The core raw material of highway, highway, airport runway and municipal parking lot construction is hot mix asphalt mixture, and asphalt mixing station (asphalt mixing station and asphalt mixing plant) is the special industrial complete equipment for producing qualified asphalt concrete. The whole equipment consists of dozens of interconnected systems and hundreds of accessories. The quality of accessories directly determines the production accuracy, discharge quality, energy consumption cost, environmental protection ability and service life of the whole machine. Many mixing plant operators often encounter problems such as frequent shutdown maintenance, imbalance of mixture ratio, excessive dust removal emission, low drying and combustion efficiency, etc. The root causes are mostly concentrated in three aspects: improper selection of core parts, extended service of wearing parts and inadequate daily maintenance.
Asphalt mixing station is also often called hot mix asphalt mixing station, asphalt mixture mixing plant and black material mixing equipment in the industry. Its core function is to mix aggregate such as gravel, sand and mineral powder evenly with asphalt binder, recycled old material and various additives after drying, heating and accurate measurement, so as to produce hot mix asphalt mixture (HMA) conforming to road construction specifications. The finished asphalt mixture is the required material for new road construction, old road milling and resurfacing, bridge deck pavement and airport runway repair. The whole production process relies on automatic control system to realize closed-loop control of temperature, proportion and output.
The whole production process is divided into four core processes: cold aggregate feeding and conveying, aggregate drying and heating, precise metering and mixing, finished material storage and loading. There are obvious differences between different models in process arrangement and accessory configuration. At present, the mainstream market is divided into intermittent batch mixing station and drum continuous mixing station, and the core accessory structure, loss position and operation and maintenance focus of the two are significantly different.
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Compare Dimensions |
batch asphalt mixing plant |
Drum continuous asphalt mixing plant |
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Core Production Process |
Single batch independent production mode is adopted, each batch of mixture is independently measured and stirred, the process is completed step by step, and the production process is intermittent circulation. |
Continuous production mode is adopted, drying, heating and stirring are integrated in the same rotating drum, and the materials are conveyed continuously throughout the whole process. |
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core configuration |
Independent drying drum + hot aggregate screening equipment + hot material insulation bin + independent double-shaft forced mixing host, multi-unit split structure |
Integrated drying mixing drum, no independent screening unit, no independent mixing host, highly integrated and simplified structure |
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Core accessories system |
Hot aggregate elevator, multi-layer vibrating screen, hot bin, independent weighing bucket, dual-shaft mixing host and other exclusive accessories, accessories system is more complex |
Spare parts such as hot aggregate screening, hot bin, independent weighing mixing host, etc., with fewer accessories, and the core accessories are integrated drum and asphalt spraying system. |
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Production precision and formulation flexibility |
The mixture ratio accuracy can reach the highest standard in the industry, and a variety of mixture formulas can be switched at any time to meet the production requirements of multiple specifications. |
No separate grading accessories, less flexibility in formula switching, more suitable for continuous production of single blend formulations |
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applicable scenarios |
High-speed, airport runway and other high-standard projects, road construction and repair projects with variable mixture specifications |
Large quantities of high-speed subgrade, municipal loop and other single formula batch construction scenarios, focusing on high-capacity continuous production |
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Key points of operation and maintenance and loss |
The core loss accessories are high-precision metering accessories, screening screens, stirring blades, and hot bin seals. The operation and maintenance focus is on metering accuracy control. |
The core loss accessories are roller lifting plate, asphalt spray nozzle and dust removal bag. The operation and maintenance focus on roller heat exchange efficiency and continuous production stability. |
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productivity characteristic |
The hourly production capacity is relatively low, and it can be flexibly started and stopped, adjust the single batch output, and adapt to small batch and multi-specification production. |
Hourly production capacity is generally higher than batch mixing station, suitable for long-term uninterrupted continuous production, large-scale production efficiency is higher |
Whether batch or drum mixing station, the whole machine consists of ten linkage systems, each system contains a variety of irreplaceable core parts, each part works together to ensure stable production of the production line, the following subsystem disassembly of each part function, function and use scenario.
