Case Study: FTL31 Vibronic Point Level Switch for Viscous Liquid Overfill Protection in a German Chemical Tank

Market Background

In Germany's chemical and lubrication system industry, overfill protection for viscous liquid tanks remains a selection challenge. Conventional float switches may respond slowly in sticky media, while conductive and capacitive sensors can be affected by conductivity, buildup, turbulence, or air bubbles. The customer needed a compact point level switch with 316L stainless steel wetted parts and suitability for viscous liquids.

Customer and Application

• Country/Market: Germany

• Customer Type: Chemical tank and lubrication system integrator

• Application: Viscous liquid tank, overfill protection (MAX safety mode)

• Media Conditions: Dynamic viscosity 1 to 10,000 mPa·s, density > 0.7 g/cm³

• Process Temperature: Up to 100°C

• Process Pressure: -1 to +40 bar

Our Solution

• Product: Liquiphant FTL31

• Key Configuration: 3-wire DC-PNP, M12 plug, 316L stainless steel housing, compact version

• Quantity: 20 units

• Delivery: Standard lead time, subject to order confirmation

• Mounting: Horizontal installation on tank sidewall, wall distance ≥ 10 mm

• Safety Mode: MAX safety mode for overfill protection

• Function Test: External function test with test magnet, LED indication

Customer Feedback

During commissioning, the customer used the test magnet for external function testing and confirmed the switching state via LED indication. Because FTL31 uses the tuning fork measuring principle with no moving parts, it did not show the mechanical sticking issues common to float switches in viscous media. The customer acknowledged the compact design and M12 plug connection.

Summary (with Key Technical Parameters)

• Measuring Principle: Vibronic tuning fork

• Suitable Media: Liquids

• Dynamic Viscosity: 1 to 10,000 mPa·s

• Density: > 0.7 g/cm³

• Solids Content: θ < 5 mm

• Process Temperature: -40 to +100°C (standard version)

• Process Pressure: -1 to +40 bar

• Wetted Material: 316L stainless steel

• Output: 3-wire DC-PNP, 10 to 30 V DC, switching capacity 200 mA

• Protection: M12 metal housing cover IP66/68/69

• Switch Point Repeatability: ±1 mm (DIN 61298-2)

• Hysteresis: Max. 3 mm

• Vibration Resistance: 50 m/s² RMS

• Shock Resistance: 30 g

• Not Suitable: Hazardous areas; FTL33 recommended for hygiene areas

Customer Feedback

The customer noted that FTL31 offers clear parameter boundaries, making it easier to confirm whether viscosity, density, temperature, and pressure match the application during selection. After installation, the device status can be observed directly via LED, reducing communication effort during commissioning and maintenance.

Conclusion

For overfill protection of viscous liquids in German chemical and lubrication systems, FTL31 provides a verifiable selection path based on the tuning fork principle. Its viscosity range, density range, 316L wetted materials, and MAX safety mode form the basis for stable operation in this application. If the application involves hazardous areas or hygiene areas, explosion-proof models or FTL33 should be considered respectively.