Flow Measurement, Ultra Sound

Flow measurement in the flue gas using the ultra sound measuring principle has become more common during the last 5 to 10 years. When the flue gas flow is measured by ultra sound, a sender and receiver unit, both with ultra sound transducers, are placed across each other on each side of the flue gas duct in an angle of 45° (or another well-defined angle between 30° and 60°) in relation to the direction of flow.

The difference in time for a sound impulse to pass the duct with the flow direction and against the flow direction is used for the calculation of the flue gas flow. Ultra sound flow measurement is especially used in processes with hot, wet gasses that might cause blockage of the pipe and corrosion of materials placed inside the process. The sender and receiver units are placed on flanges on each side of the duct with no parts directly in the process.