Paddle Switch Level Measurement

Paddle Switch Level Measurement

Paddle switch level measurement is a mechanical point-level method for bulk solids. A motor-driven paddle rotates inside the vessel; when solids cover the paddle, rotation is impeded and the resulting torque change actuates a switch output. This produces a clear full/empty/demand alarm without requiring complex configuration.

The method is widely used because it is simple, rugged, and cost-effective for straightforward solids duties. No calibration is typically required, and the switching action is intuitive and repeatable when the bulk material meets the required density and flow characteristics. With suitable construction, paddle switches can be applied in dusty environments, including areas requiring dust explosion considerations.

Application constraints are primarily mechanical. Very sticky solids can cake on the paddle and cause false indication, while extremely light materials may not generate sufficient torque for reliable actuation. Shaft length, mounting location, and process temperature limits should be matched to the vessel design and the expected mechanical loads during filling and discharge.

Typical applications include silos and bins storing grains, flour, plastic pellets, animal feed, cement, and mineral products. They are commonly used as high-level alarms to prevent overfill, low-level alarms to prevent running equipment empty, and demand alarms to trigger replenishment in day bins.

Paddle switches integrate as discrete contacts into PLC/DCS inputs and safety interlocks, providing simple commissioning and straightforward functional testing. For basic solids point-level alarming where robustness and simplicity are priorities, paddle switches remain a proven standard.

Field Instruments & Controls, Inc. an exclusive authorized representative of sales and service for Endress+Hauser.