Going with the flow

摘要

With so many different designs of flowmeter to choose from, and so much riding on the correct design, where do you start? David Almond looks at the various different flowmeter types available. Without a background in flow monitoring, trying to select the most appropriate technology for a given application can seem a daunting task. Indeed, it can appear that there are almost as many different measuring technologies as there are media to measure. Once you start to break down the application requirements and fluid characteristics, however, it soon becomes apparent that some solutions are more appropriate than others. A good place to begin is to look at what sort of flow information is required. Is it continuous or totalised? After that, how will the flow be read - visually, via electronic outputs or a combination of the two? What are the characteristics of the medium - gas or liquid, clear or opaque, viscous, aggressive, corrosive, etc? What about temperature variations, acceptable pressure drop, and even issues such as ease of maintenance? All of these factors need careful consideration. Once these questions are answered, the engineer can then look at parameters such as the required meter range, the required accuracy, and the required repeatability. With all of that in mind, let's look at some of the more common flowmeter technologies, their principles of operation, their advantages, and the sorts of applications where they excel.