Finding the Best Level Measurement for the Application

Emerson's Ingemar Serneby

Many ways exist to measure level in industrial processes. At the recent Emerson Exchange conference in Brussels, Emerson’s Ingemar Serneby teamed up with an instrument specialist with a food manufacturer to share a presentation, Finding the best level measurement solution can be easy…if you know where to look and what to look for.

This manufacturer used different methods to measure level in their vessels, but often faced problems with reliability and accuracy. What they produce for sale is dependent on the exact recipe being followed. This means that accuracy and reliability are key. Given this importance, they decided to look for an accurate, reliable method and found process radars to be a perfect fit, as well as to be easy to install and maintain.

In the presentation, they described some of the challenging applications for level measurement. Additive tanks were one given their small size and volumes, which created rapid level changes based on flows. High measurement accuracy and robustness is required, and some of these additive vessels contain important additives that require special precautions.

Process storage tanks were another application challenge since they are located externally in potentially rough environments where the instrumentation can be difficult to reach. Reliable level measurement is also critical for these tanks.

Other challenging applications included process vessels, distillation columns, lime silos and rental tanks. Challenges included high temperatures, turbulent surface levels, low dielectric properties, sticky media and high pressures. Reliability and repeatability were common requirements for the measurements.

Guided-Wave-RadarGuided wave radar (GWR) technology for level and interface indication provided the best solution. A microwave pulse travels down the probe. Part of the energy reflects back when reaching media with a different dielectric constant.

The signal is highly reliable with enhanced tolerance to coating, foam, vapor and turbulence. To address these types of challenging environments, Direct Switch technology provides a stronger signal when receiving the microwave signal back from the probe.

These guided wave radar devices provide signal quality metrics to alert for potential measurement problems to predict when maintenance might need to be performed on the instrument. Given the importance of the measurement in the quality of the product produced, having early warning of any measurement problems was very important.

Overfill prevention was another important factor. With Verification Reflector, the guided wave radar devices can verify measurement integrity with an online test to prove the device integrity and verify both the transmitter and the loop.

For some of the top-down, direct level measurements, non-contacting radar (NCR) instruments were used. For these devices, there are no probes and the microwave pulse is emitted from an antenna. Part of the energy reflects back when reaching media with different di-electric constants.

These NCR devices have Dual Port technology, which makes them a good choice for applications where dust, foam, vapors or turbulence are present.

For measuring solids, a Rosemount 5402 device effectively measures applications with sloping surfaces, high filling rates and low dielectric properties well. This is a great fit for production silos with small nozzles and internal obstructions.

Ingemar and his co-presenter closed noting that these measurement devices provide valuable information about both instruments and the process are visible in the asset management and control systems. With their embedded diagnostics, actions can be taken before failures in measurements occur. Additional problem areas can be identified earlier and device parameters can be monitored.

This results not only in increased uptime and throughput, but also in reduced operating costs and higher levels of plant safety.

You can connect and interact with other level measurement experts in the Level group in the Emerson Exchange 365 community.