Road construction halts in cold autumn and winter, leaving most asphalt mixing plants idle. Many firms only cut power without systematic winter maintenance, leading to freeze-thaw damage, blocked pipelines, faulty electric and dust removal systems after spring restart, which raises repair costs, causes unqualified mixtures, excessive emissions and schedule delays. Winter downtime offers a good chance for equipment frost protection and overhaul. This paper proposes a practical standardized winter maintenance scheme covering inspection, anti-freezing, safety management and regular upkeep, helping enterprises cut equipment loss and maintenance costs, extend equipment service life and guarantee stable, compliant spring production.
Low temperature, snow, freezing and thawing cycle and long-term downtime moisture is the main cause of asphalt mixing plant equipment loss, hidden faults, systematic winter maintenance can be a full range of avoidance of equipment damage and business risks, and effectively resist the low-temperature freezing and thawing brought about by structural corrosion, pipeline freezing and cracking, component jamming, cylinder cracking and other irreversible equipment damage, through a thorough clearing of the material, draining of accumulated water, heat preservation and anti-corrosion, replacement of low-temperature lubrication medium. Comprehensive protection of equipment assets; at the same time can be in advance to detect and eliminate the hidden hidden dangers of the burner, lifting plate, dust bag, asphalt pump, sensors and other core components, to avoid failure downtime in the spring production season, the high cost of repair and schedule delays, to ensure the stable operation of the equipment after the resumption of work; the winter maintenance and calibration of the wear parts, sensing equipment and combustion, dust removal system, can be accurately stabilized mixture ratio, discharge temperature and environmental emissions, to protect the production quality compliance. Environmental protection emissions, to ensure that the production quality compliance; normalized winter maintenance can also significantly slow down the aging speed of the drum, mixing machine, elevator and other high-priced core equipment, significantly extend the service life of the equipment, reduce the investment in equipment renewal, and at the same time use the winter gap to complete the calibration of the equipment, program upgrades, heat preservation and optimization of energy-saving and other technological reforms, and effectively improve the drying efficiency and overall production capacity in the coming year and reduce the consumption of fuel, The whole set of maintenance work comprehensively covers key equipment systems such as cold material supply, transportation, drying and combustion, asphalt storage, dust removal, screening and mixing, hydraulic lubrication, electrical automatic control and steel structure of the whole machine, so as to build the foundation for the long-term low-cost, high-efficiency, stable and compliant operation of the mixing plant.
Comprehensive shutdown inspection is the foundation of winter maintenance, which should be carried out systematically after the equipment is completely cooled down and emptied of all materials, and the locking and tagging of LOTO safety operation specification is strictly carried out throughout the whole process, and protective equipments are equipped for the work in the confined space, and the whole process of taking photos to record the wear and tear, corrosion and seepage points, and to formulate the maintenance list according to the priority of safety.
Formally carry out winter special inspection, you need to complete the whole machine downtime cooling operations, thoroughly empty the cold silo, hot silo, drying drum, conveying equipment, asphalt storage tanks, dust hoppers and other equipment inside the aggregate, asphalt, mineral powder and dust materials, while using high-pressure equipment to comprehensively clean up the equipment inside the hardened asphalt residual lumps and fine powder, to prevent the winter material buildup of lumps and corrosion of the equipment inside; at the same time, the At the same time, the equipment is equipped with thickness gauge, multimeter, lubrication filling equipment, professional lighting tools and other inspection equipment in advance, and the original equipment maintenance manuals and previous maintenance records are prepared as a reference for overhaul, and finally, the core equipment such as burner, conveying system and mixing mainframe are tested and operated without loading before the whole machine is shut down, and the abnormal noise, abnormal temperature, and alarm of the system in the process of the operation of the equipment are recorded in detail, so as to provide basis for the subsequent accurate overhaul.
