How to Select a Flow Meter

Choosing a flow meter can be a very overwhelming prospect. Sometimes it can be hard to know where to start. You have to wade through which flow meter technology out there might best serve your application and your budget. There are countless manufacturers out there with many models all offering something a little different. You also have to ensure that the specific variables of your process fall in line with the specifications of each individual model. Knowing what information you even need to start with can be difficult.

Nobody likes to spend time or waste money that they could have saved with a little preparation. When it comes to finding the best fit for your process application being organized and thorough can have big payoffs in making sure that all factors are appropriately compensated for in your choice. Accidentally overlooking some variable that ends up in equipment malfunction, damage, or failure can be avoided by asking the right questions at the beginning. Below is a fairly comprehensive list of questions to help you build a complete application profile for an optimum selection process.

Price/Customer Service

• What is your budget? While it is tempting to think that price needs to be the first consideration and to think that the lowest priced option is always the way to go, that can lead to headaches down the road. Cheaper models, options, or technologies may not provide the same length of service life, require more maintenance, or may require more downtime for things like calibration. These things all cost money in the long run and should be added to the total lifetime cost of the instrument. Ask what the average life span of the model you are looking at is.
• Ask about warranties. How long is the instrument covered and does the company you are purchasing from have a known customer service record for supporting their instrumentation in an accessible and personal manner. This can make all the difference in ensuring that an instrument has been correctly installed and to easily troubleshoot any questions that come up as part of that process.
• How long will it take to install? Will it require a shutdown of a critical existing process that will cost money or can it be installed without this issue?
• It is important to think in terms of total value and not just the initial cost. What may appear cheaper at first glance may cost much, much more in the long run.
• If you are looking to replace a part that has shut down a process, lead-time for the replacement is also an important consideration. Can you get it fast to get the process back up and running?
• Wouldn’t it be nice if you could try one out first to make sure it works? Some companies like KOBOLD are open to the idea of supplying short term demo units in special situations to ensure that it is the correct solution for the application.

The Basic Process

• Who will be using it? What do they need to use it for? Where will it be placed?
• Does the process require totalizing or batching capabilities?
• Is visual rate indication the only thing needed? Is a switch or a transmitter needed? Is local or remote indication needed?
• Getting the basic layout of the process and the people who will interact with the flow meter or its data will help you in selecting certain features.

The Immediate Characteristics/Surroundings to the Place of Installation

• What is the line size of the pipe and what is it made out of?
• Is the environment around the area stable or variable as far as elements like temperature? Is there danger of explosion? Is the area a harsh environment?
• What length of straight run of pipe is possible before and after where they instrument will be placed if the meter requires it?
• Will there be other types of instrumentation placed close to the flow meter, upstream or downstream?
• Are there space limitations at the installation site that will restrict the size that the instrument can be?
• Will the installation area require a certain angle or orientation that the instrument will be installed at?

The Media Characteristics

• Is it liquid, gas, vapor, steam, slurry, or multi-phase media?
• Is it clean or dirty?
• Is the nature of the media corrosive?
• What is the media density, viscosity, temperature, pressure, and do these remain constant?
• Is the media conductive and if so, to what extent?
• Is the media Newtonian or Non-Newtonian in nature?
• Does the media have any coating or crystallizing properties?
• Is there any suspended particulate matter? If so, how large are the particles?
• Any ferrous material in the media?

The Flow Profile

• Is it likely that the media may contain air bubbles?
• Are the process pipse always totally full of the media?
• Will the flow rate remain relatively constant, or will there be large fluctuations?
• Is there a chance of pulsating flow?
• Will the flow be largely laminar or turbulent?
• What sort of turndown is needed to accommodate the full range of flow?
• What is the minimum flow rate?
• What is the maximum flow rate?
• Will the media flow in one direction or will it be bi-directional?
• Is pressure loss from the flow meter in the line an important consideration?

Accuracy/Repeatability/Resolution

• Accuracy: How exact does the measurement need to be?
• Repeatability: How important is it for the meter to produce "grouped" results?
• Resolution: How small in increment do the measuring units need to be?
• To learn more about these three terms, visit our article about flow meter accuracy.

Certifications

• What sort of regulatory compliance are you subject to?
• Do you have hygienic requirements for the application?
• Does the media have the potential to be explosive?

Reporting/Recording/Communications

• Who needs to see the data?
• How often do they need to see it?
• How do they need to see it?
• Where do they need to see it?
• Does your process already have a particular communications protocol that the flow meter will need to integrate with?

Does it still sound intimidating and like it's a bit too much to tackle on your own? Don’t worry. We have decades of experience and knowledgeable sales engineers who know exactly how to guide you through this process. The field of instrumentation is always evolving and consulting someone is always an advantage. KOBOLD has experts at your disposal standing by to help you. Call us now or contact us by email info@koboldusa.com.