Cold material system is the first material inlet of the whole production line, the core function is to accurately match the original sand aggregate according to the construction formula, and the stability of accessories directly determines the basic accuracy of mixture grading. Core accessories include multi-cell cold bin, frequency conversion discharge gate, skirt belt conveyor, roller, cleaning scraper, anti-deviation baffle plate, pre-screening net.
The cold storage bin is generally equipped with 4-6 independent bins to store coarse gravel, fine stone, river sand, recycled old materials and other materials respectively. The frequency conversion discharge door at the bottom controls the discharge flow by adjusting the rotating speed; multiple belt conveyors collect the aggregates. The materials are uniformly transported to the drying equipment. The belt and cleaning scraper rub against the sand and gravel for a long time, which are high-frequency loss accessories. The whole system is prone to belt tearing, roller blocking, gate blocking and other faults, which directly leads to imbalance of aggregate proportion, segregation and insufficient strength of pavement construction.
The combination of drying drum and burner is the "heart" of mixing station, which undertakes the core function of aggregate dehydration and temperature rise. The wear degree of accessories is the highest in the station under high temperature and sand friction conditions. Core accessories include horizontal drying drum cylinder, drum lifting plate (lifting blade), drum wear liner, baffle ring, discharge wear baffle, inlet and outlet seals, fuel/gas burner, combustion nozzle, ignition electrode, refractory castable, hot air pipeline.
The material lifting plate inside the drum continuously turns sand and gravel to form a uniform material curtain to ensure full heat exchange between hot air and aggregate. After the material lifting plate is worn, material accumulation, insufficient drying temperature and soaring fuel consumption will occur; the burner nozzle has long-term high temperature carbon deposition, and the flame is unstable after blocking, and the heating efficiency is greatly reduced; the seals at both ends of the drum are aged and air leakage, which will introduce cold air to increase fuel consumption and intensify dust emission. High chromium alloy and tungsten carbide wear-resistant materials are preferred for the procurement of accessories of this system, which greatly prolongs the replacement cycle.
This system is a unique combination of accessories for batch mixing station, which is used to convey high temperature dry aggregate to tower and classify, so as to ensure that each specification aggregate is stored separately and weighed accurately. Core accessories include ring chain bucket elevator, lifting hopper, transmission chain, sprocket wheel, multi-layer vibrating screen, wear-resistant screen, damping spring, hot material insulation bin, bin bottom discharge gate, and material level meter.
Hopper and chain can withstand the impact of high temperature aggregate above 150℃ for a long time, which is easy to deform, crack and stretch the chain; vibrating screen screen is continuously washed by sharp gravel, which will cause damage and leakage in 6-18 months, resulting in aggregate classification disorder; hot bin gate seal aging will cause leakage and material string, which will directly damage mixture gradation. It is a key inspection accessory for operation and maintenance of high-grade highway mixing station.
The metering system determines the accuracy of asphalt mixture ratio, which is the key to the quality control of pavement engineering. The accuracy requirement of metering accessories in batch station is much higher than that in roller station. The accessories of batch mixing station include aggregate weighing hopper, weighing sensor, asphalt weighing bucket, mineral powder screw conveyor and powder weighing bin; there is no independent weighing hopper in drum mixing station, and continuous measurement is carried out by frequency conversion belt and asphalt flowmeter.
Weighing sensors and asphalt flow meters are precision accessories. Dust, high temperature and asphalt adhesion will cause measurement errors, which need to be calibrated regularly. Mineral powder spiral blades continue to transport powder, and the powder transportation amount is unstable after wear. The mixture void ratio is difficult to meet the standard. It is necessary to regularly check the wear thickness of blades.
The mixing system is responsible for the uniform fusion of all raw materials, and the wear of accessories directly affects the asphalt coating effect. Batch mixing station adopts double-shaft blade mixing main machine, core accessories include mixing shaft, wear-resistant mixing blade, blade head wear-resistant sheath, main machine lining wear-resistant plate, sealing oil seal; drum mixing station has no independent mixing main machine, mixing is completed by lifting plate inside drum, core loss accessories are drum built-in mixing blade, asphalt injection valve and injection nozzle.