Check the corrosion thinning and perforation damage position of silo wall and partition plate, measure the remaining thickness of steel plate, make up welding and spray anti-corrosion coating in advance in serious corrosion area; check whether there is air leakage, stagnation and accumulation of material in silo unloading gate, vibrator and air cannon pipeline, and test the unloading action in no-load; check the cold material belt one by one to see whether it is torn, aging, deflection, and damages of blocking skirt, disassemble the head and tail roller, and check the bearings, clearances, abnormal noise, grease, and other faults. Check the gap, abnormal noise, grease aging problems; calibrate the broken material, stall alarm sensor, repair the aging broken skin line, improve the grounding protection.
Belt conveyor focus on checking the belt wear edge, rubberized roller wear, tensioning mechanism trip; scraper elevator to check the chain stretching long, scraper wear, groove liner perforation, drive sprocket tooth surface loss; all conveyor drive motor, reducer, coupling disassembled to check the temperature, leakage of oil problems, correct the equipment running straightness, to avoid the next year, belt deflection, scraper card chain downtime. Measuring belt must be re-calibrated load cell to eliminate measurement error.
Drying drum is the core area of wear and tear: measure the thickness of the cylinder steel plate in the combustion area, check the cracks and elliptical deformation of the cylinder; check the wear of the carrier wheel, roller ring, thrust roller, surface pockmarks, coaxiality deviation; comprehensively check the lack of lifting plate, deformation, breakage, and fixed card buckle off, and replace the broken lifting plate directly to ensure that the coming year's aggregate cloth is sufficient; check the air leakage clearance of the sealing parts of the drum inlet and outlet, and the leakage of the wind will greatly increase the fuel consumption in the winter. Fuel consumption.
Disassemble the burner to clean the nozzle, fuel cartridge, fan impeller, use the flue gas analyzer to calibrate the air-fuel ratio; test the flame monitoring, pressure protection, emergency cut-off and other safety interlocking devices, to check the fuel line leakage, easy to gel hidden danger in winter.
Empty the residual asphalt in the tank, clean the bottom of the tank carbon, precipitation impurities; check the corrosion of the inner and outer walls of the tank, weld leakage, repair the insulation layer, aluminum skin outer protection broken position; asphalt circulating pumps, unloading pumps disassembled to replace the aging seals, the calibration of the temperature probe, the level meter, the temperature alarm device; combing the heating coil of the heat conduction oil, to check the leakage, coking and clogging problems, record the pipeline insulation broken points unified repair.
Open the bag box, check the dust bag holes, wear, oil paste bag by set, replace all the aging bags; clean up the bag cage corrosion, deformation components; disassemble the pulse solenoid valve, diaphragm piece, compressed air pipeline, drain the pipeline water; check the dust fan blade wear, dynamic balance deviation, repair the corrosion of the flue, the ash hopper leakage points.
Empty the hot material silo, measure the wear-resistant layer loss of the silo wall and cone bucket, and repair the cylinder and limit switch of the discharge gate; check the screen mesh of the vibrating screen for breakage and insufficient tension; check the mixing arm, wear-resistant blade and cylinder liner of the mixing cylinder for wear and tear, and replace the bearing clearance directly to avoid excessive mixing resistance and uneven mixing material in the coming year.
Comb the cable bridge, junction box, clean up dust, repair cracked insulation, grounding failure line; open the PLC control cabinet, inverter box, remove internal dust, add dehumidification heater; calibrate all thermocouples, pressure, material level sensors, back up the whole set of control program; one by one test emergency stop buttons, equipment interlocks, fire alarm devices, replacement of the failure of the surge protector.
Check the platform, ladder and guardrail for corrosion and fracture, reinforce the loose steel structure bracket; empty all the clean water pipelines and add antifreeze; seal the gaps of the equipment and do a good job of anti-rodent and anti-insect blocking; count all the loss parts and purchase and stock in advance to avoid the shortage of parts in the beginning of spring.
Organize graphic inspection report, according to the safety failure, core equipment failure, secondary loss grading order, develop maintenance schedule and budget; synchronize welding leakage, wear parts replacement, insulation repair, lubrication and oil change and other maintenance operations, all maintenance content archives to be retained as a reference basis for next year's maintenance.
