Application Cautions for Target Flow Meters
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Target Flow Meters Application Cautions for Target Flow Meters Be careful when operating target flow meters low in their flow range because accuracy can be compromised at these flow rates. Avoid abrasive fluids because the target can be damaged and measure inaccurately. Fluids that coat the target can cause it to become heavy, such that the force measurement can become inaccurate and unresponsive to flow changes. These flow meters should not be applied to slurries and high viscosity liquids. Calibration is an important part of ensuring accurate operation of target flow meters. Pressure effects, physical effects, and flow meter orientation can affect the zero adjustment of target flow meters. After calibrating the target flow meter (typically with weights), be sure to zero target flow meters after installation with a full pipe under no flow conditions to ensure compensation for these effects in the final installation. This procedure also compensates for the calibration shift that can occur when the orientation of the flow meter during calibration is different than its installed orientation. In general, in-situ zero adjustment should be performed after re-installing target flow meters. Operating a target flow meter above its maximum flow rate can cause the calibration to shift and potentially damage the suspension system of the flow meter. Note also that operating target flow meters continuously for extended periods of time can cause a mechanical shift to occur that can affect the zero because the target may not return to exactly the same position after being exposed to forces over time. Rapidly changing flow, such as slug flow conditions, two-phase flow, and start-up conditions (gas to liquid transitions), can similarly affect the mechanics of the target flow meter and hence its zero. Therefore, it is advisable to periodically verify the zero adjustment of target flow meters. |