The blotter spot test has been discussed numerous times in the pages of Machinery Lubrication magazine. It not only is one of the oldest oil analysis tests (mid-19th century) but endures as one of the most effective at detecting and even quantifying certain lubricant abnormalities.

However, the blotter spot test is not commonly known as a test for detecting and examining particles in oil such as wear debris and dirt.

As a practical matter, its ability to reveal normal and even slightly abnormal amounts of solid particles is limited, especially without the aid of a microscope. This generally is true with other applications of blotter spot testing.

In other words, the lack of a visible structure (rings, starbursts, pasty center, etc.) is an indication of the absence of the target condition. Because of this, the blotter spot test is less likely to produce a false negative compared to other more advanced analytical methods.

While each method has its own unique interferences and lower sensitivity limits, the ability of blotter spot testing to provide a reliable alert to abnormal particle concentrations is undisputable.

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Abstract: In oil analysis, well placed alarms and limits are like trip wires, alerting operators and technicians to an untoward or threatening condition. Oil analysis limits can vary considerably according to machine type, oil type, and reliability goals. This paper discusses four distinct types of limits and how they are applied to different machine and lubricant applications: goal-based limits, aging limits, rate-of-change limits, and statistical limits.

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Optical particle counters (OPC’s) have a long history of use in industrial hydraulic applications. Traditionally, their success has been limited to scientific laboratories and other highly controlled environments. However, in recent years, attempts have been made to apply the use of OPC’s to the particle counting of used hydraulic fluids and industrial lubricants. As a result, serious concerns have been raised regarding the accuracy and reliability of OPC’s in such applications. The objective of this bulletin is to present important facts from reliable and documented sources for the general benefit of existing or prospective users of OPC’s. As particle counting moves into the mainstream of machine condition monitoring, users must have reliable information to identify and select appropriate technologies.

The post The Usefulness of Particle Counting in Oil Analysis appeared first on Tesibis.

The most widely used laboratory methods for initial detection of abnormal levels of wear debris in used oils include elemental analysis, ferrous density analysis (DR, etc.), particle counting and patch testing.

For some users, because of the criticality of their machines, all of these screening tests for wear metals are integrated into the routine test slate. In such cases, when sampling is done correctly, it would be rare for the abnormal production of wear metals to go undetected.

However, when only one or two of these methods are routinely deployed, there is a distinct risk that an incipient (early stage) failure condition may be overlooked or dismissed as inconsequential.

The post Tactics For Identifying Wear Metal and Solid-particle Suspensions appeared first on Tesibis.

Optical particle counters (OPC’s) have a long history of use in industrial hydraulic applications. Traditionally, their success has been limited to scientific laboratories and other highly controlled environments. However, in recent years, attempts have been made to apply the use of OPC’s to the particle counting of used hydraulic fluids and industrial lubricants. As a result, serious concerns have been raised regarding the accuracy and reliability of OPC’s in such applications.

The objective of this bulletin is to present important facts from reliable and documented sources for the general benefit of existing or prospective users of OPC’s. As particle counting moves into the mainstream of machine condition monitoring, users must have reliable information to identify and select appropriate technologies.

The post The Accuracy and Reliability of Optical Particle Counters with Industrial Oils and Hydraulic Fluids appeared first on Tesibis.

In recent years, I’ve been part of numerous investigations relating to expensive machine failures preceded by oil samples that registered high particle counts. Each time I asked the asset owner, my client, why the aberrant particle trends were not investigated further. In most cases the response was that they didn’t think it merited the extra effort or they didn’t know how to probe further for more information.

The post What Do You Do with a High Particle Count? appeared first on Tesibis.

The inclusion of particle counting in the periodic analysis of hydraulic and lubricating fluids has provided an important new advancement to machine diagnostics. With particle counting, machinery users can monitor the principal cause of failure, not just the symptoms, or results, of failure. The benefit, when particle levels are controlled, is extended machine life and reduced failure frequency. This is the objective of the growing practice of proactive maintenance.

