Mechanical flow meters have always been a dependable option for drinking water treatment and distribution. However, the adoption of ultrasonic flow meters for these applications is growing steadily as water managers realize that technological advancements often make them a better choice.

The original ultrasonic meters were Doppler-style technology that required a particulate flowing through it to register a reading. While these meters were a fit in wastewater operations, they didn’t work well for clean water. As a result, many water professionals are still under the impression that ultrasonic flow meters don’t belong in municipal drinking water applications.

In addition to Doppler-based solutions, ultrasonic meters also leverage transit time technology, which measures the time differential between signals sent upstream and downstream. Compared to mechanical meters, ultrasonic meters can offer better accuracy, more installation flexibility and minimal maintenance.

Understanding the Advantages of Ultrasonic Meters

Ultrasonic flow meters are an economical solution, especially for larger pipe sizes, because they can be installed in a variety of situations. By comparison, mechanical meters can be more expensive and difficult to install.

Accuracy is also a key differentiator. With a rating of ±0.5%, ultrasonic meters have no moving parts—eliminating drift—and they eclipse the ±1.5% accuracy of mechanical meters. This difference can be significant for municipalities, especially over time, when it comes to their ability to find leaks and tackle non-revenue water (NRW) problems.

Ultrasonic meters also have few to no maintenance requirements, which isn’t the case for mechanical meters. A single Venturi flow meter that requires the differential pressure transmitter to be sent for calibration, for example, represents an expense of several hundred dollars annually. This also requires that the utility have a redundant system that sits on the shelf much of the year.

Application versatility is also a key factor. In many cases, mechanical meters must be sized to the flow that’s expected, so they don’t account for long-term growth. Adding load to those treatment systems is difficult without updating the meter. By comparison, ultrasonic meters have a 400:1 turndown, so they can accommodate a much wider range and they’re simple to specify.

Additionally, the cellular network that underpins ultrasonic meters is attractive for municipalities because they can have these devices tied into the same network as their billing software. This allows operators to simultaneously review individual customer data and data for the corresponding pump station.

Exploring Clamp-on Meter Technology

When contact with the fluid isn’t possible, clamp-on ultrasonic meters are ideal. Clamp-on meters greatly reduce installation cost and time because they can be installed—either permanently or temporarily—by a single user within an hour. These meters easily attach to a pipe’s exterior and are secured in place without ever penetrating the pipe or coming in contact with the internal liquid.

These meters also provide a greater extended low-flow accuracy compared to mechanical meters across a wide range of pipe sizes with no pressure head loss and no moving parts to maintain. These devices offer a lot of connectivity and there are a variety of output options, such as tying into a programmable logic controller (PLC).

Inline ultrasonic meters and open-channel models are a fit for new construction and renovation projects—as well as a replacement for aging meters in the distribution system—while the clamp-on version of ultrasonic meters is an ideal solution for retrofit projects.

Municipal water managers and engineers should consider the benefits of ultrasonic technology when analyzing flow meters for any of these scenarios.

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