Drilling fluid, or ‘mud’, is used to remove well cuttings, control the formation pressures, maintain wellbore stability and provide cooling and lubrication to the drill bits, throughout the process of drilling a well. Accurate measurement of drilling mud flow is critical to the efficiency of the drilling process, and the measurement must tolerate the density changes of the drilling mud, and occasional voids and gas bubbles. Subsequently, during casing operations, cement is used to fix the steel casing pipes in place, and cement flow and density measurement is essential to control the process. KROHNE OPTIMASS mass flowmeters are typically used for both these measurements, as the straight tube design tolerates the harsh conditions and abrasion produced by the drilling mud and cement flows. They also tolerate the high pressures, measure mass flow despite the fluid density changes, and manage the presence of occasional gas bubbles, using the specially developed Entrained Gas Management (EGM) feature.