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

Level measurement in the electrolytic alumina industry has always been a problem. Manufacturers in the industry have been suffering unreliable level measurement and false alarms during the production process for a long time. To find a level switch that can reliably perform accurate level measurement with reasonable price is what they dreamed of. Jiwei vibrating rod level switch successfully fulfilled the task. Tube-11 Vibrating Rod Level Switch is with double vibrating tube design. It has performed so well in level measurement of alumina that it is praised as a “magic level meter” by customers. People may be wondering why it was so difficult to measure the level of alumina and how Jiwei Tube-11 overcame the difficulty.

Demonstrated Performance of Jiwei Vibrating Rod Level Switch in Level Measurement of Alumina
Tube-11 Vibrating Rod Level Switches

Let’s start from the electrolytic process of alumina and process conditions in level measurement of alumina. In recent ten years, the electrolytic process of alumina has been developed rapidly. Cryolite-alumina molten salt electrolysis method is a typical production process in the 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 the so-called electrolysis process.

Demonstrated Performance of Jiwei Vibrating Rod Level Switch in Level Measurement of Alumina
Onsite installation of Tube-11

For complete production automation, it is essential to monitor material level in silos of alumina and send an alarm signal when the material level reaches to designated high level or maximum level to turn off the blower in time and stop filling alumina. Reliable level measurement of alumina has always been a difficult worrisome problem to the manufacturers in China. Some of them have tried rotary paddle switch, RF admittance level switch, fork level switch, single tube vibrating rod level switch and photoelectric switch, etc. None of the level switches mentioned above really solved the issue. Accidents and false alarms happened from time to time due to unreliable level measurement. We list the performance of all kinds of level switches for level measurement of alumina below for clarity and analysis:

Application of different level meters in level measurement of alumina:

Types of level meter

Common failure

Rotary paddle switch

1、Paddle deformation due to impact;

2、Shaft deformation due to impact;

3、False alarm happened frequently;

4、Short service time

RF admittance level switch

1、Probe deformation due to impact;

2、False alarm;

3、Inaccurate level measurement

Fork level switch

1、Material stuck between fork bodies;

2、Fork body deformation due to impact;

3、False alarm

Vibrating rod level switch with single tube

1、Probe deformation due to impact;

2、False alarm

Photoelectric switch

Stopped working under strong magnetic field

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

1. Alumina is heavy.
Alumina has a high density of 3.97g/cm3. It is also a chemical compound with high hardness. Alumina could cause a huge impact to its vessel and the probe of the 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.

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

3. Higher process temperature onsite
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 temperatures.

4. Harsh installation conditions onsite
High density alumina will cause a huge impact when it is filled into a silo by a blower. If the installation position is not carefully chosen, the probe will definitely be damaged due to the huge impact. Generally, the instrument shall be installed in a proper position so that the probe could be away from the main stream to avoid the material impact. It is recommended to install the instrument laterally where there is less possibility for the probe to be impacted or where the impact is much weaker.

It is because of the properties of alumina and complicated process conditions that accidents in its level control happen frequently, such as false alarms or the operation being stuck because of magnetization. The manufacturers in the 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 a good reputation in the automation industry aroused their interest.

After comprehensive comparison between various types of level switches from many level meter manufacturers, the team was satisfied with the 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. 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.

Demonstrated Performance of Jiwei Vibrating Rod Level Switch in Level Measurement of Alumina
Tube-11 is the first made-in-china vibrating rod level switch independently designed with a unique double tube nesting structure

Tube-11 is the first made-in-china vibrating rod level switch independently designed with a unique double tube nesting structure. The inherent vibrating frequency of inner tube and outer tube is precisely adjusted to the same value to achieve complete resonance and extremely high sensitivity and reliability. The measurable density can be as low as 0.02g/cm³.

In comparison, Jiwei Tube-11 has following features and advantages:

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 temperatures, maximum 250℃. Some 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-healing from error status.

7.The instrument has strong anti-magnetizing ability. It can work reliably in the environment with a strong magnetic field.

It is because of the advantages and features of Jiwei Tube-11 Vibrating Rod Level Switch mentioned above that Tube-11 can perform very well in level measurement of alumina. High reliability of the instrument in this application is comparable with imported brand products but its cost-effective ratio is much higher. It helped customers in the electrolytic alumina industry solve their long-standing problems in level measurement of alumina and it is widely praised and recommended by our customers.

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