• Unit 3A, Adwick Park, Swinton, Rotherham S63 5AB

TAN and TBN: Are All Acids Really Bad?

Are All Acids Really Bad? Thinking

Whenever we hear the word “acid”, we immediately think about negative associations. We can think about metals being damaged by corrosive acid or even getting an upset stomach due to acid build-up. Typically, acid in high volumes can cause some damage (think about acid reflux after eating some severely spicy food, the results are not very pretty). Just as humans have low tolerances for the build-up of acid inside of their bodies, machines experience similar attributes.

In lubricated machines, there is a test which we can perform to determine if the acid level is approaching its tolerance limit. This is called the TAN (Total Acid Number) ASTM D974. The TAN test indicates the volume of acid present in an oil. However, it is usually performed on non-engine oils. This doesn’t mean that engine oils have no acid present, on the contrary engine oils may have the highest volume of acid present.


Understanding the TAN & TBN results

During the operation of most engines, acids are produced as by-products and these can enter the oil. Hence, for engine oils, one will typically notice that TBN (Total Base Number) values are given on the data sheets. The TBN gives an indication of whether acids have been neutralized by alkalis contained in the additives of oils. For instance, regular diesel engine oils usually have a TBN of 10-15. When an oil analysis is performed, one can determine whether the TBN value has decreased or not.

If the TBN value shows a decrease, this can indicate that acids were neutralized during the lifetime of the oil within the machine. However, we need to understand the limits which should be observed before the neutralization stops. The alkali (base) product in the oil is finite and at some point, it will be reduced to a level where it can no longer protect the oil. At this point, the acids will continue to build and can start negatively impacting the machines causing wear.

One of the most important aspects of oil analysis is trending. When we trend the results of tests (viscosity, metals, TAN, TBN) we can gain a clearer picture of what’s occurring on the inside of the machine. This can in turn help us to identify steps which can be taken to protect the machine and avoid the dreaded downtime!




Typically, OEMs advise on the warning limits for TAN / TBN depending on the type of equipment. One basic rule of  thumb regarding TBN is to observe its rate of decrease. If the TBN is 50% lower than its original value then we’ve got some acid in our machine and have some time in which to rectify the situation. Similarly, the TAN test gives an indication of the actual volume of acid present. When the TAN value shows an increase of 0.3mgKOH/g those warning flags start to raise! However, it is always advised that you consult your OEM on these values as they may differ depending on application and environment.



All lubricants degrade during service, this is part of its sacrificial nature. However, the challenge occurs when the lubricant is no longer able to properly execute its required function due to degradation. This is where the warning limits and tolerances can provide critical information to users. These assist users in determining whether the environment or operation of the machine is severely impacting on the lubricant.

When should TAN be used?

For each of the six degradation mechanisms, there are tests which can be performed to help diagnose the type of degradation which has occurred. This in turn, helps to implement measures in rectifying the challenge. The beauty of these tests is that they all tell a story but they cannot be standalone tests, otherwise part of the story would not be told.

Within the industry, some experts have argued that the TAN test (as a standalone test) is not entirely indicative of the presence of degradation. This holds some truth depending on the type of degradation mechanism. In oxidation, acids are not produced until oxidation has reached the termination phase. At this time, varnish molecules are already in production as well as the acids which are conveyed in the TAN test.


Laboratory Technician apprenticeship

The TAN test is relatively inexpensive and is usually packaged with the other basic tests, such as Viscosity, wear metals or contaminants. Therefore, it is wise to include the TAN (or TBN accordingly) as part of your monthly tests on equipment. This can assist in trending any increases in acidity of the oil and possibly prevent damage to the equipment.


Finding out the entire story

As mentioned earlier, the TAN / TBN results should not be used as standalone tests. They form a component of the story which is being told by the equipment. Let’s look at a few examples to help us understand how these values add to the plot of the story being told by the equipment.

Case study 1 – Hydraulic Component

The used oil analysis for a particular hydraulic component showed an increase in the TAN value by 0.2mgKOH/g but no increases in wear metals, slight decreases in additive components and no major change to the viscosity. What should the customer do?

Hydraulic Arm

Any increase in acidity should be addressed. The increase in acidity, simply indicates that the volume of acid is building compared to the initial acid value in the oil. If we are not seeing any changes to viscosity, or an increase in wear metals it can indicate that the acid has not reached to a level where it has affected the oil. This is good news, as we now have time to determine the cause of the rise in acid before any damage occurs. Additionally, this can help us project the estimated life of the oil.

