Understanding Coriolis Flow Meters: How They Work and Why They’re Important

If you work in the fluid handling industry, you’ve likely heard of Coriolis flow meters. These innovative devices have been used to measure the Mass flow rate of liquids and gasses in a wide range of applications for decades. 

This article will explore the science behind Coriolis flow meters, how they work, and why they’re important.

What are Coriolis Flow Meters?

Coriolis flow meters are devices used to measure the mass flow rate of fluids in a closed system. They rely on the Coriolis effect, which is the apparent deflection of moving objects when they are viewed from a rotating reference frame. Coriolis flow meters consist of two parallel  flow tubes  for redundancy, a drive coil, and two or more sense coils. As fluid flows through the flow tubes, it is subjected to a sinusoidal motion induced by the drive coil, and the sense coils detect the resulting Coriolis force.

How do Coriolis Flow Meters work?

Coriolis flow meters work by inducing a sinusoidal motion in the flow tubes, causing the fluid to oscillate. As the fluid oscillates, it experiences a Coriolis force that causes it to twist and deform. The degree of twist and deformation is directly proportional to the mass flow rate of the fluid. The sense coils detect the resulting motion of the flow tubes and measure the phase shift between the drive signal and the motion of the fluid. By measuring this phase shift, the Coriolis flow meter can accurately determine the mass flow rate of the fluid.

Advantages of Coriolis Flow Meters

Coriolis flow meters offer some advantages over other flow measurement technologies:

1. They can measure the mass flow rate of fluids directly without additional density or temperature or pressure measurements.
2. Unlike most flow meters, there are no straight run requirements which means it can be installed right after bends, elbows, other equipment, etc.
3. They are highly accurate and can measure flow rates with an error of less than 0.1%.
4. They are insensitive to changes in fluid density, viscosity, and temperature, making them suitable for use with a wide range of fluids.
5. They are robust and reliable, with no moving parts that can wear out or break down.

Applications of Coriolis Flow Meters

Coriolis flow meters are used in many applications in the fluid handling industry. Some of the most common applications include:

• Chemical and petrochemical processing
• Food and beverage production
• Pharmaceutical manufacturing
• Oil and gas production
• Water and wastewater treatment
• Power generation

Types of Coriolis Flow Meters

There are two main types of Coriolis flow meters: straight tubes and curvature tubes of various shapes to avoid patent infringements, the most common being a U tube developed by MicroMotion. . Straight tube Coriolis flow meters are used for better pressure drops while the curve tubes used in 95% of all coriolis meters have better rangeability and slightly higher pressure drops..Curve tubes Coriolis flow meters can also provide redundancy and increased accuracy.

Factors to consider when selecting a Coriolis Flow Meter

When selecting a Coriolis flow meter, there are several factors to consider. These include:

• Flow rate range
• Fluid type
• Allowable pressure drop for the application
• Pressure and temperature range
• Accuracy requirements
• Material

Coriolis Flow Meters: Installation and maintenance 

Coriolis flow meters are relatively easy to install and require minimal maintenance. During installation, it is important to ensure that the flow meter is properly grounded and the flow tube is oriented correctly. It is also important to ensure the flow meter is installed in a location free from vibration and other external disturbances.

Maintenance of Coriolis flow meters typically involves periodic cleaning of the flow tube to remove any buildup of debris or contaminants. This can be done using a cleaning solution and a soft-bristled brush. Ensuring the flow meter is calibrated regularly to maintain accuracy is also important.

Coriolis Flow Meter challenges

While Coriolis flow meters offer several advantages over other flow measurement technologies, they also face several challenges. One of the biggest challenges is their relatively high cost compared to other types of flow meters. However when compared with mass flow output where other technologies require pressure, temperature, density and flow computers to obtain mass flow the overall costs are actually cheaper. If the user is only interested in uncompensated volumetric output, then yes it can be more expensive. The fluid must be clean with no gas, bubbles or particles present, if not air eliminators to knock out any gasses or bubbles and strainers (filters) to eliminate particles . 

Comparison with other flow measurement technologies

Coriolis flow meters are just one of several used in the fluid handling industry. Other common types of flow meters include:

• Differential pressure flow meters
• Magnetic flow meters
• Ultrasonic flow meters
• Turbine flow meters
• Positive Displacement
• Vortex
• Variable Area

Each flow meter type has its advantages and disadvantages, and the choice of flow meter depends on the specific application requirements.

Future of Coriolis Flow Meters

Coriolis flow meters are a mature technology that has been in use for several decades. However, ongoing developments in materials science and electronics are leading to improvements in the performance and cost of Coriolis flow meters. As a result, they are likely to continue to be an important technology for measuring fluid flow rates in a wide range of applications.

FAQs

Conclusion

Coriolis flow meters are important for measuring fluid mass flow rates in various applications. They offer several advantages over other flow measurement technologies, including high accuracy, direct mass flow rate measurement, and robustness. While they face several challenges, ongoing developments in materials science and electronics are expected to lead to further improvements in their performance and cost.