How to Choose the Right Flow Meter

• Choosing the right flow meter is a critical factor in the success of your operation, and there are countless flow meters that you can select from.
• The right flow instrumentation will provide you with pivotal data.
• But choosing the wrong meter could lead to loss of costly production time.

Price plays an obvious role in selecting flow meters. We all have budgets to follow. It is common for people to search for the best price when selecting flow instrumentation. We do want to caution using this as your main factor when in the selection process. If you place the price at the top of your criteria, it will be easy to get the wrong flow meter for the application or one that does not perform well. The bargain price you thought you had will dissipate having to buy ancillary equipment and performing expensive maintenance.

Flow Meter Price vs Popularity

Another common factor is popularity. It’s important to research the flow meters most used in your industry. Be that as it may, using this as the only factor in your decision making will also cause problems. When flow instrumentation is not suitable for an application, measurement can be inaccurate. This leads to the loss of valuable materials and loss of revenue.

Advancements in technology can also put instruments on the market that are not well-known but provide a better solution. An example of this is how inline ultrasound flow meters had to be recalibrated when introducing a new fluid. New technology has solved these problems and allows for the use of these flow meters.

Volumetric Flow or Mass Flow Measurement

Flow instrumentation use either Volumetric flow measurement or Mass flow measurement. Choosing between a volumetric flow meter or a mass flow meter is dependent upon your application. Before choosing flow instruments make sure to understand the purpose of your application and its components.

Flow Meter Categories Based on Fluid

Flow instrumentation does not work within every application. For instance, electromagnetic flow meters need a conductive liquid. They also will not work with hydrocarbons. This is one example, listed below are the main flow 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
• Vapor – Vortex, Ultrasonic, Diaphragm, Floating Element

Properties of the Application & Fluid

It is imperative to understand the physical properties of the application site, such as:

• configuration of the pipe before and after the flow meter and the length of straight pipe at the inlet and outlet of the flow meter
• size of the pipe – some flow meters have a poor performance with very small pipes and some cannot measure fluids in larger pipes
• material of the pipe
• surrounding environment and whether it is stable or variable
• Will these flow meters work at a certain angle? This can affect a flow instrument’s performance

It’s also important to understand the properties of the fluid measured. Below are some of the primary components:

• Type of fluid – liquid, gas, slurry, vapor
• 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 fill
• Flow range – the min. and max. of the flow
• Corrosive nature of the material – corrosive liquid or gas can deteriorate inline sensors

Flow Instrumentation Specifications

Lastly, the specifications of the application must be considered when choosing the right flow meter.

Accuracy

To even suggest that accuracy is a variable seems ridiculous. Who would want an inaccurate meter? But the importance placed on accuracy varies dependent on the application. Furthermore, 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. It’s not about accuracy, rather consistency. Many will say that the repeatability of a flow meter is considered more important than accuracy

Turndown Ratio or Rangeability

This implies the range that flow meters can accurately measure the fluid. Usually, it’s best to choose a flow instrumentation with the greatest range available without compromising other components that are more critical.

There are many variables to consider when searching for the perfect flowmeter for your application. 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.

Communication

One last critical considering is the communication protocol that flow instrumentation is compatible with. For example, if you’re using Modbus, but the flow meter you choose can only use EtherCAT, then you’re going to have issues in connectivity. While communication can usually be worked around easily, it adds both equipment and design costs and challenges that can be avoided easily when planning ahead.