21st Century Condition Monitoring
Jack Poley | TLT On Condition Monitoring September 2011
Improved system efficiencies and technology usher in a new era in oil analysis.
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There are two primary forms of condition monitoring: oil analysis (OA) and vibration signature monitoring (VIB). Both have been around for a number of decades. OA (circa 1948) is listed first because it preceded VIB (circa 1970) by roughly 20 years. However, VIB had a major advantage over OA from its inception* in the form of online monitoring capability. This obvious advantage resulted in VIB being implemented for industrial applications with much more intensity than OA.
OA didn’t reach online status until the outset of the 21st Century when sensors of varying types and capabilities began to appear on (mostly) critical applications such as military and highly remote components.
THREE-TIERED OIL ANALYSIS SYSTEM
In previous columns in TLT, we’ve focused on the notion of a three-tiered system for modern oil analysis:
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Tier 1:
Online (sensors in contact with the lube)
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Tier 2:
Onsite (insightful testing where the machine is sited)
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Tier 3:
Offsite (traditional full-service laboratories).
I’ve maintained that the viability and synergy of all three tiers represented a paradigm shift in the OA and condition monitoring (CM) models. While OA always spanned more applications than VIB, the addition of online capabilities now implies that OA has caught, and likely surpassed, VIB as the primary CM tool for nearly any venue and application, particularly so with Tier 1 now in play.
Similar to VIB, OA became real-time while also maintaining its previous inherent advantages such as identifying oil quality issues that could lead to excessive wear and VIB. Of the two primary CM tools, OA is often more timely. VIB, however, is not suddenly obsolete, and it should be noted that new techniques are being explored and implemented in VIB monitoring, most notably in acoustic monitoring technology. Nevertheless, OA seems to have the lead position, owing to its ability to identify potential trauma well in advance of VIB (more often than not for most machinery settings).
Tier 2, however, also plays a vital role in terms of vetting Tier 1 triggers and alarms as CM practitioners are increasingly demanding early warning. Being able to make some useful decisions without waiting for a Tier 3 result sometimes means the difference between a save and a failure. Further, when Tier 1 is not employed, Tier 2 can play a more primary role in CM and preventive maintenance.
We can assume that OA and VIB will continue to make strides toward early trauma warning, and that having CM data sooner (rather than later) will, hereafter, be a continuing goal. There are, however, other paradigm shifts that will need to be taken into consideration, in addition to the desire to perform inspections closer to the machine.
PARTICLE COUNTING
While particle counting has been around for a long time, its efficacy has come under increased scrutiny of late because numbers of particles, heretofore detected, are being trapped by fine filtration systems.
Fine filtration strategies are becoming increasingly prevalent, and in numbers of different machinery component types. Particulate evidence lost is genuine cause for concern.
1.
Finer filtration means that particle removal will be increasingly greater, clearly interfering with OA detection capabilities with respect to particulates.
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Well, if the particles are now being captured by the filter in greater numbers, why not look at the filters themselves to see what and how much is being trapped? That’s exactly what’s beginning to happen. The military has been a leader in developing this technology and, per usual, it will find its way to the private sector in due course. Filter Debris Analysis (FDA) is becoming a
de facto term for the study of filter-trapped debris.
2.
Clearly a significant change in a machine’s filtration scheme, with respect to targeted particle sizes and removal efficiency, requires a change in one’s approach to assessing particle levels:
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Levels that were acceptable before are likely now to be unacceptable.
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New limits and trending approaches will need to be determined.
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Wear metals, though very small, will be affected to some extent.
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FDA will become increasingly more useful (revealing) and important in the CM process.
3.
There is the continuing issue of particle-size detection limitations, dependent on method.
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It is highly advisable to select at least one test to complement traditional spectrometric metals analysis (SOA), wherein various wear, contaminant and additive metals are detected (
Note: the severe particle size detection limitations of SOA are shown in Figures 1 and 2).
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The complementary test to parallel SOA can be chosen from a rather wide variety of methodologies. While a sensor seems most appropriate on the surface, there are other ways of addressing large particulates (
See Figures 1 and 2).
Figure 1. A graphical representation of particulate study methods.
Figure 2. Effective coverage for various particulate study methods.
SUMMARY
21st Century CM is well on its way to revealing more concepts and techniques than ever before, and it will be fun and challenging to watch and participate in its development. While a three-tiered testing system ushers in a new paradigm in the oil analysis arena, other techniques and technology will soon be coming to the forefront.
We’ll discuss these and other notions in future columns.
* It may be argued that OA has two online aspects dating back to the beginning of the 20th century: lube pressure and lube temperature. While these are critical pieces of information, they also are often representative of failures in progress that could not be fully mitigated, i.e., too little information, too late. More is needed, and earlier.
Jack Poley is managing partner of Condition Monitoring International (CMI), Miami, consultants in fluid analysis. You can reach him at jpoley@conditionmonitoringintl.com.
For more information about CMI, visit www.conditionmonitoringintl.com.