Ultrasonic Flowmeters

Ultrasonic Flowmeters

Ultrasonic Flowmeters measure volumetric flow by comparing how long an acoustic signal takes to travel with the flow versus against it. In the differential transit-time method, two sensors alternate between transmitting and receiving, and the transit-time difference is directly proportional to flow rate. This creates a measurement that does not rely on mechanical moving parts or an internal restriction.

For many gases and liquids, ultrasonic measurement is attractive because it can be independent of electrical conductivity and, for homogeneous fluids, relatively insensitive to pressure, density, temperature, viscosity, and other property shifts. The open bore produces no additional pressure loss, and the absence of moving parts minimizes wear, which supports long service life and low upkeep.

Two installation approaches cover most use cases. Inline ultrasonic meters are used when traceable accuracy is required, typically supported by factory calibration, robust industrial construction, and comparatively short inlet-run needs. Clamp-on meters mount on the outside of the pipe, enabling retrofit or temporary measurement without interrupting the process. Clamp-on also extends ultrasonic measurement to very large diameters (up to DN 4000), while inline solutions typically address pipeline sizes up to DN 300.

Typical applications include water and utility networks, chemical transfer - including aggressive media under high pressure - process balancing, and large-diameter pipelines where head loss must be minimized. Clamp-on meters are used for surveys, pump performance checks, and allocation studies on existing infrastructure, including plastic, steel, and composite or lined piping. Inline ultrasonic is also applied where guaranteed accuracy is required for metering duties, including high-accuracy gas service and custody-transfer LNG systems.

Selection should consider fluid homogeneity and acoustic signal quality: bubbles, heavy solids loading, or strong stratification can challenge transit-time measurement. Pipe material, wall condition, and the available straight-run length influence achievable uncertainty, especially for clamp-on installations. When those factors are addressed, ultrasonic flow measurement provides a strong combination of hydraulic efficiency, maintainability, and measurement performance across a wide range of services.

Forberg Smith, an exclusive authorized representative of sales and service for Endress+Hauser.