01
Mar

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Technical points of installation and commissioning of asphalt mixing equipment

As we all know, asphalt mixture mixing equipment is the key equipment of asphalt pavement construction. The installation and commissioning of the mixing equipment directly affect its operation state, pavement construction progress and quality. This paper mainly describes the technical points of installation and commissioning of large-scale asphalt mixture mixing equipment.

model selection

adaptability

The equipment model shall be comprehensively studied and selected according to the enterprise qualification, contracted project scale, task volume of the project (bid section), combined with the climate of the construction area, effective construction days, enterprise development prospect, enterprise economic strength and other factors. The equipment capacity shall be 20% greater than the construction task.

Progressiveness

The selected equipment shall have the technical level suitable for the current construction requirements and be scalable. For example, the number of cold and hot silos should be 6 to meet the accurate control of mix proportion; The mixing cylinder shall have an interface for adding additives to meet the requirements for adding fiber materials, anti rutting agents and other additives.

Environmental protection

When purchasing equipment, you should fully understand the environmental protection indicators of the equipment to be purchased, which should comply with the provisions of national environmental protection regulations and the requirements of the environmental protection department in the area of use. In the procurement contract, the environmental emission requirements of the heat transfer oil boiler and the dust collector device of the drying system shall be specified. The equipment operation noise shall comply with the national regulations on the noise at the boundary of the enterprise. The asphalt storage tank and heavy oil storage tank shall be equipped with the collection and treatment facilities of each spilled flue gas.

install

The installation work is the basis for determining the use quality of equipment. It should be highly valued, carefully organized and implemented by experienced engineers.

preparation

The main preparations are as follows: first, entrust a qualified architectural design unit to design the basic construction drawings according to the plane layout provided by the manufacturer; Second, apply for power distribution and transformation equipment according to the requirements of the equipment operation manual. When calculating the distribution capacity, consider the power consumption requirements of emulsified asphalt, modified asphalt and other supporting equipment, and leave 10% ~ 15% of the surplus passenger volume; Second, the living electricity in the station must be additionally installed with transformers of appropriate capacity to ensure the stable operation of production equipment; Fourth, the high and low voltage cables in the site shall be designed to be buried, and the distance between the transformer and the main control room shall be 50m in total; Fifth, since the power installation procedures need about 3 months, they should be handled as soon as possible after the equipment is ordered, so as to ensure the power consumption during commissioning; Sixth, boilers, pressure vessels and measuring equipment should go through relevant approval and inspection procedures in time.

Installation procedure

The foundation construction process is as follows: review the drawings → setting out → excavation → foundation compaction → reinforcement binding → embedded parts installation → formwork erection → silicon pouring → maintenance.

The foundation of the mixing plant is generally designed as raft foundation, and the foundation must be treated flat and dense. If the soil is loose, it must be replaced. It is forbidden to directly pour the underground foundation by using the pit wall, and the formwork must be installed. If the average temperature of day and night is below 5 C for 5 consecutive days, thermal insulation measures should be adopted according to the winter construction requirements (for example, foam board in the formwork, heating and insulation in the shed). The installation of embedded parts is a key process. The plane position and elevation must be accurate and fixed firmly to ensure that the embedded parts do not move or deform during pouring and vibration.

After the foundation construction is completed and the acceptance conditions are met, the foundation acceptance must be carried out. During the acceptance, the rebound instrument is used to measure the concrete strength, the total station is used to measure the plane position of embedded parts, and the level is used to measure the foundation elevation. After passing the acceptance, the hoisting process is started.

The hoisting construction procedure is as follows: mixing plant → hot material lifting equipment → powder bin → powder lifting equipment → drying drum → dust collector → belt conveyor → cold bin → asphalt tank → heat transfer oil furnace → main control room → accessories.

If the outrigger of the finished product warehouse on the first floor of the mixing plant is designed to be embedded with bolts, the above floors can be hoisted only after the concrete strength poured twice reaches 70%. The lower stair guardrail must be installed in time and firmly before lifting layer by layer. For the parts that cannot be installed on the guardrail, the hydraulic lift truck shall be used for operation, and the safety facilities shall be equipped to do a good job in safety protection. When selecting the crane, its lifting quality shall meet the requirements. Before the lifting operation, it must fully communicate and disclose with the lifting driver. In case of strong wind, precipitation and other weather, the lifting operation is prohibited. At the proper time of hoisting construction, equipment cables shall be laid and lightning protection equipment shall be installed.

Process inspection during the operation of the mixing equipment, periodic static self inspection shall be carried out, mainly to comprehensively inspect the structural components of the mixing equipment to ensure that the installation is firm, the verticality is qualified, the protective railing is intact, the liquid level of the high-level tank of heat transfer oil is normal, and the power and signal cables are correctly connected.

Idle commissioning

The idle commissioning process is as follows: test run the motor → adjust the phase sequence → no-load operation → measure the current and speed → observe the operation parameters of distribution and transformation equipment → observe the signal returned by each sensor → observe whether the control is sensitive and effective → observe the vibration and noise. If there is any abnormality during idle commissioning, it shall be eliminated.