Snow and frost in winter are easy to raise the water content of gravel aggregate, resulting in the pile and silo aggregate freezing and caking, arching and blocking, unloading and other problems, which reduces the capacity of the mixing plant and increases the drying fuel consumption, so the aggregate anti-freezing is the key front work of winter maintenance, and the daily need to do a good job of all-round aggregate anti-freezing management and control: the site of the yard needs to be hardened and set up a drainage slope of 2% -4%, the fine aggregates, regenerated RAP materials, cushioning high! Stacking, aggregate layered stacking, increase side slopes and the implementation of the first-in-first-out turnover, to avoid long-term static freezing, at the same time, the fine materials and RAP materials covered with waterproof tarpaulin, large stations can build closed storage sheds, through the reduction of the moisture content of the aggregate to effectively reduce the consumption of drying fuel, different specifications of aggregates piled up to prevent mixing of different specifications; winter shutdown before the need to completely empty the cold material silo, clean up the silo wall agglomeration, the silo with additional heat preservation and anti-rain and snow facilities. Rain and snow facilities, overhaul vibrators, air cannons and other arch-breaking equipment, and in the unloading part of the spraying of low viscosity anti-freeze coating; comprehensive overhaul of the belt cleaning and soot blowing device, increase the inclination angle of the chute, add wear-resistant lining, cold areas can be added to the belt heating and air blowing device to reduce the material bonding blockage; try to choose the daytime temperature during the work of the transfer of aggregates, moderate use of the environmental antifreeze agent, regular testing of the water content of aggregates In order to solve the problems of freezing of aggregate and poor material supply in winter from the source, the recycled RAP aggregate with stronger water-holding property is protected and controlled separately, and the frozen blocks are handled centrally before the start of production in spring.
The low temperature environment in winter will greatly increase the heat loss of the drying system, superimposed on the problem of high moisture content of the aggregate, which is very likely to cause the equipment fuel consumption soaring, the discharge temperature does not meet the standard, etc. Therefore, in winter, it is necessary to focus on the drying and combustion system maintenance and optimization of the working conditions, through improving the heat exchange efficiency, reducing heat loss, and stabilizing the combustion conditions to achieve energy-saving and stable production; the daily maintenance of the drying drum need to be comprehensively overhauled in the lifting system, replacing the deformed and damaged lifting boards, making up for the deformed and broken lifting boards, and replacing the broken lifting boards. The daily maintenance needs to comprehensively overhaul the drying drum lifting system, replace the deformed and damaged lifting board, make up the fixed buckles, optimize the lifting arrangement, ensure the formation of uniform material curtain of aggregates to fully exchange heat, and at the same time, repair and upgrade the thermal insulation structure of the drum, flue, and dust box, replace the sealing felt of the import and export to block the infiltration of cold air, calibrate the coaxial degree of the drum to avoid the damage of bias abrasion, and thoroughly clean up the adhesive caking of the cylinder wall to reduce the resistance of thermal conductivity to reduce the heat loss by 7%-10%; synchronize with the combustion engine to carry out the deep Simultaneously carry out in-depth cleaning and maintenance of the combustion machine, clean up carbon impurities in the combustion head, filter element, fan impeller and other parts, calibrate the air-fuel ratio with the help of flue gas analyzer, strictly control the exhaust gas emission, install thermal insulation for the fuel pipeline, replace the low condensation fuel for the winter season, overhaul the fuel pump and preheating device to ensure the low-temperature and stable ignition, comprehensively test the flame detection, over-pressure cut-off and other safety devices, and accurately calibrate the precision of the variable-frequency fan air volume adjustment to meet the winter production demand; Spring production needs to use gradient heating method to preheat the equipment, real-time control of flue gas temperature to avoid the dust removal system condensation paste bag problem, combined with the moisture content of the aggregate dynamic adjustment of combustion power and drum speed, step by step put recycled material, to avoid sudden drop in furnace temperature, balancing the drying efficiency and fuel consumption.
Low-temperature asphalt viscosity will rise sharply, it is very easy to solidify in the tank, pipeline and pumps, triggering clogging of the pipeline, measurement is not allowed, the pump body burned and other issues, so the asphalt storage and heating system in winter need to carry out a full set of anti-freeze, anti-gel maintenance, should try to empty the tank before shutdown asphalt, can not be emptied to the need to continue to low-temperature cycle heating, and at the same time, thoroughly rinse the pipeline, filters and pumps, remove the coking of the pipe wall and empty the tank. Pipe wall coking and empty the bottom of the tank water, slowing down the hardening of asphalt aging; daily maintenance of the tank body need to do thickness measurement, welding and anti-corrosion treatment, repair of thermal insulation, electric heat tape and thermal oil coils, replacement of aging thermal oil, calibration of the temperature, level, pressure and other monitoring equipment and alarm devices, disassembling and overhauling the asphalt pumps, valves and other accessories and replacement of worn seals, bearings, to eliminate leakage hazards; differentiated anti-freezing for different shutdown scenarios Differential frost protection is required for different downtime scenarios, 24-hour low-speed asphalt circulation in winter intermittent production, to maintain a stable temperature in the tank at 60-82 ° C and continue to open the pipeline heat tracing, the whole winter long-term shutdown is required to completely empty all piping equipment and closed blocking, the asphalt to do a good job of full-coverage insulation, supporting the back-up power supply to ensure that the insulation system is running stably; the opening of the spring production needs to be 24 hours ahead of time, slowly warm up the preheating equipment, the whole cycle! Asphalt check blockage and leakage problems, accurate calibration of asphalt metering accuracy and many trial mixing debugging, modified asphalt storage tanks need to slow down the rate of warming to avoid local overheating and aging, to ensure that the official mass production of mixture quality and stability to meet the standards.
As the core environmental protection equipment of the mixing plant, the dust removal system is very easy to cause dust paste bag, pressure difference rise, emission exceeds the standard and bag corrosion and damage in winter due to temperature difference and condensation, therefore, it needs to carry out systematic winter maintenance around humidity control, heat preservation and anti-freezing, and increase the temperature of flue gas and take away the water vapor of box body by drying the aggregate before equipment shutdown, and thoroughly empty the dust hopper of after shutdown, blowing residual dust of the pipeline and open the door to eliminate cold from the source. Ventilation and drying, from the source to eliminate condensation hidden danger; at the same time, comprehensive overhaul dust bag, bag cage, pulse valve, diaphragm piece, fan, flue and ash unloading equipment, timely replacement of aging and damaged parts, drain the air pipe water and add drying equipment as needed to avoid pipeline icing and equipment stalling, the winter also needs to be on the box body, ash hopper, the flue complete package of thermal insulation and add electric heat, the metal wall to do anticorrosive treatment, sealing equipment Gap, do outdoor parts of the thermal insulation protection and timely cleaning of snow, restarted in the spring is required to first no-load preheating equipment, exhaust moisture, test the performance of pulse cleaning, and the whole process of monitoring the flue gas temperature and the box differential pressure, effectively eliminate low-temperature condensation paste bag problem, to ensure that the dust removal system is stable and up to the standard operation.
Low temperature environment, condensed water vapor and rodent damage are the main causes of failure of electrical control system of mixing plant, which can easily lead to line corrosion, sensor data drift, PLC motherboard moisture and other problems, and seriously lead to the overall loss of control of the equipment, therefore, the winter electrical maintenance needs to strictly implement the full set of protection work of full closure, dehumidification, anticorrosion, and data backup, and perform the process of locking up and tagging the power failure before the equipment shutdown, and save PLC program, proportioning parameters and equipment operation in double backup. Program, proportioning parameters and equipment operation data, thoroughly clean up the control cabinet and cooling filter dust; winter need a comprehensive inspection of cable lines, terminals and wiring box, replacement of aging sealing accessories, repair corrosion points and do anticorrosion treatment for the electronic control cabinet body plus the installation of constant temperature dehumidification equipment, check the grounding system, to eliminate condensation, static electricity and lightning damage; at the same time, clean up and calibrate the temperature, weighing, level and other types of sensors, comprehensive testing of emergency stops, safety interlocks and so on. At the same time, clean and calibrate various sensors such as temperature, weighing, material level, etc., comprehensively test the safety devices such as emergency stop, safety interlock, over-temperature alarm, etc., and repair the damaged lines; continuously turn on the dehumidifying equipment during the period of equipment sealing, block the holes of cabinets, and do a good job of waterproofing and protection of the outdoor electrical equipment, and complete the insulation test of motors, the second calibration of the sensors, and the unloaded test run of the whole machine before the start of production in the spring to ensure the stable and reliable operation of the electrical automatic control system.
Combined with the winter shutdown of the mixing plant in various regions of the country, the high incidence of faults in the beginning of spring production, organize the causes and solutions to the ground, in advance of the maintenance to avoid thoroughly:
Causes: high water content of aggregate, no heat preservation of silo, vibrator failure, chute friction coefficient is large, low-temperature freezing block bonded to the inner wall.
Solution: The material pile is fully covered with rain and snow tarpaulin, and the silo is equipped with heat preservation and air cannon; low-friction liner is replaced, and the silo is regularly emptied and cleaned in winter; dry coarse aggregate preheating equipment is used before feeding in the spring.
Causes: broken drum insulation, uneven fabric with worn lifting board, cold air leakage from drum sealing, imbalance of air-fuel ratio of burner, high moisture content of aggregate.
Solution: Repair the whole set of insulation layer, replace the deformed lifting board, replace the import and export seals; flue gas analyzer to calibrate the combustion conditions; source control of aggregate water content.
Causes: Interruption of heat preservation in winter, damage to pipeline heat tracing, no circulation for a long period of time, water at the bottom of the tank to accelerate the solidification of asphalt.
Solution: shut down to keep the minimum heat preservation cycle; repair the accompanying heat pipeline; long-term shutdown to empty all the pipelines; regular discharge of water at the bottom of the tank.
Causes: flue gas temperature below the dew point, box body without insulation, compressed air containing water icing, bag oil bonding.
Solution: drum heating to ensure high flue gas temperature; box with heat insulation; compressed air supporting dryer; thoroughly clean and dry the box before shutdown.
Causes: Control cabinet condensation and moisture, line corrosion, low temperature reduces the accuracy of the sensor, rodents chewing line.
Solution: control cabinet with a constant temperature dehumidifier; outdoor sensors are stored indoors in winter; the whole line is blocked to prevent rodents, terminals are coated with anticorrosive grease; all calibrated before production.
Causes: low-temperature solidification of grease in summer, untimely lubrication filling, emulsification of oil in water.
Solution: Uniform replacement of low-temperature synthetic lubrication medium in winter; complete filling of lubrication points before shutdown; regular oil sample testing, timely replacement of water-entrained deteriorated oil.
Regardless of whether the mixing plant is completely shut down or intermittent production in winter, it is necessary to carry out maintenance work according to the daily, weekly and monthly standardized cycle and take photos and archives of the whole process, so as to control the state of the equipments in a systematic way, among which the daily maintenance is based on the daily inspection and guarding, timely clean up the snow on the equipment platforms and the anti-skid channel, check the situation of equipment freezing and cracking, seepage and rodents, verify the operating status of antifreeze, silo guarding, dust removing and asphalt heat preservation system, and randomly check the key bearing lubrication and equipment oil fluid. Key bearing lubrication and equipment oil level, check the condensation alarm of control cabinet, standby power supply and heating equipment condition, verify the integrity of fire and emergency facilities; carry out weekly local in-depth maintenance, one by one, test the cold bin vibrator, air cannons and other aggregate equipment, clean up the belt freezing material lumps, check the drying drum, pallet and burner condition and fuel antifreeze state, empty the dust impulse pipeline accumulation of water, checking the dust hopper freezing and blocking problems, regular circulation of asphalt Regularly circulate the asphalt pipeline, check the heat preservation and valve sealing, clean up the dust in the electric control cabinet, add low-temperature lubricating grease, and at the same time, check the corrosion of the steel structure of the whole machine and repair the anticorrosive coating; carry out the deep overhaul of the whole machine every month, comprehensively dismantle and overhaul the conveying and cold material system and correct the coaxiality of the equipment, detect the thickness of the drying drum cylinder, replace the broken parts and complete the calibration of the equipment, dismantle the clean combustion system and calibrate the air-fuel ratio, test the combustion system, and test the air-fuel ratio and the fuel oil. The company disassembled and cleaned the combustion system, calibrated the air-fuel ratio, tested the safety interlock, overhauled the dust bag, pulse valve and repaired the flue anticorrosion, tested the working condition of the hot material silo, replaced the wear-resistant parts of the mixing equipment and the aging bearings, completed the electrical operation and maintenance work, such as the motor insulation, the sensor and the calibration of the metering equipment, the program backup and so on, uniformly replaced the equipment with the special low-temperature oils, drained the water, repaired the heat preservation structure, statistically prepared for stocking in advance of the loss parts, and planned for the technical reform and upgrading work of spring in the context of the working condition of equipment. Spring technological transformation and upgrading work.
