Industrial Solid Level Measurement Technologies

Rotary Paddle Fixed-Point Detectors

A rotary engine turns paddles through a spring. This rotation is continuous as long as the material does not come into contact with the blades. If these shovels stop but the engine keeps turning, the spring expands until it hits a limit switch that stops the engine and provides an external electrical contact. When the level is low, the spring returns to its position, the motor starts again, and the switch output changes its position. The pallet can be flexible or rigid to adapt to different working conditions.

Electromechanical Continuous Level Meters

This system uses a small mobile weight supported by a cable from the top of the silo via pulleys. A programmer and motor set a duty cycle for the weight. This weight descends inside the hopper until it collides with solids; then, the cable loosens and a detector reverses the direction of movement of the weight, causing it to rise to the top of the hopper where it stops, repeating the cycle. An indicator shows the point where the weight reversed its motion, indicating the level at that time.

Ultrasonic Continuous Level Measurement

This device is a pinger that sends a horizontal beam to a receiver placed across the tank. If the sound level is lower than the beam, the system enters a relay locking oscillation. When solids intercept the beam, the system stops scrolling, and acting on reset, an alarm or the unloading machinery of the deposit is triggered.

Radiation Level Meters

A radiation meter utilizes a gamma radiation source, arranged outside and at the bottom of the tank, which delivers radiation through the bed of solids to be captured by an external detector. The degree of radiation received depends on the thickness of the solid between the source and receiver.

Differential Pressure Level Meters

This method is used for the continuous monitoring of levels in fluidized beds. Two air bleed holes are located in the reservoir below and above the bed. A pneumatic or electric differential pressure transmitter measures the pressure after these orifices. It possesses a quick response and can work at temperatures greater than 300 ºC.

Scale-Based Level Measurement

A scale meter measures the level of solids directly through the weight of the hopper plus the product. Since the weight of the hopper is known, it is easy to determine the weight of the product and the level. The hopper rests on a load cell acting on the lever of a scale. It is an expensive system, but it can work at high pressure and temperature.