1、 Reasonable design, installation, and use are the fundamental factors for making good use and accurate use
Firstly, in terms of design, the distance from the adjustment baffle at the discharge port of the quantitative feeder to the weighing roller should not be less than 1 meter. This ensures that the material has a stable zone before entering the effective weighing section, and there should be no changes in the material within the stable zone. It can be said that in the design, the center distance between the front and rear rollers of the quantitative feeder belt should not be less than 3.5 meters. Only by adopting such standards can the material stability of the quantitative feeder be ensured during operation. Otherwise, stability cannot be guaranteed and measurement cannot be accurate. The first line raw limestone quantitative feeder of Shaanxi Fufeng Company is an example. There should also be a standard for the height of the quantitative feeder in the design. It is unreasonable to have a height less than 60 centimeters without a discharge cone below. The reason is that the height of the quantitative feeder is too low, and the running and overflowing materials stored under the belt during operation cannot be cleaned up in a timely manner. Especially, the materials stored under the drum are piled up for a long time and solidify, which makes it easier to rub against the belt and cause speed fluctuations of the quantitative feeder. The belt runs off and is worn, ultimately resulting in inaccurate measurement. All the quantitative feeders at the cement batching station of Shaanxi Jingyang Company are a typical example. So, from a safety perspective, the most reasonable height for the quantitative feeder should not be less than 80 centimeters. This is beneficial for on-site maintenance personnel to promptly and safely handle material leakage from the quantitative feeder, and is a guarantee for accurate measurement of the quantitative feeder. One more thing to note in the design of quantitative feeders is that the layout of each quantitative feeder on site should be reasonable, and there should be reasonable spacing between equipment to avoid mutual influence. There should be a safe passage on site for each quantitative feeder to facilitate inspection and daily maintenance. Otherwise, it cannot be used accurately. For example, in the 7th and 8th cement grinding and batching stations of Tongchuan Jidong Cement Company, 8 quantitative feeders are arranged together and affect each other. Without a safe passage, it is impossible to inspect and maintain them on a daily basis. Even with the American Hassler belt scale configured, the final results are inaccurate. This fully proves whether the installation environment for quantitative feeders is reasonable and plays a very important role in the proper use of quantitative feeders.
The reasonable installation and use of the quantitative feeder is also a very important link. The installation must strictly follow the installation regulations, ensure that the center of the feeding port is perpendicular to the center of the quantitative feeder belt, ensure that the rollers inside the scale are installed flat and in the same horizontal plane, and the non parallelism between the rollers is not more than 0.5 millimeters. The radial runout of the rollers is less than 0.2 millimeters, and the axial displacement is less than 0.5 millimeters. Violating the above installation regulations will result in inaccurate use of the quantitative feeder. The center of the feeding hopper of the clinker quantitative feeder in the cement batching station of Jingyang Company deviates from the center of the belt, causing the material to fall off during the operation of the quantitative feeder, resulting in inaccurate measurement of the speed fluctuation of the belt deviation caused by the quantitative feeder. The most common unreasonable use observed on site regarding the use of the quantitative feeder is that all the adjustment baffles at the feeding port of the quantitative feeder are opened, causing the material on the belt to run around and fall into the weighing section, reducing the accuracy of the measurement. Long term wear and tear of the landing material on the belt has caused the quantitative feeder belt to deviate, resulting in speed fluctuations and inaccurate measurement. To make good use of the quantitative feeder, it is necessary to adjust the discharge port baffle to ensure that the amount of material on the belt remains within the range of 85% to 120% of the maximum load, and there must be no overflow of the belt. From the above discussion, it can be seen that the reasonable design, installation, and use of the quantitative feeder are the key and fundamental factors for making good use of the accurate quantitative feeder.
2、 Constant standards, constant thoughts, and constant observations
Calibration is an important step in ensuring the accurate use of quantitative feeders, and it is essential for us to learn how to calibrate. It is necessary to strictly follow the user manual provided by the supplier for calibration, learn the methods of each step, understand the purpose and significance of each step, and advocate the 8-word policy of "calibration, thinking, calibration, observation" repeated cycle. Many truths and knowledge will definitely be gained from calibration.
Calibration method for quantitative feeder (belt scale) and chain plate scale
1. First, clean the material on the weighing belt and close the discharge gate valve tightly. On site testing of the effective weighing section and re inputting it into the parameter table to verify the effective weighing section is the most important part of the calibration work. The parameter values of the effective weighing section of the phosphogypsum quantitative feeder of Fengxiang Company do not match the actual values on site. The instrument display value and theoretical calculation value did not reflect the problem during calibration, but the quality analysis of this scale found a problem during use. After inspection, it was found that the parameter values of the effective weighing section do not match the actual values. The effective weighing section refers to half of the distance from the weighing roller to the front roller and half of the distance to the rear roller.
2. Measure the length of a belt in meters. Start the scale body and let it run at maximum speed. Use a stopwatch to measure the time it takes for the belt to rotate several times, and calculate the speed unit of the quantitative feeder when unloaded in meters per second. Observe whether the flow display value of the secondary instrument is zero. If it is not zero, it indicates that the zero point of the scale body has drifted before, and record this value. Then hang the calibration weight on the scale body and let it start running at maximum speed. Observe whether the flow rate displayed on the secondary instrument is the maximum rated flow rate. If the flow rate displayed on the secondary instrument is the maximum rated flow rate, it proves that the scale is accurate during use before calibration. If the flow display value of the secondary instrument does not match the maximum rated flow value, it proves that the scale was inaccurate during use before calibration, and the flow deviation should be recorded for correction of past production output.
3、 Zero point verification
Firstly, input the length of the belt and the time required for N turns of the belt into the secondary instrument, and start the scale body at maximum speed. Select the automatic calibration state on the secondary instrument and start zero calibration. If there is zero drift, adjust the parameters for correction. The zero point verification work must be carried out three times, and during this work, attention should also be paid to whether the speed display of the secondary instrument matches the theoretical calculation value. If it does not match, it proves that there is a problem with the secondary instrument, and it is necessary to check and solve the problem.
