Why Inspection 2.0 Is Your Best Strategy for Early Fault Detection

Inspection, in its most basic form, has been around forever. However, like most things in life, what you get out of an activity depends entirely on what you put in. This column is about radical reinvention of the whole concept of machine inspection. It has little to do with conventional practices of doing daily machine rounds.

With Inspection 2.0, you don’t just “look” at a bearing, seal, coupling or pump. Instead, you “examine” these components with a keen and probing eye. Inspection 2.0 is intense and purposeful. It seeks to penetrate and extract information from what’s been referred to as machine sign language. Inspection 2.0 requires polished linguistic skills to translate this sign language into prescribed activities and instructions that stabilize reliability.

The technologies of machine condition monitoring have been advancing at a near break-neck pace in recent years. These innovations will continue for decades to come. Still, for the vast majority of machines, there is currently no fault-detecting technology more effective than the razor-sharp and relentless focus of a human being.

The potential of a human being as a condition monitoring instrument is enormous. This potential depends on transformation, specifically from the going-through-​the-motions inspections of the past to mission-intensive detective work inspections of the future. That is the essence of Inspection 2.0.

Figure 1. Condition monitoring and the time domains of machine failure

Low-hanging Fruit

Often the simplest solution is the best solution and the right solution. How do you get the optimum level of reliability at the lowest possible cost? How do you achieve a synergistic blend of condition monitoring activities that unifies Inspection 2.0 with the range of other options being advanced and currently available?

Inspection presents some benefits and advantages that are difficult, if not impossible, to duplicate with other condition monitoring options. These include:

• Inexpensive, simple, lasting deployment
• Operator-driven (total productive maintenance emphasis)
• More emphasis on examination skills, less on technology
• The power of frequency and the one-minute daily inspection
• Root-cause-oriented to avoid developing fault bubbles; more proactive, less reactive
• Early fault detection; more predictive, fewer misses and “just-in-time” saves

We all seek more for less, and no one likes the pain and frustration that often come with exceedingly complex solutions to simple problems. KISS (keep it simple stupid!) solutions should always be your first priority. Their application is at the core of Inspection 2.0. No array of sensors and computer intelligence can outperform a human inspector at a large number of condition monitoring tasks.

Inspection Frequency Trumps High Science

Why not perform oil analysis everyday on just about every machine? Yes, it sounds expensive, but it doesn’t have to be. Oil analysis can be done with your senses, aided by inspection windows. Visual oil analysis is real oil analysis. Who said a laboratory is a requirement for oil analysis anyway?

Many of you are familiar with the P-F interval from the teachings of reliability-centered maintenance (RCM). As shown in Figure 1, “P” is the point-of-failure first detection, while “F” is the end-point of functional inoperability. Although the P-F interval is a theoretical concept that has useful application, it is rarely applied in real-world machines. This is because the real world comes with many variable events. These events distort the predictability of the P-F interval. They include:

• Multiple components on a single machine or drive train, each with its own P-F tendencies
• Multiple failure modes for any single component
• Variable duty cycle (speeds, loads, shock, temperature, etc.)
• Remaining useful life (RUL) varies with age. For any given fault mode, the P-F interval shrinks as the machine ages.
• Failure detection methodology and effectiveness vary (ability to detect faults early)

The best countermeasure for uncertain P-F intervals is frequency. For certain machines, real-time monitoring using imbedded sensors is justified, especially high-speed, high-risk machines. However, for nearly all other machines, the simple solution for early detection is daily inspection aided by inspection windows and tools.

Even the world’s best laboratory oil analysis programs can’t see faults in the “non-sample.” Inspection 2.0 asks you to deploy your senses intensely every time you walk by the machine. The oil sample is examined carefully, but it never leaves the machine. See my “Sight Glass Oil Analysis” article at MachineryLubrication.com.

The power of frequency is illustrated in Figure 2. In this example, the failure development period (from inception to functional failure) is one month. If your condition monitoring interval is quarterly or bi-monthly, you won’t catch the fault prior to functional failure (this is a condition monitoring “miss”). If you use a monthly monitoring interval, you catch the fault with an 18-day P-F interval (lead time to corrective measure). Note, the longer the P-F interval the better.

If your condition monitoring interval is weekly, your P-F interval jumps to 25 days (better). However, if you are able to inspect this machine daily using detection-sensitive Inspection 2.0 methods, your P-F interval is 30 days, which is better than weekly testing with the best condition monitoring technology (vibration, oil analysis, thermography, etc.). By comparison, a poor daily inspection technique yields a P-F interval of just seven days.

Figure 2. Failure detectability technique and inspection periodicity influence the P-F interval.

Align Inspection Strategy with Failure Mode Ranking

As with any condition monitoring program, inspection strategy needs to be aligned with a ranking of failure modes for individual machines. The order of the ranking is risk-based, i.e., probability of occurrence times the consequences of occurrence. This alignment ensures efficient use of inspection resources and proper deployment of inspection methodology based on need. In other words, each failure mode on the ranking requires a corresponding inspection task or observation that enables the earliest possible detection.

