Why operators choose open channel flow meters for impressive accuracies

When the most appropriate and advanced flow metering technology isn’t being utilized for open channels and partially filled pipes, the readings can be off by as much as 20 to 50%. In some cases, utilities aren’t even bothering to measure flow.

Not having a firm grip on the rate of inflow can create major treatment problems. Either too much effort will be spent diverting inflows into containment storage when it isn’t necessary or not enough raw sewage will be diverted until it can be addressed. The latter presents a significant risk for the release of untreated sewage, which is bad for the environment and can lead to fines.

The good news is that economical and reliable open channel flow meters are available to tackle those issues.

Important considerations when selecting an open channel meter

For those considering open channel flow meters, there are several factors to evaluate when matching an application with a specific technology.

The construction of the channel is important. Is it a standard rectangular, trapezoid or circular design? Is there a flume in which the flow is constricted and the floor changes levels, and is it free flowing?

Another key factor is how much accuracy is required. Are you paying close attention to accuracy—is 3% necessary to get the proper results or can you get away with 10%? How close are you to permitting limits?

With those considerations in mind, Badger Meter offers several products that can solve any open channel measurement needs.

The Dynasonics^® IS-4000 Open Channel flow meter is an economical solution that includes a non-contact ultrasonic level sensor to detect water level and then calculate flow rate and total volume. This meter is a popular choice for its precise measurements, reliable operation and application flexibility, which includes water treatment plants, storm and sanitary sewer systems and industrial discharge applications. When used with a well-maintained Parshall flume, the IS-4000 flow meter can provide flow rates and totals with a high degree of accuracy.

Typically, the cost of an IS-4000 meter falls within a discretionary maintenance budget, so it’s relatively easy for water managers to justify purchasing.

The Dynasonics^® IS-6000 Doppler Area Velocity flow meter is an open channel meter that directly measures flow velocity, level and temperature with a single submerged sensor. It provides operational excellence for demanding applications, such as wastewater treatment plant influent, wastewater collection systems, combined sewer systems, stormwater monitoring and industrial discharge. Although it is a more expensive option than the IS-4000 meter, the IS-6000 meter is more appropriate when conditions make taking an accurate level reading difficult.

With the submerged sensor, the IS-6000 meter also presents an advantage in measuring velocity using the pulse/Doppler style to profile the entire flow. By comparison, signals used for non-contact velocity measurement can be impeded by steam, condensate building or foam.

Both the IS-4000 and the IS-6000 meter offer data logging capabilities as well as Modbus RTU and Ethernet communication protocols.

With previous open channel flow metering products, installation was a tricky proposition where even the slightest misstep could lead to highly inaccurate readings or even a complete failure. By comparison, these newer products are much simpler to install and program, thereby helping water professionals avoid most common problems.

The IS-4000 and IS-6000 meters are performing well in numerous open channel applications across the globe and are increasingly sought as meters of choice.