In this situation, the customer can resample the oil at a shorter interval and trend the increase in acidity over time. Any changes to the environment or operations should also be noted as these may impact on the oil. Some customers may opt to change the oil to avoid these increases in acidity however, if the root cause for the increase in acidity is not addressed then the customer can face shorter oil drain intervals. This in turn, can impact on the health of the asset and lead to unforetold expenditure associated with these shorter oil changes.


Case study 2 – Marine Diesel Engine Component

A marine operator noticed the TBN levels decreasing quickly (at a rate of 30% within one month) for one of the diesel engines on his vessel in the fleet. Additionally, the viscosity had decreased by 10% and the wear metals werMarine Diesel Enginee approaching their warning limits. He also noticed that there was some fuel dilution present (3%) but this had not reached the OEM’s warning limit of 6%. How should we advise this marine operator?

For rapid declines in TBN and a decrease in viscosity, any operator should be concerned. Once the viscosity decrease (or increases) out of its range, we can suspect that something is occurring to cause this deviation. When there are decreases in viscosity, the associated degradation mechanism is thermal degradation. However, in this case, there is also the presence of fuel dilution which typically decreases the viscosity of the oil.

Fuel dilution should be investigated and addressed as one of the possible causes for the degradation of the oil. Additionally, the decrease in viscosity can lead to the increase of the presence of wear metals as seen in the report. The operator can perform some inspections on the rings, fuel injectors and fuel lines to determine if there are any leaks into the system.

Any changes to the operations or environment of the engines should also be noted. The storage and handling of the lubricants for these vessels should also be investigated to rule out fuel dilution via contamination. Sometimes, when engine oil is being transferred, the equipment may have been used to transfer other fluids and the engine oil can become contaminated. Additionally, increases in temperature should also be noted to rule out the possibility of thermal degradation.


About The Author

Sanya Mathura MLE

Managing Director and Founder of
Strategic Reliability Solutions Ltd

Sanya is an entrepreneur based in Trinidad & Tobago with a passion for adding value to the industry through strategic reliability solutions (it is also the name of her company). She is a strong advocate for women in STEM and a published author (with a couple more books on the way). While she has her bachelor’s degree in Electrical & Computer Engineering, after getting into the lubrication industry, she fell in love with reliability and pursued her Masters in Engineering Asset Management. Later on, she attained her ICML MLE certification and became the first person (and only female) in the Caribbean to do so.

To get your hands on Sanya’s brand new book, please click here


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Ferrous Wear and Iron Analysis

Ferrous Wear and Iron Analysis


What is FW and Iron on my sample report?

Ferrous Wear and Iron Analysis

Why don’t they always correlate?

Ferrous Wear (FW), is a measure of ferrous debris within an oil sample irrelevant of particle size. The measure of FW allows you to see a total value of magnetic particles within a sample. Iron (Fe) is a ppm measure of iron particles less than 10um in size within a sample. The ppm Iron gives you a concentration of Iron particles <10um.

Therefore, the two results seen on most used oil analysis reports may not correlate as it is in fact two separate measurements. The reason for capturing both these measurements is down to the interpretation of the analysis, the small ppm measurements of Iron allow us to monitor the differing severities of wear while the FW reading allows us to notice when abnormal wear is occurring or just when someone has took a dodgy sample!


How do we test FW and Iron?

The FW instrument uses a magnetic field which calculates the change of permeability when the sample is introduced and outputs a value of FW.

The Iron ppm content is measured by spectroscopy, at PCMS we utilise the ICP. Inductively Coupled Plasma which works by exciting the sample and measuring the movement of atoms within the sample to provide a concentration of 23 different elements.

Ferrous Wear and Iron Analysis    Ferrous Wear and Iron Analysis

Who would benefit from Ferrous Wear Analysis?
All industries with ferrous components within their assets. Anyone who needs to understand the causation of the wear to be able proactively resolve and prevent the issue happening again.

When do we perform Wear Debris Analysis?
PCMS will carry out this type of analysis on their own initiative if uncharacteristic results are seen for a particular asset.

How our testing works
Using the test methods explained above, along with optical analysis, our amazing analysts will be able to provide you a story of your lubricant and assets relationship and journey.

To find out more about FW and Iron Analysis please click here

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Filter Debris Analysis

Filter Debris Analysis


What the…?

FDA is exactly what it says on the tin, analysis of the debris from within a filter!