Beware of Short P-F and Sudden-death Failures

As mentioned, the P-F interval is almost impossible to predict for a variety of machine-specific reasons. In fact, the interval can vary from seconds to decades. Maintenance departments like long reaction times to schedule needed corrections. Still Murphy’s law always looms to ruin an otherwise perfectly good day.

The best strategy to mitigate sudden-death failures is to focus on the early detection of root-cause fault bubbles. This is a fundamental proactive maintenance strategy (see the left side of Figure 1). Fault bubbles are escalating conditions that threaten the onset of an active failure event. As much focus should be spent on preventing the inception of failure as on detecting a failure in progress. Every failure mode has one or more root causes. Ensure good root-cause alignment with your inspection strategy.

Following are a few examples of short P-F and sudden-death failure modes and fault bubbles. What intervention strategy focused on root causes would you apply to detect and neutralize these threatening conditions?

• Oil filter rupture
• Wrong oil or severely degraded oil
• Fish-bowl conditions (disturbed and mobilized bottom sediment)
• Severe shaft misalignment
• Stiction/silt lock of hydraulic valve (motion impediment)
• Grease “soap lock” starvation of an autolube system
• Impaired oil supply of a splash-lubed gearbox
• Heavy fuel dilution of a diesel generator
• Heavy chemical contamination of a compressor oil
• Gross seawater contamination of a shipboard hydraulic fluid
• Shock loading of a large thrust bearing

Inspection Windows and Zones

Inspection 2.0 is searching, detective work. It puts the machine under the microscope day by day. To do this, the machine’s exoskeleton must be penetrated. You have to find ways to see through steel plate and cast iron. You must also “ready” machines for world-class inspection. New products, including modernized sight glasses, are being developed to bring vision to critical zones within the machine.

One of my favorites is the bottom sediment and water (BS&W) bowl. If this sight glass is properly positioned, anything that is heavier than the oil will accumulate there for quick inspection with a good light. This includes sediment, water, sludge, wear debris, coolant, dead additives and dirt. If your BS&W bowl is clear, bright and without sediment, there are many things that could be going wrong with your oil and machine that are not going wrong simply because this sight glass passes inspection.

Figure 3 shows the use of windows for convenient zone inspections. Also included are lists of example root causes and faults that can be visually detected using these windows. For more information on zone inspections, see my “Use Zone Inspections for Early Problem Detection” article at MachineryLubrication.com.

Figure 3. Zone inspections for early problem detection

Inspection 2.0 is a Nurturing Strategy

Applied tribology is a behavioral science. This means that in most plants the practice of tribology and lubrication is people-intensive. I often say that lubricants are what we buy and lubrication is what we do. The main reason machines fail prematurely is the result of what people do or don’t do.

Inspection is a subset of tribology (and lubrication) and likewise is very much a behavioral science. People have to passionately want to find faults and reportable conditions. The people I’m referring to are operators, technicians, lube techs, millwrights, mechanics, etc. It’s no longer just “looking” during the inspection route and then checking the box on the report. Instead, it’s about intense examining, probing, digging and searching. The people factor will make or break any good reliability and maintenance undertaking. This is perhaps more true with inspection.

People respond to work tasks and challenges differently. Much of it has to do with leadership and the maintenance culture. In my “Remedies for a Bad Maintenance Culture” article, I stressed that a positive, nurturing maintenance culture is a critical plant asset. Consider that when people do good work, they feel good about themselves and their job. When people do bad work, they feel bad about themselves and their job. The simple solution is to enable people to do good work that is recognized and celebrated.

Culture drives behavior. Behavior influences quality of work. Quality work is fundamental to plant reliability and the cost of reliability. Of course, this most definitely includes inspection activities. The following list delineates the minimum requirements for building a strong inspection culture:

• Training and inspection skill competencies (optimizing inspection skills readiness)
• Celebrating inspection “saves”
• Inspection KPIs and other performance metrics
• Installing penetrating inspection windows (optimizing machine inspection readiness)
• Availability and use of inspection aids and tools (optimizing tool inspection readiness)
• Promptly responding to inspection-​generating alerts and red flags

At the top of the list is training, lots of training. Inspection is so important that I predict in the near future you will see the emergence of new training courses and curriculum focused only on inspection. With that will come certification testing.

Side-by-Side Comparison

What differentiates Inspection 2.0 from conventional inspection practices? It’s mostly about execution. The time has come to reinvent this largely mundane and repetitive task. Think about how to make it 10 times more effective with very little extra cost. The table above details several of the main differentiators that distinguish and empower Inspection 2.0 to this higher level of performance.

You’ll be hearing much more about Inspection 2.0 in future issues of Machinery Lubrication magazine. This is an exceptional low-hanging-fruit opportunity in machine reliability as well as a foundational element for lubrication excellence. Take the initiative to adopt Inspection 2.0 by bringing its powerful capabilities into your organization.

About the Author

Jim Fitch

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... Read More