by Matt Migliore
The days of mechanical-movement diaphragm switches and gauges may officially be in the rear-view mirror of the pressure industry, as a new breed of digital sensing and transmitter technologies emerges on the market. And while pressure switches remain a valuable solution for certain applications, the combination pressure sensor and transmitter is, by most accounts, showing a significant spike in demand as end-users are attracted by the energy savings opportunities and added capability of newer high-tech pressure measurement solutions.
Technology & Applications
According to Craig Martin, a product manager for pressure systems manufacturer Dwyer Instruments (www.dwyer-inst.com), piezoresistive, capacitive, and, to a lesser extent, Hall-effect sensors are the leading demand drivers for pressure sensing instruments today. Piezoresistive sensors are generally specified down to five inches, while capacitive sensors are capable of supporting applications down to one-tenth of an inch.
From an application perspective, Martin says stricter environmental and energy requirements are pushing users away from mechanical pressure sensing systems toward higher-end digital solutions that offer improved accuracy and reliability. He says the big markets Dwyer serves include pharmaceutical, semiconductor, and building monitoring, where pressure systems are primarily used for exhaust, room and building pressure, and filtration monitoring in cleanroom and general industrial environments.
Other industries where pressure technology is in particularly high demand include oil & gas, refining, chemical, and power. According to "The World Market for Pressure Transmitters, 2nd Edition," a study published by Flow Research Inc. (www.flowresearch.com), the ramping of efforts to find new supplies of oil and gas to support growing demand worldwide is a strong driver of pressure technology uptake.
Flow Research also sees growth in alternative fuels and steam flow measurement as positives for pressure technology. "Certainly the area of renewable energy is one that will require pressure measurement; an ethanol plant is a type of chemical plant, so pressure measurements are necessary there," says Jesse Yoder, president of Flow Research. "Another area is steam flow measurement, where differential pressure and multivariable pressure transmitters are used with primary elements to determine steam flow."
Added Features, Lower Prices
Advances in technology have made digital pressure transmitters more accurate and reliable in recent years, and support for leading communication protocols, such as HART, FOUNDATION fieldbus, and PROFIBUS, are giving end-users added functionality for plugging their pressure measurement systems into larger process monitoring platforms. At the same time, pressure transmitter prices are now falling below $100, making it easier for end-users to make a case for the added functionality of a digital solution against the up-front cost savings of a $30-$40 DP switch.
According to Martin, in many cases a DP transmitter integrated with a variable frequency drive (VFD) or a programmable logic controller (PLC) produces long-term efficiencies well above and beyond the up-front cost savings of a DP switch. However, Martin acknowledges there are certain applications where a DP switch is a better fit than a combo DP transmitter/VFD or PLC system. For example, he says a switch remains a good safety solution for high- or low-point shutdown to avoid problems that might occur if the process continues above a pre-determined upper- or lower-level threshold in a given application.
Selection Strategy
When evaluating pressure technologies, Martin says users must first know the pressure ranges of the application under consideration. In addition, he says it is important to determine whether the application calls for simple visual pressure monitoring or if it will ultimately require integration with a larger process monitoring system. "The key [to evaluating pressure technology] is to know what kind of benefits you’re looking for," says Martin.
According to Flow Research’s Yoder, the key characteristics users should be looking for in new pressure technologies are high accuracy, reliability, diagnostic capability, and support for communication protocols.
The Future
Going forward, Martin says pressure technology users can expect a continuing trend toward lower pressures and higher accuracies. More specifically, he expects the DP transmitter market will increasingly move from analog calibration to digital pushbutton calibration. Martin says, whereas the internal circuitry of analog systems require users to fiddle with turn pots and/or potentiometers to calibrate the device, Dwyer offers systems with digital internals that enable users to calibrate the device with a single touch of a finger. "Digital pushbutton calibration capability is definitely a trend for the future in DP transmitter technology, as well as in instrumentation and control systems in general," says Martin.
Dwyer is now offering digital pushbutton calibration with some of its pressure transmitters, and Martin says it is working to standardize its entire product line with pushbutton calibration capability. On the high end, he says Dwyer’s pushbutton calibration includes a digital display with menu options, while lower-end pressure transmitters offer a simplified approach to pushbutton calibration without the display and menus.
According to Flow Research’s Yoder, pressure technology users should also keep an eye on the wireless technologies that are now beginning to come to market. Ultimately, he says wireless capability should offer users new opportunities to take advantage of the added intelligence and diagnostic features of digital pressure measurement devices.
Matt Migliore is the editor of Flow Control magazine. He can be reached at [email protected].
For more information on "The World Market for Pressure Transmitters, 2nd Edition," visit www.worldpressure.com.
