What is a Coriolis flowmeter and where is it used
A Coriolis meter is a mass flow meter that measures the mass flow rate of a fluid through a tube. These meters are widely used in the offshore oil and gas industry. A Coriolis flowmeter won’t be affected by temperature, density, viscosity, and conductivity while most of the other flow meters are affected by this. This meter measures the mass and density of the fluid by Coriolis effect. A Coriolis flowmeter is capable to measure the fluid mass for a wide range of temperatures with high accuracy. Due to its flow design, it can be used to measure viscous and non-conductive fluids which are very difficult by other flow meters. By using this single flow meter we can measure mass flow, volume flow, density, and temperature. Coriolis force can be explained as if a moving mass exposed to an oscillation that is perpendicular to its moving direction then Coriolis force will be created and this force is dependent on the mass flow. The measurement of this flow meter is depended on the generation of the Coriolis force. The Coriolis flow will be generated if both the translational and rotational movements will occur simultaneously. The amplitude of this force is depended on the moving mass and velocity
How Coriolis meters are constructed and how does it work
The major components of Coriolis flowmeters are the sensor and a transmitter. The sensor in the Coriolis flow meter is a flow tube assembly. The sensor is connected to the electronic assembly with the help of a cable. The flow tubes which is used are oscillating tubes and the tubes are mostly U shaped. So when the fluid flows through the oscillating tubes a force is created and it is called the Coriolis force and this force will be measured by the sensor. The flow tube will get the oscillation energy from the electronics
The fluid which is to be measured will flow through the U shaped tube and the tube is made to vibrate perpendicular to the fluid flow. So the fluid that flows through the tube will be in contact with this vibration and this would make the fluid twist. So if the twist angle is high then the flow would be good. If there is no flow in the meter but has fluid in the tube then the inlet and outlet sides of the tubes would experience the same force and that would be in the same direction. But in case of flow through the tube then there would be acceleration or change in direction in the inlet side and deceleration in the outlet side. This will create a twist in the flow tubes and this would make the inlet to pick off earlier than the outlet and the magnitude of the time delay between the outlet and inlet sides of the tube is directly proportional to the mass flow of the fluid.
How does Coriolis flowmeter measures density
The fluid density can be measured by checking the natural frequency changes of the oscillation of the tube. The natural frequency is depended on the mass of the tube and the fluid. So when the total mass increases the natural frequency reduces. So the total mass would only change due to the change in fluid density because the mass of the tube is constant and the fluid volume in the flow tube is also constant.
How to install a Coriolis flowmeter and what are the factors that must be considered while doing it
We must make sure that the flow meter is installed with proper upstream and downstream straight pipework. These flow meters are not affected by installation effects but we must consider the fact that it must not be installed close to a valve that opens and closes regularly because it would cause pulsation and vibration in the flow. The flow meter could be affected by the stress from the adjoining pipework, so in order to avoid this, the flow meter must be fixed properly to the pipeline. It can be done by clamping the adjoining pipework properly to the upstream and downstream of the meter. Backpressure must be kept at sufficient levels to prevent cavitation.
How to select a Coriolis flowmeter
- It must be selected according to the operating temperature range that is required for the application
- It should be selected according to the operating pressure range
- It must be selected according to the rate of changes in the flow
- Over range must be considered while choosing this flow meter, over range can cause damages to the meter.
- The flow tubes could be damaged in case of debris, so it must be considered while selecting it
- It must be selected according to the flow range
What are the advantages of Coriolis flowmeter
- Highly accurate
- It can directly measure mass with no re-constraints
- Maintenance is low
- It can be used to measure density, temperature, mass, and volumetric flow
- This meter is capable to measure the mass flow rate, volumetric flow rate, and density and temperature of the fluid.
- This meter can be used to measure slurries and Newtonian fluids
- No installation constraints regarding this meter
- This meter is capable to measure the mass flow rate itself without the help of other instruments
What are the disadvantages of Coriolis flowmeter
- Initial capital is very high
- It cannot be used for gas measurements
- High-pressure drop for certain model
- This flow meter can’t be used for larger pipelines
What are the applications of Coriolis flowmeter
- Oil and gas
- Food and beverage
- It is used for process control
- Container filling