The goal of condition monitoring and evaluation activities is to identify problems, or potential problems, in operating machinery and systems early enough that proper corrective action can be taken with minimal to no impact on productivity. 

Getting to the correct intervals for vibration-based condition monitoring and evaluation activities has been one of the biggest challenges that the industry has faced.  No single definitive guidance source exists.  Historically, when portable vibration monitoring was in its infancy, data was collected using instruments the size of a sewing machine.  These were very cumbersome instruments that typically needed to be plugged in for power and had no internal memory.  They either provided results with gauges or a similarly sized x-y chart plotter.  Data was typically collected no more frequently than quarterly and often only done when something “sounded funny” or as a dedicated activity before an outage or maintenance availability.  But these results were more of a “snapshot in time” than something that could be used for proper planning purposes.

Technology, by the late 1980s, became smaller, battery-powered, and significantly more capable of collecting higher-resolution data, especially when matched with desktop analytical software.  Programs started out collecting data quarterly.  But often machines that “looked good” at the beginning of a quarterly cycle failed before the end of that same cycle.  The convenience that came from the smaller, more capable instrumentation, made it much more practical to move from quarterly data collection to monthly data collection.  This change, based on global experience collecting data on millions of machines of average operational criticality over the last 35-or-so years, significantly improved the condition monitoring program effectiveness for these machines.  Some industrial insurance providers even stipulated the requirement for monthly data collection as a condition for insurability and many machine manufacturers did the same as a requirement to honor warranty requirements.

Today, the most common interval for collecting vibration data on average criticality machines with portable instruments remains monthly.  The most common failure mechanisms can usually be discovered in progress and in sufficient time to take planned, scheduled corrective actions in a timely manner.  Of course, machines with higher criticality or that experience more rapid failure mechanisms are candidates for more frequent data collection and evaluation.  Those machines that require more frequent data collection than monthly should seriously be considered for a permanently installed (wired or wireless) vibration monitoring system.  From the program’s cost-effectiveness perspective, the threshold between using portables and an automatic, permanently installed system that can collect data multiple times per day is monthly.  Any machine that requires collection more often than monthly is a great candidate for a permanently installed automatic system.