Paddle Switch Level Measurement

Paddle Switch Level Measurement

Paddle switch level measurement (rotary paddle) is a mechanical point level detection method for bulk solids, commonly used for full, empty, and demand alarms in silos. It is positioned as a universally usable solution for straightforward solids applications, with robust housing and compact construction that fit many standard silo installations. Variants are available to match different bulk materials and mounting arrangements, supporting common alarm and control functions in solids storage.

The measuring principle is simple: a motor-driven paddle rotates freely in air; when bulk solids cover the paddle and stop its rotation, the device actuates a relay output. This “rotation stopped” mechanism translates directly into a switching signal indicating material presence at the installation point. Because the detection is based on mechanical resistance from the solids, it is especially intuitive for discrete “covered/uncovered” duties rather than continuous measurement.

Advantages include straightforward operation and minimal configuration - highlighted by the absence of calibration requirements for typical use. The design is often selected for cost-effective point detection where the primary requirement is a dependable alarm rather than high-resolution measurement. Robust construction and suitability for dusty environments (including dust-explosive areas with appropriate variants) make paddle switches common in many bulk handling facilities.

Typical applications include silos and bins handling flowing bulk solids, such as powders, granulates, and similar materials, including services with grain sizes up to about 50 mm as referenced for this category. Common use cases are high-level alarms to prevent overfill, low-level alarms to protect feeders from running empty, and “demand” switching to trigger replenishment cycles. These functions support stable material flow and reduce process interruptions due to unplanned stockouts or plugging events.

Good application practice considers bulk solid flow behavior, mounting location, and potential mechanical wear. Paddle selection should reflect product density, particle size, and the likelihood of compaction or crusting at the sensor elevation. Mounting should avoid direct impact from fill streams where possible, and relay logic should be aligned with alarm philosophy to prevent nuisance trips during transient filling or aeration events. Where hazardous area requirements apply, appropriate device variants and wiring practices should be used to maintain compliance.

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