Continuous metrological improvement of technology - differential fat reduction [multihead weigher]

Author: Smartweigh–Multihead Weighter

Combining many years of practical activities in the work, the editor has carried out general and in-depth scientific research on the dynamic weighing and metrological verification of various countries in the world, and clearly put forward a solution on how to improve the metrological verification precision of rotary mixers. The status quo of the measurement and verification method of rotary stirring machinery. 1.1 The rotary quality method is generally used.

There are various ways of measuring and verifying plate materials for building decoration materials, grain, oil, food, mining, etc., or controlling seasonings online. The most typical ones are: electronic belt scales, flushing plate flowmeters, nuclear scales, and pan material scales. These types of precise measurement methods have their own characteristics, but the limitations are very large.

Introduction to the processing technology of the belt scale: carry out the integral calculation of the load data signal and the speed regulation data signal (transmission belt speed ratio) on the total area of ​​the enterprise (weighing section) to obtain the total flow value, and use it as the control target. Note: According to the control of the towing speed, change the total number of raw materials to be pulled out, so that after the raw materials are formed at the feeding port of the transport trough, their thickness is stable and uniform, and the load of the belt conveyor will not change regardless of the speed ratio of the tractor. The metrological verification and linearity of this method must be better than other feeding methods.

Note: Feeding and weighing are done on 2 belts each. 1.2 Status of continuous quality method for continuous stirring machinery. Including: Cement Stabilized Soil Mixing Machinery, Concrete Continuous Mixing Machinery, Asphalt Continuous Mixing Machinery, Continuous Mixing Machinery, etc.

In today's conditions, such devices cannot be compared with batch methods in terms of metrological verification precision. Therefore, the continuous mixing method has not been favored by many customers, which is one of the reasons. According to scientific demonstration, it can be seen that the mixing and processing technologies specified by these two measurement verification methods have available places, and the use of continuous mixing is not affected by temporary technical limitations.

Today, the rotary mixing machinery in our country all use the capacity method or the electronic belt scale/spiral scale. Two kinds of measurement and verification methods are used. The development trend of rotary mixing processing technology was introduced from Europe in the 1970s. No improvement from start to finish. In fact, both methods can achieve high precision in Europe. For example, Schenck's transmission belt batching scale in France has a dynamic batching accuracy of 2%. But it is not good in my country, the reason depends on the constraints of infrastructure such as machinery processing industry and raw materials in my country.

Today, the measurement accuracy of electronic belt scales in my country's road field is generally only about 5%, which is not far from the capacity-based measurement verification, and the long-term reliability is poor. Section 2: Innovations in Continuous Weighing - Differential Signal (Weightless State) Scales. Since the 1990s, multihead weigher (English Loss-in-weight) has been continuously applied in industrial production.

Electronic belt scales, spiral scales, accumulative scales, etc. are gradually replacing the multihead weigher. As a new and upgraded measurement verification method, more and more raw material production and processing are selected. 2.1 Basic standard: Take the scale measurement verification bucket and the feeding organization as the whole, continuously sample the scale measurement verification data signal according to the instrument panel or the upper computer software, and calculate the scale measurement verification elastic coefficient per unit time as the instantaneous total flow, and then according to the Various software and hardware configurations of filters are technically solved to obtain“specific total flow”. Accurate measurement of water flow is very important, it is the basis for the accurate measurement of multihead weigher.

This picture includes a classic way: Finally, according to the PID feedback optimization algorithm, the FC performs the actual operation of the control close to the overall target total flow, and outputs the adjustment data signal to control the soft starter and other feeding control boards. 2.2 Applying the differential signal weighing scale (multihead weigher) in concrete: It can be seen from the basic principle that it will not be harmed by the mechanical equipment change between the scale and the feeding organization, it only measures the net weight difference (difference weight), and The advantages of traditional dynamic measurement methods are well known. Under the condition that the control target is the total flow (t/h, kg/min), if the raw material transportation capacity and the metrological verification precision are relatively high, the weightless state method can be used as the best plan for metrological verification.

2.2.2 The production process of the multihead weigher: 2.2.3 The design scheme of the multihead weigher should pay attention to the factors that endanger the measurement accuracy: the multihead weigher takes into account the characteristics of the static data scale and the dynamic scale. Therefore, in the design of the control system, it is specified : 1. The appropriate transport rate range, in general, the specific work range is 60% to 70% of the rated value transport capacity. When applying the communication and exchange speed change, the strain frequency is 35-40HZ. A wide range of adjustment is guaranteed.

Also because the transport speed is too low, the reliability of the system software is weak. Second, the selection of the sensor range and the calculation formula are appropriate. That is to say, the sensor also uses 60%~70% of its measurement range, and the data signal transition range is wide, which is very beneficial to improve the precision.

