How to select the right flow meter for your application?

Price versus popularity, of a flow meter

Flow meter categories based on fluid

Some flow meters can be easily eliminated because they simply will not work with the application. For instance, electromagnetic flow meters will not work with hydrocarbons and require a conductive liquid to function. Many flow meters cannot measure gases or slurries. Listed below are some of the main flow meter categories paired with the fluid type the meters can handle.

• Gas – Coriolis Mass, Thermal Mass, Ultrasonic, Variable Area, Variable Differential Pressure, Positive Displacement, Turbine
• Liquid – Coriolis Mass, Thermal Mass, Ultrasonic, Variable Differential Pressure, Positive Displacement, Turbine, Electromagnetic
• Slurry – Coriolis Mass, some subsets of Variable Differential Pressure, Electromagnetic, Ultrasonic
• Vapour – Vortex, Ultrasonic, Diaphragm, Floating Element

Fluid properties

It is crucial to know the properties of the fluid being measured, below are some of the primary components:

• Type of fluid – liquid, gas, slurry, vapour
• Density
• Viscosity
• Temperature
• Pressure
• Condition of the fluid – foreign objects in it, suspended particles, air bubbles,
• Other contaminants
• Flow consistency – consistent or breaks, fill the pipe or partially fill or varies
• Flow range – the minimum and maximum of the flow
• Corrosive nature of the material – corrosive liquid or gas can deteriorate inline sensors

Flow meter specifications

Last but not least, also the specifications itself have to be taken into consideration when selecting the right flow meter.

Accuracy – Naturally, an important factor of a flow meter is accuracy. To even suggest that accuracy is a variable seems ridiculous. Who would want an inaccurate meter? However, not all flow meters possess the same accuracy; some applications do not even require precision.

Repeatability – Repeatability means the number of times (%) you get the same results running the same test or measurement under the same conditions. Accuracy requires repeatability, but repeatability does not require accuracy. It just needs consistency.  Therefore, it can be said that repeatability of a flow meter is often considered even more important than accuracy.

Turndown Ratio or Rangeability – This implies the range that a flow meter can accurately measure the fluid. Usually, it’s best to choose a flow meter with the greatest range available without compromising other components that are more critical.

Hygiene requirements – Flow meters for food, pharmaceuticals, and the medical industry especially demand sterile environments.

Cost – As stated above, this should include installation, maintenance and repairs over time. How much the meter costs to operate, like its electrical demands, can also increase the overall cost of the flow meter.

As you can see, there are a lot of variables to finding the right flow meter and the ones we have listed are only the basics. This does not even touch on the various options in different models. The best way to get the right meter is to get help with your search and team up with experts in the field. Experience matters.

It is important to get your information from people who know these complex and important devices. To let Bronkhorst help in the search for the right flow meter for your needs, please contact us.

• When you have selected the right flow meter, the next step is installing this instrument. Graham Todd gives some useful tips when installing a mass flow meter.