Mobrey

SLURRY CHARACTERISTICSThe relationship between the measurement of ultrasonic attenuation and the percentage solids of a particular slurrytype is dependent on the density of the slurry particles and their average size distribution. This is known fromexperience for most slurry types, and is expressed as a number, which is the ultrasonic attenuation in deciBels (dB),per mm gap between sensor faces, per one percent suspended solids.The relationship between attenuation and suspended solids isshown graphically in Figure 2. Calibration of the unit involvesadjustment of the zero point, by setting up the sensors inclean liquid (supernatant), and then setting the slope of thestraight line graph, either according to past data or from sitesamples.In the memory of the MSM400 there is information on variousslurry types, to enable simple initial set-up. More accurateadjustment can then be made once site samples have beentaken.Attenuation(dB)Zero RefSlopeFigure 2 :% SolidsUltrasonic Attenuation versusSuspended solidsCalibration:The Mobrey experience with using ultrasonics for suspended solids monitoring has been developed over 25 years.Calibration systems for the MSM400 use this experience, allowing the plant operator to choose whether to set up theunit based on Mobrey site and slurry experience, or whether to take site samples to fine tune that data to suit thespecific site conditions. The MSM400 is versatile enough to allow simple or complex calibrations.6IP258