FDA can be carried out on and provide beneficial data for any filter from any fluid filled system. The benefits are huge however we will speak specifically today on the wear debris analysis phase of FDA.


Why on earth..?

Filter Debris AnalysisWould you like to know if wear is occurring in your asset? Would you like to also know the type of wear and possible repercussions that may be heading your way? If so carry out FDA… its that simple.

During routine oil analysis we try to take samples before any filters, so that within the sample we capture any insoluble particles that are circulating within the lubricating system. This is good practice so we can try to understand where the contaminants are originating and how to control or stop them.

However, we only sample periodically, maybe monthly, quarterly. There are masses of particles which we do not see in between samples, these particles are then hidden away by the filter media.

There are of course many more reasons for FDA to be carried out, one of which being to reduce the interval between filter changes. Coupled with regular ISO analysis on your lubricant samples we can help you determine the capacity to which the filters are being utilised. This will help industries save thousands of pounds which can then be spent elsewhere.



Ok so we want to find out what is happening within our filtered asset, it sounds clunky oil results have been less than satisfactory…

The debris is extracted from the filter without destruction of the actual filter media. The debris is then run through many instruments such as the ICP to allow us to categorise and quantify the elementals within the debris. For example, the ICP will allow us to see the concentrations of wear metals such as Iron, Copper, Chromium through to the amount of silicon in there which could be indicative of ingested contaminants.

Example data for an FDA report:

FDA Report

The second phase of the analysis is to manually evaluate the physical characteristics of the debris particles, this allows us to diagnose how the particle came to circulate the system. The topography, colour size and shape allow us to identify the type of wear which may be occurring or what the particle is!

This came from this..

FDA Image

Who would benefit from it being done or who needs it?
All filtered assets however large fleet industries can save lots of money by reducing the amount of filter changes carried out while improving reliability at the same time!

When does it need to be done?
On filter change

How will it be done?
A filter is sent to the lab in as sterile a way as possible by the customer then we work our magic

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Oil Analysis Process

What is the Oil Analysis Process?

We often get asked what our Oil Analysis procedure is and what takes place. Many want to know how the whole process works and what it entails, so we have broken it down for you:

Step 1 – Determining the Test Suites

Firstly we must understand the asset(s) as a bare minimum to ensure that at the very least we are carrying out the industry standard test suite. There is no use carrying out tests which have no value to the end report, for example carrying out a TBN on a lubricant which has no TBN additive present is a waste of our time and our customers money which can be better spent on relevant tests.

Once the basic test suite is in place we must then tailor the suite to ensure the specific asset, environment and industry is captured in the data. For example the same asset land based may need a completely different test suite to the same asset off shore. The contaminants also vary from site to site so the test suite must reflect this. PCMS pride themselves on being as nosey as possible so we understand our customers sites and assets inside and out.

There may also be individual requests from our customers and certain customers may require unusual tests to understand specifics about their assets. We ensure we understand our customers needs so they get the information they are looking for every sample.

All this being said there are certain assets working on 1ltr of oil and others on 10,000ltrs so we ensure the most valuable tests and data are carried out when there is not enough sample to go around. The same can be said for access, if we can only obtain a sample on annual site shutdowns we may want to carry out more in-depth analysis to ensure our recommendations and findings are as future proof as possible.

To determine the test suites we must also understand the sampling points and any interferences this may cause. We are lab analysts but we also have onsite experience and understand not all samples can be “perfect” or even representative however if they are consistent we can work with this and ensure the data is as relevant as possible.

  1. Understand the asset
    – Ensuring the industry standard for the asset as a minimum is carried out.
    – Understanding how the asset works and what faults/trends we are likely to see along the asset’s life cycle so we can capture them with the analysis.
  2. Understand the asset’s operating environment
    – Ensuring the analysis catches any contaminants or wear types associated with the asset, process, and environment.
  3. Understand the customers’ requirements (what they want to know about their asset)
    – Are they concerned with wear/contamination/oil health predominantly or everything?
  4. Understand the customer and assets limitations
    – Asset oil sump size – there must be enough oil to take the size sample required.
    – Can the customer access the asset on a routine time-based programme or does the analysis need to be more in-depth as can only be accessed at certain times?
  5. Understand the physical sampling points
    – Where is the sample being taken from?
    – Will this affect the analysis results?
    – Is there anything we can do to cater for this?


