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Common faults and solutions of asphalt mixing plant
February 23, 2022
asphalt mixing plant,road construction machinery,concrete mixture,vibrating screen,drying drum
Asphalt mixing plant is a complete set of large-scale mechatronics equipment indispensable to road construction machinery. It is an equipment for mixing a large number of aggregates, fillers and asphalt. Therefore, its installation, commissioning and operation must strictly follow certain procedures, otherwise it will fail, reduce the construction efficiency and affect the quality of concrete mixture. Common faults include cold material feeding device fault, mixer fault and screen fault.
1. Cold material feeding device failure
The flow of cold materials in the cold storage bin shall be checked frequently to avoid intermittent feeding and gushing. The speed of the feeding belt shall be maintained at medium speed when the productivity is calibrated, and the speed regulation range shall not exceed 20% - 80% of the maximum speed
The failure of the cold material feeding device is generally the shutdown of the variable speed belt conveyor, which may be because there is too little material in the cold hopper and the direct impact on the belt conveyor is serious when the loader is loading, resulting in overload and shutdown. It should be ensured that there is enough granular material in each cold hopper; The variable speed belt conveyor has abnormal function, which may be due to the failure of the corresponding control frequency converter in the control cabinet, which shall be repaired or replaced. If each belt slips, deviates or is difficult to start, the belt tension shall be readjusted. The machine may be stopped inadvertently if the pull wire is abnormal.
2. Mixer failure
The main screen failure is that there are holes in the screen, which will cause the aggregate of the previous gear to enter the silo of the next gear. The mixture will be sampled for extraction and screening. The asphalt aggregate ratio of the mixture is too large, and oil cake will appear on the road after paving and rolling. Therefore, always check the working condition of the vibrating screen:
(1) the vibrating screen shall be installed correctly, especially to ensure that the screen is inclined according to the required angle in the length direction. Since the length of the vibration damping spring of the vibrating screen will be shortened due to wear, resulting in the decrease of the inclination angle of the vibrating screen, the vibration damping spring should be replaced in time in case of wear. However, during replacement, it should be noted that all springs should be replaced at the same time, and the free length of the new spring should be consistent with that of the original spring, so as to ensure the longitudinal inclination and transverse levelness of the vibrating screen.
(2) during use, regularly check the tension of the drive belt and whether it is arranged in a straight line (if the V-belt is excessively extended due to wear, it shall be replaced in groups); Check whether the bearing is overheated; Check whether the screen is firmly clamped in place and damaged; Check whether all connecting parts, bolts and nuts are loose, especially all connecting parts on the eccentric shaft assembly. If they are loose, find out the causes and eliminate them in time.
(3) Always check whether the hot material screening device is overloaded and whether the screen is blocked or broken. When it is found that the material accumulation on the screen surface is too high, stop the machine for adjustment.
(4) Good lubrication is very important to the vibrating screen, and the requirements of the lubrication cycle table in the equipment operation manual shall be strictly implemented
(5) when the flow of the cold silo needs to be changed due to the imbalance of the supply of hot silo, it shall be adjusted gradually, and the supply of a silo shall not be suddenly increased, otherwise the gradation of aggregate will be seriously affected.
4. Abnormal negative pressure
Negative pressure refers to the atmospheric pressure in the drying drum. The pressure in the drum is affected by two aspects: one is the blower, which produces positive pressure in the drum; On the other hand is the induced draft fan, which generates negative pressure in the drum. Under positive pressure, the dust in the drum will fly out from around the drum, affecting the environmental protection. Therefore, the negative pressure cannot be too large, otherwise the cold air will enter the drum and take away the heat energy, and the fuel consumption will increase greatly.
(1) Check the induced draft fan damper for action. If the induced draft damper control is not turned to manual, then turn the damper to the hand wheel to see the opening of the damper, and check whether the damper bearing is damaged or the damper blade is stuck. If it can be opened manually. If there is a fault in the electric actuator or there is a problem in the actuator itself, check and eliminate it.
(2) If the damper of the induced draft fan can act, check the opening of the pulse board on the upper part of the dust removal box, and then check whether the control circuit and solenoid valve are normal and whether the air circuit is abnormal. Find out the fault and eliminate it.
