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When Flow Disturbers Affect Accuracy

A vital aspect of process control is ensuring flow meter accuracy. However, there is always the risk of upstream and downstream flow disturbers potentially causing issues. While this can be addressed during the process of design, there are circumstances where disturbers simply cannot be eliminated.

A flow disturber refers to anything that causes an impedance in the up or downstream flow of a flow meter, including elbows, reducers, and piping configurations. Valves are also able to create flow disturbances, including control valves.

Flow disturbers may cause an asymmetric velocity profile or swirl, which may result in considerable flow measurement errors. The inaccuracy may be due to under-reading or over-reading. The amount and direction of inaccuracy depends on various factors. These include flow velocity and profile and the type of metering technology.

It is not always possible to ensure sufficient straight pipe before or after the meter. Site compactness may be a factor or regulators may demand a flow measurement requirement after a facility is already online. In some cases, flow meter locations aren’t determined until the system has already been built.

In some cases, flow straighteners or conditioners can be installed to cut down on the amount of straight pipe needed. These devices include perforated plates or tube bundles. However, these devices will not work with every type of flow meters. Also, pressure losses may occur based on the flow conditioner type and installation.

When straight run pipe is not possible, a flow meter like the McCrometer V-Cone® flow meter is designed to “flatten” out the flow profile, resulting in true flow measurement through the meter. The meter can be mounted near a flow disturber and installed between a pair of double elbows while still maintaining accuracy.

To read more, go to https://www.mccrometer.com/technical-articles/how-to-get-accurate-flow-measurements-despite-flow-disturbers.

The Avanti Company was founded in 1977 by Paul and Justine Devlin and is headquartered in Avon Park, FL. We provide water meters, metering systems, AMI support, on-site flow meter testing, sewer flow monitoring, inspection and assessment services for the water, wastewater, agricultural, petroleum and industrial marketplaces. Avanti represents products from McCrometer, Itron, Badger Industrial, Hach Flow, Honeywell/Elster, 64 seconds, Infosense, Nicor, Aclara, and others. Please visit our website at www.avanticompany.com, email us at info@avanticompany.com or call us at 863-453-5336 for assistance with all of your flow meter and metering system needs.

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