Liquid Solid Interface Measurements

Monitoring Solid Levels in Liquids

Monitoring solid levels in liquid environments is important for many industrial and environmental applications. In an industrial vessel, accumulated sediment or sludge can cause equipment damage, create blockages or clogs, result in expensive maintenance, and impact the overall system’s efficiency.

Traditional methods of monitoring solid level can be labour-intensive and may not provide real-time data. Submersible ultrasonic level sensors are a reliable solution for continuous monitoring.

Ultrasonic Technology Measuring Principle

Submersible ultrasonic level sensors operate on the principle of ultrasonic wave propagation. The sensor’s transducer emits high-frequency sound waves into the liquid environment. When these waves encounter a change in density, such as the interface between the liquid and the solid, they reflect back to the transducer.

The sensor measures the time it takes for the sound waves to travel to the surface and return. Time-of-flight is used to calculate the distance between the sensor and the solid layer surface.

Applications

Liquid-solid interface monitoring is beneficial for many applications, such as:

  • Environmental Monitoring: Monitoring sediment accumulation in ponds, lakes, and other natural water bodies helps with environmental conservation efforts by providing data on sedimentation rates and patterns.
  • Wastewater Treatment: Monitoring sludge levels in sedimentation tanks and clarifiers prevents overflows, enables optimization of the removal process and ensures efficient operation.
  • Automotive Water Recycling: Monitoring sediment build-up in reclaim tanks and grease inceptors at car washes alerts of maintenance requirements and avoids clogging issues.
  • Evaporation Ponds: Monitoring pond floor height changes from salt crystallization in evaporation ponds enables brine depth tracking for efficient process control.
  • Industrial Processes: Monitoring sediment levels in process tanks maintains product quality, ensures process efficiency and helps to optimize maintenance schedules.

Advantages of Submersible Ultrasonic Sensors

ABM manufactures a submersible ultrasonic level sensor designed to meet the demands of many liquid-solid interface monitoring applications. Benefits of the sensor include:

  • Accuracy and Reliability:  ABM’s sensor is designed to provide accurate measurements in challenging environments. The sensor features automatic temperature compensation and a self-cleaning transducer face, which removes air bubbles that could interfere with measurements, ensuring reliable performance.
  • Robust Design: The sensor is built to withstand harsh environments and chemical exposure, with a 316L stainless steel enclosure and Teflon transducer face. This durability makes the sensor suitable for long-term deployment in demanding industrial and environmental applications.
  • Versatile Use: Ultrasonic waves travelling through water will reflect off any surface with a change in density from water, allowing for versatile use in many applications, from shallow tanks to deep settling ponds.

Operation and Installation Considerations

Operating Environment:

  • Ultrasonic sound waves can be affected by signal attenuation or scattering. Factors such as air bubbles, temperature gradients, high turbidity or variations in liquid composition can impact sensor performance. Assessing the operating environment and considering potential interference will aid in successfully deploying the sensor.

Installation and Calibration

  • Proper installation is essential for accurate measurements. At least 1″ of the sensor must always be submerged in the liquid. The sensor must be mounted above the maximum solid level to avoid sediment covering the sensor face or signal loss.
  • To measure liquid level, the sensor must be mounted on a buoy or float to move with the liquid surface.
  • To eliminate liquid level change on interface measurement, the sensor must be mounted fixed to the tank wall, with the distance from the sensor face to the tank bottom known, as shown in Figure 1.
  • Additionally, calibration must be tailored to the specific tank and liquid/solid conditions to ensure accuracy.

Figure 1: Measurement of solid layer thickness – d(s) is determined by subtracting water layer – d(w) measured by the sensor from the total distance – d(t). Equation: d(s) = d(t) – d(w).

Conclusion

ABM’s submersible ultrasonic level sensor is the ideal solution for monitoring liquid-solid interfaces. The sensor offers high accuracy, durability, and versatility across various applications in many industries, including environmental, wastewater, and automotive.

The submersible sensor is a valuable tool to help improve process control and efficiency in environments where solid build-up is a concern.

In addition to solid-liquid interface, the sensor is also ideal for oil-water interface to measure the thickness of oil on the liquid surface or to monitor the liquid level above a pump for control and to prevent the pump running dry. Learn more about the submersible ultrasonic level sensor here.

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