The Five Cardinal Signs of a Healthy Machine

Jim Fitch, Noria Corporation

You cannot monitor your way to a healthy machine just like frequent tests for cholesterol and blood pressure do not make their readings lower. Or do they? Monitoring physical conditions brings vision and awareness to health. It is continuous feedback about how we're doing. In a similar manner, from measured readings we can report and categorize machine conditions as being safe, cautionary or at alarm levels (critical).

Bad news needs a rapid and strong delivery. And it needs an equally spontaneous response. Indifference and procrastination to nonconforming conditions becomes habit forming. It is true that no one likes a negative report, but it doesn't make it go away; just like we cannot ignore-away the trauma of sudden-death machine failure. It is better to have to deal with 20 minor health inconveniences than the jolt of one terminal case of cancer.

By responding to an aberrant alarm or condition in near real-time, we likely can spare ourselves from having to react later to show-stopping operational failures. Again, early detection and response are key; just like in the medical analogy. Of course, choosing ignorance by not monitoring is negligence and gives the machine complete control of the timing and severity of the failure. We do have choices in machinery maintenance just like we do in caring for our own personal health.

Be a Machine-health Hawk
Keep tabs on what defines health. Customize your list of condition indicators for the targeted machines. Be a hawk for any deviation such as abnormal trends or step changes. Make a habit of responding as seriously and promptly to small alerts as you do to large. There's a cultural benefit because this practice won't go unnoticed. It can recast your company's maintenance mindset from failure-reactive to health-proactive.


Use feedback and continuous improvement to fine-tune your data-stream of machine condition indicators by periodically adjusting your measurement techniques and alarming strategy. Apply a combination of technology- and inspection-based alerts. Yet, keep the strategy as simple and streamlined as possible by removing unreliable and cumbersome methods from your watch-list.

The following is my list of five cardinal signs of a healthy machine. They won't all apply to every machine, but the strategic premise is clear. So too, the list below only introduces the condition to be monitored. Most of these cardinal signs are highly developed with wide-ranging modalities in the field of in condition-based maintenance. For more information on these strategies, consult the many searchable articles and case studies available at

  1. Healthy, Uncontaminated Lubricant. Over time, lubricants age and lose their wear and corrosion protective properties. With rare exception, these conditions cannot be restored without adding new lubricant to the compartment. Usually, but not always, the aged lubricant will need to be first removed (drained, purged or flushed). Even healthy lubricants can become periodically contaminated, which can sharply impair lubrication performance as well.

  2. Volume and Level Control. Just like an automobile engine, many machines require a relatively precise level of lubricant volume. Too much or too little lubricant can rob our machines of years of reliable service. This relates to both oil level and grease volume. Sudden changes can denote both failure cause and symptom. Don't underestimate the importance of this machine-health condition.

  3. Mechanical Stability. Machines become mechanically instable for a host of reasons. Many of these reasons recur throughout the machine's life. Maintaining mechanical stability is essential to achieving machine reliability. Numerous causes contribute to mechanical instability including excess bearing clearance/preload, misalignment, unbalance, soft foot and others. Use technologies such as vibration, acoustic emission, proximity sensors and load cells to detect mechanical problems early.

  4. Thermal Stability. Normal mechanical and fluid movement during machine operation creates friction and heat. Heat also is generated, transmitted or concentrated from combustion, radiation, compression, heaters, etc. Temperature changes can serve as an important indicator of an abnormal operating condition. Some heat sources are specific (hot spots) and demand immediate attention. In other cases, a system may experience gradual thermal excursions that can be more difficult to diagnose.

  5. Leakage Control. Certain equipment types are prone to leakage such as fluid power systems and machines that circulate lubricants to multiple frictional zones. The root causes of leakage can vary considerably. Some leakage is internal (say, across a piston or valve); in other cases, it may be out-leakage (fluid loss) or in-leakage (contaminant ingress). Leakage can rapidly destabilize the system and must be brought under control.

Time to Get Cracking
By making periodic on-condition adjustments (corrections) to a machine's operating environment, a long, reliable service life is achievable. For critical machinery, the strategy is a maintenance imperative. Focus on the cardinal signs described above to develop your customized condition-monitoring strategy. Be watchful and use the data generated to plan and schedule maintenance events. Doing so takes the control of reliability away from your machine and puts it proactively in the hands of your reliability team. Now it's time to get cracking.

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About the Author

Jim Fitch, a founder and CEO of Noria Corporation, has a wealth of experience in lubrication, oil analysis, and machinery failure investigations. He has advise...