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Installation and Maintenance of Electrical System of Asphalt Concrete Mixing Plant

Thomas Huang posted this article in June 30, 2020

Asphalt concrete mixing station is an important equipment for expressway construction. In production, whether the electrical system works is reliable, to a large extent determines whether the asphalt concrete mixing station can be produced normally. This article focuses on the installation and maintenance of the electrical system of the asphalt concrete mixing station. It briefly describes the four main points in its installation, use and maintenance. It is hoped that it will be helpful to the work of the road construction counterparts.
Asphalt concrete mixing station is an important equipment for highway construction. It integrates various technologies of machinery, electrical and automation. Asphalt concrete mixing station (hereinafter referred to as: asphalt station) production capacity, automation level and measurement accuracy of the control system, energy consumption rate has now basically become the main factor to measure its performance.
 From a large perspective, the installation of asphalt stations mainly includes basic fabrication, mechanical metal structure installation, electrical system installation and commissioning, and asphalt heating and pipeline installation. The mechanical metal structure can be installed in one step under the condition that the asphalt station foundation is constructed, and adjustments and changes are rarely made in future production. Asphalt heating and pipeline installation are mainly for the service of asphalt heating, and the workload of installation mainly depends on the equipment for storing and heating asphalt. In production, the reliability of the electric drive and control system is one of the important factors affecting the normal production of asphalt stations. This article only focuses on the installation and maintenance of the electrical control system of the asphalt station. Based on the actual situation on the spot, the four points of the installation and maintenance of the electrical system of the asphalt station are briefly discussed, and they are discussed and learned with their peers.
1. Familiar with the system, familiar with the principles, reasonable wiring, and make wiring connections.
 Regardless of whether the asphalt station is installed for the first time or relocated to a new site for installation, technicians and maintenance personnel engaged in electrical installations must first familiarize themselves with the control mode and principles of the entire electrical system in conjunction with the working process of the asphalt station, familiar with the distribution of the system and some key controls The specific role of the device, so that the installation work is relatively easy.
According to the drawings and the installation location of the electrical components, the wiring is concentrated from the peripheral part to the control units or the periphery to the control room. The cable layout must be selected for the appropriate path, and the weak current cable and the strong current signal cable are required to be divided into slots.
The electrical system of the mixing station includes strong electricity, weak electricity, AC, DC, digital signals, and analog signals. In order to ensure that these electrical signals can be effectively and reliably transmitted, each control unit or electrical component outputs the correct control signal in time. And can reliably drive each actuator, whether the connection of the electrical circuit is reliable has a great influence. Therefore, in the installation process, it is necessary to achieve reliable connection of each wiring point and installation and fastening of electrical components.
The main control units of the asphalt station generally adopt industrial control computers or PLCs (programmable logic controllers). Their control process is basically that after the internal circuit detects an electrical input signal that satisfies a certain logical relationship, it outputs in time a certain logical relationship Electrical signals drive relays or other electrical units or components. The work of these relatively precise components is generally relatively reliable. If a fault occurs during operation or debugging, first check whether all relevant input signals are input, and then check whether there are any output signals required to be output, and whether they are output according to logic requirements. In general, as long as the input signal is valid and reliable and meets the logic requirements, the output signal will be output according to the internal program design requirements, unless the terminal (wiring board) is loose or the peripheral components and lines related to these control units are faulty. Of course, in some special cases, there may be damage to the internal components of the unit or a circuit board failure.
2. Do the earthing (or zero connection) protection of the electrical system, as well as the lightning protection grounding and sensor shielding grounding of the whole machine.
From the grounding system of power supply, if the power supply adopts the TT system, the metal frame of the mixing station and the electrical cabinet shell of the control room must be reliably grounded when installing the mixing station. If the power supply adopts the TN-C system, when installing the mixing station, the metal frame of the mixing station and the electrical cabinet shell of the control room should be reliably grounded and reliably connected to zero. On the one hand, the conductive structure of the mixing station is realized. The protection is connected to zero, and repeated grounding of the zero line of the electrical system of the mixing station is realized. If the power supply adopts the TN-S (or TN-C-S) system, when we install the mixing station, the metal frame of the mixing station and the electrical cabinet shell of the control room can be reliably connected to the protection line of the power supply. Regardless of the type of power supply, the grounding resistance of the grounding point shall not be greater than 4 Ω.
In order to prevent the mixing station from being damaged by lightning strikes, when installing the mixing station, the lightning rod should be installed at the highest point of the mixing station, and all the components of the mixing station should be within the effective protection area of the lightning rod. The grounding down conductor of the lightning rod should be a copper wire with a cross-section of not less than 16mm² and an insulated protective sheath. The grounding point should be located at least 20 m away from other grounding points of the mixing station without pedestrians or facilities, and this connection is guaranteed The grounding resistance of the site is below 30 Ω.
When installing the mixing station, the shielded wires of all sensors must be reliably grounded. This ground point can also connect the ground lead of the control unit, but this ground point is different from the protective ground point and Lightning grounding point, the grounding point should be at least 5 m away from the protective grounding point, and the grounding resistance is not greater than 4 Ω.
Do the debugging work carefully.
During the initial assembly of the mixing station, the commissioning work may take a lot of energy and time, because many problems may be found in the commissioning, such as wiring errors, inappropriate parameter setting of the component or control unit, inappropriate installation location of the component, damage to the component, etc. The reason, what is the specific reason, must be judged and corrected or adjusted according to the drawings, actual conditions and inspection results.
After the main body of the mixing station and the electrical system are installed in place, careful commissioning should be done. First, manually control the no-load trial operation from the single motor single action. If there is a problem, check whether the circuit and electrical components are normal. If the single motor single action trial operation All are normal, you can enter some units to manually or automatically control the no-load test operation, if they are normal, then enter the whole machine automatic no-load test. After these tasks are completed, do the whole machine with load test machine. After the commissioning work is completed, it can be said that the installation work of the mixing station has basically been completed, and the mixing station is already equipped with production capacity.
Do a good job of temperature adjustment in the control room, frequently clean dust from electrical components and external units, check electrical components frequently, and do maintenance work on mechanical transmission parts.
The control room of the asphalt station is basically the core of the electrical control system of the full mixing station. If the temperature in the control room is too high, it will affect the normal and reliable operation of the electrical components and the system, so the temperature in the control room must be adjusted. Due to the large dust in the field, this has a great impact on the reliable operation of electrical components such as relays and contactors, so it is necessary to frequently clean the dust of various electrical components. In order to make the mechanical transmission mechanism of the mixing station operate normally, the lubrication of the mechanical transmission part should be done in time.

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