Belt conveyor is a kind of large-scale mechanical transportation equipment. It is one of the most commonly used transportation equipment in coal mine. It has the advantages of high transportation efficiency, large transportation capacity, low power consumption and long transportation distance.
It can adapt to the harsh working environment underground. In the working process of belt conveyor, the load distribution is uneven and the stress is complex. Once a fault occurs, it may cause major safety accidents.
Therefore, it is very important for the safety of the actual production process to diagnose and find the faults of the belt conveyor in time, locate and deal with them accurately. This paper will analyze the common faults of belt conveyor, study the fault diagnosis technology, and establish the fault monitoring system and database evaluation model.
1. Working principle of belt conveyor
According to the position and function, the belt conveyor can be divided into head, body, tail, conveyor belt and other auxiliary devices. The conveyor belt is connected into a stepless annular belt, and the belt is installed on the pulleys on both sides by using the spiral tensioning device.
The drum is driven by the motor. The friction between the belt and the pulley drives the belt and the driven pulley to rotate, so as to achieve the purpose of cargo transportation. This paper will take the belt conveyor as the research object, analyze the fault types of each component, establish the fault model of the belt conveyor, facilitate the system to analyze the faults of different components according to different failure forms and working conditions parameters, and give solutions and maintenance measures in time.
2. Fault analysis and maintenance measures of belt conveyor
2.1 Motor fault analysis
The belt conveyor is a constant speed transportation device, and the motor usually adopts three-phase asynchronous motor. When the motor fails, the main failure forms are: the motor cannot be started or starts abnormally, and the motor temperature is too high.
Fault causes and solutions of motor failure or abnormal start:
1) Transmission line failure. If the motor cannot supply power, check the power supply line of the motor.
2) The motor is self-locking after power failure. Check whether each protection system operates, and power off and reset after operation.
3) The voltage is too low. Check whether the power supply voltage is normal.
Fault causes and solutions of excessive motor temperature:
1) Overload operation of belt conveyor. The operating current of the motor under load shall be measured with a clamp ammeter. If the rated current on the nameplate is exceeded, the motor will be overloaded. Check the state of the motor bearing, check whether it is stuck, calculate the motor load, and reduce the load as much as possible.
2) Poor lubrication. The lubricating oil of all transmission parts shall be supplemented in time.
3) Dust falling from motor fan. The motor vents and fans should be cleaned regularly.
2.2 Fault analysis of reducer
The main failure modes of reducer are oil leakage and overheating. The fault causes and solutions of oil leakage of reducer are as follows:
1) The shell is broken. The shell should be repaired and an oil baffle should be added at the end of the bearing.
2) The sealing device is damaged or aging. Replace the sealing ring regularly and tighten the fastening bolts.
When the lubricating oil temperature in the reducer exceeds 40 ℃, it is considered that the reducer is overheated. The main reasons and solutions are as follows:
1) Too little oil or too long service time. The oil shall be filled according to the standard and replaced in time.
2) The working condition is bad and the bearing is damaged. The inside of the reducer should be treated and the damaged parts replaced.
2.3 Failure of supporting rod
The idler is mainly composed of shell, bearing, shaft and seal. The common failure forms include: shell wear, bearing damage and spindle bending deformation.
Friction is generated between the surface of the supporting roller and the bearing. When there is an included angle between the rotation tangent direction of the supporting roller and the running direction of the belt, the wear between the supporting shell and the bearing will be intensified, and the supporting shaft will be broken with the operation of the equipment. During transportation, impurities such as coal and oil are brought into the bearing to pollute the lubricating oil and cause severe wear of the bearing. When the gravity distribution of materials on the conveyor belt is uneven, in the long-term harsh working environment, the load at one end of the support will be large, resulting in the bending and deformation of the main shaft of the support.
As an important part of the belt conveyor, the idler will cause belt slip, belt tear and abnormal loss after damage. The bearings and main shafts of the idler should be tested regularly, the grease should be replaced in time and the sundries should be cleaned up. In the process of transportation, the uneven load of materials should be avoided.
2.4 Roller Failure
The main failure forms of the drum include: rubber coating damage, simplified fracturing, shaft damage and bearing seat damage. When the belt conveyor is running, when the running friction between the drum and the belt is greater than the allowable pool circumference of the material; Small displacement will be formed between the insiders, resulting in the wear of rubber coating. When the belt conveyor operates under high load for a long time, the drum load is large, and the rolling Jane will be fractured and welded under the condition of poor welding quality. During welding, mixed gas backing welding shall be adopted first, and then submerged arc automatic welding shall be adopted to ensure the penetration of weld root without penetration.