Step 2 – Test Kit Requirements

So we know what tests we will carry out and we have a good understanding of what our customers eat for breakfast, dinner and tea. Just kidding their assets, processes and site of course! Now we must ensure we provide our customers with a test kit that is practical yet precise to allow for the correct amount of sample to be obtained in the most efficient, effective and sterile way possible for the customer. This means everything from the sample bottle to the sampling equipment needs to be spot on.

Some customers like to hoard sample kits and order 3000 at a time, which is fine and we ensure all our kits are packaged in a way that they will not ingest contamination during storage! Other customers like to have a specific amount of kits with information pre filled delivered on specific days every month.. This is also fine we have a super efficient system and set of staff who live for this sort of organisation!

We understand the customer is “always” right but we also try our best to advise out customers on what we think will work best for them with regards to the type of kits and equipment they require. We understand not everyone likes a glass sample bottle but sometimes transformers just need that bit of extra shine!

Here is a breakdown of what we consider when we are putting your kit together:

  1. What analysis are you having?
    – So, we have determined your unique test suites, we need to now make sure your sample kit caters for this
    – Are your bottles sufficient to provide the correct amount of sample for the tests and any rechecks?
    – What if we have to carry out a test unexpectedly to clarify another result? we need a little bit extra Headspace – there needs to be room for expansion of the fluid in the bottles
    – What is the sample type? Fuel? Transformer? Maybe you need a glass sample bottle
    – Where will you be sampling from? Do you need a vacuum pump or a wide mouth bottle?
    – Do you need tubing? Do you need the tubing pre cut per asset?
    – Do you need components in a box or specific kit packs for each asset with pre filled information
  2. How often do you need the kits?
    – Do you require 12 months’ worth?
    – Shall we send the kits to a specific schedule?
  3. Who needs the kits?
    – We understand many people may require kits at different places on one site we can send the kits to whoever wherever whenever


Step 3 – Awareness Training

So we have delivered you some super tailored kits and developed a specific testing plan.. What now?

This is the most daunting part for most of our customers and we are more than proud to say we have no secrets! We want our customers to understand everything to ensure that any adaptations can be made in an instant to ensure reliability is always the key focus. Our training ranges from teaching people what oil analysis is to the geeky science stuff that goes into the interpretation of all that data. We don’t want our customer to read a recommendation and think “well if they say so” we want them to full understand why and have the knowledge to ask the relevant questions as their site develops and grows.

We have determined tests suites for your assets and industry.
We have also assembled your kits based on your requirements and tests suites.
Now training may be needed.

Awareness training is tailored to industry, site and assets to ensure the training is relevant and useful.
The topics that are covered are:

  • Oil sampling rules
  • Oil sampling challenges based on site and industry
  • The importance of reference oils
  • The importance of trends
  • Basic lubrication chemistry
  • Basic oil analysis results interpretation

For more about our training courses available, please click here


Step 4 – Collect Samples

Our training will allow people to confidently take samples using basic principles and procedures to ensure that all important data is as consistent and representative as possible. PCMS can assist from showing a customer where to sample every single asset to coming on site and doing it for you!

Samples need to be collected following the guidance from the oil awareness training described in step 3.

Sampling procedures and intervals vary depending on asset type, industry, and criticality; however, the sample point must always follow the rules of sampling:

  • The sample must be representative of the asset environment
  • The sample must be collected from the same place by the same method every time
  • There must be enough sample for the testing required
  • The asset lubricant level must be checked after sampling
  • The sample must be properly labelled


Step 5 – Testing & Analysis

The samples have been collected and sent to the lab as soon as possible!

Now it’s down to us! We will test the Lubricants, coolants and fuels under a test suite suitable to the asset and environment. The samples are sorted and logged into our bespoke system which allows for tailored alarm sets and analysis parameters. We carry out all our analysis under ASTM and ISO methods to ensure accuracy and conformity of results.

Standard testing will be carried out within 3 working days of receiving the sample.

To see a comprehensive list of all of our test suites and sample types, please click here


Step 6 – The results

So what do we need to know from all those tests?

  • We need to understand is the asset wearing?
  • Is there any contamination?
  • And how’s the lubrication, coolant and fuel doing?

All the data is represented in a raw format with a simple explanation below the report which includes any findings, diagnosis for those findings and a recommendation on any remedial work or resampling rates.

Our results portal online is all our own with numerous ways to see, download and manipulate your data.

The results from the laboratory should be reported as soon as complete on a report format which can be fully understood by the end user.