After the mixing blade sheath is worn, the aggregate cannot be completely wrapped by asphalt, and the road surface is easy to loose and seep; the asphalt nozzle of the roller is blocked, which will cause uneven asphalt distribution, and the local asphalt aggregate ratio exceeds or is insufficient, which greatly increases the probability of project rework.
Asphalt belongs to high temperature viscous liquid binder. The whole system accessories shall be kept warm continuously to prevent asphalt solidification from blocking pipelines. Core accessories include vertical/horizontal thermal insulation asphalt storage tank, built-in heating coil, asphalt circulating pump, heat conduction oil pipeline, thermal insulation valve, asphalt metering pipeline, filter core and spray gun head.
The whole set of accessories is kept in a constant temperature environment of 140-180℃ for a long time, and the pump body seals and valve gaskets are easy to age and leak; the pipeline filter accumulates asphalt impurities for a long time, and the asphalt supply is interrupted after blocking, and the production line is shut down; the wear of the tank agitator blades will cause asphalt precipitation and coking at the bottom of the tank, affecting the asphalt bonding performance.
Modern mixing stations are mandatory to be equipped with dust removal equipment to meet environmental protection emission standards, and at the same time recover stone powder for recycling and reduce raw material costs. Core accessories include bag filter box, high temperature dust filter bag, bag cage, Venturi tube, pulse injection solenoid valve, dust hopper, dust unloading screw conveyor.
High temperature filter bag is the core wearing parts, continuous erosion of aggregate dust, high temperature flue gas erosion will cause bag damage, dust direct exhaust after bag damage, environmental protection test exceeds the standard; pulse solenoid valve failure will lead to incomplete dust cleaning bag, dust collector pressure difference increases, drying system exhaust blocked, drying efficiency decreases. At present, environmental protection control is becoming stricter, and regular replacement and maintenance of dust removal accessories are just needed for station operation.
With the popularization of road recycling policy, most mixing stations are equipped with old asphalt milling material supporting system to realize waste recycling and reduce the purchase cost of stone and asphalt. Core accessories include recycled material cold bin, recycled material conveyor belt, special lifting screw, recycled material feeding chute, wear-resistant lining. Recycled material mixed with a lot of gravel, old asphalt caking, conveying accessories wear rate is much higher than the original aggregate conveying accessories, need to choose thickened wear-resistant materials.
The finished product bin is used for temporary storage of hot mix asphalt mixture to ensure continuous loading and avoid frequent start and stop of production line. Core accessories include insulation finished product bin, bin anti-segregation diversion cone, bottom discharge gate, wear-resistant lining plate, material level monitor, discharge chute wear-resistant baffle. The lining plate and discharge baffle of bin body rub with high temperature mixture for a long time, which is easy to wear and perforate, resulting in mixture retention and agglomeration and poor discharge.
The intelligent center of the whole mixing station coordinates the operation of all equipment, data acquisition and fault warning. Core accessories include PLC programmable controller, temperature sensor, weight sensor, frequency conversion control cabinet, operation display screen, various types of pressure, material level monitoring probe, safety interlock protection switch. Sensors and controllers belong to precision electronic accessories. Signal failure is easy to occur in high temperature and dust environment. Dust prevention and heat insulation protection shall be done daily, and data shall be calibrated regularly.
The asphalt mixing station is under high temperature, high dust, strong sand friction and continuous heavy load conditions for a long time. The wear rate of different accessories varies greatly. The replacement cycle is affected by the abrasion resistance of aggregates, the mixing ratio of recycled materials, the annual production tonnage, the daily maintenance level and the material of accessories. The following is the general standard replacement cycle of the industry. The station can establish a parts replacement account in combination with its own production situation to implement preventive replacement to avoid sudden shutdown losses.
