CIDRA
Corporation Develops New Sonar Flow Technology
It
isn’t very often that a new type of flowmeter comes along. CiDRA
Corporation of Wallingford, Connecticut is in the process of introducing a
flowmeter that has all the earmarks of being a genuinely new flowmeter
technology. The new meter is called the CiDRA SONARtrac™ flowmeter, and
it uses array processing technology to generate a volumetric flowrate in
closed pipes.
CiDRA was
founded in 1997 as a company that combined industrial and optical skills
to deliver real time process monitoring to the downhole oil & gas
market. The downhole oil & gas business unit was sold to Weatherford
in November 2001. CiDRA’s
target markets include industrial process control systems and scientific,
laboratory, and manufacturing instruments. The company has 135 employees.
CiDRA’s
SONARtrac™ flowmeter works by taking advantage of naturally occurring
vortex-like disturbances that occur in turbulent pipe flows. Clamp-on
strain based sensors embedded in the sensor portion of the flowmeter sense
the pressure created by these vortices on the pipe wall. The array
processing technology comes in because these vortices occur in coherent
series, somewhat like the cars in a train. By analyzing the output from
the SONARtrac sensor array, the flowmeter derives the volumetric flowrate.
At its core, the method is similar to the way in which a ship uses sonar
technology to determine the speed and direction of an approaching object,
by interpreting the underwater sound field.
One of the most appealing features of this new flowmeter is it mounts on the outside of the pipe. While this clamp-on feature is similar to an ultrasonic meter, the sonar meter works on fundamentally different principles. SONARtrac meters use a series of ring-like sensors banded on to the outside of the pipe. Pressure sensors contained in the rings are sensitive to the strain in the pipe wall caused by the turbulent vortices, and this is the data used to compute flowrate.
Some
people may compare this flowmeter to an ultrasonic meter. However, it
measures pressure waves at vastly lower frequencies than ultrasonic
meters, and it does not send out a signal through the flow as ultrasonic
meters do. It may also be compared to a vortex flowmeter, since it
analyzes trains of vortex-like disturbances in the flow to determine
flowrate. However, unlike a vortex meter, SONARtrac does not require
inserting anything into the flowstream to generate these vortices;
instead, it relies on vortices that naturally occur in turbulent flow.
CiDRA currently has Beta site installations at a number of industrial process plants, including pulp & paper and chemical. Quoted accuracies are in the 0.5% range, although these have yet to be verified by independent testing labs. CiDRA projects that commercial units will be available in the second half of 2003.