Sunday, March 27, 2016

Operating Principles, Applications, and Advantages of Coriolis Mass Flowmeters

coriolis effect
Image courtesy of
Wikipedia

Oscillation without flow
(courtesy of Wikipedia)
The Coriolis effect acts on a medium that is accelerated through a rotating system, like a ball on a rotating disk its movement is straight, however, if the observer turns with the disk the ball is apparently deflected.

The same effect occurs with a water hose that rotates around its own axis, like a skipping rope. As soon as water flows through the host also twists. The twisting is stronger or weaker, depending on the amount of water flowing through the hose.

Oscillation with flow
(courtesy of Wikipedia)
The Coriolis effect also appears with an oscillating movement, and in a Coriolis flowmeter, two symmetric metal tubes are set vibrating by an internal driver coil. The tubes oscillate with a resonance frequency similarly to that of a tuning fork.

The oscillation is measured precisely by two pick-ups at the inlet and outlet sections. If liquids or gases flow through the tubes, a phase shift occurs the pickups measure the spatial and temporal displacement (twist). The amount of twist is proportional to the mass flow rate of fluid passing through the tubes. The greater the amount, the stronger the tubes oscillate outwards.

Finally, sensors and transmitters are used to measure the twist and create a linear flow signal as an output for monitoring and control.

Coriolis mass flowmeters are widely used throughout the process measurement and control field. Their basic operating principle, combined with modern sensor and signal processing technology,
Rotamass by Yokogawa
Yokogawa ROTAMASS
Coriolis Flowmeter
provide a list of positive aspects.
  • Directly measure mass flow rate based on the principle of measurement.
  • Measure the mass flow rate with high accuracy of ±0.1%.
  • Provide a wide usable measurement range.
  • Deliver density measurement based on oscillating frequency.
  • Not materially impacted by fluid viscosity or density.
Coriolis flowmeters also do not need straight pipe sections upstream or downstream of the flowmeter. They also have the ability to measure non-conductive fluids.

The video below is produced by Yokogawa, a world class manufacturer of industrial process measurement and control instrumentation. It provides a clear and insightful illustration of the Coriolis principle and how it is used to provide accurate mass flow measurement.