Open Channel Flow Meter Selection Guide: How to Choose the Right Flow Measurement Solution

Selecting a flow meter for an open channel or partially filled pipe is different from selecting a conventional full-pipe flow meter.

In a full pipeline, the pipe is completely filled with liquid and the flow rate can be calculated based on the pipe cross-section and flow velocity. In an open channel, however, the liquid level changes continuously, and the flow area changes with the water level.

This is why customers looking for an open channel flow meter, wastewater flow meter, or flow meter for partially filled pipes need to consider more than pipe diameter alone.

The first question is whether the application is actually an open-channel or partially filled pipe application.

An open-channel flow measurement system can be considered when:

• ✓ Water flows through an open channel
• ✓ The channel is not pressurized
• ✓ The pipeline is only partially filled
• ✓ Wastewater flows through a drainage channel
• ✓ Water passes through a flume or weir
• ✓ The water level changes significantly during operation

Typical applications include: Wastewater treatment plants, Sewage systems, Industrial drainage, Irrigation channels, Stormwater drainage, Water discharge monitoring, Natural streams, Partially filled pipelines.

If the pipeline is always completely full, a conventional full-pipe flowmeter may be more appropriate.

Before selecting an open-channel flow meter, customers should provide as much of the following information as possible:

Some open-channel applications use a hydraulic structure such as a Parshall flume or weir. These structures create a known relationship between water level and flow rate. However, not every open-channel application has a standard flume or weir. For applications without a standard hydraulic structure, the actual channel geometry, water level and flow conditions need to be evaluated.

Yes. Ultrasonic open-channel flow measurement can be used for many wastewater and sewage applications. However, the installation environment should be evaluated carefully because wastewater may contain suspended solids, sludge, floating material, air bubbles, foam, or turbulence. Excessive bubbles, foam or unstable flow can affect ultrasonic measurement.

Partially filled pipes are a common application where customers are unsure which type of flowmeter to select. If the pipe is not completely full, simply selecting a conventional clamp-on full-pipe ultrasonic flowmeter may not provide the required measurement. A dedicated partially filled pipe/open-channel measurement solution should be considered.

Even a technically suitable flowmeter may produce unstable readings if it is installed at a poor location. Whenever possible, choose a location with: stable water flow, minimal turbulence, no sudden changes in channel geometry, and sufficient distance from pumps, gates, and sharp bends. A stable flow profile generally helps improve measurement reliability.

The Lanry DOF6000 is designed for open-channel and partially filled pipe flow measurement applications. It can be considered for: Wastewater, Sewage, Drainage, Industrial wastewater, Irrigation, Open channels, Partially filled pipelines.

The system combines flow velocity and liquid level measurement to determine flow rate according to the actual hydraulic conditions.