During idle commissioning, it is also necessary to detect the sealing condition of compressed air pipeline, the pressure value and action of each cylinder, and the position signal of each moving part. After idling for 2h, check whether the temperature of each bearing and reducer is normal, and calibrate each load cell. After the above commissioning is normal, you can buy fuel and start commissioning the heat transfer oil boiler.

Commissioning of heat transfer oil boiler

Dehydration of heat transfer oil is the key work. The heat transfer oil must be dehydrated at 105 ℃ until the pressure is stable, then heated to 160 ~ 180 ℃ working temperature, supplemented with oil at any time and vented repeatedly to achieve stable inlet and outlet pressure and stable liquid level. When the temperature of the insulation pipeline of each asphalt tank reaches the normal working temperature, asphalt, gravel, mineral powder and other raw materials can be purchased for feeding and commissioning.

Feeding commissioning

The commissioning of combustor is the key to feeding commissioning. Taking the heavy oil combustion engine as an example, qualified heavy oil should be purchased according to its instructions. The method of rapid detection of heavy oil on site is to add diesel oil, and the heavy oil that can be dissolved in diesel oil is high-quality heavy oil. The heating temperature of heavy oil is 65 ~ 75 ℃, and too high temperature will produce gas and cause fire break. If the parameters of the combustor are set correctly, the smooth ignition can be realized, the combustion flame is stable, and the temperature increases with the increase of opening, and the cold material system can be started for feeding.

Do not add stone chips with particle size less than 3mm in the initial test run, because if the flame goes out suddenly, the stone chips that have not been dried will adhere to the roller guide plate and the vibrating screen with small screen holes, which will affect their future use. After feeding, observe the aggregate temperature and hot bin temperature displayed by the computer, discharge the hot aggregate of each hot bin respectively, take it out with a loader, measure the temperature and compare it with the displayed temperature. In practice, these temperature values have differences, which should be carefully summarized, measured repeatedly and distinguished, so as to accumulate data for future production. When measuring temperature, infrared thermometer and mercury thermometer shall be used for comparison and calibration.

The hot aggregate from each silo shall be sent to the laboratory for screening to check whether it meets the corresponding range of screen holes. If there is mixing and bin mixing, the cause shall be found out and eliminated. The current, reducer and bearing temperature of each part shall be observed and recorded. Under the condition of waiting for materials, observe and adjust the positions of two thrust wheels of flat belt, inclined belt and drum, and observe that the drum operation should be free of impact and abnormal sound. Analyze the above inspection and observation data to confirm whether the drying and dust removal system is normal, whether the current and temperature of each part are normal, whether the action of each cylinder is normal, and whether the time parameters set by the control system are applicable.

In addition, in the process of feeding and commissioning, the opening and closing positions of hot material bin door, aggregate scale door, mixing cylinder door, finished product bin cover, finished product bin door and small door shall be correct and the action shall be smooth.

Trial production

After the completion of feeding and commissioning, communicate with the construction technicians to carry out trial production and pave the pavement of the test section. The trial production shall be carried out according to the mix proportion of the mixture provided by the laboratory. The trial production can be switched to the batching and mixing state only after the measured temperature of the hot aggregate meets the requirements. Taking AH-70 asphalt limestone mixture as an example, the aggregate temperature should reach 170 ~ 185 ℃ and the asphalt heating temperature should be 155 ~ 165 ℃.

Arrange a special person (tester) to observe the appearance of asphalt mixture at a safe position on one side of the transport vehicle. The asphalt shall be evenly wrapped without gray particles, obvious segregation and agglomeration. The actual measured temperature shall be 145 ~ 165 ℃, and the appearance and temperature records shall be made. Take samples for extraction test to check the gradation and asphalt aggregate ratio, so as to check whether the control of the equipment is accurate.

Attention shall be paid to the test error, which shall be comprehensively evaluated in combination with the actual effect after paving and rolling. The conclusion of whether the equipment control is accurate cannot be drawn in one trial production. The conclusion can be drawn only by analyzing the computer statistical data, the actual consumption of materials, the quantity of finished products and the test data when the cumulative output of mixtures of the same specification reaches 2000t and 5000t. The asphalt metering accuracy of large asphalt mixture mixing equipment shall reach ± 0.25%. If it fails to reach this range, the causes shall be found out and solved.

Trial production is a stage of repeated commissioning, summary and improvement, with heavy workload and high technical requirements. It requires close cooperation of all departments and certain experience of management and technical personnel. The author believes that the trial production can be considered to be completed only after all parts of the equipment operate stably and reliably, all parameters are normal and the mixture quality is stable and controllable.

Staffing

The large-scale asphalt mixture mixing equipment shall be equipped with 1 manager with engineering machinery management and working experience, 2 operators with high school education or above, and 3 electricians and mechanics. According to our practical experience, the division of types of work should not be too detailed. It should be specialized and versatile. Operators should also participate in maintenance and can replace each other in their work. We should choose people who can bear hardships and love to study for management and operation, so as to improve the comprehensive ability and work efficiency of the whole team.

check before acceptance

The management personnel of large-scale asphalt mixture mixing equipment shall organize manufacturers and construction technicians to summarize the commissioning process, test and evaluate the trial production mixture quality, equipment control performance and safety protection facilities, and compare them with the requirements of the procurement contract and instructions to form written acceptance data.

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