Presentation of the METAS pipe viscometer

Calibration of flow devices is important in several areas of pharmaceutical, flow chemistry and HPLC applications where dosage of process liquids or accurate measurement of the flow rate are important. The process-oriented liquid itself might influence the performance of the flow device. Therefore, the calibration of the flow meter or microfluidic device with the process-oriented liquid is important and the simultaneous determination of the dynamic viscosity under flow conditions is a valuable information for viscosity dependent flow metering methods or other process parameters. To offer the simultaneous calibration of the dynamic viscosity of the process-oriented liquid at the corresponding flowrate, METAS has built a pipe viscometer for the traceable in-line measurement of the dynamic viscosity in the current flow facilities for low flow rates from 1  L/min to 150 mL/min and pressure drops up to 10 bar. To guarantee the tracability, the most challenging part remain the determination of the inner diameter of the micro tube. This can be determined by measuring the pressure drop as a function of flow rate and applying the law of Hagen-Poiseuille with a well known liquid (water) or perform the measurements with the  -CT at METAS, which determines the inner diameter by x-ray diffraction. The setup of the facility, the uncertainty calculation for the in-line measurement of the dynamic viscosity and the validation measurements are discussed in this paper.