Demonstrated Performance of Jiwei Vibrating Rod Level Switch in Level Measurement of Alumina

Let´s start from electrolytic process of alumina and process conditions in level measurement of alumina. In recent ten years, electrolytic process of alumina has been developed rapidly. Cryolite-alumina molten salt electrolysis method is a typical production process in electrolytic alumina industry. In this process, fused cryolite is used as a flux to melt alumina and prepare Cryolite-alumina molten salt under high temperature 950℃～970℃. Carbon body is used as an anode and liquid aluminum is used as a cathode. When strong direct current is applied on the electrodes and electrochemical reaction occurs at both poles. That is so called electrolysis process. The production process flow chart is shown in Fig.1. 

 Fig.1 Electrolytic alumina process flow chart

As the table above shows, the failure of those level switches in this application is due to special process conditions in electrolytic alumina industry and high level of requirements are placed to the level switches onsite. Overall, there are following causes:

Alumina has high density of 3.97g/cm3. It is also a chemical compound with high hardness. Alumina could cause huge impact to its vessel and the probe of level switch when it is filled into the vessel. That is the reason why the probe of the level switch could be deformed and the normal process operation stops.

The electrolysis of alumina is a process of electrochemical reaction under high direct current. Therefore, strong magnetic field exists around the high current onsite. It requires strong anti-magnetizing ability of the level meter.

Process temperature of electrolytic alumina is very high. While the tolerable process temperature for most of level meters from domestic manufacturers is only 40～60℃.It is impossible for them to perform reliably under extreme high temperature.

It is because of the properties of alumina and complicated process conditions that accident in its level control happens frequently, such as false alarm or the operation stuck because of magnetization. The manufacturers in electrolytic alumina industry desperately need a reliable level meter with stable operation for level measurement of alumina.

In order to minimize the impact of failure in alumina level measurement on electrolytic alumina production, a large electrolytic alumina group in Shandong province contracted with the Institute of Petrochemical Technology to find a solution. The technical team from the institute investigated and evaluated all possible level meters in the market. Excellent performance of Jiwei Tube-11 in various industrial applications and good reputation in automation industry aroused their interest.

After comprehensive comparison between various types of level switches from many level meter manufacturers, the team was satisfied with quality and reliability of Jiwei Tube-11 in the end. Through communication with our engineers and collaborative experiments, Jiwei Tube-11 was successfully applied for level measurement of alumina under complicated harsh working conditions. The electrolytic alumina group in Shandong province purchased a batch of Tube-11 Vibrating Rod Level Switch and installed them for level measurement of alumina. Fig.2 are pictures in application onsite. The problem of probe deformation has rarely happened and the problem of false alarm has never happened since Jiwei Tube-11 Vibrating Rod Level Switches were installed. The performance of Tube-11 has far exceeded customer´s expectations and it is highly praised by the customer for its demonstrated quality and reliability. Compared with other level meters, successful application of Jiwei Tube-11 Vibrating Rod Level Switch in level measurement of alumina relies on its design and manufacturing process.

1. First made-in-China Vibrating Rod Level Switch that is designed with double vibrating tubes. The sensitivity and reliability of the instrument, as well as its redundancy to material buildup are all greatly improved.

2. The probe is designed with an integrated structure. A stainless steel tube with thicker wall and length extending tube with larger diameter are also used to enhance impact resistance of the product and avoid probe damage due to material impact.

3. It is designed for high temperature, maximum 250℃. Some of electronic components in vehicle level are purchased, which can work reliably under 80℃ ambient temperature. It greatly increases the reliability of the product. That´s why the tolerable process temperature of Jiwei Tube-11 is much higher than most of its counterparts in the market.

4. It complies with SIL requirements. Low temperature drift and high precision electronic components are widely used in Jiwei’s electronic circuits. It greatly improves the reliability of the hardware and software.

5. Modular design of electronic circuit which is encapsulated with potting compound makes the product meet the requirements of “three protections” and easy for replacement and maintenance.

6. Its software complies with SIL requirements. It supports multiple automatic functions, such as automatic detecting, automatic diagnosis and self-healing, to locate the failure accurately and improve the efficiency of error diagnosis, sometimes even self-heal from error status.