Lubricant oil, the blood in the machine

There is a reason blood tests are such a common diagnostic tool: our blood contains a wealth of information about what is happening inside our bodies. We know that, in a healthy person, its normal composition lies within certain ranges. Changes in parameters such as blood cell counts can therefore provide valuable clues that something may be worth looking into.  Moreover, blood circulates throughout our body and, along the way, picks up all sorts of molecular signals and contaminants that reflect processes happening in different parts. An excess of urea, for example, may be a sign of a kidney problem.

In machines, something similar happens with lubricant oil. The composition of in-service lubricants also needs to remain within certain parameters to ensure that machines work properly and avoid damage. Also, much like blood, lubricant oil circulates throughout the machinery it protects, picking up contaminants and debris from deteriorating parts that can help catch problems early and minimise machine downtime. Therefore, oil tests can be as informative about the health of machines as blood tests are for people’s health.  

Machine lubricants require regular changing to maintain their performance. And since oil condition can deteriorate at different rates even in similar machines depending on how they are used [1], oil changes at fixed intervals may not be enough for high-performance industrial machinery. Changing it too early wastes money and produces unnecessary environmental impact, while changing it too late may result in reduced performance or unexpected breakdowns. This is why regular oil tests are an integral part of good industrial maintenance. Next, let’s see what type of information these tests can give you about lubricant oils and the machines they protect.

Seeing the future in the oil

Maybe “seeing the future” is a bit too much, but oil analysis is certainly a way to keep you apprised of your machines’ condition and catch potential problems before they become emergencies [2]. Just as with blood tests, oil analysis can involve different tests that look at critical health indicators. In the case of machines, these are some of the main things we can learn from their oil:

  • Viscosity: A critical property, it determines if the oil is still flowing and lubricating as it should.
  • Chemical deterioration: Lubricants gradually change chemically as they are used. Measurements such as oxidation, nitration, sulfation and acid or base number can help determine whether the oil is approaching the end of its useful life.
  • Contamination: Depending on the operating conditions of the machine, contaminants such as water, glycol (antifreeze), soot or fuel (gasoline or diesel) can find their way into the oil. This not only deteriorates the lubricant, but can also be a sign of underlying issues with the machinery.
  • Wear: Even with adequate lubrication, machine pieces gradually wear, and some of this material ends up in the lubricant. Oil analysis can detect these particles and their composition. A sudden increase in wear particles can indicate abnormal wear rates, while their composition can give clues into which components are most affected. 

One of the more widely used tests for oil analysis is Fourier Transform Infrared (FTIR) spectroscopy. FTIR spectroscopy devices shine an infrared beam of light through a sample and measure how the sample absorbs that light. The chemical components in the sample absorb light differently, so the resulting absorption pattern, or spectrum, can tell you about the oil’s chemical composition and, importantly, how it changes over time.

In oil condition monitoring, FTIR spectroscopy is typically used to analyse indicators of chemical deterioration and contamination through trend analysis. That is, a series of periodic samples are analysed and changes over time are recorded. This allows relatively small changes in oil contaminants and chemistry to be detected and tracked before they develop into more significant problems.

FTIR is just one of several complementary techniques used in oil analysis. Other methods include viscometry to measure oil viscosity, elemental analysis techniques such as inductively coupled plasma optical emission spectroscopy (ICP-OES) to measure concentrations of metals associated with wear, and particle counting to assess particulate contamination. In combination, these techniques can give you very detailed information about your lubricant oil.

However, much like blood testing equipment ranges from simple handheld glucose meters to specialized labs with high-tech gear and strict standards, there are many ways to test the oil in your machines. Choosing the right approach depends on several factors, and one of the most important is the scale of your operation.

The hidden variables: scale and volume

Oil condition monitoring requires specialised equipment and expertise, so outsourcing to a dedicated laboratory is often a practical choice. However, depending on the scale and operational needs of an organisation, investing in its own analytical capabilities may make economic sense.

Imagine you run a company with two delivery vehicles and you want to practise preventive maintenance and test their oil. You may decide to test each of them two or three times a year to make sure there are no developing issues. Under these conditions, it hardly seems worth buying specialised equipment or training an analyst. The best solution for you, then, is probably to send samples to a laboratory and have a specialist give you a full report.

But what if your company grows to 500 vehicles? Your testing volume rises from 4–6 samples per year to 1,000–1,500. At this scale, setting up an in-house oil analysis laboratory with dedicated equipment and staff may become worthwhile. However, the number of machines is only part of the equation. Imagine that, instead of a delivery company, you own a Formula 1 team. Your cars operate under extreme conditions and require multiple oil tests per race, as an undetected issue could be extremely costly.  Indeed, F1 teams are known to require over a thousand oil analyses per season, a similar testing volume to our hypothetical delivery van fleet.

Ultimately, the decision of investing in in-house capabilities comes down to a cost-benefit assessment. The sheer number of samples that need analysing may make developing your own analytical infrastructure worth it in the long run. Alternatively, failure in a critical piece of equipment may have a very high cost, like losing half your F1 team or stopping operations for an extended period. In these cases, preventing a single failure is enough to pay for several years of oil analysis [2]. Whether that testing is best performed on-site, in-house or by an external laboratory will depend on the organization’s particular needs.