Along with this important trend has come the practical questioning of particle counter accuracy. It is estimated that by the year 2000, as many as 50 million particle counts will be performed on fluid samples each year. Hence, a failure to do particle counting with reasonable accuracy could effectively undermine user confidence and erode this incredible rate of growth.

While calibration techniques are available for most types of particle counters, the frequency and proper use of these techniques is not well understood. Likewise, it can be questioned whether the type of fluid and test particles (calibration fluid) used in calibration of particle counters is sufficiently close to field oils and field contaminants. Additionally, accuracy is also influenced by bottle cleanliness, fluid agitation, deaeration, dilution, dilution fluid cleanliness, and operator error.

The post Comparison of Particle Counts Between Eight Commercial Oil Analysis Laboratories appeared first on Tesibis.

A proactive maintenance approach has been particularly successful in reducing or eliminating one of the most serious equipment maintenance problems: contamination of lubricant or hydraulic fluid systems. According to the bearings division of 1RW, “contamination is the number one cause of bearing damage that leads to premature removal.” Caterpillar states that “dirt and contamination are by far the number one cause of hydraulic system failures.” Similarly, J.I. Case states that “systems must be kept clean, spotlessly clean, in order to achieve the productivity they are capable of.” Finally, Oklahoma State University reports that when fluid is maintained 10 times cleaner, hydraulic pump life can be extended by 50 times (Fig. 1 ).

The most common types of contaminant induced failures in machinery are wear, sticking, seizure, erosion and corrosion. Contaminants can include solid particles, moisture, air, chemicals and other foreign materials. Figure 1 – Cleaner hydraulic fluid extends pump life.

The rate at which contamination enters a system is typically underestimated, and the effectiveness of filters in removing this contamination is often overstated. According to a study of hydraulic equipment at Oklahoma State University, “it has been demonstrated that apparent ingression rates of 10-100 million particles greater than 10 microns (per minute) characterize field systems (Figure 2).” Filters often have great difficulty removing these high contamination levels since they are subject to frequent changes in temperature, fluid viscosity, pressure, and flow; plus the effects of shock, vibration and fatigue. Other common problems are filter bypass valves that are stuck open, damaged or missing filter gaskets, and filters that are installed crooked or backwards.

The post Contaminant Monitoring Targets Root Causes of Machinery Problems appeared first on Tesibis.

To some contamination control might seem a little like an old tune. After all, hasn’t filtration been around nearly as long as lubrication? And, what’s new that hasn’t already been thoroughly explored and widely applied? For one, when it comes to cleanliness, knowing is definitely not doing. Many maintenance professionals know oil should be clean but the use of filtration and contamination control lacks rigor and discipline. Why? Hidden behind steel plates, within the dark interior of our machine, the particles of dirt move about like a microscopic wrecking crew–invisible to the outside world. Even within a sample bottle they are too small to see. The dirt effectively is “out of sight” and therefore, usually also, “out of mind.” People don’t respond to what they don’t see. As in most cases, embedded in the problem one finds the solution, or rather, opportunity. Simply stated, how do we turn the unseen into the seen?

For many world class organizations, when it comes to battling invisible particles, the preferred weapon is the invisible filter- a.k.a., the particle counter. Why is a particle counter called an invisible filter? Because it has the remarkable ability to change behavior. The old saying, “what gets measured gets done” says it well. Everything else left the same, the frequent use of a particle counter, with conspicuous reporting of results, often leads to an amazing downward trend in contamination.

Why? Because people are reacting to the feedback, by slowly altering past practices. When combined with education, little things and big things alike are done differently. For instance, greater care and attention is given to lubricant storage, cleanliness of oil cans and top-up containers is controlled, transfer systems are fitted with filters, tank hatches are sealed tightly, and breathers and filters are serviced regularly. In sum, the best filter is the unneeded filter, the invisible filter, the particle counter. So, take the time to learn from the experience of others and develop a plan to emulate proven successes. To the astute, opportunity-seeking student of machine reliability, there are very few lessons so important. Class dismissed.

