I have written several articles on inspection recently, as I strongly believe it is foundational to condition monitoring, machine reliability and asset management. My last Machinery Lubrication column introduced the term “Inspection 2.0” to differentiate conventional inspection practices from the intense, probing and purposeful methods needed to optimize benefits. As common as inspection activities may be in any plant, Inspection 2.0 is largely untapped in my opinion. In fact, it is delusional to imagine world-class reliability without the coexistence of world-class inspection.
Inspection 2.0 borrows from many battle-tested philosophies, including the practice of autonomous maintenance advanced by total productive maintenance (TPM) doctrine. However, not detailed in these philosophies is the “how-to” to move an organization past the inspection status quo to the real game-changing opportunity that eludes their view. I plan to address these differences and the “how-to” tactics in several upcoming Machinery Lubrication articles.
This article introduces the concept of machine readiness as a critical enabler to Inspection 2.0. An inspector who is eager to determine the state of machine health - good or bad - needs help from the machine. What hurts, where does it hurt and what are the symptoms of being hurt? Information exchange, like basic communication, is a two-way street. There is a need to enhance the quality of machine-transmitted conditions so the inspector gets a clear and complete picture of the state of the machine’s health.
Now, assume that each and every machine in your plant is not yet Inspection 2.0 ready. That is very likely the case. Opportunity is knocking!
Work Backward
Start by compiling a list of machine faults and root causes you want your inspection program to reveal. This is generally a list of all the things that could go wrong that you definitely don’t want to go wrong without adequate (early) warning. There is usually a need for some prioritization related to the list. Criticality analysis helps define the probability and consequences of failure. Failure mode ranking (e.g., failure modes and effects analysis) delineates specific failure mode pathways, starting with root causes, that could possibly occur.
Next, take this prioritized list and construct an inspection gameplan that will reveal each of these alert conditions in real time. For instance, how might shaft misalignment be quickly recognized or aerated lube oil immediately detected? Is the machine currently able to reveal these inspection facts? If not, what modifications are necessary? Do the same with the other failure modes as you move down the list.
Smart Machine, Smart Inspections
Your machines can be smart, real-time communicators of the state of machine health. It is disappointing that very few original equipment manufacturers (OEMs) build machines to a suitable state of inspection readiness. This puts the burden on the asset owner to source needed parts and devices to be retrofitted on machines either at commissioning or during a scheduled shutdown.
Yes, there are often costs associated with retrofits and other machine modifications, and some of these changes can present risks related to human-agency failures from machine disturbances and defective parts/installations. However, if the modifications are properly engineered, sourced and installed, the benefits over the long term can be enormous. Don’t pretend to save money by skipping this step. After all, inspection blindness is a far greater concern from the standpoint of machine reliability. You can’t inspect and report what you can’t see.
The following examples of machine-readiness practices, accessories, instruments and devices can substantially enhance and enable inspection readiness.
Good Housekeeping
Outside Dirt - This is always a good place to start. Keep your machines clean, inside and out. We all know that dirt is destructive to the machine’s internal frictional surfaces, but it also masks many important inspection alerts, such as surface distress shown by cracked paint, tempered metal tints, chronic corrosion, runaway fretting, seal wear/damage and leakage points.
Inside Dirt and Fouling - Dirt and sludge can make oil so opaque that other oil properties become invisible. These might include water contamination, glycol, aeration, wear particle suspensions, etc. When oil is kept clear and bright, the slightest change in this state serves as an early sign of concern that should be reported for more detailed analysis. Additionally, sludge can stain sight glasses, preventing the oil level and other conditions from being easily determined.
Plates, Tags and Labels - Machine components should be properly labelled to avoid reporting errors. Other labels and markings are important, too, including filter and breather installation dates, lubricant type and gauge reading alerts.
| 26% | of lubrication professionals say enabling inspections of their in-service oil and machinery would be the most likely reason for making machine modifications at their plant, based on a recent poll at MachineryLubrication.com |
Inspection Windows
An inspection window is effectively a portal used by the inspector to see within the machine. Many types of products can function as windows, such as the following:
Oil Level Gauges - These can be electronic, mechanical or a device that provides a visual indication of the oil level. Abnormal oil levels are often very meaningful and for many machines can lead to sudden-death failures. High oil levels might represent in-leaks (cross-contamination) of coolant, fuel or other lubricants. Low oil levels can be caused by high oil consumption or out-leaks. Oil level gauges should be marked to show the normal range for stopped machines as well as running machines, depending on the machine type. Level gauges should also be positioned for convenient viewing, especially by the person performing oil top-ups and changes.
Sight Glasses - Good sight glasses are far more than oil level gauges. They can communicate key transient conditions associated with localized areas of the machine. See my Machinery Lubrication article on zone inspections for a detailed narrative on the vast amount of information these inspection windows can provide. They include bottom sediment and water (BS&W) bowls, inline sight glasses (to confirm oil flow) and clear piping/hoses for fluid inspections.
Part-Movement Windows - Many machines need windows to verify proper movement of parts, such as oil rings, collar oilers, slingers and flingers. Certain belt, screw, chain and gear drives may need an inspector’s line of sight.
Expanded Metal Guards - Couplings and other exposed rotating or reciprocating mechanisms are typically protected from accidental contact by the use of guards. These guards often restrict visual observation of the movement mechanisms. However, they can be replaced with expanded metal so that both functions (safety and inspection) can be enabled.
Ferro Sites for Magnetic Particle Collection - These are magnets flooded in oil and placed behind inspection windows. Ferro sites are usually located on the return line where the ferromagnetic debris is the highest. The window can be periodically opened to clean the magnet.
Lubricant Sampling
Sump Drains with BS&W Valves - It’s good to be paranoid about what might be sitting on the bottom of your sump or reservoir. It probably isn’t anything your oil supplier sold you. BS&W bowls can provide a quick visual inspection. You can also pull a bottle sample if a simple ball valve is installed.
Sample Ports - These can be located in return lines, live zones or other strategic locations for quick sampling and at-machine inspections. In addition to visual inspections, you can perform a simple blotter spot test or a crackle test for the presence of free water.
Grease Purge Traps - What emerges out of a grease purge port during relubrication or during normal operation is an indication of lubricant health in the core of the bearing. Different traps and collection devices can be installed and used to inspect the discharged grease for hardness, oil content, particles, color, etc.
Inspection Devices
Numerous inspection devices are used to quickly assess solid debris concentrations and other types of lubricant contamination. These devices include magnetic plugs, debris traps, Y-strainers, last-chance filters and corrosion gauges.
Instrumentation
Today, there is a fairly wide selection of sensors and gauges that can provide effective real-time information on machine conditions. These include vacuum gauges, temperature gauges, proximity probes, flow meters, free-water alarms and load sensors. Most of these instruments can report digital or analog readings at the machine and are viewable by inspectors.
Additionally, oil analysis is no longer the exclusive domain of the laboratory. An assortment of instruments can be installed directly on the machine to assess viscosity changes, moisture readings, particle counts, wear debris concentrations and changes in oil chemistry. Vibration accelerometers can also be imbedded or affixed to operating machinery for periodic examination by inspectors.
Final Thoughts
As mentioned previously, there are costs and even a bit of risk associated with getting a machine to the proper state of inspection readiness. Reliability is always an investment. It’s monetized later, usually in multiples. Most investments work this way.
You are not trying to maximize inspection readiness but rather optimize it. You want to get it right, so make the right choices. Be penny wise, not pound foolish. It’s false economy to try to save money by not investing wisely. It’s like education. If you think it is expensive, try ignorance.
About the Author
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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...
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