Back to AWWA C751-19(R23) Magnetic Inductive Flowmeters
The performance and the reliability of these meters with no moving parts will be discussed. The meters require less maintenance and are more accurate than mechanical meters in use today. Magmeters are used in a wide variety of applications including the measurement of wastewater, raw water, treated water, and revenue generation and in different stages of the treatment process such as the measurement of settled water, supernatant water, and backwash water and for proportional chemical addition (pacing). These meters have also been widely used in large-diameter intercity custody transfer pipeline applications.
By selecting the proper wetted materials, such as PFA or PTFE (Teflon) and ETFE (Tefzel) polymers or ceramic liners and noncorrosive alloy electrodes, magmeters can measure not only water but also the most corrosive liquids and caustic solutions. Magnetic flowmeters also offer configurations suitable for highly abrasive applications. The selection of polyurethane, ceramic, and soft rubber liners with tungsten-carbide–tipped electrodes will withstand mineral slurries with up to 70 percent solids content.
Magmeters have no internal mechanical components in the measuring section and do not create any flow restrictions in the pipeline. They are used in many cases where flow restrictions are undesirable. Magmeters are available in a wide range of pipe sizes, from 1/12 in. (2 mm) to 10 ft (3 m) in diameter with the most common sizes from 1/2 in. (15 mm) to 20 in. (600 mm).
Magmeters are easy to install in new applications with relatively short straight pipe runs required for accurate measurement and more difficult to install in retrofit applications due to the nonstandard face-to-face dimensions, which vary between manufacturers.
Magmeters will operate reasonably well even in applications where they are oversized or undersized. Many vendors provide options such as displays, totalizers, multiple outputs, and the ability to measure bidirectional flow conditions to fit the most demanding applications.
However, magmeters, like any other flow measurement devices, need to be selected prudently for the conditions under which the equipment is expected to operate to get the best performance from the meter. Meter manufacturers will typically specify accurate metering velocity ranges in excess of 1–30 ft/s (0.3– 10 m/s). It is common to see meter sizes selected so that flowing velocities will be between 2–15 ft/s (0.66–5 m/s). In some applications where the minimum velocity requirement for a specific flowmeter size must be met, it may be necessary to install the magmeter in a reduced pipe section where the flow velocity is greater.