Ultrasonic Flowmeters

Ultrasonic Flowmeters

Ultrasonic flowmeters measure flow by sending acoustic pulses through the process fluid and evaluating how the flow field alters the signal. In transit‑time designs, two transducers are arranged so that sound travels both with and against the flow; the differential transit time is directly proportional to flow velocity. Endress+Hauser describes this “differential transit time” method as the basis for ultrasonic flow measurement and notes that, for homogeneous fluids, the measurement can be performed reliably independent of electrical conductivity, pressure, temperature, or viscosity. Depending on the application, ultrasonic systems may use single‑path or multi‑path arrangements to improve robustness in large pipes and custody‑transfer service. A major benefit of ultrasonic technology is that it can be applied with minimal intrusion into the process. Because there is no obstruction in the pipe, pressure loss is negligible and there are no moving parts to wear, which supports a low-maintenance lifecycle. Endress+Hauser distinguishes between inline ultrasonic sensors for applications that require traceable, guaranteed accuracy (supported by traceable factory calibration) and clamp‑on sensors that mount on the outside of the pipe. Clamp‑on meters enable temporary measurement campaigns, commissioning checks, or retrofits without interrupting the process, and Endress+Hauser highlights retrofit installation and the ability to measure aggressive fluids under high pressure because the sensor never contacts the media.

These mechanical options broaden the application envelope across industries. Endress+Hauser notes clamp‑on sensors can be used on pipes made of plastic, steel, and cast iron composite materials (lined or unlined), and that they can be applied to very large diameters, up to DN 4000. Inline sensors, meanwhile, are presented as robust industrial designs aligned with ASME and EN practices, using short inlet runs and serving pipelines up to DN 300 for high‑accuracy duty. Together, these form factors allow ultrasonic metering to be deployed both as a permanent “measurement point” and as a diagnostic tool for troubleshooting, validation, and performance testing on existing assets.

Typical applications split along the inline vs clamp‑on boundary. Inline ultrasonic meters are common where accuracy, repeatability, and traceability are critical, including custody‑transfer or allocation measurement for gases and liquids; Endress+Hauser points specifically to custody‑transfer LNG metering with FLOWSIC. Clamp‑on meters are frequently used for retrofit flow measurement on utilities (cooling water, treated water, effluent), for temporary verification of installed meters, for balancing distribution networks, and for establishing baseline performance of pumps, heat exchangers, and treatment trains when a shutdown is not practical. In many plants, clamp‑on ultrasonic measurement is also used during commissioning to confirm actual line hydraulics before final control tuning.

Good ultrasonic performance depends on matching the technology to the fluid and the installation. Transit‑time meters assume a reasonably homogeneous flow path; significant entrained gas, large solids fractions, or strong stratification can degrade signal quality and must be evaluated during design. Clamp‑on accuracy is sensitive to pipe wall condition, lining thickness, internal scaling, and acoustic coupling, so careful installation, correct pipe data entry, and verification against a reference are important when the measurement will be used for control or reporting. While ultrasonic meters often tolerate shorter straight runs than some technologies, avoiding severe swirl and ensuring a stable acoustic path improves signal quality and diagnostic confidence. When these factors are addressed, ultrasonic flowmeters offer a powerful combination of nonintrusive measurement, wide applicability across liquids and gases, and flexible deployment options that support both operations and engineering studies.

Carotek, your trusted Endress+Hauser Representative.