In this paper, the operation of the coal roller screen system is introduced, and the abnormal situations encountered in the operation are analyzed in detail. At the same time, the PLC control system is sorted out in terms of logic control. By analyzing the faults in coal roller screen operation, the corresponding solutions are put forward. For the similar abnormal situations that occur in the actual operation of coal roller screen, this paper provides a solution idea with popularization value, and can provide theoretical and technical guidance for other similar faults.
coal roller screen is a material screening device for fuel screening in coal conveying system of thermal power plant. In the actual use process, due to the different viscosity and particle size of external materials and the difference in the use of the equipment itself, it will lead to some abnormal situations in the operation of the equipment. This paper analyzes the classification of common faults and abnormal faults, and puts forward specific solutions for common faults and abnormal situations.
The common faults in the use of power plants are mainly in the following aspects:
2.1 The motor and screen shaft stop working, the main reason is that the internal foreign matter stuck into the screen shaft causes the power switch to trip, the treatment method is to remove the foreign matter stuck on the screen shaft and check the motor insulation.
2.2 In the process of operation, the abnormal sound is large, and the bearing seat and bearing lubrication should be checked in time.
2.3 The vibration is large during operation. Check whether the motor and reducer base are fixed at the vibration site and whether the cushion cushion of the swinging spring is loose.
2.4 Screen shaft grinding tooth wear is serious, when the material viscosity is large, the material will accumulate at the screen shaft, when the gap between the two screen shafts is small, the material loading difficulties will lead to outage, at this time, the screen shaft and wall hanging materials should be cleaned in time.
2.5 The push rod position switch signal is lost. When the material is large, the baffle will be squeezed, resulting in the loss of the baffle position signal, which will lead to the loss of the chain signal. The push rod limit can be adjusted and the control loop self-locking can be kept for electrical optimization.
3Coal roller screen abnormal situation analysis and solution is generally composed of 8-10 groups of screen shafts, in the use process will encounter abnormal outage phenomenon, which brings potential risks to the safe and stable operation of equipment. coal roller screen equipment malfunction during interlocking automatic operation. At this time, the upper computer prompts the equipment failure, and the control box sometimes prompts a shaft fault during the on-site inspection, and sometimes no fault prompts, which brings difficulties to the troubleshooting of coal roller screen abnormal faults.
In view of this abnormal outage phenomenon, maintenance personnel judge that there are mainly two aspects of maintenance and electrical factors that can lead to this situation.
3.1 The first maintenance system failure situation and solution: First of all, the reducer and base, screen shaft investigation.
3.1.1 Check the internal coal accumulation, clean up the debris deposited between the screen shaft and the lower part of the screen shaft, and clean up the debris wound on the screen shaft.
3.1.2 Reinforce the motor base to prevent the comb teeth of each screen shaft from biting at the moment the equipment is started, resulting in motor overload.
3.1.3 Check each reduction oil level of the coal roller screen to prevent overload caused by lack of lubrication of the reduction gear box.
3.1.4 Each rotating part is lubricated. Due to the large dust in the coal transport system, the increased friction of the rotating part will also lead to system overload.
3.1.5 Check whether the coal roller screen push rod baffle is blocked or jammed with foreign matter. When the push rod is not pushed in place, it is easy to cause the push rod signal loss. In this case, the foreign matter of the baffle should be cleaned and dredge in time.
3.2 The second electrical system failure and solution: for the local control box and program control alarm analysis and on-site electrical control loop inspection, mainly from the following aspects:
3.2.1 In case of abnormal outage, use a clamp ammeter to measure the current of the motor when each screen shaft is rotating to check whether there is an increase in the current of each motor.
3.2.2 Check whether each thermal relay inside the coal roller screen control box works, and check whether the protection setting is in line with the actual situation. At the same time, the infrared temperature measuring gun is used to measure the temperature of the electrical components in the motor, reducer and control box to check whether the equipment runs for a long time leading to the aging of the electrical components.
3.2.3 Observe the indicator status of the PLC module in the control box during abnormal outage, and judge whether the start command sent from the coal delivery program is normal. If there is an alarm motor, check whether the corresponding thermal relay is active. If there is an action, the thermal relay can be reset when removing external faults. If the thermal relay does not operate, it is necessary to check the auxiliary contact of each contactor.
3.2.4 When there is no external alarm during abnormal outage, the program control system will be shut down, and the cause of the loss of the running signal shall be checked according to the PLC program. The main reasons include poor contact coil contact caused by the actual length of contactor operation, loose wiring of PLC input signal point, PLC output indicator failure, and PLC internal logic failure. After checking the PLC control program of the coal roller screen system, sorting out the operation signals of key equipment can eliminate the abnormal outage of equipment caused by the loss of control signals one by one.
3.2.5 Simulation of the running signals of each motor in the coal roller screen can check whether the secondary loop corresponds to the PLC input channel, and determine whether the contactor runs reliably.
3.2.6 Check the push rod signal. When there are large pieces in the material, the push rod position signal is easy to disappear instantly, resulting in chain shutdown of the belt. At this time, the electrical control loop can be optimized for the push-rod signal, and the relevant signal has the function of self-retention.
3.2.7 In the case of chain operation after shutdown during normal chain operation of the equipment, it is necessary to check the coal transmission program control logic program and check the operation signal of the upper and lower chain equipment. If it is found that the signal is lost due to the electrical control loop, the fault of the relevant electrical loop should be eliminated in time according to the logic programming program. Through the above two methods, it can be ensured that the fault is handled in time when the coal roller screen is abnormal, and the maintenance personnel can adopt different processing methods according to the abnormal faults. After a period of no-load and heavy-load tests, it is confirmed that the optimized control system can effectively cope with various complex operating conditions, and greatly reduce the failure rate of the coal roller screen system.
Aiming at the phenomenon of abnormal no-fault display outage in coal roller screen, this paper analyzes the causes and countermeasures of the abnormal phenomenon through the combination of mechanical and electrical aspects. Through fault analysis, the maintenance personnel provide effective technical support for the occurrence of such phenomena in the coal transport system. At the same time, it also greatly facilitates the operation and maintenance personnel to judge the on-site fault, and can eliminate the fault point in the first time.
