How Does a Coriolis Flow Meter Work?
A Coriolis mass flow meter measures mass through inertia. Liquid or a dense gas flows through a tube which is vibrated by a small actuator. This acceleration produces a measurable twisting force on the tube proportional to the mass. More sophisticated Coriolis meters employ dual curved tubes for higher sensitivity and lower pressure drop.
In this article the design and evolution of the Coriolis flow meter is explained in more details.
Coriolis meters, while considered the most accurate flow meters, are susceptible to errors when bubbles are present in the liquid. The bubbles can create “splashing” within the tube, generate noise, and change the energy needed for tube vibration. Large cavities increase the energy needed for tube vibration inordinately and can lead to complete failure.
Common Applications for Coriolis Flow Meters
Coriolis mass flow meters are used predominately in scientific applications where they measure both corrosive and clean gases and liquids. They are also used in:
- Pulp and paper processing
- Petroleum and oil
- Chemical processing
- Wastewater handling
Learn more about Coriolis meters and its applications.
How to Install a Coriolis Flow Meter
A Coriolis flow meter should be installed so that it will remain full of liquid and so air cannot get trapped inside the tubes. In sanitary installations, the meter must also drain completely. The most desirable installation is vertical pipes with upward flow. Horizontal lines are acceptable, but it is not recommended to install a Coriolis flow meter in vertical pipes with a downward flow.
In newer Coriolis designs, normal pipe vibration should not affect the performance of the Coriolis meter if the process piping properly supports it. No special supports or pads are needed for the flow tube, but standard piping supports should be located on either side of the meter. If the installation instructions require special hardware or support, the particular meter design is likely to be sensitive to vibration, and the pulsation dampeners, flexible connectors, and mounting/clamping attachments recommended by the manufacturer should be installed carefully.
If air bubbles are likely to be present in the process fluid, it is recommended to install an air release upstream of the meter. It is also recommended to install (upstream of the meter) strainers, filters, or air/vapor eliminators as required to remove all undesirable secondary phases. Control valves should be installed downstream of the meter to increase the back-pressure on the meter and lower the probability of cavitation or flashing.
How to Calibrate Your Coriolis Flow Meter
In-line calibration (for ISO 9000 verification) of Coriolis flow meters consists of comparing the output of the meter against a reference standard of higher accuracy, such as a dead-weight calibrated weigh tank. Coriolis flow meters that need to be calibrated in-line must be provided with a block and bypass valves so that the reference standard (master) meter can be installed and disconnected without interrupting the process.
In less critical installations where weigh tanks are not used, a master meter, such as another Coriolis or a turbine meter calibrated at a flow laboratory, can be used to calibrate the flow meter. When a volumetric reference is used in calibrating a mass flow meter, the fluid density must be very precisely determined.
Click here to learn more about the accuracy of the corioliss mass flow meters.