Wearing parts of drying drum: lifting plate, wear-resistant lining plate and discharge baffle of drum, which can be replaced after 1000-3000 hours of operation under normal conditions or 50,000 - 150,000 tons of discharge; tungsten carbide and high chromium alloy upgraded materials, the service life can be increased by 2-3 times; seals at both ends of drum are shut down for maintenance and replacement every year, and air leakage and dust leakage occur and replaced immediately.
Mixing system wear-resistant accessories: batch station double-shaft mixing blade, wear-resistant sheath, main engine lining plate, 500-2000 hours or 20,000 - 100,000 tons of discharge replacement; drum mixing station built-in mixing lifting plate replacement cycle and drying lifting plate to keep consistent.
Conveyor lifting accessories: belt conveyor belt 1-3 years replacement, belt cleaning scraper quarterly inspection and replacement as needed; bucket elevator hopper, transmission chain, chain wheel heavy load condition 1-3 years replacement; mineral powder, recycled material screw conveyor blades, lining 1000-4000 hours maintenance replacement.
Screening equipment accessories: vibrating screen wear-resistant screen life cycle 6-18 months, high sand hardness, recycled material mixing amount shortened to half a year.
Dust removal and environmental protection accessories: high temperature dust removal bag regular use of 1-3 years, cumulative discharge of 200,000 - 500,000 tons of overall replacement; pulse solenoid valve, Venturi tube 3 years maintenance replacement, bag cage without severe impact can be used for a long time.
Combustion system accessories: combustion nozzle, ignition electrode every 500-1500 hours cleaning maintenance, carbon deposition, flame deviation directly replaced; burner refractory castable annual shutdown overhaul repair.
Asphalt pipeline metering accessories: asphalt pump seals and valve gaskets shall be replaced annually; asphalt filter elements shall be cleaned monthly and replaced immediately if blocked or damaged.
Discharge, bin wear parts: cold bin, hot bin, finished bin lining wear plate, discharge gate wear block, 1-2 years key wear area replacement.
For daily operation and maintenance, it is suggested to establish a spare parts loss account, record monthly production tonnage and spare parts replacement time, predict replacement nodes in combination with the account, replace them uniformly in the off-season and shutdown interval of the project, avoid shutdown maintenance during construction peak period, and greatly reduce the construction period loss.
70% of the service life of accessories depends on the quality of daily maintenance. Standardized daily inspection, weekly inspection and quarterly overhaul maintenance can extend the service life of wearing parts by 30%-80%, stabilize the quality of mixture and reduce the procurement cost of fuel and accessories. The following subsystems give the operating points of landing maintenance.
Before starting up every day, observe the combustion flame state, no black smoke, flame stability wrapping aggregate is normal, in case of floating fire and black smoke, timely clean nozzles and adjust oil-gas ratio; monitor the flue gas temperature at the inlet and outlet of the drum in real time during operation, abnormal temperature rise or drop, check the wear of lifting plate and seal air leakage; stop to enter the drum every quarter, comprehensively check the deformation, cracking and wear thickness of lifting plate, and clean asphalt and stone lumps on the drum wall; Regularly fill special high-temperature lubricating oil into the roller drive reducer, check the tightness of the transmission chain; repair the refractory layer of the burner every year, repair the castable falling off, and prevent the cylinder from burning at high temperature.
Clean the caked sand at the bottom of the cold storage bin every day to prevent the gate from jamming; adjust the tightness of the belt conveyor, correct the deviation belt in time, replace the worn and cracked cleaning scraper; check the chain tension of the bucket elevator every week, supplement lubricating oil, check whether the hopper is deformed and cracked; clean the blocked stones of the screen every time the vibrating screen stops, tighten the screen pressure plate, check whether the damping spring is broken, and replace the screen immediately if it is damaged, so as to avoid aggregate classification failure.
After daily production, clean the residual mixture inside the mixing host to prevent asphalt agglomeration and hardening from wearing the blades; check the wear thickness of the mixing blade sheath every week, and replace the sheath separately if the local wear is serious, without replacing the propeller shaft as a whole; check the seal oil seals at both ends of the host, and replace them in time if asphalt leakage occurs to avoid dust entering the bearing and causing jamming; strictly follow the equipment regulations for mixing time, and do not overload to shorten the mixing time and aggravate the wear of accessories.
Maintain constant temperature circulation of asphalt storage tank, empty pipeline asphalt during long-term shutdown to prevent solidification and blocking; disassemble asphalt filter every month to clean impurities, check pump body operation noise, abnormal noise represents internal seal wear; calibrate asphalt metering pipeline flowmeter regularly to ensure accurate oil-stone ratio; all heat conduction oil pipelines and valves shall be well insulated to avoid heat loss and local cooling asphalt solidification.
Check the pressure difference data of dust collector every day. High pressure difference means dust accumulation blocking in bag, start pulse dust cleaning system; check the injection state of pulse solenoid valve every week, and repair solenoid valve in time without air flow in single channel; open the cover every quarter to check whether there are holes, aging and damage in bag, and replace damaged bag sets to avoid dust leakage; regularly empty dust collection hopper, recycle stone powder and put it into mixture to reduce waste of raw materials.
The control cabinet shall be well treated with dust prevention, heat insulation and waterproof to avoid corrosion of circuit board by high temperature flue gas and dust; the weighing sensor, temperature and material level probe shall be calibrated every month to eliminate measurement error; the safety interlock switch of equipment shall be checked, and the fault shutdown protection function shall be kept normal, and the illegal removal of safety accessories shall be prohibited; the spare sensor and controller core electronic accessories shall be stored, and the fault shall be replaced quickly to shorten the shutdown time.
The asphalt mixing station accessories on the market are divided into original OEM accessories and upgraded wear-resistant auxiliary factory accessories. Low-priced inferior accessories save short-term procurement costs, but wear fast, frequent failures, and comprehensively increase the total cost of downtime, maintenance, and raw material loss. Purchasing accessories can not only compare unit prices, but also need to be screened from five dimensions: material, process, adaptability, quality assurance and full life cycle cost. The complete selection and evaluation standards are given below.
High chromium alloy steel, high manganese steel, tungsten carbide surfacing, ceramic composite wear resistant materials are preferred for high temperature friction working conditions accessories (lifting plate, stirring paddle, lining plate, screen); ordinary 45 carbon steel is only suitable for low load, low output small equipment, long-term use wear rate is 2-3 times that of wear resistant alloy accessories; asphalt pipelines and seals are made of high temperature asphalt corrosion resistant special rubber; dust removal bags are made of high temperature resistant composite needle-punched filter materials, which are suitable for flue gas working conditions above 180℃. When purchasing, the supplier is required to provide material hardness test report and wear resistance test data, so as to prevent inferior products from being replaced by good ones.
Manufacturer qualification and matching adaptability
core precision accessories (Burner, PLC control system, weighing sensor) give priority to original OEM parts, size, installation interface, operating parameters are fully matched, no assembly failure; lifting plate, blades, bags and other vulnerable wear parts, you can choose ISO, CE production qualification of professional wear parts manufacturers, such manufacturers can provide upgraded thickening wear models, service life is better than the original standard parts; Before purchasing, check the model of mixing station (LB1000/LB2000/LB3000, roller 3000/4000, etc.), confirm that the size and installation hole position of accessories are completely matched, so as to avoid assembly and rework after arrival.
Rationality of product process design The drum lifting plate preferably selects the bionic arc lifting structure, which has uniform material curtain, high heat exchange efficiency and less wear; the stirring paddle adopts the split replaceable sheath design, only the sheath is replaced for local wear, and the stirring shaft does not need to be replaced as a whole, so as to reduce the long-term consumption cost; the bag dust collector adopts the low-resistance pulse dust cleaning bag to reduce the energy consumption of the fan; the belt conveyor adopts the thickened anti-tearing conveyor belt, and the buffer roller is matched to reduce the sand impact wear.
