The Fault Analysis and Solution of Weighing System in Concrete Mixing Plant
In the whole process of automatic production of concrete mixing station, the weighing system software determines whether the concrete produced by it meets its compressive strength specification. The weighing system software of mixing station has completed the accurate weighing of various ingredients in concrete, which is also the most important stage in the whole process of automatic production of concrete. However, in the usual processing process, the weighing system software is likely to have various problems. Today, let's talk about the software failure problem of weighing system in mixing station and its solution.
The whole process of weighing system software in concrete mixing station
The mixture ratio of concrete mortar with different compressive strength is different. The dosage of sand, stone, coal ash, concrete, water and water reducer must be typed in the main management program of the mixing station in advance. In the case of producing concrete, the mortar mixture ratio will be activated immediately. Then, according to PLC, the metrological verification components are turned on and off. Stone controls the warehouse door of seasoning warehouse, granular materials control the screw conveyor, and water and water reducer control the centrifugal water pump or water reducer motor.
The next step is the whole weighing process. After the raw materials are put into the weighing vessel, the weighing sensor is deformed by the weight, so that the resistance value of the bridge circuit of the weighing sensor changes, and the working voltage of the bridge circuit also changes. After this signal is solved and enlarged, the weighing information content is converted into a data signal according to the solution of the signal transmitter, and then the net weight of a certain material is displayed on the desktop computer host or on the display. At this point, the weighing system software of the mixing station has completed the whole weighing process.
Common failure problem
The office environment of the mixing station is extreme, and there is a lot of dust in the air. However, the weighing system software is also very high-precision machinery and equipment, so it is difficult to avoid all kinds of faults in the weighing system software. In general, the following types of problems are more common.
1. After feeding, the display information of net weight value is zero.
2. During the whole weighing process, the net weight value is high and low.
3. The deviation of scale weight value is too large.
4. After cutting, the weight of the scale is still very large, or it can't be zero.
Fault problem handling mode
The problems of weighing system software can generally be clearly seen on the display immediately, unless the display itself is broken. In addition, the software failure of the weighing system will definitely cause changes in the mortar mixture ratio of concrete and endanger the quality of concrete. Therefore, after finding that there is a problem with the weighing system software, it should be turned off immediately for inspection, and the fault should be removed before production.
1. Check the route
If the weighing value is zero, the first thing to consider is whether the route of the weighing sensor is broken or the connection head is in virtual connection. If the route is detailed, let's consider whether the sensor is damaged. From the appearance, distinguish whether the route and sensor components are damaged or burned. According to the inspection route, the first fault problem can be solved.
2. Check the weighing sensor
At present, the most common strain sensor in mixing station is resistor strain sensor. According to the malleable photosensitive resistor, the external working pressure is applied to the resistance strain gauge, and then according to the strain force effect of the resistor, the strain force is converted into a slight change in resistance by the resistance strain gauge, and then converted into a working voltage output according to the accurate measurement bridge circuit.
First of all, check whether the switching power supply of the sensor is normal, and accurately measure the encouragement with the digital multimeter AC voltage range-whether the working voltage in the middle is 12V. If the switching power supply is all right, then use the DC mV gear of the digital multimeter to accurately measure the signal and the output voltage in the middle of the signal, and its working voltage value is generally in the range of 0-50mv. If the accurate measurement value is 0MV, one condition means that there is no material in it, and another condition is that the sensor is damaged.If the accurate measurement value exceeds 50mV, it also strongly proves that the sensor has already been destroyed.
There is also a way to distinguish the advantages and disadvantages of sensors, according to the resistance value resolution method. When the sensor is not connected to the power supply, the resistance between the positive and negative encouraging wires should be 381 Ω 2 Ω, and the resistance between the positive and negative signal wires should be 351 Ω 2 Ω. In addition, there are also encouragement and signal-in-the-middle resistors, and their resistance values in the middle of encouragement and signal and signal-are all in the middle of 300Ω+3Ω resistance values, which proves that there is no problem with the sensor. If there is no upper resistance range, it is very likely that the sensor has already been destroyed.
If you can't tell, it means which sensor guide is faulty. You can disassemble the sensors one by one and distinguish them according to the resistance value, or connect the switching power supply independently to see if the weighing data information is accurate, so as to distinguish the advantages and disadvantages of a sensor. The sensor is damaged, which is likely to cause the first and fourth failure problems.
3. Signal transmitter. Under all normal conditions, the output signal of the signal transmitter is in direct proportion to the amount of material inside. If the standard weight with the same net weight is continuously placed on the scale during the whole weighing process, the output working voltage will not increase relatively, so it can be distinguished as an intelligent transmitter fault. This method is suitable for analog input signal transmitters.
In recent years, more and more weighing system software has applied data signal transmitter, as shown in the following figure, which is a four-channel signal transmitter internal wiring method. Four channels means that at most four groups of weighing information can be converted and transmitted, which is more efficient and more accurate than analog input signal transmitter.
The data signal transmitter finally transmits signals according to the two terminals RXD and TXD. In addition, they have their own matching working display lights. The RXD terminal is used to receive signals, and its display light flashes every time the intelligent transmitter receives a frame of data. Its on or off indicates that the intelligent transmitter has not read data. TXD terminal is used to push signals, and its display light flashes once every time the intelligent transmitter pushes a frame of data. Its on or off indicates that the intelligent transmitter has not transmitted data. In addition, the sensor signal of each security channel has its matching display light, which indicates that everything is working normally, and whether it is on or off for a long time indicates that the sensor signal of a security channel is abnormal.
Therefore, for the signal transmitter with a large amount of data, it is the first time to distinguish whether it is working normally according to the display lamp. Secondly, because its output signal cannot be measured by multimeter. Therefore, a new signal transmitter can be replaced by an alternative method. If the fault is solved, it shows that there is something wrong with the signal transmitter. If it is a problem of signal transmitter, it may lead to the problems 1, 2, 3 and 4.
Summary of solving difficult problems
First, check whether it is a route or a sensor problem from the appearance, and then check whether the sensor is damaged one by one. Not only can you connect the power supply to check whether its output signal is normal, but you can also check whether the resistance value is normal when the power supply is turned off. In addition, the most common way to solve the sensor problem is to replace it with a new sensor. If the problem is solved, it shows that there is a problem with the replaced sensor, which is the most immediate and effective way.
In the usual maintenance of weighing system software, if we want to try our best to prevent the failure of weighing equipment, it is also indispensable in the usual maintenance. Usually, it is necessary to limit the production of sensors. Is there a problem of mechanical equipment intervention, or is it stuck by dirty things? For example, the sensor is stuck by dirty things, and it always has a deformation, which will cause the scale to always have a net weight value, which is the fourth fault problem often mentioned above. After cutting, the scale weight value is still very large, or it can't be zero. The probability of this kind of situation is very high, so it is necessary to observe one sensor at a time.
If granular materials, water and water reducer can't be called zero, it is necessary to consider whether the conductive soft connection at the opening has a downward tensile force due to symmetry. If the conductive soft connection can be said to be zero after being removed, it indicates that the conductive soft connection is tightly connected and must be loosened.
The problem of weighing equipment should be solved from a very simple way, and it is not necessary to blindly follow the trend and suspect that the sensor is destroyed at the beginning. According to the enumeration method to reduce the fault category, in addition, the faster way is to choose the substitution method immediately and disassemble the new electronic devices, which can quickly and accurately locate.
