Edited by Sharyn Macnamara
Particle counting is considered one of the most important tests for used oil analysis. Many problems can be identified quickly and easily by monitoring the number and size-distribution of particles in an oil sample. While there are various test methods to determine the additive and chemical composition of a sample, the ISO Code, as per ISO4406, is the most common unit of reporting the number of particles found in a sample.
Photos supplied by ISO-Reliability Partners
Particle counting is considered one of the most important tests for used oil analysis. Many problems can be identified quickly and easily by monitoring the number and size-distribution of particles in an oil sample. While there are various test methods to determine the additive and chemical composition of a sample, the ISO Code, as per ISO4406, is the most common unit of reporting the number of particles found in a sample.
Photos supplied by ISO-Reliability Partners
“Most mines and industrial companies conduct particle counting and oil analysis,” says Craig Fitzgerald from ISO-Reliability Partners. The former determines the contamination levels in the oil, while the latter looks at how the oil has broken down chemically during its period of service. Warning signs are oxidation, changes in viscosity and depleted additive levels.
In terms of mineral oils specifically, which are commonly used in industry, viscosity is reduced by 50% for every 10°C increase in temperature. This will affect the performance and ability of the oil to separate metal parts. Fitzgerald points out, “The hotter the oil runs, the shorter the lifespan of the oil and the lubricated components. It is an inverse relationship.” It is reasonable that the rate of wear increases as the oil degrades.
When it comes to keeping an eye on the oil temperature in equipment, engines tend to have a built-in temperature sensor, while industrial equipment uses a thermocouple. Essentially a probe, it submits a reading to the operator’s screen that will either sound an audible alarm or shut the equipment down automatically as a precautionary measure to prevent any kind of catastrophic failure.
“What we find is that personnel tasked with carrying out oil analysis; for the most part do not know how to interpret the results properly,” highlights Fitzgerald. This is where the expertise of a company like ISO-Reliability Partners comes into play. It is an original equipment manufacturer (OEM) of class-leading micro fine oil filtration solutions, vacuum dehydration systems, automated water removal for compressed air, and high efficiency industrial air scrubbing. Its expertise combines the sciences of lubrication, filtration, and tribology.
ISO-Reliability has the capability to analyse in-operation oil samples and implement proactive measures to counter machine wear as part of predictive maintenance. The company’s reputation and success span 25 years, with it owning and managing the iconic Filter Focus brand, and Fitzgerald having incorporated all his intellectual property into the new company.
“We can look at an oil analysis and quickly determine what the issues are,” says Fitzgerald . “We further extrapolate information and provide a more in-depth than a generic computer-issued analysis based on currently accepted standards. For example, while industry may find 220ppm of iron (Fe) particulate to be acceptable, it will result in unnecessary and accelerated wear. It might be a level considered acceptable by industry, but what we are saying is that it should not be acceptable and that we can improve on those standards quite significantly.”
The company deploys particle counting and oil analysis to verify and confirm the quality and value of its micro-fine filtration solutions. “We conduct a ‘before’ and ‘after’ oil analysis to gauge the effectiveness of microfiltration. This is important to demonstrate to customers the true value of superior fluid cleanliness and invest in these test methods, products, and technology,” says Fitzgerald.
He explains that Total Base Number (TBN) refers to the quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide required to neutralise all basic constituents present in 1 gram of sample. TBN determines the effectiveness of the control of acids formed during the combustion process. Total Acid Number (TAN) is a measurement of acidity that is determined by the amount of potassium hydroxide in milligrams that is needed to neutralise the acids in one gram of oil and provides a more complete picture of the actual operating conditions within an engine. In addition, TAN has very good test repeatability though poorer reproducibility.
“If your TBN is, say, at 10, you can then run that engine oil until it gets to a value of 50% of its original . If analysis indicates your oil is not too contaminated with wear particulate, you do not have to drain the oil just yet. It can still run for maybe 1 000km or another 50 hours. In this way, oil analysis can be used to determine what is the most efficient oil drain interval,” says Fitzgerald.
While oil analysis is common in industry, if not utilised to its full value, particle counting is even less so. For example, a diesel sample is simply tested against the relevant SABS specification. Without proper particle counting, the user has no idea of the number of contaminants being forced through the injectors and eroding their openings and resulting in over-fuelling.
“The importance of fluid cleanliness cannot be over emphasised,” says Fitzgerald . Particle count data is a critical element of any proactive condition-monitoring programme, from minimising abrasive bearing wear to determining if a hydraulic fluid is clean enough for reliable operation.
The most common unit of reporting fluid cleanliness is the ISO code system. This convention is covered under the ISO standard 4406:99. In this standard, the number of particles in three different size categories, >4mm, >6mm and >14mm, are determined in one millilitre of sample.
ISO 4406:99 states that the number of particles in each size category should be counted, with the absolute count converted to an ISO code, using the ISO range code chart. Although the most common standard, ISO 4406:99 is not the only method by which the cleanliness of an oil sample can be reported. Other standards include NAS 1638 and MIL-STD 1246C, as well as outdated standards such as the SAE fluid cleanliness rating system.