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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Even the very best motor oils cannot safeguard against sludge when free water is present. Within several minutes after starting an engine, the oil typically reaches the thermostat setting. This heat can drive off the moisture, even in cold winter conditions. However, it can sometimes take 15 to 20 minutes of continuous driving before the condensed moisture has dissipated.

When water accumulates in sooty used oil and remains in the engine for an extended time, the damage to the oil is irreversible. This is why short-trip “Aunt Minnie” drivers need to change their car’s oil more frequently.

How frequently? If you are a short-trip driver like me, consider performing a simple blotter spot test before a scheduled oil change in order to regulate the optimum oil change interval to your driving conditions and climate. If you see undispersed soot, characterized by an inability of the soot to wick outward into the card stock, this may indicate that you need to change your oil more frequently.

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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.

The practice of transferring suspended particles to the surface of a membrane for analysis has been around for decades. It is perhaps the earliest method for inspecting solid contaminants and wear debris in a used sample of oil. It is of no surprise that these methods have enduring use today. In fact, some are the basis of recently adopted standardized methods by ASTM and ISO.

While membrane-based procedures for preparing particles for analysis can be time consuming and messy (usually involving the use of glassware and solvents), the benefits can be substantial compared to alternative methods. The main advantage is the ability to both quantitatively and qualitatively describe particle contamination, depending on the method used. As in the case of microscopic particle counting, you see what you’re counting and can confirm visually what appears to be a particle. You can also characterize particle type (e.g., dirt, wear debris, rust, fibers, etc.).

Because of the importance of these techniques to a modern and well-engineered oil analysis program, it seemed like a good time to review the options. There are actually eight different methods that are worth mentioning. Most have previously been covered in Noria publications, but a couple have not. We’ve used all but one of these methods in our failure investigation work here at Noria. A narrative of the methods is provided below and a summary that compares and contrasts them is shown in Table 1.

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With the widespread use of plant-level particle counters, maintenance organizations are becoming more sophisticated and skilled in the management and control of oil cleanliness. This has led to the discovery of a host of new tactics and practices that involve combining the particle counter with other important onsite oil analysis tools and methods.

Contamination can be defined as any unwanted substance or energy that enters or contacts the oil. Contaminants can appear in many forms, and can be highly destructive to the oil, its additives and machine surfaces. It is often overlooked as a source of failure because its impact is usually slow and imperceptible yet, given time, the damage is analogous to eating up the machine from the inside out. While it is not practical to attempt to eradicate contamination from in-service lubricants, control of contaminant levels within acceptable limits can be accomplished and is vitally important.

Contaminants such as particles, moisture, soot, heat, air, glycol, fuel, detergents and process fluids are commonly found in industrial lubricants and hydraulic fluids. However, particle contamination is typically recognized as the most destructive to the oil and machine, which explains why the particle counter is the most widely used instrument in oil analysis today. Additionally, the central strategy to its success in reducing maintenance costs and increasing machine reliability is proactive maintenance.

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Without the lens of a microscope, bacteria and viruses might only be recognized as painful symptoms of sickness and disease by those who are infected. Just as technology is an important enabler in human pathology, it also serves in the detection and diagnosis of a host of machine health issues, including the invasion of lubricant contamination.

However, for most machinery maintainers, the threat posed by fluid contamination runs contrary to human intuition. Just like a viral infection, in lubrication, it’s what we can’t see that hurts us most. The naked eye is generally blind to the destructive potential of most types of contaminants. In fact, none of our “unaided” human senses can be relied upon to detect and recognize significant concentrations of contamination.

When I first entered the oil analysis field in the 1980s, portable and user-level oil analysis technology was years ahead of its time. This is not so today. Contaminant monitoring instruments have advanced rapidly in the past two decades as has the awareness of its importance. What was previously only the domain of analytical chemists is now an essential maintenance tool available to field technicians and condition monitoring specialists. Thankfully, the “now generation” is largely a population of sophisticated consumer electronics users who also have an insatiable appetite for instant information.

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