Problems of the hottest liquid level transmitter i

Problems and improvement of liquid level transmitter in the measurement of blast furnace slag flushing water level

Abstract: in view of the poor quality of blast furnace circulating slag flushing water and the special environment of each pool. From the perspective of practicality, reliability and economy, this paper introduces the application characteristics and scope of contact and non-contact instruments in the water level measurement of blast furnace slag flushing water, and introduces in detail the working principle and instrument structure of the improved measurement method, while replacing the previous use structure, performance and installation of plastic bags. After a period of use, the stability, reliability and accuracy of instrument measurement have been significantly improved, and the service life of the instrument has been greatly extended, providing guarantee for the safe water supply of blast furnace. It has achieved practical, reliable, economic and safe results

key words: poor isolation water quality of input liquid level transmitter

introduction

in order to popularize water resources and meet environmental protection requirements, our company should vigorously use closed circulating water to flush slag in the design of blast furnace, separate water and slag through sedimentation tank and filter tank, and then fish the precipitated slag with crane grab. Due to the repeated use of slag flushing water, the quality of slag flushing water is poor, and the environment of each pool is special. It brings great difficulties to instrument selection and measurement. At present, the instrument used by our factory is domestic yszk-h type input liquid level transmitter. The advantages of this instrument are low price (about 3000 yuan), stable and reliable operation, convenient installation and maintenance, etc. However, due to the inherent problems such as high temperature of slag flushing water, high water hardness (CaCO3) and many slag deposits, the original reliability, stability and accuracy of the instrument are greatly reduced, and the service life of the instrument is greatly shortened. When the slag precipitation is serious, the instrument cannot work normally, resulting in the instrument being reported as useless. Because the instrument cannot provide reliable, stable and accurate signals, the water level is too high or too low, which will bring major hidden dangers to the safe operation of the blast furnace. Therefore, we pay special attention to these problems in the process of equipment management, and through continuous accumulation of experience, we have taken some effective technical improvement measures to ensure the safety and stability of production

1 use non-contact instruments

1.1 industrial monitor

industrial monitor can better overcome the problem of poor water quality, avoid the range of activities of driving, have the advantages of intuitive image and low price, but the disadvantages are: ① in winter, due to the large temperature difference between the slag flushing water temperature and the air, thick fog gas is generated on the pool surface, making the monitor ineffective; ② In rainy days, snowy days or at night, the light line dark monitor also loses its function. It can be seen that the industrial monitor is not applicable here

1.2 ultrasonic liquid level gauge

ultrasonic liquid level gauge completely solves the problem of poor quality of slag flushing water, works stably and reliably, and is an ideal instrument for measuring liquid level. However, there are special requirements for the installation of the ultrasonic liquid level gauge. It will not be able to avoid the range of activities of the crane, and it is easy to be damaged by the crane grab, and the price is expensive (about 17000 yuan). Therefore, from a practical and economic point of view, the ultrasonic liquid level gauge is not applicable. As shown in Figure 1

Figure 1 working principle of ultrasonic liquid level gauge

2 using contact instrument

2.1 input liquid level transmitter

input liquid to realize the reduction of packaging materials. The level transmitter has the advantages of low price, stable and reliable operation, convenient installation and maintenance, and can adapt to the special environment of the pool at the same time. Its installation method is: put the transmitter probe directly into the bottom of the pool through the protective sleeve. The working principle is shown in Figure 1. When the water level changes, the pressure sensing diaphragm of the probe will make corresponding displacement changes, so that the transmitter output standard current (4 ~ 20 mA) signal is transmitted to the intelligent digital display meter, which displays the actual water level of the pool. However, due to the high temperature of the slag flushing water (about 80 ℃), the aging of the electrical components of the instrument probe is accelerated. Because the water hardness (CaCO3) is as high as 660 mg/l, while the hardness of industrial water is 109.45 mg/l) polyvinyl alcohol (PVA) hydrogel has high compatibility with human tissue, non-toxic side effects, no degradation, stable chemical properties, good elasticity, high water content, so that the probe pressure sensing membrane surface rapidly scales, changing the original mechanical properties. With the extension of time, this phenomenon becomes more and more serious, The stability, reliability and accuracy of the instrument are getting worse and worse. Due to the large amount of slag sediment, the probe is buried in about a month. At the initial stage of probe burial, the measured display value of the instrument lags behind the change of the actual water level. In the middle and late stage, due to the increasing hardening density of slag after sedimentation, the inlet of the probe is completely blocked, so that the water level change information cannot be transmitted to the pressure sensing diaphragm of the probe, so that the input level transmitter completely loses its function and is scrapped

2.2 improvement and production of the measurement method of the input level transmitter

in view of the poor quality of the slag flushing water and the special problems of the pool environment, after long-term exploration, we have adopted the following improvements to the measurement method of the input level transmitter, as shown in Figure 2, install an isolation tank in the pool, install a pulley at the top of the isolation tank, put a floating ball in the pool, and tie the floating ball with one end of nylon rope, Fasten the transmitter probe at the other end, and then put the middle of the nylon rope on the pulley. Inject the cooling water cooled by the water pump into the isolation tank, and the height of the water level is determined by the upper range of the liquid level transmitter. Open an overflow hole at the determined water level to keep the water level in the isolation tank unchanged. The working principle is: when the water level of the pool is at the highest, the floating ball drives the transmitter probe to the lowest part of the isolation tank through the pulley. At this time, the output of the liquid level transmitter is the highest (20 mA), but when the water level of the pool is at the lowest, the floating ball drives the transmitter probe to the highest part of the isolation tank through the pulley. At this time, the output of the liquid level transmitter is the lowest (4 MA). It can be seen that the output of the improved liquid level transmitter is completely one-to-one corresponding to the change of water level, and the purpose of measurement is achieved

Figure 2 liquid level transmitter improvement figure

3 conclusion

by using floating ball and isolation tank, the contact instrument is converted into non-contact measurement. Thoroughly and effectively solved the problems of poor quality of slag flushing water and special pool environment. After a period of use, the stability, reliability and accuracy of instrument measurement have been significantly improved, and the service life of the instrument has been greatly extended, providing guarantee for the safe water supply of blast furnace. It is practical, reliable, economical and safe. However, due to the use of pulley transmission, the pulley has certain friction during transmission, which reduces the accuracy of the instrument. When in use, the pulley transmission part should be maintained frequently. (end)