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In condition monitoring, any property that is important to machine reliability and life extension should be a property that is measured, assuming it is technically and economically feasible. Of course, this is the point of considerable consternation by the oil labs when it comes to crankcase oils.

How does one perform practical particle counts on opaque fluids, achieving precision and cost efficiency at the same time? Before we examine the specific challenges of particle count methodologies, let’s review the various ways to assess the presence of destructive particles (other than soot) in used motor oils.

The post Diesel Engine Oil Particle Counting Methods appeared first on Tesibis.

Oil contamination can be defined as any foreign material found in the lubricant which is not added by design. Usually, contaminants are not beneficial and may even be detrimental to the performance of the oil and/or operating machinery. Contamination is the root cause of a high proportion of machine and lubricant degradation and failure. Often overlooked as a source of failure because its impact is usually slow and imperceptible, contamination is both a significant threat to reliability and quality efforts but at the same time also an opportunity, because improvements are very attainable. Research on an array of fluid dependent machinery, such as bearings and rotating equipment, hydraulic systems, gearboxes, diesel engines, turbines, clearly supports the idea that very often machine reliability is a function of contamination control.

Particles, moisture, heat, air, glycol and fuel are all contaminants found in industrial lubricants. Particles and moisture are especially common and typically present the greatest risk to machine reliability and lubricant performance. Particles and moisture, either acting alone or in unison, lead to fluid oxidation, additive depletion, viscosity failure and loss of lubricity, especially where heat is present. Once the fluid’s lubricating qualities are degraded they no longer provide the ‘cushion’ between moving machine surfaces. Because the fluid can no longer perform as it was designed, wear and ultimate failure ensue.

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This isn’t your usual article on how important clean oil is to lubricant health and machine reliability. Yes, we are going to talk about particle contamination, but we’re going to take a much closer look at the destructive traits of this nearly invisible material that cohabitates with our lubricants.

As it turns out, there is a lot more to particles than their size and count. This column will peer into the intricacies of the physical and chemical properties that make up and characterize solid particle contamination.

I’ll begin by discussing 10 particle characteristics that should be important to lubricant analysts and lubrication professionals. Each of these characteristics or traits influences the health of lubricated machinery. While the name of the trait may be familiar, the damage it causes may not be.

The post Particle Contamination – 10 Important Things You Should Know appeared first on Tesibis.

I often mention the wear debris universe when I lecture on oil analysis topics. This refers to the extensive array of wear particle technologies and tactics that can help reveal the true tribological condition of a machine.

Individually, these tools are often inconclusive when it comes to identifying the source, cause and severity of abnormal wear conditions. They may not even be able to identify the problem at all. Yet when used in combination, they can expose a vivid image of a current or impending failure condition.

A skilled analyst should be well aware of the strengths and weaknesses of these technologies and tactics. Not all of these tools need to be at your fingertips, but nonetheless should be available when called upon. Too often, an inexperienced technician will attempt to draw a premature conclusion from little more than a sliver of information in the wear debris universe.

Examples might be a muted iron trend from elemental data or stabilized ISO codes from particle counting. Used alone, these technologies might telegraph to the diagnostician the erroneous appearance of machine health (or disease). Unseen may be an incipient but serious wear condition in need of attention.

Common front-line technologies used for screening purposes include ferrous density analysis, elemental spectroscopy, particle counting and patch testing. Collectively, these technologies pack a powerful punch and are credited with scores of predictive maintenance “saves”.

However, in a high percentage of cases, these technologies would not have earned their hero status if it weren’t for the other tests and methods that peered deeper into the core of the problem.

These include secondary sampling points, filter debris inspection, magnetic plug analysis, sump sediment analysis, SEM-EDS, XRF, ferrography (all methods), acid-dissolution spectroscopy, particle heat treatment, particle impaction testing, chemical microscopy, digital shape profiling, percent of large ferrous particles, rotrode filter spectroscopy, TGA, gravimetric analysis, ultracentrifuge (separation of soluble metal fraction), pore blockage particle counting … and the list goes on.

The post Virgin Particles and Weak Signals: Finding Meaning in Wear Debris appeared first on Tesibis.