Different scales, different solutions

Oil condition monitoring can use different analytical techniques and devices depending on testing needs. At the point of use, handheld instruments, minilabs or compact benchtop instruments can measure specific indicators, such as moisture ingress, fuel contamination or accelerated wear. This kind of point-of-use testing is commonly found not only in small operations, but also where immediacy matters or where remoteness makes shipping samples impractical.

Sometimes, the number of samples that need analysing, the frequency with which measurements are required or the potential costs of a mechanical failure make it worth setting up an in-house laboratory. Such a setup can have the advantages of lower per-sample costs, immediacy of results and in-depth knowledge of the needs of the operation and the characteristics of the machines involved. These laboratories may have a suite of complementary analytical capabilities, with several benchtop instruments like FTIR spectrometers, particle analysers or viscometers. In the case of in-house laboratories, testing procedures and QA will usually be tailored to the particular needs of the operation and managed internally.

Finally, there are also centralised labs for in-use oil analysis. These labs may need to analyse hundreds or even thousands of samples a day from customers with very different needs. Therefore, we will find a wide breadth of analytical equipment and, importantly, heavy automation that can handle high sample volumes. Moreover, these laboratories need to produce consistent, defensible results across large numbers of samples from different customers. This calls for rigorous QA procedures, which may include external audits and cross-laboratory checks, as well as adherence to internationally recognized analytical standards, such as ASTM D7418 and ASTM E2412 for FTIR-based oil condition monitoring [3].

Oil condition monitoring across industries

Different industries illustrate how testing volume, frequency and operational needs influence the choice of analytical solutions. In power generation, it is common for many facilities to send their oil samples to external labs. However, where equipment is critical and downtime is costly, some facilities implement their own point-of-use testing programs to obtain rapid, frequent information on indicators such as wear, contamination, or oil degradation.

Point-of-use testing is also common in the marine industry. In the case of in-service vessels, it is not always feasible to send samples to a laboratory. In many cases, the solution is for the maintenance crew to have their own testing kits or handheld devices to allow for frequent testing [4]. More sophisticated systems can combine onboard testing or monitoring with remote analytical support ashore.

Some mining operations deal with the same combination of remoteness and need for immediacy as the marine industry, while also dealing with scale and risk. Mines include many different machines, some of which require very high performance. A failure in these machines can seriously disrupt operations, making frequent oil analysis with rapid turnaround an important precaution. This can make well-equipped in-house laboratories particularly attractive to large mining operations [5].

In the case of manufacturing, scale can become the deciding factor. Once a plant or group of plants has enough lubricated assets to generate potentially hundreds of per month, setting up an in-house laboratory with a dedicated lubrication team can become cost-effective. As in mining, the consequences of equipment failure can also be extremely costly, potentially halting production, damaging products or putting perishable goods at risk. This makes rapid access to in-house oil analysis particularly valuable for critical production equipment.

Finally, in aviation, individual operators may not generate enough samples to justify their own oil analysis infrastructure, and they may therefore rely on specialised laboratories as part of the aircraft’s overall maintenance programme. Larger organisations such as major airlines or military aviation organisations may instead set up their own analytical infrastructure.

Why choose just one?

Although different industries may favour point-of-use analysis, in-house laboratories or specialised analysis centres, it is rare for any operation to rely on only one of these layers. An on-site technician for a power plant may regularly test specific indicators for a few critical pieces of equipment, but the facility will still periodically send samples to a specialised laboratory for more comprehensive analysis. Similarly, even if a manufacturing plant demands enough sample throughput to justify an in-house lab, they may still rely on a specialised lab for problematic or unusual samples.

Conclusion

As blood tests do for people, oil condition monitoring provides valuable information about the health of machines. However, the best approach to oil analysis depends on the needs of each operation.  Where remoteness or the need for rapid results makes it necessary, point-of-use testing can provide immediate information. Where testing volumes or risk of costly failures justify greater investment, in-house laboratories may become attractive.

Specialized contract laboratories remain an important part of oil condition monitoring at every scale, providing routine analysis for some operations and additional analytical capabilities for others. Their specialist expertise, advanced instrumentation and adherence to internationally recognized analytical standards can help ensure reliable, consistent results.

But what are the standards for oil condition analysis, and why do they matter? Let’s find out in our next article. Stay tuned!

References 

1. Rodrigues et al. (2020). Predicting motor oil condition using artificial neural networks and principal component analysis. Eksploatacja i Niezawodność – Maintenance and Reliability, 22(3).

2. U.S. Department of Energy (2010). Operations & Maintenance Best Practices: A Guide to Achieving Operational Efficiency. Release 3.0, Chapter 6.

3. ASTM International. ASTM D7418: Standard Practice for Set-Up and Operation of Fourier Transform Infrared (FT-IR) Spectrometers for In-Service Oil Condition Monitoring; and ASTM E2412: Standard Practice for Condition Monitoring of In-Service Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry.

4. CIMAC (2011). CIMAC Recommendation No. 30: Used Engine Oil Analysis – User Interpretation Guide.

5. Pacific Northwest National Laboratory (2005). Development of On-Board Fluid Analysis for the Mining Industry – Final Report. PNNL-15299.