While it is clear that hot-wire anemometry is a traditional flow technology, thermal flowmeters fit some of the criteria for new-technology flowmeters. And recent technological advances are resulting in thermal meters that perform at a significantly higher level. If these technological developments continue, it may be necessary to reclassify them as new-technology meters.
* Variable Flows: Most variable area flowmeters are read manually. They have a float that rises in proportion to the force of the flow. A calibrated glass, metal, or plastic tube has markings that indicate flowrate.
Variable area flowmeters are mainly used where high accuracy is not required. They are valuable for a flow/no-flow reading and where a visual reading is all that is necessary. More recently, however, some suppliers have developed variable area meters with an output signal, making them more usable in a process environment.
Beyond the Top 10
In addition to these 10 technologies, there are several others including target meters. More exciting is the development of what appear to be genuinely new flow technologies. One is the Sonartrac flowmeter from CiDRA Corp., which uses sonar techniques to measure volumetric flow. The meter senses pressures on a pipe caused by naturally occurring vortex-like disturbances in turbulent flows. It is intended for industrial applications.
Photon Control of British Columbia takes a different approach. This company is developing a series of optical flowmeters for the oil & gas industry. Like most new-technology flowmeters, these optical meters have no moving parts and are non-invasive. The company has licensed technology from TransCanada Pipelines to develop optical flowmeters for the energy sector.
It is very unusual for a new flowmeter technology to come along. All of a sudden, we seem to be blessed with several new technologies at once. This is partly a result of the fact that, for the past several years, companies have been able to focus on something other than fieldbus. It is also because technology continues to evolve and grow, and inventive minds are continuing to focus on new ways to measure flow.
Jesse Yoder, Ph.D., is president of Flow Research, Wakefield, Mass. He has 16 years of experience as an analyst and writer in process control. Yoder specializes in flowmeters and other field devices, including level, pressure, and temperature products. He has written 60 market research studies in industrial automation and process control, has published numerous journal articles, and is the author of the Worldflow Handbook, which includes a detailed guide to flowmeter selection. He also is the author of The World Market for Flowmeters (published in February 2003), a market study that includes all 10 flow technologies. He may be reached at 781/245-3200 or email@example.com.