At PCMS our results show the following

  • What we have found
  • A diagnosis of what we found
  • Recommendations of what to do next

Our results are uploaded to our online results portal where 4 different types of pdf can be pulled off, 4 different types of charts, and 12 different types of CSV

We understand different industries, cultures and people process information in different ways which is exactly why we have so much flexibility in how our results can be downloaded.

For more information about our oil analysis service click here,  complete our contact form or email us at info@pcmseng.co.uk

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Why Should You Perform Oil Analysis?

Why Should You Perform Oil Analysis?

rail oil analysis

The most evident reason to undergo oil analysis is to understand what the condition of the lubricant is but it also can be used to assess the condition of the asset that the lubricant has been taken from. There are 3 categories of oil analysis:

  • Fluid Properties
  • Contamination
  • Wear Debris


Fluid Properties

The Fluid Properties analysis identifies the oil’s current physical and chemical state. It also defines its remaining useful life (RUL).

By doing this test, the following questions are able to be answered:

  1. Does the sample match the specified oil identification?
  2. What is the oil’s RUL?
  3. Is the correct oil being used?
  4. Are the correct additives present and active?
  5. Have any of the additives depleted?
  6. Is the viscosity of the oil as expected? If not, why?


It is important to detect the presence of contaminants as they can be destructive. Under oil analysis will identify destructive contaminants and specify their potential sources, whether these are internal or external.

The kinds of questions that can be answered from oil analysis are:

  1. What is the cleanliness of the oil?
  2. What types of contaminants can be found in the oil?
  3. What is the source of the contaminants?
  4. Are any other lubricants or fluids detected?
  5. Is there any evidence of any internal leakage?

Wear Debris

Wear Debris oil analysis identifies the existence of particles produced as a result of mechanical wear, corrosion or other machine surface degradation.

The types of questions that it may answer are:

  1. Are there any abnormalities to the machine degradation?
  2. Is wear debris produced?
  3. Which components are the most likely source of the wear materials?
  4. What is the type of wear and what is its cause?
  5. What is the severity of the wear condition?

It is imperative to know whether any actions need to be undertaken to ensure the health of the machine and to elongate the life of the oil.

Oil is the “lifeblood” of a machine and can be compare to blood in the human body, therefore oil analysis can be treated as the same as a blood test. These are completed to detect any abnormalities and to breakdown the overall health of the lubricant and the asset that the lubricant is being used. One test type alone doesn’t have the capability to detect all the functional elements that may be affected. Therefore the three types are used. In the same way the blood taken from a human is analysed, studied and a conclusion is made of the treatment needed to be taken, a full report can be made from analysis with a comprehensive action plan of any “treatment” that may need to be done on either the oil or the asset.


Oil Analysis Basics

To complete successful oil analysis, samples need to be taken in a careful manner.

All samples are subjected to several tests using highly complicated and advanced machinery. It is then down to qualified laboratory technicians to interpret the data. This is more effective the more that the technicians know about the assets that the samples have been taken from. Without this information, the results may be imprecise.

Here is a list of the information that would be advantageous for the technician to know:

  • Anything that may affect the machine. This is most commonly the machine’s environmental conditions. This can be any extreme temperatures, high humidity, high vibration, etc.
  • The originating component (steam turbine, pump, etc.), make, model and oil type currently in use
  • The permanent component ID and exact sample port location
  • Proper sampling procedures to confirm a consistently representative sample
  • Occurrences of oil changes or makeup oil added, as well as the quantity of makeup oil since the last oil change
  • Whether filter carts have been in use between oil samples
  • Total operating time on the sampled component since it was purchased or overhauled
  • Total runtime on the oil since the last change
  • Any other unusual or noteworthy activity involving the machine that could influence changes to the lubricant condition

An oil analysis report can display a large amount of information that may not be easy to digest. It takes a good level of understanding to be able to interpret the data. Oil analysis can be costly and the equipment and machines used to undertake the tests are very expensive. Many companies have a large budget to deal with the cost of oil analysis to help as part of their condition monitoring strategy but unfortunately many staff are unable to understand, to the full extent, what the reports identify, therefore not benefiting the company.