3. The mechanical system design scheme to ensure the liquidity of raw materials, and to ensure that the feeding time is short and the feeding is not frequent. Generally, feeding once every 5-10 minutes. Auxiliary transmissions should be smooth and linear. 2.2.4 Main application: With the rapid development trend of motor control technology, multihead weigher adopts new technology application, and its measurement accuracy varies from 0.3% to 0.5%.

The key to this technology is the use of data weight sensors, which can make the net weight of the weight sensor 0.1%~0.2% or even higher. 2.2.4.1 Application of data weight sensor: In order to consider the necessity of dynamic and accurate measurement, it is very important to select a sensor at the input end of the weighing system software. Especially in the place where the system must be intelligent, the immediate or indirect number of the sensor seems to be very important. At this time, the precise measurement uncertainty and the precise measurement rate are usually a pair of differences, and the two cannot be combined. tools, but must be measured on a case-by-case basis.

At this stage, many traditional digital and analog sensors are used in China's weighing industry, and the resulting pulse signal is not large. As an example, the basic principle of resistor strain force is used to produce a weight sensor with a large output, and its output is generally 30-40 mV. Therefore, its data signal is very susceptible to the influence of radio frequency, and the transmission distance of the cable is also very short, generally within 10 meters.

Select multi-sensor series vessel weighing system software (silo weighing scale), service platform weighing system software or balance scale weighing bridge (electronic truck scale or rail scale), the data system software can complete the“self-proclaimed amount”. Because of the multi-channel digital sensor system software, there is no matching resistor problem. The user can enter the detailed address of the respective sensor, the net weight and sensitivity of the scale, and the scale can be automatically carried out.“four corners”or“edge”The balance of the English alphabet does not need to be adjusted repeatedly.

When several sensors are connected to the simulation system software, the characteristics of each sensor cannot be very well identified, and each sensor must be calibrated and each sensor must be calibrated using a voltage divider in the terminal block. The device is calibrated. Since there is a paired t test in the whole process of adjustment, it is repeated several times. For data system software, allow independent verification of each as a single sensor.

Therefore, the time spent calibrating the intelligent sensor system software is only 1/4 of the system simulation. The system software can“self-diagnosed”, that is, the diagnostic procedure can continuously check whether the data signal of each sensor is terminated, whether the output is significantly exceeded, etc. If a common fault occurs, information or alarms will be automatically displayed on the instrument panel or operation panel. Customers can use the function keys on the control panel to search for each sensor, identify the common fault cause and carry out common fault removal.

The ability to visually diagnose and clear common faults is obviously a key advantage for customers, and in the simulation of analog sensor system software, such advantages are very, very worthy of emulation. Typical simulation sensor system software In the weighing industry, the screen resolution of the analog-to-digital converter is 16 bits, and there are 50,000 available counts; and the screen resolution of each sensor in the data system software is 16 bits. With 20 bits, there are 1,000,000 available counts. Thus, a system software with 4 digital sensors can produce 4,000,000 counting screen resolutions.

It is an advantage of high pixels, especially in the case where the weight of the weighing frame itself is heavy and the weighing is small. For example, in batch weighing system software, sometimes some raw materials are only a small part of the secret recipe, but the requirements for accuracy are still very high. Such conditions are equally difficult to achieve in traditional system simulations.

2.3 Application status at home and abroad (obtained in chemical plants, metallurgical industry, plastics, chemical fibers, etc.) In many fields, there is work experience in applying multihead weigher. For example: concrete seasoning. In recent years, it has been widely used in many fields such as rubber products, chemical fibers, and optical fibers.

In some industrial production, the continuous weightless state measurement verification can ensure the uniform mixing of blanking materials, and the mixing must be weakened, which simplifies the processing technology. This product is very complete abroad. For example, the French Schenck Enterprise, the Buda Benla Enterprise, and the French Pioneer Enterprise, etc., their technology will lead the world internationally. Among them, the warriors use digital sensor technology, and the dynamic precision reaches 0.25%.

The precision of the static data balance scale has been achieved in the whole process of industrial production. Use in rotary mixers and future hazards. In the measurement verification work of continuous mixing machinery in my country, it still stays on the traditional measurement verification method. Therefore, the application and promotion of multihead weigher is very important for the processing technology of cement stabilized soil mixing, concrete continuous mixing, and asphalt continuous mixing. It also has great practical significance for the precise manipulation of the total flow.

Due to the simple structure of the rotary stirring process and the low maintenance cost, once the product mix ratio is improved, the current low market share of rotary stirring will be changed. Especially in the field of road and hydropower engineering, where high regulations are imposed on production-increasing machines, the multihead weigher is a key step in increasing the precision of metrological verification.

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