Some years ago, I noted with interest that the US Navy could tell the difference between Soviet submarines based, in part, on the different sounds the subs propellers made. In fact, a large Japanese heavy industrial and electronics company was at one time in hot water with the U.S. Government for selling the Soviet Navy sophisticated machining tools that could reduce the differences between propellers, and thus reduce our ability to tell one Soviet submarine from another.

Back then, in the mid-1980s, I told a friend of mine and colleague, ultrasonic flowmeter engineer Al Brown, that I thought we would eventually get a bunch of sophisticated new signal processing technology from the defense industries, and that it would mean a new day for flowmetering. We spent some idle time speculating on what that new day might turn out to look like.

Now we are beginning to find out.

To the best of my knowledge, there has not been a completely new industrial flowmetering principle produced since the invention of the Coriolis mass flowmeter. That means that for more than 30 years, all we”ve done is enhance existing technologies.

To a certain extent, it says a lot about the inventiveness of flowmeter manufacturers when one of the most common flowmeters in existence is the Woltman-style turbine flowmeter, which was invented in 1790. Even the newest flowmeters are incredibly old when compared to the lifecycle of electronic components, or even most consumer goods. Product lifecycle in many industries is measured in months or years, not decades. Technology lifecycles are usually much longer. The basic building block of semiconductors, for example, is still the transistor, although a computer from 1970 is virtually unrecognizable next to a computer from 2003. A magnetic, turbine, or positive displacement flowmeter from 1970 looks and operates much the same way as a current model. Techniques in flow measurement are developed very slowly, it appears.
It has been so long since a new technique was produced that when one pops up onto the screen, it is instantly visible.

Finally, I”ve seen a new one.

Suppose you took a passive sonar array, much like the ones that a submarine uses, and you clamped it onto the outside of a full pipe. What would you try to measure inside the pipe? What would listening to the inside of the pipe tell you?

Inside any full pipe with a Reynolds number higher than about 2500, there is turbulence. This turbulence is not random, and is made up of lots of eddies and vortex-like structures in the fluid that form and decay fairly quickly. These vortex structures occur in coherent series and can be tracked. These structures propagate down the pipe at the velocity of the fluid in the pipe. In the same way that the Von Karmann vortices formed by the bluff body in a vortex-shedding flowmeter, these turbulence structures cause pressure changes in the pipe that can be detected by sensors.

So measuring the pressure changes caused by these vortical structures inside the pipe from the outside can be used to determine the velocity of the fluid, just like a submarines sonar array is used to determine the speed and direction of another submarine.

Most of the horsepower for this determination, of course, is in the signal processing algorithms applied to the signal picked up from listening to the inside of the pipe. Remember the US Navy and the Soviet submarines? At the height of the Cold War, the necessary signal processing technologies required not only trained operators but also large and dedicated computer hardware and software systems. Twenty-odd years later, microprocessors and DSP technologies have matured to the point that it is possible to consider producing a commercial process instrument that will use a measurement array with highly sophisticated signal processing to measure flow.

Enter the CiDRA Corporation. Theyve produced just such an instrument, and in tests run at Alden Flow Laboratory in Massachusetts, their flowmeter has performed at the 0.5 percent of rate accuracy level.

CiDRA says theyve done more than 60 beta test installations in many different industries and applications, including air and gas flows, and laboratory results are replicating in the field. The smallest prototype flowmeter they have produced is a 1 unit, and the largest is a 60 unit. All of these are clamped on the outside of the pipe, and completely noninvasive. Bidirectional flow is standard, since the technology provides not only velocity but also direction information.

CiDRA chief technology officer Daniel Gysling says that the first release of the product will have standard sizes of 4, 6, 8, 10 and 12 with other sizes available on special order.

It will be interesting to watch what the actual performance and industry acceptance of this completely new technology for measuring flow will be. The Coriolis mass flowmeter grew to be a $400 million per year market in over 30 years, and is still being used in new applications. Its market is not saturated even now.

What will the market for this new technology flowmeter be?

Walt Boyes is a is a principal in Spitzer and Boyes LLC, offering engineering, expert witness, development, marketing, and distribution consulting for manufacturing and automation companies.