How do I choose the right flow meter?

Answer 1

Simply defined, a flow meter is a device that measures how much fluid is flowing through a pipe and at what rate. In practice, however, flow meters are a little more complicated. They vary depending on the application and the degree of precision you expect, among other things.

Here are a few important points to keep in mind before purchasing a flow meter.

1. Choosing a flow meter for basic necessities

If you don't need to know the flow rate or the volume of fluid flowing through a line, then you don't need a flow meter. For example, flow meters are generally not required for domestic pumping purposes, but having one may come in handy. For simple domestic water pumping systems, a basic, cheap flow meter will do the job.

2. Choosing a flow meter based on the type of fluid

Different flow meters are designed to measure fluids of different viscosity. Viscosity is a measure of friction that's generated by a fluid when it flows. Water has low viscosity and oil has a higher viscosity. So, if you had to measure the flow rates of both water and oil, you would require two different types of flow meters.

A simple way to find the right device is by looking at a flow meter's Reynold's number. Different Reynold's values correspond to fluids of different viscosity, enabling you to pick the right flow meter for the fluid at hand.

3. Choosing a flow meter based on its measurement range

'Turndown' is the indication of the lowest and the highest values a flow meter can measure reliably and therefore an extremely important factor. Choose a flow meter within a flow range that's broad enough for your needs.

4. Choosing a flow meter based on accuracy

The accuracy of a measurement can depend on more than one factor. A low cost, low-quality flow meter is likely to provide low accuracy measurements and the same is true in reverse. The accuracy may also be affected if the wrong type of flow meter is installed. Select a flow meter depending on your application's tolerance for error.

5. Choosing a flow meter based on type

Electromagnetic, positive displacement, Karman vortex, paddle wheel, floating element, coriolis, ultrasonic, diaphragm, thermal, variable area, variable differential pressure, oscillatory and turbine are some of the different types of flow meters you can choose from.

Each type of flow meter is best suited for a certain type of application or fluid. Choosing the right type is critical because the accuracy of measurement depends heavily on this factor.

Here are a couple of examples. Coriolis flow meters are great for measuring the mass (not volume) of viscous fluid flowing through a line. Electromagnetic flow meters, meanwhile, can take measurements across a wide range.

Besides viscosity and flow range, a few other factors also need to be taken into consideration while selecting a flow meter. These are:

Fluid temperature

Fluid pressure

Fluid electrical conductivity

Contaminants in the fluid