Quality accessories manufacturers provide 1-2 years warranty, wear-resistant alloy accessories can extend the warranty period; focus on the supplier's storage capacity, the national multi-warehouse stock can achieve parts within 48 hours to the site, greatly shorten the downtime waiting time; give priority to the supplier that provides on-site installation guidance, parts wear detection, equipment operation and maintenance technical support, assembly, use problems can be quickly solved.
Total Life Cycle Costing (TCO) Purchasing accessories cannot simply compare the price of a single piece, but need to comprehensively calculate the service life, downtime loss and manual replacement cost. For example, ordinary carbon steel lifting plate unit price is low, but 1000 hours must be replaced; tungsten carbide wear-resistant lifting plate purchase price is high, but 3000 hours do not need to be replaced, comprehensive annual parts procurement, downtime costs, wear-resistant high-end accessories comprehensive expenditure is lower, is the best choice for long-term operation of large-scale mixing station.
Drying drum accessories: priority counter-current thickening high chromium material plate, supporting integrated wear-resistant material ring, drum seal selection of multi-layer high temperature resistant flexible seals; burner selection of oil and gas dual-use low nitrogen energy-saving model, supporting stainless steel anti-clogging nozzle.
Mixing system accessories: dual-shaft mixer with split tungsten carbide paddle head, ceramic composite wear plate lining; drum mixing station customized thickening mixing lifting plate, supporting anti-blocking asphalt spray nozzle.
Dust bag accessories: according to the flue gas temperature at the outlet of the drum, select a filter bag with a temperature above 200 ℃, and select an oil-resistant waterproof composite bag for the high-recycled material blending station to prevent asphalt soot adhesion and blockage.
Conveying and screening accessories: vibrating screen selection wear-resistant polyurethane screen, strong toughness, impact resistance; belt selection of anti-tear temperature-resistant rubber conveyor belt, matching alloy cleaning scraper.
In the process of asphalt mixing plant accessories procurement, common mistakes focus on one-sided pursuit of low prices and neglect of accessories material and wear resistance, seemingly saving procurement costs, but due to rapid wear of accessories will cause frequent downtime maintenance, resulting in far more than the price difference of accessories construction period and economic losses; At the same time, many procurement personnel ignore the equipment model adaptability, confusion batch station and drum continuous mixing station accessories specifications, blind procurement of general accessories, easy to cause assembly dislocation, equipment operation failure; In addition, lack of core wearing parts inventory planning, failure to match environmental protection accessories in combination with production conditions, neglect of product warranty and after-sales guarantee are also high-frequency problems. Zero inventory configuration is easy to lead to long-term shutdown of production line after parts are damaged. The selection of ordinary normal temperature dust removal filter bags that do not meet high temperature conditions will be quickly damaged, resulting in punishment for environmental protection exceeding standards. However, when purchasing small workshop accessories without formal warranty, after-sales claims cannot be enjoyed after short-term damage, which greatly increases the risk and cost of station operation and maintenance.
As the core production equipment of road infrastructure, asphalt mixing plant is based on the stable operation of various core accessories. From cold material transportation, drying and heating, mixing and mixing to dust removal, environmental protection, and intelligent control, each type of accessories performs irreplaceable functions. Accessory wear, incorrect selection, and lack of maintenance will directly affect the quality of asphalt mixture production and station operations. Cost and environmental compliance.
In daily management, the station operator shall distinguish between core precision parts and high-frequency wear resistant parts, establish standardized daily inspection, regular replacement and off-season overhaul maintenance system; abandon low-price priority thinking in procurement link, select high-quality parts in combination with equipment model, production tonnage, recycled material blending ratio, comprehensive material, service life, after-sales service and whole life cycle cost. Reasonable matching of high-quality accessories + standardized operation and maintenance can not only prolong the service life of the whole machine of mixing station for 20-30 years, but also stabilize the quality of mixture, reduce the expenditure of fuel and consumables, and assist the efficient and green construction of highway and municipal engineering.
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