Technical Characteristics and Silo Versatility
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Vibronic Principle for Bulk Solids: The sensor’s tuning fork is piezo-electrically driven to its resonance frequency. When covered by solids, the vibration frequency or amplitude changes; the electronics detect this shift and trigger a switch. This technology is highly reliable for low bulk density powders where other principles might fail.
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Flexible Extension Pipe: The FTM51 can be customized with an extension pipe ranging from 300 mm to 4,000 mm. This allows for precise high-level or low-level detection at specific depths, particularly when the sensor is installed through the top of a silo.
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SIL2 Functional Safety: Developed in accordance with IEC 61508, the FTM51 is certified for use in safety-instrumented systems, ensuring reliable overfill prevention in critical industrial processes.
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Build-up and Abrasion Diagnostics: The device includes a selectable display for monitoring material build-up and fork abrasion. This enables predictive maintenance by alerting operators if the sensor is being worn down by abrasive media like sand or chalk.
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Immunity to External Interference: The measurement is unaffected by external vibrations from agitators or conveyors, and the sensor design naturally resists the effects of material build-up on the tuning fork.
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Specialized Coatings: For sticky or aggressive materials, the sensor is available with PTFE or ETFE coatings. Polished versions (0.8 µm) are also available for hygienic applications in the food industry.
Technical Specification Matrix
| Feature | Technical Details |
| Measuring Principle | Vibronic (Tuning Fork for Solids) |
| Sensor Design | Extension pipe version (up to 4 m / 13 ft) |
| Process Temperature | -50 to +280 °C (-60 to +540 °F) |
| Process Pressure | -1 to +25 bar (-14.5 to +360 psi) |
| Sensor Material | 316L (optional PTFE or ETFE coating) |
| Bulk Density | ≥10 g/l |
| Output Signal | Relay, PNP, NAMUR, PFM, Thyristor |
| Safety & Compliance | SIL2, ATEX, IECEx, FM, CSA |
Primary Applications
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Large Grain and Flour Silos: Detecting high and low levels in tall storage structures for the food and animal feed industries.
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Chemical Powder Processing: Monitoring dye powders, chemical catalysts, or fine plastic granules.
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Abrasive Solid Detection: Use in silos for chalk, gypsum, or cement where the abrasion detection feature protects the sensor’s longevity.
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Dust-Hazardous Environments: Certified for use in Zone 20/21/22 where combustible dusts pose an explosion risk.
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High-Temperature Bulk Storage: Reliable point level switching in processes involving hot solids up to +280 °C.
