During the 1980s, online monitoring meant using expensive, permanently installed protection systems to detect the onset of catastrophic failures, sound alarms and shut down equipment to protect it (and the surrounding area) from consequential damage. The systems were typically cost-effective only for large, costly, complex turbines and generators.
Since then, lower-cost systems capable of detecting impending failures have slowly gained acceptance, driven by advances in networks, integration with control and information systems, stronger diagnostic and decision capabilities, innovative sensor technologies, lower costs and above all, powerful pressures for higher plant performance and maintenance productivity.
Modern systems are being applied to equipment ranging from those complex turbines to production machinery, compressed air systems, electrical cabinets, boilers, fans, pumps and valves. They’re solving chronic reliability problems, streamlining maintenance labor and inventories, updating ancient equipment to compete in the 21st century and helping even the most advanced facilities reach higher levels of reliability.
“We’ve had a long history of continuous improvement — 2005 set several records,” says Scott Brown, reliability engineer at Vectren Power Supply’s Evansville, Ind., plant. “We’ve got a 92% operating requirement, and when you’re that high, you’ve got to look at doing new and different things. This is a tool to get us to the next level. And the cost isn’t prohibitive — payback is less than one year based on PMs alone.”
As opposed to portable
Most plants perform condition monitoring by sampling equipment vibration, temperatures, oil, ultrasonic emissions or electric power parameters at intervals using portable equipment. This approach can be very effective, but online monitoring may be better in certain applications (see sidebar, “Online advantages”).
“Permanently installed, continuous monitoring systems that are intelligent, scalable, support a distributed architecture, and are based on open industry standard networks represent the most significant development in condition monitoring over the last several years,” says Tom Alford, product marketing manager, condition monitoring hardware, Rockwell Automation (www.ra.rockwell.com). Plants can deploy intelligent monitoring systems that meet their specific needs and are easily installed, integrated and maintained because they leverage existing plant networks.
Still, many plants have had a tough time making a business case for online systems.
Although they’re becoming less expensive due to advances in sensor and system technology, increasing sales volumes and competition among suppliers, they typically still bear a higher initial cost per point than mobile equipment, which many facilities already own. How do you explain that your investment in mobile technology is inadequate and gathering dust for lack of manpower?
Talk about manpower. It’s obvious that done right, many hours are invested in doing rounds.
So many plants don’t get around to doing it right, even for well-established PdM programs like infrared and vibration. But even partial discharge monitoring is increasingly going online, says Greg Stone, dielectrics engineer, Iris Power Engineering (www.irispowr.com).
On motors at 4 kV and higher, “80% to 90% of stator problems that lead to rewinds start as sparking in the insulation,” Stone says. “Detecting those usually gives about a two-year heads-up.” Technically, online monitoring isn’t needed because you could test every six months or so with portable equipment. “Continuous monitoring is done as a matter of convenience,” he says. “Other plant priorities too often displace walkarounds. It’s not unusual to see measurements missed for two or three years.”
But plans to switch to online may run into cultural resistance. For example, many plants have adopted an approach that uses operators to collect data, and machinery/maintenance specialists to interpret it. “These companies want their operators to get out in the plant, take ownership and actively participate by noticing asset conditions as they make their daily rounds,” says Steve Sabin, editor of General Electric’s ORBIT magazine (www.bently.com/orbit.htm). “Some do not want to fully automate data collection because it would tend to disengage these operators.”
However you slice it, today’s pressures for higher productivity mean predictive maintenance must become more prevalent. “More and more companies will be adopting predictive maintenance and using it as the key element to drive their maintenance programs,” says Jack Nicholas, senior technical advisor, Allied Reliability (www.alliedreliability.com). “Instead of the individual going out to get the data, the data will come to the individual. That will be a much more efficient, effective way to do it.”
To protect and serve
Developments in online technologies are exciting, but some of the most compelling reasons to implement them focus on people. The first is safety. “It can be dangerous or impossible to collect data from some assets,” says Sabin. Many assets are difficult and unsafe to access, particularly when operating.
“The paper and steel industries are looking at $20,000 to $25,000 per hour of downtime, and there are fire hazard and safety issues,” says Ed Bondoc, product manager, surveillance systems for SKF Reliability Systems (www.skf.com). “In some countries, you are not allowed to walk under a machine. Essentially, you are not allowed to do rounds.”