Ultrasonic Flowmeters

Ultrasonic Flowmeters

Ultrasonic flowmeters determine flow by measuring how sound waves propagate through a fluid stream. In the differential transit-time method, two transducers alternately transmit and receive signals; with flow, the downstream signal arrives sooner while the upstream signal is delayed. The measured transit-time difference is directly proportional to flow rate, enabling volumetric measurement without inserting obstructions into the pipe.

With no moving parts and a free cross-section, ultrasonic meters introduce essentially no pressure loss and avoid wear from the process fluid. For homogeneous fluids, the measurement can be largely independent of pressure, density, temperature, conductivity, and viscosity, which simplifies compensation and keeps performance stable across operating windows. Long service life and minimal upkeep make the technology well suited for both continuous metering and periodic verification.

Technology options include clamp-on sensors for retrofit or temporary measurement and in-line designs for higher accuracy and custody transfer duties. Clamp-on installations can be implemented without interrupting the process and can be applied to a wide range of pipe materials, including lined and unlined metallic and non-metallic piping. In-line sensors, factory calibrated and built to recognized piping standards, reduce sensitivity to coupling variables and enable shorter inlet runs in many layouts.

Common applications include water distribution and treatment, chemical transfer, and energy services where pressure loss must be minimized. Ultrasonic metering is frequently used on large-diameter lines and for verification of existing meters, balancing fast deployment with data quality. In high-value custody transfer services such as LNG, multipath ultrasonic technology supports high accuracy and stability when the flow profile is properly conditioned.

Selection should address fluid homogeneity, expected Reynolds number range, straight-run and profile conditioning, and the feasibility of clamping versus cutting the line. Clamp-on performance is sensitive to acoustic coupling, pipe condition, and internal scale, while in-line meters require attention to alignment and upstream disturbances. When these factors are controlled, ultrasonic flow measurement offers a low-loss, low-maintenance path to reliable volumetric flow across a wide range of line sizes.

Miller Mechanical Specialties, an exclusive authorized representative of sales and service for Endress+Hauser.