Stationary Overfill Prevention Systems
Stationary overfill protection safeguards storage tanks and process vessels against overfilling with flammable or water-polluting liquids. Secu-Tech combines proven thermal limit sensors with FAFNIR transducers into a certified package — compliant with Germany's Water Resources Act (WHG) and available with SIL 2 / ATEX approval for hazardous areas.
Thermistor-based overfill prevention per WHG
The principle is simple and field-proven: an encapsulated PTC element in the level probe changes resistance with temperature. In air or gas it heats up; when immersed in liquid it cools rapidly. The matched transducer evaluates this change and drives the alarm or control output. The sensors contain no moving parts, are self-testing, maintenance-free after installation, and require no on-site calibration.
Two certified variants cover the typical use cases:
LS300-LS500 for EX applications
ATEX-certified overfill protection for flammable and aggressive liquids (hazard class AI). The LS 300 level probe in the tank, paired with the LS 500 transducer with switching output, forms a SIL 2 certified safety function – including full and empty alarms. A wide range of probe variants (LS 300 Standard / heavy duty / connector / Duo / Trio) and transducer formats (LS 500 wall-mount or DIN-rail) suit every tank type and size, from collecting vats and storage tanks to fuel and high tanks.
More on LS300‑LS500 for EX applications →
76A-NB220 for non-EX applications
Proven WHG overfill protection for water-polluting liquids in non‑hazardous areas. The 76 A level probe combines with the NB 220 transducer – either as NB 220 H with a potential-free changeover contact for connection to a higher-level PLC, or as NB 220 QSF with built-in optical and acoustic alarm plus acknowledge button. Probe variants 76 A, 76 C (factory-fitted cable) and 76 N (fully wetted parts in stainless steel 1.4571, AdBlue-compatible) cover virtually every application.
More on 76A‑NB220 for non‑EX applications →
Typical applications
- Bulk storage tanks for mineral oils, diesel and heating-oil
- Collection basins and safety pans
- Process and elevated tanks in the chemical industry
- Vessels holding aggressive, water-polluting or flammable (hazard class AI) liquids
- Rail tank-car loading installations and pilot/prototype plants
Both systems meet the requirements of Germany's Water Resources Act (WHG) and are installed by the tens of thousands across Europe.
