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Large Scale Instrument Detection and Fault Control Methods
There are many causes of failure of large scales, and the phenomenon of failures is also complex. Sometimes several failure phenomena occur at the same time. Therefore, when dealing with faults, a variety of methods can be used to carefully analyze the cause of the fault, examine in detail the links that may cause the fault, and then eliminate the fault as soon as possible to resume normal use.
In recent years, with the improvement of product quality in the production process, special scales used in some key processes such as metallurgy, petrochemicals, and coal have grown from weighing tens of tons to hundreds of tons. Thousand tons of load. At the same time, with the rapid development of the logistics industry, the transport volume of large-tonnage trucks has exceeded 100 tons per vehicle. At the same time, hundreds of tons of truck scales, hundreds of tons of track scales, hundreds of tons of crane scales, on-board scales, and thousands of tons of hopper (tank) scales have also emerged. Although many products have large weighing values, they are limited by the space location and the carrier is too small to consider the placement of the standard device. Of course, there are some products that are due to the lack of experience of designers and ignore the detection problems of weighing instruments.
1. Concept description of a large scale
Weighing instruments refer to instruments that are based on the principle of lever balance of force. The purpose is to measure the mass of an object. It is mainly composed of load-bearing system, indication system and force transfer system. In recent years, with the economic development, many industries have required the use of special weighing instruments. For example, in the coal, metallurgy, and petrochemical industries, the weighing of large-scale scales has grown to several hundred tons, and there are even thousands of tons of load. On the other hand, with the rapid development of the logistics industry, many large-scale automobiles have reached hundreds of tons of vehicles per vehicle. It can be seen that the detection of weighing instruments is becoming more and more important. As a weighing and weighing device, a large-scale weighing instrument has the advantages of simple metering, high resolution, digital weighing display, complete function, stable and reliable performance, and weight signal transmission. However, due to the harsh and complex environment of some enterprises, combined with frequent weighing and overloaded use, and lack of necessary maintenance, frequent failures have seriously affected the normal operation of the enterprise.
2, large scales fault diagnosis
To troubleshoot, first of all try to find and confirm the cause of the failure, and find the source of the failure should be mainly based on the phenomenon of failure and the system components, components, connectors, components and their performance after the failure and possible impact Determine the types of failures, enumerate all the factors that may cause failures, and eliminate them one by one by various means and methods to determine the location of the failure. Therefore, the fault handling of large-scale scales should generally follow such steps: observation → analysis → detection → repair → verification. In the course of using, there are many kinds of fault phenomena. If the cause of the fault is generally classified into mechanical fault and electronic fault, it can be divided into two major categories. Mechanical failure refers to the permanent deformation of the scale body, the top dead scale body of the limit device, the displacement of the scale body, the foreign matter stuck between the bottom of the scale body and the gap between the frame and the border, the breakage of the connector, the leveling of the scale body, and multiple stages. Loose connection between the scale body, sensor displacement and foundation sinking. Electronic failure refers to the failure of the instrument, sensor, and junction box, the looseness of the connectors of the total signal cable, the welding or welding off of the solder joints, the breakage of the signal cable, and the deterioration of the insulation performance.
3, a large scale detection method
3.1 standard weight method
The standard weight method is one of the earliest detection methods used. It uses weights to detect the entire metering instrument's measurement performance. The weight of the weight used by it must be 1/3 of the maximum allowable error of the weighing instrument. However, the checked weighing instrument must test the accuracy of its maximum weighing when it is first tested, and can be adjusted according to the actual use conditions in the subsequent tests. If the maximum weighing is not detected, at least 2/3 of the maximum weighing capacity must be detected. . This method is generally not suitable for the current large-scale scales, and some weighing instruments weighing hundreds, thousands of weighing, there is not so much standard weight. In addition, the loading and unloading of weights is also a problem. The weights will not be fixed during transportation, and displacement will occur. As a result, the vehicles will be unbalanced and they will easily roll over.
3.2 Standard Weight Replacement Method
When the maximum weighing capacity of the checked weighing instrument is too large and there are not enough standard weights to detect the entire weighing performance, other constant loads are generally used instead of the standard weights. At least 1 ton of standard weight is to be prepared before testing, or the standard weight of 50% of the maximum weight of the inspected weighing apparatus, whichever is the greater. If the repeatability error of the scale is not more than 0.3e, then the maximum weighing can be reduced by 65%; if the repeatability error of the checked weighing instrument is less than 0.2e, 80% of the maximum weighing can be reduced; the repeatability error is to be checked. The maximum weighing of 50% of the weighing device is determined by applying it on the carrier three times. For the time being, some large scale weighing instruments weighing 80 to 80 tons can use 35% standard weight instead of twice. Although this is the case, great human and material resources are also needed.
3.3 Integrated detection method
The three international recommendations R61 Gravity Automatic Loading Weighing Apparatus, R134 Automatic Road Vehicle Automatic Weighing Apparatus, and R107 “Discontinuous Accumulative Automatic Weighing Apparatus†developed by the International Legal System Metrology Organization have all referred to a detection method. Integrated detection method." This detection method is to use the free device of the checked weighing apparatus to determine the agreed value of the article quality, which is mainly used to detect the accuracy of the dynamic weighing of the weighing instrument. In addition, there are some more common methods, such as calculations, the basic steps of the calculation method is to first detect the value of the output signal under no-load conditions, followed by 1/10 the maximum weight of the standard weight, The output signal value is detected again, and then two consecutive 1/10 maximum weights are added to detect the signal value and compared with the previous linearity. The precondition for adopting the calculation method is to determine the relevant parameters of the checked weighing instrument: 1 The accuracy of the weighing sensor; 2 The calculation data of the design stiffness of the carrier; 3 The linear indicator of the weighing display controller; 4 The carrying capacity of the weighing instrument basis force.
3.4 Overlay detection method
At present, it is widely used in all sensor production units in the country, so it can be used to detect sensors with higher accuracy than scales. Why can't we use it for measuring instruments? We mentioned earlier that the use of detection methods is legally supported. It involves a legislative issue, that is, determining the feasibility status of the superposition method in the measurement of related instruments, followed by the specific operation method and the step problem. If the weighing instrument is to be tested by the superposition method, the hydraulic system and the detection structure are not the standard weights on the checked instrument, which is much safer to transport than standard weights. However, there are still some technical problems that need to be solved in the application of the superposition method. For example: the problem of detecting the structure, the problem of the loading point, the problem of the point of substitution, the stability of the power source, and so on.
4 Conclusion
With the rapid development of China's economy, large-scale scales are increasingly used in industrial production. Weighing instrument accuracy is the premise that it can be used, but in the actual operation process, often because there is no scientific and reasonable detection method, can not determine the accuracy, which directly affects the use of large scales. Therefore, China must increase investment in metrology construction and apply more scientific and technological achievements to large-scale scales. This will only make breakthroughs in the detection of large scales. The use of large-scale scales can keep up with the rhythm of China’s industrial economy. Promote the development of China's economy.
references:
[1] Fan Guihua, Discussion on the detection methods for large scales[J]. China Food Quality Report, 2013
[2]Jin Zhaoxu, Failure Analysis and Processing of Large-scale Weighing Apparatus [J]. Branding and Standardization, 2012(02).