining accuracy cannot meet the design requirements, resulting in surface roughness, fit clearance, form and position tolerances, and contact stiffness not meeting the requirements, after a period of use of the hydraulic pump,? There may be internal leakage and insufficient flow when the load is high, which seriously affects the normal operation of the hydraulic system. Moreover, for faults caused by the machining quality of hydraulic pumps, the difficulty of troubleshooting is often high, and the search for the cause of the fault is relatively difficult. If it is necessary to deal with it, the pump often needs to be disassembled.
2.5 Hydraulic system electrical faults
During the process of stacking and retrieving materials from the bucket wheel machine, the oil pump may operate under overload due to excessive coal extraction, and the operator may not be able to effectively determine whether the hydraulic system motor is operating under overload, resulting in overheating of the motor stator winding and damage to the insulation layer. At the same time, failure to regularly maintain and inspect the hydraulic circuit system of the bucket wheel machine, or inadequate maintenance and inspection, has resulted in some electrical hazards not being detected in a timely manner, leading to safety accidents. In addition, the rainy weather caused water to enter the electrical system due to the need to protect the hydraulic system, leading to electrical faults in the hydraulic system.
3. Diagnosis and treatment of hydraulic system faults in bucket wheel machines
3.1 Diagnosis of hydraulic system faults
To effectively handle hydraulic system faults in bucket wheel machines, it is necessary to first make effective judgments on the faults in the bucket wheel machine hydraulic system. Only by accurately identifying the type of fault and identifying its cause can it be better handled. For the hydraulic system of bucket wheel machines, the commonly used fault diagnosis method in the process of handling its faults is the function tracking screening method, also known as the hydraulic fault reverse analysis method. This method mainly starts from the fault characteristics of the hydraulic system after the fault occurs, and then analyzes the various influencing factors of the fault according to the relevant connections of hydraulic functions. Using this method to search for faults in bucket wheel machines is often more convenient. As long as the hydraulic functions and principles of the hydraulic system are clear, searching for faults in the hydraulic system is often simpler. Therefore, this method is widely used in the current fault handling of bucket wheel machine hydraulic systems. In the process of applying this method, it is important for Z to master the working principle of the bucket wheel hydraulic system and fully understand the specific role of each component in the system.
3.2 Hydraulic system fault diagnosis steps
The hydraulic system faults of bucket wheel machines are generally caused by the failure of a certain component in the system. Diagnosing the hydraulic system faults of bucket wheel machines is essentially finding the faulty hydraulic component. If the function tracking screening method is used to diagnose the hydraulic system faults of bucket wheel machines, the following diagnostic steps should be followed to timely understand the faults of the hydraulic system. Steps should be analyzed for the types of hydraulic system faults. For bucket wheel hydraulic systems, their faults can be divided into five types, namely flow faults, pressure faults, direction faults, general mechanical faults, and electrical faults. The second step is to review the schematic diagram and installation layout of the hydraulic system. By understanding the service life, environment, maintenance, and previous maintenance of the hydraulic system, and inspecting each hydraulic component to determine its performance and function, a preliminary assessment of the quality of the bucket wheel hydraulic system can be made. The third step is to list the components related to the fault, and then analyze each of these components one by one. The fourth step is to arrange the component fault inspection sequence in order of difficulty, and list the key inspection components and the key inspection parts of the components. The fifth step is to inspect each component in order from easy to difficult. The sixth step is to conduct a re inspection based on the results of the initial inspection. The seventh step is to repair and replace the faulty components based on the inspection results. After completing the troubleshooting, Z will restart the system.
3.3 Measures for Handling Oil Cylinder Malfunctions
Oil cylinder failures mainly include oil cylinder leakage and oil cylinder "crawling". In order to effectively address the problem of oil cylinder leakage, it is necessary to choose products that meet the requirements for oil cylinder cups and skeleton oil seals, and check whether these components are aging before installation. Before installing the seal, it is also necessary to check for burrs at the contact area, confirm that there are no burrs and that the smoothness meets the requirements before installation can proceed. In response to the problem of oil cylinder crawling, it is necessary to timely exhaust the cylinder during the operation of the bucket wheel machine. Before adjusting the exhaust device, the working pressure inside the cylinder must be reduced to the specified requirements. At the same time, the tightness of the sealing ring at the end cover of the hydraulic cylinder must be adjusted reasonably. If there is corrosion or fraying inside the cylinder, it must be bored or chrome plated again. This enables effective handling of cylinder faults.
3.4 Hydraulic pump fault handling measures
In the process of dealing with hydraulic pump faults in bucket wheel machine hydraulic systems, large capacity oil suction filters and large-diameter oil suction pipes can be used to reduce local resistance in the pipeline, while effectively preventing air from entering the system and forming cavities, thereby eliminating the situation of rapid changes in oil pressure inside the pump. At the same time, an accumulator or muffler can be installed at the outlet of the pump to absorb the impact of pulsation. If the pump and motor are installed on top of the oil tank, rubber shock absorbers should also be used to avoid hydraulic pump failures.
3.5 Hydraulic system electrical fault handling measures
Provide training on hydraulic system electrical knowledge and skills for operators and electrical maintenance personnel, so that they can better understand and master the structure, working principle, and electrical knowledge of hydraulic systems, as well as simple methods for judging whether the oil pump motor is overheated or has abnormal sound; Regular liquid testing? Inspect and patrol the electrical equipment of the system, and immediately shut down for maintenance if any abnormalities are found to avoid unnecessary electrical failures; When taking over the shift, the operating personnel should check the hydraulic system thoroughly and close the local operation box door before rainy days.
Conclusion
This article analyzes common faults in the hydraulic system of bucket wheel machines, and based on the analysis of the causes of these faults on site, proposes fault diagnosis and treatment measures for bucket wheel machine hydraulic systems. Firstly, the fault diagnosis steps are clarified, and then countermeasures for cylinder faults and hydraulic pump faults are proposed.
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