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By Jeff Postelwait
Online Editor
Two major applications for wireless sensing in manufacturing are process measurement and equipment condition monitoring (ECM). While wireless field transmitters for process measurement have been on the market for several years now, equipment condition monitoring systems have used wireless sensing only sparingly.
Today, critical baseload units are often large coal-fired units sized at 500 MW and higher. Problems or failures of critical bearings or shafts in such a large turbine-generator can take down the whole unit. Such large machines are equipped with wired sensors that feed a condition monitoring system. Engineers may have a history of equipment condition data and analysis. If the engineer is truly fortunate, collaboration can extend to an equipment monitoring service provided either by the turbine manufacturer or by a third-party firm providing ECM services.
Beyond the main turbine-generator, the equipment condition data usually becomes spottier. Problems with equipment can all cause unit outages or lost generating capacity though unit runbacks or firing limits. But few plants are equipped with condition monitoring systems for all of their equipment. Engineers must rely on manual and intermittent data collections and hope for the best.
Condition monitoring for rotating equipment is a decades-old field. The most basic practice is to take vibration measurements of machine shafts or bearing casings. The magnitude and phase relationships of this vibration are compared with historical values to infer changes in condition. The other major data inputs are lube oil analysis, motor electric current, infrared thermography and ultrasonic measurements.
The high cost of permanently mounted sensors and continuous monitoring systems has limited its penetration to only the most critical 1 percent to 5 percent of installed rotating equipment. Discrete manufacturing operations are even less likely to have installed continuous monitoring. Instead, common practice is to use hand-held systems to capture periodic vibration signatures.
New Wireless ECM Systems
Suppliers have introduced new products intended to improve this situation. The deployment of micro-generator energy harvesting for the first time in a wireless sensing application is an important development for condition monitoring. Besides being a natural fit, this combination enables simplified retrofit of new ECM applications on existing machines.
Honeywell introduced a wireless Equipment Health Monitor (EHM) for its OneWireless product portfolio. This offering used sets of wireless sensors, which are networked to a Honeywell OneWireless mesh network. The analytical capability is provided by a partnership between Honeywell and SKF, the well-known ECM supplier. Honeywell also assembled a "starter kit" for its solution, consisting of the sensors, gateways and software needed to monitor four machines. Besides adding wireless sensing, the EHM package enabled Honeywell to promote the IEEE 802.11 compatibility of its OneWireless infrastructure and the incremental value of that infrastructure once installed.
Data Deluge
What more should utilities be looking for as these types of systems reach the market? Besides getting data from sensors, condition monitoring requires analytics. When data sets arrive, the processes required can afford to be less than fully automated. However, with a much larger number of machines providing several equipment data sets each day, a deluge of data is created. This data deluge must be managed in order to extract valuable information.
ECM solutions should enable utilities to spend less time managing data and more time focusing on important findings that automated analytics uncover. Collaboration on data among plant personnel, in-house ECM experts, equipment suppliers and service firms will likely become an important future activity. The expansion of ECM brought about by wireless may enable structural changes in the business as well, since it may become possible and economical for many more people to collaborate and deliver value in this domain.
ECM in the Future Power Industry
Today's utility engineer may be responsible for performance of a 500 MW or 750 MW unit, where problems with any of roughly 50 rotating shafts located somewhere on the unit can affect unit availability. Tomorrow's utility engineer is going to confront an even greater challenge. For one thing, the low-cost baseload generation of future power markets will include far greater amounts of wind power.
North American utilities are now building wind generation on a much larger scale. In 2007 over 5,500 MW of new wind generating capacity was installed in North America. Wind power growth will present major challenges for equipment condition monitoring. The size of today's utility wind turbine is 3 MW to 5 MW, less than 1 percent the size of a baseload fossil unit. Utility-sized wind farms, then, consist of dozens or even hundreds of units. These units are located in remote areas that optimize high prevailing wind rather than easy access for engineers and maintenance crews.
Large wind farm operators will face the challenge of dealing with multiple generating equipment suppliers, which can create barriers to globally accessing real-time equipment condition information. Especially in a wind farm, this information is essential for improving operational performance. To succeed, utilities must be able to manage wide-area production networks.
The power grid will be developing into a much more complex system that includes many thousands of new and much smaller units along with traditional large generating units. Tomorrow's baseload generating capacity will include very large and very small units alike. This will make condition monitoring a greater challenge for utilities, who will rely on a much larger number of machines to deliver power (and profits) during peak hours.
Editor's Note: This article was adapted with permission from an article written for the September 2008 issue of Power Engineering magazine, by Harry Forbes, a senior analyst with ARC Advisory Group.
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