Commentary: Ultrasonic for Leak Detection

By Don Bloom

Environmental and personal safety issues have created the need for more effective leak detection and location capabilities on inter-refinery pipelines. An underlying need for such functionality is the preservation of assets. As pipelines age and there is increased construction in the vicinity of existing pipelines, the potential impact of pipeline leaks increases.

Clamp-on, ultrasonic technology offers an attractive way to perform leak detection and location on existing (and new) pipelines by the measurement of the mass of the liquid in the pipeline. Mass measurement is a more accurate alternative to the use of modeling based on volumetric flow and pressure gradients. The ultrasonic technology used to provide mass measurement-based leak detection can also provide operational information for custody transfer batch tracking and pig detection.

Nonintrusive ultrasonic flowmeters have several important characteristics that make them a good fit for leak detection:
• Sensitivity: Most ultrasonic flowmeters are extremely sensitive at and around zero flow. This permits the system to detect and integrate extremely small leaks and even provide the capability to detect the opening of valves along the pipeline.
• Bidirectionality: Nonintrusive ultrasonic flowmeters are bidirectional in operation. They possess the ability to measure flow accurately and with repeatability for flow in either direction. This attribute eliminates the need for additional instruments, valves, and expensive piping configurations.
• Liquid Differentiation: The nonintrusive ultrasonic flowmeter measures the speed of sound (or sonic velocity) of the liquid in the pipeline. Hence, when the liquid in the pipeline changes, the meter has the ability to detect and, in the case of some types of meters, identify the liquids flowing at any given time. This attribute obviates the need for additional devices such as density meters.

Don Bloom is a vice president with Controlotron (www.controlotron.com), a manufacturer of liquid and gas flow measurement solutions. One of Controlotron’s core product offerings is a nonintrusive leak detection system for pipeline applications.