Oil analysis: how to detect contaminants

We have talked a lot about predictive maintenance here. All industrial equipment and components are subject to failure even before the time predicted in the design parameters.

This usually occurs for external reasons, such as dust, rain, sun, contamination from the environment and factory process, etc.

With proper care, it is perfectly possible for equipment to have a service life beyond that stipulated by the manufacturer.

To identify the actual service life and identify wear and tear, the safest and most accurate option is predictive maintenance. With this procedure, companies will be able to save time and resources, after all, unnecessary replacement of parts and components that may be in good condition, regardless of the time of use, is avoided. One of the most effective predictive maintenance tools is oil analysis.

Oil analysis: what is it?

Oil analysis allows quick and accurate laboratory evaluations of the lubricating oil used in equipment. With this predictive maintenance tool, carried out in the laboratory, it is possible to detect both the wear of the moving parts of the equipment and the presence of contaminants.

Oil samples are analyzed and, only at ALS Oil & Lubricants, results will be consolidated within 24 hours.

There are several types of laboratory techniques that are applied to oil analysis. Since this publication focuses on contaminant detection methods, we will describe ferrography and spectrophotometry here.

– Oil analysis: ferrography

Ferrography is a predictive maintenance technique that analyzes the particles present in lubricants to identify the degree and reason for wear in machines and equipment.

Identification is made through morphology (i.e. lubricant shape), appearance, color, particle size, viscosity, opacity and other characteristics.

Don’t be fooled. Despite its name, ferrography does not only work with ferrous substances and particles.

In fact, this method of oil analysis deals with ferrous alloys (steel, cast iron, stainless steel and steel), ferrous compounds (ores) and non-ferrous alloys (aluminum, bronze, chromium, nickel, silver, among others), as well as materials and substances such as soil, sand, rubber, etc.

– Oil analysis: spectrophotometry

Spectrophotometry is a predictive maintenance technique that allows the identification of chemical contaminants in lubricating oil. All this is possible because the analyzed oil undergoes a combustion process and consequently disintegrates atomically.

The objective of this technique is to more accurately identify wear and contamination in fluids.

Spectrophotometry is a technique widely used in research and quality control in various specialties such as pharmaceuticals, food, fine chemistry and even astronomy.

For each application area there is a specific set of accessories and procedures.

In predictive maintenance it is used to identify the chemical elements of the lubricating oil. All this is possible because the analyzed oil undergoes a vaporization process at extremely high temperatures (thousands of degrees). This “disintegrates” the substances down to the atomic level.

Elements such as Iron, Chromium, Aluminum, Copper, Lead, Tin and others used in metallic alloys allow to evaluate the wear of components.

Others such as Calcium, Phosphorus, Zinc and others are associated with additives. And we still have Silicon, Potassium, Sodium, etc. that help us to study the contaminants present in the fluids.

Spectrophotometry is based on the principle that color intensity is a measure of the amount of a material in solution. Another principle we must consider is the amount of light absorbed by each substance. And this is how spectrophotometry works.

Using a device called a spectrophotometer, the ALS equipment measures and compares the amount of light absorbed by a substance. Thus, oil analysis can provide both a quantitative and qualitative reading to identify, from the interaction of light, the concentration of substances.

Chemical elements emit light with their own color (electromagnetic spectrum) and this is how they are identified. The intensity of this light is related to the amount of the chemical element in the sample.

At ALS we prefer atomic emission spectrometry for this work as it allows much better ranges and distinctions in terms of attrition and contamination than other spectrometric techniques (absorption, X-ray and others).

Conclusion

In this post we highlight two of the main oil analysis techniques: spectrophotometry and ferrography. There are a number of other extremely valuable techniques and your company needs help with the expertise necessary to identify which predictive maintenance tool best suits your company’s needs.

Predictive maintenance and oil analysis are with ALS!

Author: Prof. Tarcísio Baroni