Application of Flap-11 Magnetic Level Indicator in TDI Liquid Level Measurement

Toluene diisocyanate (TDI) is an organic compound. All isomers of TDI are colorless or yellowish with a pungent odor. It is volatile and hypertoxic. TDI is an important part of polyurethane raw materials, which is widely used in light industry, chemical industry, electronics, textile, medical, construction, building materials, automobile and other fields.

The synthesis process of sponge in Shantou Sponge Factory mainly includes chain growth reaction, foaming and cross-linking. The main source of foaming gas CO₂ gas generated by the reaction of TDI with water, so a large amount of TDI is used as raw material in the factory. Because TDI is hypertoxic, it is necessary to prevent it from overflowing as well as empty running, so timely monitoring and control of the liquid level is significant.

From communication with clients, we know that the operational condition is complex:

1. The narrow spaces between storage tanks are easy to bump and damage the equipment.

2. High humidity affects instruments with low Ingress Protection Level.

3. Strong vibration and stirring in the tanks.

4. Tall tanks need remote/distant observation.

5. Explosion-proof instruments are required, because TDI is inflammable, explosive and toxic.

The client used sight glass to measure the liquid level of TDI storage tanks. However, glasses become compromised through leaking seals, clouding, and breakage, as well as unable to realize automatic control. So, the client finally selected the Jiwei Magnetic Level Indicator after detailed discussion. Jiwei Magnetic Level Indicator devices are popular in applications measuring high-temperature, high-pressure, and corrosive liquids. When the application is challenging, magnetic level transmitters (remote transmitters) provide consistent, accurate measurements.

Magnetic level indicators are commonly low-cost in comparison with other level technologies, and can provide visual indication of TDI level from a distance.

Item	Magnetic level indicator	Sight glass
Cost	Moderate	Low
Visibility	Clear	Cloudy
Service life	Long	Short
Failure rate	Low	High
Heat resistance	Medium to high	Low
Pressure resistance	Medium to high	Normal
Hardness	High	Low
Accuracy	±5mm	Cloudy
Maintenance	Easy	Hard
Explosion proof	Flame-proof/Intrinsic-safe	None
Signal transfer	Transmitter can be added	None

Through the comparison, except the cost, all the other performances of MLI are obviously better than that of sight glass. Sight glass usually consists of two armored castings that sandwich a piece of glass, allowing direct visibility of the liquid level. A Magnetic Level Indicator is typically made up of a float containing a magnet that follows the liquid level inside of a chamber, and it is designed based on the law of equilibrium in U connected vessels and magnetic coupling effect to achieve real-time level measurements and display. When deciding which technology to use, it is important to look at the long-term cost of ownership rather than just the upfront cost of the unit. Sight glass technology typically has a lower upfront cost than an MLI. However, an MLI has many benefits during installation and normal operations that result in a lower total cost of ownership in the long run.

Jiwei Flap-11 Magnetic Level Indicator series products possess features and strength of similar products in the market. Based on that, Jiwei has carried out extensive study on common problems of existing products in the market, and developed innovative techniques in design and production process to overcome the problems. Jiwei has been focusing on details of manufacturing technologies, strict control of production flow and quality inspection to ensure all products reach the highest level possible on quality and reliability. Jiwei has applied for 7 patents (both invention patents and utility patents) on Flap-11 series products, of which 5 have been authorized and 2 are under approval.

Advantages of Jiwei Flap-11 Magnetic Level Indicator:

1. With 304 seamless stainless steel, strong and reliable.

2. Exceeds national Ingress Protection standard IP54, Jiwei MLI’s Ingress Protection is up to IP67, with strong sealing. The unique sealing design and production process make the protection level MLI reach IP67, effectively preventing the damage of the display panel caused by water and dust.

3. The accurate magnetic coupling system makes the measurement more reliable.

4. Display panel with a broader design, greatly increases visual distance and viewing angle. With a larger sharp scale and digits, the display panel appears beautiful and elegant.

5. Explosion proof approvals for Flameproof Enclosure and Intrinsic Safety, including SW-11 Magnetic Switch, SW-21 Compact Magnetic Switch and Reed-11 Remote Transmitters.

After installing all Jiwei Flap-11 Magnetic Level Indicators, the clear visibility, strong sealing technique, stable performance, distance indication and easy maintenance have convinced the client.