Paddle Switch Level Measurement

Paddle Switch Level Measurement

Paddle switch level measurement is used for point level detection in bulk solids. A motor-driven paddle rotates freely in air; when the bulk solid reaches the paddle, resistance increases and the device detects the torque change to actuate a switch. The output is discrete - typically “covered” vs. “not covered” - making paddle switches well suited for full/empty detection and basic alarming in solids storage.

This technology is valued for straightforward, rugged performance in many dry bulk applications. It is generally tolerant of dusty headspaces and does not require calibration to dielectric properties or complex echo processing. For many facilities, paddle switches remain a cost-effective way to add reliable bin-level alarms without introducing sensitive electronics or complex setup.

Limitations track mechanical realities. Very light powders with low bulk density may not provide enough resistance to trip the switch reliably unless paddle geometry is matched to the material. Sticky or cohesive products can cake around the paddle, potentially creating continuous torque or causing delayed release. Mechanical wear, bearing life, shaft sealing, and vibration exposure should be evaluated, especially in continuous-duty or high-temperature installations.

Common applications include grain and feed silos, cement and lime bins, plastics pellets, wood products, and minerals - especially where a simple high-level or low-level switch is needed. Paddle switches are also used in chutes and hoppers as a “material present” signal to protect downstream equipment from running empty or to prevent overfilling.

Selection is typically based on insertion length, paddle style (size/shape), enclosure rating, and approvals for dusty or hazardous areas. Good practice includes defining fail-safe behavior and ensuring the switch location matches the operational intent (e.g., high-high alarm positioned to allow response time). Preventive maintenance planning - checking rotation, seals, and actuation behavior - keeps lifecycle cost predictable.

George E. Booth Co., an exclusive authorized representative of sales and service for Endress+Hauser.