The new intermittent and continuous asphalt mixing plant in the factory will complete the optimization of cold-resistant structure, which can significantly reduce the probability of frost damage failure in winter, while the old equipment can also be upgraded to enhance the cold-resistant ability through targeted technical reforms, in which the new equipment equipped with the whole equipment integrated thermal insulation structure, the drum, the flue, the asphalt tanks, the dust removal box are equipped with a thicker thermal insulation and removable thermal insulation cover and its own thermal tracing system, which effectively reduces heat loss and fuel consumption in winter, with the optimization of the thermal insulation and the removal of thermal insulation cover. It can effectively reduce the heat loss, reduce the fuel consumption in winter, match with the optimized herringbone lifting structure of high-efficiency counter-current drying drum, which has better heat exchange effect for the aggregate with high moisture content, and match with the frequency-conversion burner that can adaptively adjust the fire according to the low-temperature working conditions, and at the same time, it is equipped with the closed cold silo, self-belted shed, low-friction UHMW lining and integrated air cannon vibration system and other anti-freezing supporting structures of the aggregate to prevent the freezing material blocking the silo problem at the source, and it is relying on the full-automatic Intelligent asphalt temperature control system relying on fully automatic heat conduction oil circulation accompanied by heat, can realize low-temperature automatic warming, shutdown constant temperature guarding, effectively avoiding asphalt gel curing, with pulse air drying unit, dust hopper accompanied by the function of the full thermal insulation and anti-freezing dust removal box, completely eliminating the hidden danger of winter condensation and paste bag, and the intelligent anti-freezing PLC system can realize the constant temperature and dehumidification of cabinets, remote monitoring of the temperature of the equipment, low-temperature automatic early warning, supporting the sensor with low temperature compensation function, greatly improving the low temperature and low temperature control system, which can be used to prevent the freezing of materials. The intelligent anti-freezing PLC system can realize the remote monitoring of the cabinet temperature and dehumidification, low temperature automatic warning, and the matching sensor with low temperature compensation function, which can greatly improve the precision of low-temperature operation. In addition, the equipment is adapted to the warm mixing agent and the foam asphalt production process, which can reduce the temperature of the mixture production, strengthen the suitability for the low-temperature construction in winter, and reduce the energy consumption of drying. Upgrade, effectively reduce the annual winter maintenance workload and maintenance costs.
Winter maintenance of asphalt mixing plant is not an extra cost, but a core investment to reduce equipment loss, control operating expenses and ensure stable production in the following year. Low-temperature freezing and thawing, aggregate freezing, pipe gel, dust condensation, electrical moisture, lubrication failure is the core of the six winter risk points, the whole set of maintenance work needs to be based on the shutdown of the front of the comprehensive inspection, sub-system freeze protection, low-temperature replacement of special supplies, sub-cycle regular inspection, winter safety control of the five dimensions of the implementation of the ground.
Construction companies can base on the standardized maintenance plan in this article, combine their own intermittent/continuous, mobile/fixed mixing plant equipment types, adjust the focus of maintenance with the local winter temperature, set up a complete winter maintenance ledger, purchase perishable parts in advance, complete the replacement of worn parts, and calibrate a full set of metering and combustion systems. Systematic winter maintenance not only avoids high repair costs in spring and delays in the construction period, but also reduces the loss of fuel and spare parts in the long term, prolongs the service life of the mixing plant, and realizes stable, low-cost and environmentally friendly operation of the mixing plant throughout the year.
