Specifying the Right Variable Area Flow Meter: Part 3 of 3
Yesterday I covered flow rate and reference conditions and talked about how important (or not) these are to specifying a variable area (VA) flow meter. Today, I’ll finish up my tips by reviewing fluid density and viscosity as well as accuracy.
Fluid: Density and viscosity
We always have questions about the fluid such as gas or liquid. What are the density and viscosity? Is it corrosive or opaque? If it a know fluid such as air, nitrogen, water, etc. The questions get much easier because the world has defined how these known fluids behave so we can easily determine density and viscosity for common fluids such as air, water, nitrogen, etc. Which leads to the questions as to why do we need to know fluid density and viscosity? Fluid density and viscosity are important because these two values allow us to select the right flow meter (meter size). We call this sizing. What is behind sizing? Briefly, performance data has been collected on all of the different meters we offer. We query the performance data and look for flow meters that fit the supplied process conditions (density and viscosity). Usually there are many flow meters that fit your conditions. From there it becomes a matter of preference, available options, price or accuracy. This leads me to my last topic on VA meters, which is accuracy. Read more…
3. Flow rate – minimum, maximum, normal
Variable area (VA) flow meters will respond like the canary in the mine when the air quality changes. If process conditions change there usually is an impact on flow rate. For example if back pressure changes on gas flows the float/flow will change just as changes in liquid viscosity will have a similar impact to the float/flow.