Due to the error or surface contamination during drum processing, the surface diameter is different. As shown in Figure 2, the traction component between the conveyor belt and the drum has an inclination with the running direction of the belt, resulting in the deviation of the belt. If it works for a long time, it will cause the damage or fracture of the roller shaft. When the transportation slope of belt conveyor is large, the bearing seat of roller bearing is easy to be damaged under long-term high load operation.
The belt deviation caused by drum installation position error or inconsistent diameter should be repaired or replaced as soon as possible. In the short term, the belt tension can be maintained by adjusting the drum direction at the head and tail of the belt conveyor. In a humid working environment, rosin can be added to the surface of the drum to prevent slipping, and the lubricating oil in the bearing can be changed regularly.
3. research and design of monitoring system
3.1 System scheme design
Through the above analysis of the fault types of various parts of the belt conveyor, the main causes of the fault and the solutions and maintenance measures are found out. In order to monitor the operation state of the belt conveyor and find and deal with the fault in time, it is also necessary to establish an online monitoring system. The monitoring system is composed of monitoring substation and various sensors.
The specific structure and location distribution are shown in Figure 4. The monitoring substation includes the interface between processor module and LCD module and other external equipment. The processor module is responsible for processing and analyzing the collected information, comparing the operation data of each component with the database, and diagnosing the fault state.
The LCD module is responsible for the visual display of the data, which is convenient for the staff to understand the fault status of the belt conveyor in time. The sensor module includes temperature sensor, smoke sensor, coal stacking sensor, speed sensor, tear sensor, vibration sensor and deviation switch. The deviation switch is installed at the head, tail and middle of the machine. When the conveyor belt touches the switch, the idler deflects and sends out a deviation fault signal.
3.2 System hardware selection
The monitoring substation takes the embedded processor as the core, comprehensively considers the system function and practical application, and selects arm series s3c2440AL chip. The system adopts GWD100 mining temperature sensor to collect the temperature signal of the operating environment of the belt conveyor. This sensor can resist the interference of coal dust and other factors and has high reliability. PT100 thermistor temperature sensor is used to measure the temperature signal of motor, reducer and other equipment. The temperature measurement range is – 200 ~ 800 ℃, and the accuracy is 0.03 ℃. GQL gas sensitive smoke sensor is used to detect the smoke caused by fire and is used for fire alarm function.
The GMP-D speed sensor is used to measure the speed of the motor output shaft to judge whether the motor can not be started normally. The measurement range of the speed sensor is 0 ~ 2000 R / min. GUJ30 coal stacking sensor is connected with the sub station processor. When the sensor outputs high voltage, the coal stacking protection function is realized. GBC80 mining vibration sensor is used to detect the vibration signal of roller, reducer, motor and other equipment bearings to judge whether there is abnormal jitter. The tear sensor GVD1200 is installed between the upper and lower conveyor belts. When the conveyor belt is torn and touches the sensor, it sends out a high voltage fault signal.
4. system database reasoning
In addition, the corresponding relationship between working condition parameters and faults of belt conveyor should be established, and a comprehensive fault database should be established. In the analysis process, each component fault is regarded as a separate event, and each fault cause and solution are regarded as a subset of the event. Each subset reflects a fault state, and any subset will lead to the occurrence of the fault event.
The database uses the frame representation to describe the fault information and maintenance measures. The fault type code is: “g” + two digit code of fault event + two digit code of sub event + two digit code of fault cause. For example, the code of motor unable to supply power caused by transmission circuit fault is:
G01 (motor fault) + 01 (motor cannot supply power) + 01 (transmission line fault) = g010101
According to the input working condition parameters and fault threshold information of belt conveyor, the fault diagnosis system selects the appropriate fault database for reasoning, and looks for the corresponding fault events and subsets. The reasoning process is shown in Figure 5. The system searches according to the frame representation rules and event codes. If the information does not match the fault database rules, it will be fed back to the user to modify and improve the fault database rules; if it matches, it will judge whether each parameter exceeds the threshold, and if not, the conveyor is normal. In the process of judgment, relevant cases are added continuously to improve the diagnostic accuracy of the system.
5 Conclusion
This paper presents a fault diagnosis and monitoring system for belt conveyor, establishes the corresponding hardware system and fault database, and sets the corresponding maintenance measures for different fault types and causes. Using sensor information acquisition and information processing technology, the working condition parameters of belt conveyor are analyzed and the fault causes are analyzed accurately.
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