1. Cold material feeding device failure
The flow of cold materials in the cold storage bin shall be checked frequently to avoid intermittent feeding and gushing. The speed of the feeding belt shall be maintained at medium speed when the productivity is calibrated, and the speed regulation range shall not exceed 20% - 80% of the maximum speed
The failure of the cold material feeding device is generally the shutdown of the variable speed belt conveyor, which may be because there is too little material in the cold hopper and the direct impact on the belt conveyor is serious when the loader is loading, resulting in overload and shutdown. It should be ensured that there is enough granular material in each cold hopper; The variable speed belt conveyor has abnormal function, which may be due to the failure of the corresponding control frequency converter in the control cabinet, which shall be repaired or replaced. If each belt slips, deviates or is difficult to start, the belt tension shall be readjusted. The machine may be stopped inadvertently if the pull wire is abnormal.
2. Mixer failure
The abnormal sound may be caused by the dislocation of the fixed support of the drive motor caused by the instantaneous overload of the mixer, or the damage of the fixed bearing, which needs to be reset, fixed or replaced. If the mixer arm, blade or internal guard plate is seriously worn or falls off, it needs to be replaced, otherwise the mixing material will be uneven and gray. If the discharge temperature of the mixer is abnormal, clean the temperature sensor and check whether its cleaning device works normally.
The main screen failure is that there are holes in the screen, which will cause the aggregate of the previous gear to enter the silo of the next gear. The mixture will be sampled for extraction and screening. The asphalt aggregate ratio of the mixture is too large, and oil cake will appear on the road after paving and rolling. Therefore, always check the working condition of the vibrating screen:
(1) the vibrating screen shall be installed correctly, especially to ensure that the screen is inclined according to the required angle in the length direction. Since the length of the vibration damping spring of the vibrating screen will be shortened due to wear, resulting in the decrease of the inclination angle of the vibrating screen, the vibration damping spring should be replaced in time in case of wear. However, during replacement, it should be noted that all springs should be replaced at the same time, and the free length of the new spring should be consistent with that of the original spring, so as to ensure the longitudinal inclination and transverse levelness of the vibrating screen.
(2) during use, regularly check the tension of the drive belt and whether it is arranged in a straight line (if the V-belt is excessively extended due to wear, it shall be replaced in groups); Check whether the bearing is overheated; Check whether the screen is firmly clamped in place and damaged; Check whether all connecting parts, bolts and nuts are loose, especially all connecting parts on the eccentric shaft assembly. If they are loose, find out the causes and eliminate them in time.
(3) Always check whether the hot material screening device is overloaded and whether the screen is blocked or broken. When it is found that the material accumulation on the screen surface is too high, stop the machine for adjustment.
(4) Good lubrication is very important to the vibrating screen, and the requirements of the lubrication cycle table in the equipment operation manual shall be strictly implemented
(5) when the flow of the cold silo needs to be changed due to the imbalance of the supply of hot silo, it shall be adjusted gradually, and the supply of a silo shall not be suddenly increased, otherwise the gradation of aggregate will be seriously affected.
4. Abnormal negative pressure
Negative pressure refers to the atmospheric pressure in the drying drum. The pressure in the drum is affected by two aspects: one is the blower, which produces positive pressure in the drum; On the other hand is the induced draft fan, which generates negative pressure in the drum. Under positive pressure, the dust in the drum will fly out from around the drum, affecting the environmental protection. Therefore, the negative pressure cannot be too large, otherwise the cold air will enter the drum and take away the heat energy, and the fuel consumption will increase greatly.
(1) Check the induced draft fan damper for action. If the induced draft damper control is not turned to manual, then turn the damper to the hand wheel to see the opening of the damper, and check whether the damper bearing is damaged or the damper blade is stuck. If it can be opened manually. If there is a fault in the electric actuator or there is a problem in the actuator itself, check and eliminate it.
(2) If the damper of the induced draft fan can act, check the opening of the pulse board on the upper part of the dust removal box, and then check whether the control circuit and solenoid valve are normal and whether the air circuit is abnormal. Find out the fault and eliminate it.
