Silicon dioxide, also known as silica, is used across many industries – from paint and plastics manufacturing to food and pharmaceutical, and in producing modern insulation materials.
In chemical process engineering especially, this fine-grained, often fluidized powder places high demands on storage, conveying, and level monitoring.
An insulation material production project shows how UWT sensor solutions operate reliably even with extremely fine-grained, pneumatically conveyed silica.
Despite heavy dust loads and low bulk density, these sensors enable precise and process-secure level and point level measurement.
In a plant that produces heat and sound insulation boards, highly dispersed silica (SiO₂) is temporarily stored in vertical silos approximately 25 m high before further processing. The aim was accurate material detection – both for continuous level measurement and point level detection.
THE APPLICATION
- Combined Level and Point Level Detection for Fine Powder.
- Each silo required three measurement tasks to be addressed:
- Continuous level measurement for inventory monitoring
- Point level detection for full and empty indication to control filling and discharge cycles
- Material flow monitoring in the discharge pipe for early detection of blockages and bridging
A SPECIAL CHALLENGE FOR THE SENSORS
During pneumatic conveying, the silica is fluidized and blown into the silo. The air supply aerates the fine powder, resulting in extremely low bulk density and high dust generation.
In this state, the material offers only minimal reflection and almost no mechanical resistance, pushing conventional sensors to their limits. After filling, the material settles in the silo and, during pneumatically assisted discharge, forms a typical conical pile – posing a risk of bridging that can disrupt material flow.
PROCESS CONDITIONS AT A GLANCE
- Medium: Highly dispersed silica (SiO₂), pneumatically fluidized
- Silo: Stainless steel, approx. 25 m / 82 ft high
- Bulk density: < 20 g/l (1.25 lb/ft³)
- Process temperature: Ambient to +60 °C
- Explosion protection: ATEX Zone 21
- Specials: High dust load, low dielectric constant, conical pile
OUR SOLUTION
NivoRadar® NR 3300 – Radar Measurement Under the Most Challenging Conditions. For continuous level measurement, the NivoRadar® NR 3300 with lens antenna was selected because it provides precise and stable results even under demanding conditions like fluidized silica.
KEY ADVANTAGES AT A GLANCE
- 3° beam angle (80 GHz technology): ideal for narrow silos
- Swivel flange (stainless steel, up to ±10°): ensures precise sensor positioning for conical bulk piles and funnel-shaped silo bottoms
- UWT LevelApp with alignment assistant: visual adjustment and simple commissioning directly via smartphone
- Purge air connection with check valve: keeps the antenna free from fine dust and prevents material from entering the purge line
- Robust materials such as 316L, PEEK, FKM: relevant for silica in sensitive applications (e.g., food/pharma), not required for insulation materials
Thanks to the adjustable flange, the radar was aligned so that the beam precisely captures the bulk cone and extends down to the conical silo bottom. The integrated purge air function reliably prevents dust build-up on the lens antenna – especially during filling – ensuring consistently accurate measurement results.
Vibranivo VN 2020 with Vibrasil
Point Level Measurement for Ultra-Light Powder; For point level detection of full and empty statuses and discharge monitoring, operators rely on the proven Vibranivo® point level sensor with Vibrasil® technology. The special Vibrasil® probe is designed specifically for very light and pneumatically conveyed bulk solids such as powders or silica. With high sensitivity and fast switching response, it ensures reliable detection even with materials that have a bulk density of less than 5 g/l (0.31 lb/ft³).
Full detection with fluidized silica
At the insulation material manufacturer, the VN 2020 with Vibrasil® 70 was installed as a full detector beneath the silo roof. Since the silica is fluidized during pneumatic conveying, a highly sensitive point level sensor is required. The vibrating probe featuring an additional paddle, greatly increases the active surface area, allowing the sensor to reliably detect even airborne material with extremely low bulk density.
Cone area – empty detection with high sensitivity
In the lower silo section, the Vibrasil® 90 is used as an empty detector. Its polished, extended tuning fork offers high sensitivity – slightly lower than the Vibrasil® 70 version – but still reliably detects when the silot is empty as soon as the fork is uncovered. Installation was simple and maintenance-friendly, carried out externally via a 1½” socket.
Discharge branch
Process monitoring during pneumatic conveying. The Vibranivo® with Vibrasil® 70 is also used in the discharge branch. Additional discharge aids, such as vibration and pneumatic conveying, help to maintain material flow. The sensor monitors the discharge pipe reliably, ensuring that the conveying process for this extremely light material remains uninterrupted.
Especially with highly dust-generating silica, Vibrasil® technology has proven to be a reliable and low-maintenance solution. In combination with screw conveyors and pneumatic discharge, the Vibrasil® probe also offers a practical, application-oriented setup.
Since fine, dry silica can form an explosive dust atmosphere under certain conditions – for example, during pneumatic conveying or injection processes – hazardous (Ex) zones are not uncommon. UWT is well prepared: both the NivoRadar® 3300 and the Vibranivo® carry international Ex certifications, ensuring maximum process safety.
RESULT
Process Stability – from Filling to Discharge. By combining continuous radar measurement with point level detection, full monitoring from filling and storage through to discharge was achieved. Despite dust, air, and low bulk density, the sensors provide consistently deliver stable signals. Maintenance requirements were significantly reduced, and process reliability was improved.
The silica storage application clearly demonstrates: Whether it’s radar or vibrating measurement technology – UWT offers the right solution for every challenge. Advanced technology, practical installation, and smart features ensure a reliably running process, even with difficult powders.
