There’s nothing new under the sun.
A recent innovation in flow measurement is the radar Doppler velocimeter used to measure open channel flow — i.e., Marsh-McBirney’s Flo-Dar, which was introduced in the mid-1990s. Before that, MicroMotion introduced the Coriolis Mass Flow Meter in the 1970s. Ultrasonic transit time flowmeters were developed in the 1970s — over 30 years ago. Even multivariable smart transmitters have been around since the early 1980s, applied by Honeywell to differential pressure flow elements. Magnetic flowmeters were first developed in the 1940s, fluidic flowmeters in the 1920s, vortex and vortex precession flowmeters in the 1950s, and thermal flowmeters have been around for years as well.
Flow measurement technology doesn’t change very often.
What is changing, and what might serve as a better yardstick to measure the world of flow measurement, is the way flowmeters and other field sensors are used.
Early flowmeters were stand-alone and were used to measure, totalize and record flow quantity locally. The first turbine meters were used to measure the flow of water in a utility system. One of the reasons for the continuing widespread use of positive displacement flowmeters is that they are extremely accurate over wide flow ranges and can be used for custody transfer of expensive fluids. Orifice plates, and other primary devices, continue to be used because of improvements made in differential pressure transmitter technology. While the flow element itself hasn’t changed since the 1930s, the transmitter that computes and relays the flow signal has undergone a revolution from the 1960s to the 1990s and today.
While flowmeters such as laminar flow elements have essentially not changed since the 1950s, the differential pressure flow transmitter certainly has, as reflected by the data and analysis presented in The Consumer Guide to Differential Pressure Flow Transmitters (availableat www.isa.org). These changes can be more significant to the measurement of flow than the invention of a completely new primary device.
In ultrasonic flowmeters, the multipath flowmeter was produced over 30 years ago. It was not until the 1990s that microprocessor-based transmitters and signal processing algorithms made it possible to produce ultrasonic transit time flowmeters accurate enough to replace positive displacement flowmeters for oilfield custody transfer.
The next improvement may be to reduce manufacturing cost so that ultrasonic transit time flowmeters can be made inexpensively enough to compete with low cost flowmeters like turbines and paddlewheels. Already one manufacturer (Dynasonics) produces an ultrasonic flowmeter for under $1,000.
Like many other field sensors, flowmeters are no longer exclusively stand-alone devices. Rather, they can be nodes on a network. The network can be analog, or it can be digital. It can be a LAN or it can be a WAN or an Enterprise-Wide Network. Looking at flowmeters in this way is one of the most important new things to come along in the past 10 years.
Look at what this means for municipal utilities. They continue to use nutating disc and rotary piston positive displacement meters with mechanical registers. Why? Because they work for 20 years, without maintenance, are inexpensive and do not lose their accumulated total in the event of a power loss. But most municipalities are installing automated meter reading (AMR) systems that make each of those “old technology” flowmeters a key component in the Enterprise-Wide WAN that makes up the modern water distribution system.
Similarly, in industrial service it is still important to select the flowmeter most suited to the service — not the fanciest, newest technology around. Even a paddlewheel flowsensor can be enabled as a wireless embedded Web server, using technology from Xsilogy or Ipsil, among others.
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.