Paddle Switch Level Measurement

Paddle Switch Level Measurement

Paddle Switch Level devices provide point-level detection in bulk solids using a motor-driven paddle that rotates freely in air and stops when material exerts sufficient resistive torque. The increase in torque triggers a mechanical or electronic switch, generating a discrete signal for alarm or control. This electromechanical method is widely used for bin and hopper level indication.

Advantages include simplicity, broad acceptance in solids handling, and clear switching action that is largely independent of dielectric constant. Paddle switches are typically economical, easy to install, and easy to understand during troubleshooting. They are also tolerant of many dusty environments, and the switching threshold can be consistent when the product’s mechanical loading characteristics are stable.

Selection requires matching the device to the mechanical behavior of the bulk solid. Very light powders may not generate enough torque for reliable actuation, while heavy or abrasive solids can accelerate wear or overload the mechanism. Bridging, rat-holing, and material compaction can create false “covered” conditions, so placement relative to fill patterns and discharge zones is important. Temperature, pressure, and hazardous-area considerations influence sealing and construction choices.

Typical applications include high and low alarms in silos storing grain, feed, flour, cement, lime, plastic pellets, wood products, and many mined or processed minerals. Paddle switches are used to start/stop filling, protect downstream conveyors, and signal “bin empty” conditions to prevent starved feeders. They are especially common where a rugged, discrete indication is needed without the complexity of continuous measurement.

Interfaces are commonly relay contacts for direct PLC/DCS input and alarm annunciation. Reliable long-term operation is supported by choosing appropriate paddle geometry and insertion length, ensuring proper shaft sealing, and planning periodic inspection for wear in abrasive services. Where uptime is critical, maintaining spare assemblies and standardizing mounting hardware can simplify field replacement.

Miller Mechanical Specialties, an exclusive authorized representative of sales and service for Endress+Hauser.