I discovered a great article, The Signs of Failure, in the fall edition of Resource Engineering & Maintenance magazine. Emerson’s Dan Nower, a member of the Machinery Health Management team wrote the article.
Dan shares the thought that most rotating machinery failures give notice before they fail. This is not unlike those of us who ignore those funny noises coming from our cars, only to have the car breakdown in the most inopportune spot. Having the problem taken care of before the breakdown, would have saved a personal “unplanned shutdown”.
…more than 50 percent of industrial maintenance man-hours is spent fixing equipment after a failure has occurred, whereas less than 18 percent of the time is spent determining when equipment might fail and acting accordingly.
He highlights the way equipment monitoring has been done over the past 25 years. It’s based on maintenance technicians using handheld data collectors to periodically and manually collect vibration data on the equipment along the maintenance route. This data is then uploaded to a computer and available for analysis. This method can help identify:
…the earliest signs of bearing and gear wear, along with many other potential machine faults, and provides an indication of severity while the technician is still at the machine.
Some plants advance beyond this periodic, manual monitoring with continuous, online monitoring. Types of rotating equipment monitored include gas turbines, steam turbines, generators, compressors, fans, motors, and pumps. Vibration and temperature sensors provide information back to operators and maintenance technicians with indications of:
…changing vibration patterns and rising temperatures — sure signs of impending trouble.
Prioritization of the equipment monitored is important to focus the maintenance efforts and avoid unplanned shutdowns from critical machinery failure. Dan notes how machinery health management software:
…categorizes the significance of each machine in a production environment, focusing greater attention on those machines that would likely shut down all or a major section of the plant if they fail. Online monitoring assures that the condition of these machines is being assessed continuously.
By having a continuous history of data collected by the vibration and temperature sensors, the software can help predict when problems may occur based on the trajectory of the data. Early warning provides the maintenance team a chance to make the necessary repairs before greater damage occurs. Dan describes it as a:
…combination of machine health and process status/health gives operators much greater ability to recognize and manage controllable scenarios in order to avoid problems that might otherwise lead to degraded machine health.
One of the difficulties in monitoring some the rotating equipment was the process of wiring the sensors in place. Wireless vibration monitors, based on the IEC 62591 WirelessHART standard, are now available to eliminate some of the blind spots that currently exist.
Combining elements of protection monitoring, prediction monitoring, performance monitoring, and integration with the process automation systems provides the operations and maintenance teams the visibility to help maintain the health of the plant’s rotating equipment and to avoid unplanned shutdowns.