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Focus on Flowmeter Selection for Water & Wastewater Industries: Part III

So far in this series, we’ve looked at how flow rate, flow variability, fluid, meter type, and level of accuracy affect flowmeter selection. What else must the designer consider? Flowmeter location. Without the right location, the designer’s carefully selected flowmeter can cause inaccuracy, higher operating costs and create safety issues.

Where you put the flowmeter is as critical as the other factors in finding the best flow measurement solution.

For maximum accuracy, flowmeters should be located in non-turbulent flow areas, ideally upstream of disturbances, such as elbows, tees, and control valves. If this is not possible, almost all flowmeter technologies should be placed no closer than five pipe diameters (internal diameter) downstream and at least one diameter upstream from the nearest source of turbulence. Exceptions to this rule are positive displacement and V-Cone Differential Pressure flowmeters.

Once a good location is found, make sure there is power. Flowmeters are often placed in remote areas that may lack power connections, so a perfectly specified, well-located meter can still be unusable. If power is not readily available, the best choice may be a propeller meter. They are mechanically driven and can give both instantaneous and total flow readings without external power. Self-powered electronic prop meters are also available with batteries that have an eight-year service life.

Even when meters are properly located in areas with perfect flow dynamics and a power source, things can still go wrong. For example, how would you like to read a meter that is twelve feet in the air, or submerged in a vault, or only accessible to someone under 3 ft tall! When a meter must be put in an inaccessible location, the designer’s only hope for an inexpensive solution may rest on the meter’s ability to be fitted with a remote readout. These readouts, which communicate with the meter, can be ordered with or retrofitted to inaccessible meters, and can be mounted up to 300 feet from the main sensor. Remote mounted readouts not only make taking meter readings more convenient, but create a safer working environment as well.

Over the last three months, we’ve looked at the main factors to consider when choosing a flowmeter for water and wastewater applications. If all of these criteria are met, the designer will be well on his way to choosing a flowmeter that will assure the profitability of his company - and the viability of his future - at the lowest possible cost.

If you have any questions concerning this newsletter or about McCrometer’s line of flowmeters, please contact your nearest McCrometer flowmeter expert at 951-652-6811 or visit our web-site www.mccrometer.com

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