How to Select Level Switch for Level Measurement of Fumed Silica
Fumed Silica Production Process and Level Measurement
Fumed silica is an important nano-scale inorganic chemical material with properties such as low density, fine particles, large surface area, strong attachment, and moisture absorption. It is used to enhance strength, increase viscosity, and achieve thixotropic and extinction effects in various industries such as agriculture, pesticides, medicine, food, cosmetics, and silicone rubber. For example, fumed silica is often mixed with fertilizer to improve the fluidity of powdery fertilizer for transportation and storage, as well as to avoid agglomeration due to moisture. In industrial production, the selection of level meters to monitor and control fumed silica levels is crucial. Let’s begin by examining the fumed silica production process and the challenges of level measurement.
1. Fumed Silica Production Process
Fumed silica is an ultrafine silica powder produced through gas-phase hydrolysis from methyltrichlorosilane under high temperatures in an oxygen-hydrogen flame. During the production process, a level switch is required for the storage tank to control the level of fumed silica, preventing environmental pollution and material waste due to overflow.
2. Challenges in Level Measurement of Fumed Silica
Level measurement for fumed silica is a challenging task because the resulting product is typically stored in a vertical silo approximately 10 meters tall during the production process. Fumed silica is lightweight with a very low density (0.01–0.03 g/cm³) and a low dielectric constant. To avoid material compaction due to gravity and adjust chloride content attached to the surface of fumed silica (to control the pH value of the product), nitrogen gas is often filled into the storage silo from its bottom. This introduces material rolling and waving, causing airborne “dust” within the silo. Reliable level measurement of fumed silica is essential to comply with environmental protection and safety standards and prevent air pollution from material overflow. Therefore, selecting an appropriate level switch for the application is critical.
3. Level Switch Selection for Fumed Silica Measurement
Several types of level switches are available in the market, including rotary paddle switches, capacitive level switches, RF admittance level switches, and vibrating level switches. The latter category includes vibrating rod and fork level switches and is commonly used for granular and powder bulk solids.
- Rotary Paddle Switch: Not suitable for measuring fumed silica due to its low density, which is insufficient to stop the spinning motor and trigger the micro switch.
- Capacitive Level Switch and RF Admittance Level Switch: Both types rely on detecting capacitance changes between the probe and the vessel caused by material level changes. However, the dielectric constant of fumed silica is too low for these level switches to be effective.
- Fork Level Switch: This type of switch measures the state of harmonic resonance of the fork bodies. Driven by piezoelectric ceramics, the fork level switch is not dependent on the dielectric constant of the measured material. Precisely adjusted for complete harmonic resonance, the switch attains maximum sensitivity to measure ultra-low density mediums.
After comparing various types of level switches, the fork level switch emerges as the most suitable choice for fumed silica due to its ability to measure ultra-low density powdery solids reliably.
Jiwei Fork-11 Level Switch
The Jiwei Fork-11 level switch features wider and thinner fork bodies compared to similar products on the market. It is precisely adjusted to achieve complete resonance and pre-adjusted sensitivity according to the density of the measured material. The minimum measurable density can be as low as 8 g/l (0.008 g/cm³). Jiwei Fork-11 has been successfully applied in multiple projects for the level measurement of fumed silica.
Customers often express concerns about potential measurement inaccuracies caused by large amounts of fumed silica drifting above the material surface and attaching to the highly sensitive fork bodies. However, the pre-adjusted resonance of Fork-11 ensures larger redundancy for material buildup, provided there is no “scarring” on the fork bodies. In severe cases involving long-term measurement of strongly adhesive materials, nitrogen purge devices can be recommended to clean the fork bodies before filling material and prevent heavy material buildup or scarring.
Jiwei specializes in designing and manufacturing level meters for production process automation. We offer professional solutions for various challenges in industrial level measurement and our products match global market brands in terms of high reliability and cost-effectiveness. Jiwei level meters have been tested in complex applications and have earned recognition from a growing number of customers for their high quality and reliability.