Coriolis Flow Meters
Coriolis Flowmeters, also known as simply coriolis meters, offer a number of practical advantages which make them an ideal choice for applications in a wide variety of industries. These advantages include superior accuracy, multi-parameter measurement capability, no straight run piping requirement, and the ability to measure mass flows directly with no external pressure or temperature compensation required.
There are many process flow measurements, such as those used in mixing and dosing applications in petrochem, or pharmaceutical, or the food & beverage industry, that require accurate mass flow readings. This can create challenges for older, traditional flow measurement technologies such as turbine or positive displacement which volumetric flow directly and may only infer mass flow. Coriolis flow meters measure mass directly without the need to take into account changes to media temperature, pressure and density as volumetric flow meters do. Moreover, most flowmeters are sensitive to turbulence, which means that a certain amount of straight, rigid pipe must be installed both upstream and downstream of the meter in order to reduce turbulence and accurately measure flow (Download PDF). Coriolis meters do not have this requirement. If necessary, an elbow or reducer bushing may be placed directly at the meter inlet with no impact on the meter’s accuracy.
Smartmeasurement’s ALCM Coriolis series are offered with the highest accuracies available in industry. Accuracy grades of 0.1, 0.15, 0.2 and 0.5% of reading are available. The ability to maintain these levels of mass flow accuracy regardless of media temperature, density or viscosity and then install the meter in areas with extremely tight space constraints and no available straight pipe runs makes the Coriolis meter a potential life saver for many applications where a traditional-technology flowmeters will not work.
Coriolis Flow Meter Operation
As fluids passes through oscillating parallel curved tubes, the time delay, or phase shift that occurs between the upstream and and downstream sides of the tubes is directly proportional to the mass flow rate. The frequency is directly proportional to the density of the flowing media. As flow passes an electromagnetic drive system causes the tubes to vibrate toward and away from each other at their resonant frequency caused by the tubes stiffness and their mass. A pair of Hall Effect sensors detect the potions of the tubes relative to one another at the inlet and outlet side of the parallel tubes. If no fluid is flowing through the tubes, they simply vibrate towards and away from each other in parallel and the outputs of the upstream and downstream sensors are in phase. However, as fluid begins to flow through the tubes, the Coriolis effect causes the downstream side of the loop to slightly lead the upstream side creating a slight twist on the tube. The twisting effect causes a phase shift, or time delay between the up and down stream sensors which is directly proportional to its mass flow. Inside of the meter’s display module, phase is converted to time and the time delay is then converted to a mass flow reading.
See Diagram Below:
SmartmeasurementTM offers a wide ranges of Coriolis tube geometries including the classic U shape employed by the ALCM-UT, the more popular Microbend geometry used by the ALCM-MB, the low-flow-optimized Delta, or triangle tube of the ALCM-DT, and the near straight tube geometry employed by the ALCM-ST.
Read about the other types of Flow meters: