The importance of getting to know properly your oil sample
Oil analysis is the laboratory analysis of a lubricant’s properties, suspended contaminants, and wear debris. It is performed during routine predictive maintenance to provide meaningful and accurate information on lubricant and machine condition.
By tracking oil analysis sample results over the life of a particular machine, trends can be established which can help to eliminate costly repairs.
Introduction to Oil Analysis
Oil analysis is fundamental for industrial equipment used in a wide range of industries which are expected to maintain a high level of productivity. Fulfilling this demand is dependent on reliable, well-maintained equipment. Successfully monitoring fluid condition with laboratory oil analysis can ensure equipment uptime and reduced maintenance costs, industrial oil and fluid testing encompass all fluid conditions for a variety of applications.
Throughout the time, oil analysis has helped to diagnose the internal conditions of components and their lubricants in virtually every industry that involves heavy-duty machinery or stationary industrial equipment. Any company that operates equipment using oil (lubricant or hydraulic) can obtain substantial returns from a minimal investment in this type of testing. Although some years ago, oil analysis test methods were surprisingly simple to perform, today the processes comprise the most advanced analytical tools and technologies.
Commercial oil analysis uses a combination of physical and chemical tests to monitor lubricant and component conditions.
Oil Analysis Categories
Oil analysis tests can be classified into three categories:
- Analysis of oil properties including those of the base oil and its additives;
- Analysis of contaminants;
- Analysis of wear debris from machinery.
In addition to monitoring the oil contamination and presence of wear metals, modern usage of oil analysis includes the determination of additives in oils to conclude if an extended drain interval may be used. Maintenance costs can be reduced using this analysis, allowing to determine the remaining useful life of additives in the oil.
By comparing the results of new and used oil, a tribology can determine when an oil needs to be replaced. Careful analysis might even allow the oil to be “sweetened” to its original additive levels by either adding fresh oil or replenishing additives that were depleted.
Oil analysis professionals and analysts usually perform tests according to certified ISO and ASTM standards. The certification oil analysis laboratories and personnel certifications have emerged to ensure the highest levels of oil testing and analytical quality. Some of the typical standard analysis tests are as followed in Table 1:
The choice of which tests are needed is strictly determined by what the user wants to find with the testing. Determination of Viscosity or acid number tests, for example, may be useful if it is just to monitor lubricant health.
A typical predictive maintenance technique is ferrography, which analyses iron in oil. To monitor equipment health, metals and ferrous density testing may be the best alternative. Most oil analysis users look for a combination of equipment health, lubricant health and lubricant cleanliness.
As seen from Table 1, there is a test designated as “Spectrochemical Analysis” which might be the cornerstone of an effective oil program, since it can detect 21 elements that can represent wear metals, contaminants and additives present in the lubricant oil.
This testing can identify problems in their developmental stages allowing equipment managers and maintenance personnel to fix small issues before they become serious problems or originating catastrophic consequences.
According to the same table, we can visualize the use of breakthrough tests, such as Analytical Ferrography, which identifies types of wear occurring.
Oil Analysis has become considerably important in certain areas such as Petrochemical, for example, since refineries operate continuously and it is fundamental to enhance equipment reliability and guarantee world class condition monitoring.
Machine condition monitoring based on oil analysis has become an important, if not mandatory, maintenance practice for many manufacturing companies producing all sorts of products. An effective oil analysis program will keep your equipment running through effective condition monitoring of oil wetted components.
Table 1 – Typical Oil analysis test
|Test description||Standard Method|
|Determination of TAN or TBN value by titration||ASTM D974|
|Kinematic viscosity @50ºC||ISO 3104|
|Determination of the Flash Point by the Pensky-Martens closed cup method and
flash point and fire point in open cup (ASTM D92)
|Determination of the Flash Point in open cup||ASTM D92|
|Apparent density @50ºC||ASTM D1298|
|Determination of sulphur content by x-ray fluorescence (FRX)||ASTM D4294|
|Determination of corrosion by the copper blade method||ASTM D130-12|
|Ash Content||ASTM D482|
|Air Release Properties||ASTM D3427|
|Carbon Residue – Conradson||ASTM D189|
|Chlorine, Total, In Oil By Dexsil Field Kit||ASTM D5384|
|Cloud Point||ASTM D2500|
|Colour, ASTM||ASTM D1500|
|Dielectric Breakdown||ASTM D877|
|Ferrography – Analytical||ASTM D7690|
|Foaming Characteristics||ASTM D892|
|Fuel Dilution, Diesel||ASTM D7593|
|Fuel Dilution, Gasoline||ASTM D7593|
|Glycol, ASTM||ASTM D2982|
|Insoluble Contaminants of Hydraulic Fluid||ASTM D4898|
|Interfacial Tension||ASTM D971|
|Pour Point||ASTM D97|
|Ramsbottom Carbon Residue||ASTM D524|
|Refractive Index||ASTM D1807|
|Oxidation Stability (Tost)||ASTM D943|
|Particle Count (Laser)||ISO11500, 4406|
|Water by Karl Fischer – Fuel/Oils||ASTM D6304|
|Water by Distillation||ASTM D95|
|Pentane & Toluene Insoluble||ASTM D893|
|Spectrochemical by ICP (21 Standard Elements and non-standard elements)||ASTM 5285|
|Trace Sediment in Lube Oils||ASTM D2273|
|Rust Test||ASTM D665|
|Saponification Number||ASTM D94|
Other parameters to consider
Although the analysis is fundamental, also other parameters such as the sampling have considerable importance. Oil sampling is a procedure for collecting a volume of fluid from lubricated or hydraulic machinery for the purpose of oil analysis. It is important to ensure that procedures are used to minimize disturbance of the sample during and after the sampling process. Oil samples are typically drawn into a small, clean bottle which is sealed and sent to a laboratory for analysis. A complete sample information should also be provided for an accurate interpretation of the test results with well-informed maintenance or diagnostic recommendations.
Oil samples should be taken in representative regular intervals, being indicative of the real condition of the lubricant and the component. It is important to know the sampling point before reviewing the report. When the moment comes to review the latest set of sample results, it is unlikely that you will have the time to look up each piece of supporting data for each sampling point. Familiarity with the machines monitored, in all senses of the term (operational, mechanical, maintenance and servicing) is essential for relating mechanical, operational and documentary machine information to the oil analysis results.
Recording supporting information, like filter changes can also help correlate changes and problems highlighted by the report to maintenance activities. Frequent communications should be established between the oil analysis laboratory and the user, to optimize laboratory interpretations and recommendations. Test reports should be reviewed promptly so that critical machine or lubricant conditions are addressed fast and equipment damage and production losses are as minimal as possible.
With that said we can conclude that an effective oil analysis program requires an organized and sustained effort by both user and laboratory to achieve optimal machine health and reliability.