Go with the flow – gas flow measurement
By H Springer, Mecosa and A Mangell, Bronkhorst UK
Electricity+Control, December 2013 (pages 14 - 17)
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Choosing a flowmeter for gas flow measurement can be a daunting task. Not only are there many manufacturers advertising their brands and types of flowmeters, but there are also many varying technologies available at significantly different cost structures. The outputs vary from local indication, through the standard 4 – 20 mA signal to advanced digital bus protocols.
Differential pressure (DP) is the dominant method of gas flow measurement and liquid flow measurement, although there are clear signs that other existing or evolving technologies such as coriolis, ultrasonic, vortex and thermal are growing, as considerations such as accuracy, reliability and lifecycle cost ascend the customer’s agenda.
Flow control experts tend to distinguish between ‘new technologies’ and ‘traditional technologies’, grouping coriolis, magnetic, ultrasonic and vortex flowmeters under the new technology flowmeter category, with methods such as differential pressure, turbine, positive displacement and variable area under the ‘old’.
Various specifying criteria like compatibility, repeatability, reliability, simplicity and purchase price dictate that the different types of new technology flowmeters and old technology flowmeters each have their own advocates and optimum applications.
Compatibility with existing meters, familiarity with a traditional technology and a low purchase price are not necessarily the most valid specifying criteria for many applications. New technology flowmeters offer increased levels of accuracy, fewer maintenance issues, impressive digital output capabilities and competitive lifecycle costs, which surely make them worthy of serious consideration.
- Accurate measurement of gas flow is critical in the operation and control of industrial and laboratory processes.
- New technology flowmeters offer increased levels of accuracy, which make them worthy of consideration.
- In the food and beverage sector, the chemical industry and in semiconductor fabrication, flowmeter accuracy is often the determining factor between optimum quality and reject products.