What to Look for When Reviewing an Oil Analysis Report

  1. Read and check the data on the oil type and machine type for accuracy
  2. Verify that reference data is shown for new oil conditions and that trend data is at an understood frequency (preferably consistent)
  3. Check the measured viscosity
  4. Verify elemental wear data and compare to reference and trended data. Use a wear debris atlas to match elements to their possible source
  5. Check the elemental additive data and compare to reference and trended data. Use a wear debris atlas to match elements to their possible source
  6. Verify elemental contamination data along with particle counts and compare with reference and trended data. Use a wear debris atlas to match elements to their possible source.
  7. Check moisture/water levels and compare to reference and trended data
  8. Verify the acid number and base number and compare to reference and trended data.
  9. Check other analysed data such as FTIR oxidation levels, flash point, demulsibility, analytical ferrography, etc.
  10. Compare any groups of data that are trending toward unacceptable levels and make justifications based on these trends
  11. Compare written results and recommendations with known information on the oil and machine, such as recent changes in environmental or operational conditions or recent oil changes/filtration
  12. Review alarm limits and make adjustments based on the new information

When an oil analysis report is created, the technician may include a summary section that is intended to put the results and any recommendations in less complex terms. As the technicians who complete the analysis may have never been in to contact with the asset that the sample has been taken from or have no knowledge of the history of the asset, many recommendations will be generic and may not be tailored to the individual circumstances.

With this being in mind, it can be the responsibility of the person receiving the analysis report to take any actions from their knowledge of the asset, the lubrication or the environment.


Oil Analysis Tests

For a standard piece of equipment undergoing the normal recommended oil analysis, the test slate would consist of “routine” tests. If more testing is needed to answer advanced questions, these would be considered “exception” tests.

Routine tests vary based on the originating component and environmental conditions but should almost always include tests for viscosity, elemental (spectrometric) analysis, moisture levels, particle counts, Fourier transform infrared (FTIR) spectroscopy and acid number. Other tests that are based on the originating equipment include analytical ferrography, ferrous density, demulsibility and base number testing.


Several methods are used to measure viscosity, which is reported in terms of kinematic or absolute viscosity. While most industrial lubricants classify viscosity in terms of ISO standardized viscosity grades (ISO 3448), this does not imply that all lubricants with an ISO VG 320, for example, are exactly 320 centistokes (cSt). According to the ISO standard, each lubricant is considered to be a particular viscosity grade as long as it falls within 10 percent of the viscosity midpoint (typically that of the ISO VG number).

32% of lubrication professionals would not understand how to interpret an oil analysis report from a commercial laboratory, based on a recent poll at MachineryLubrication.com

Viscosity is a lubricant’s most important characteristic. Monitoring the oil’s viscosity is critical because any changes can lead to a host of other problems, such as oxidation, glycol ingression or thermal stressors.

Too high or too low viscosity readings may be due to the presence of an incorrect lubricant, mechanical shearing of the oil and/or the viscosity index improver, oil oxidation, antifreeze contamination, or an influence from fuel, refrigerant or solvent contamination.

Limits for changes in the viscosity depend on the type of lubricant being analysed but most often have a marginal limit of approximately 10 percent and a critical limit of approximately 20 percent higher or lower than the intended viscosity.

Acid Number/Base Number

Acid number and base number tests are similar but are used to interpret different lubricant and contaminant-related questions. In an oil analysis test, the acid number is the concentration of acid in the oil, while the base number is the reserve of alkalinity in the oil. Results are expressed in terms of the volume of potassium hydroxide in milligrams required to neutralize the acids in one gram of oil. Acid number testing is performed on non-crankcase oils, while base number testing is for over-based crankcase oils.

An acid number that is too high or too low may be the result of oil oxidation, the presence of an incorrect lubricant or additive depletion. A base number that is too low can indicate high engine blow-by conditions (fuel, soot, etc.), the presence of an incorrect lubricant, internal leakage contamination (glycol) or oil oxidation from extended oil drain intervals and/or extreme heat.


FTIR is a quick and sophisticated method for determining several oil parameters including contamination from fuel, water, glycol and soot; oil degradation products like oxides, nitrates and sulfates; as well as the presence of additives such as zinc dialkyldithiophosphate (ZDDP) and phenols.

The FTIR instrument recognizes each of these characteristics by monitoring the shift in infrared absorbance at specific or a range of wavenumbers. Many of the observed parameters may not be conclusive, so often these results are coupled with other tests and used more as supporting evidence. Parameters identified by shifts in specific wavenumbers are shown in the table below.

Elemental Analysis

Elemental analysis works on the principles of atomic emission spectroscopy (AES), which is sometimes called wear metal analysis. This technology detects the concentration of wear metals, contaminants or additive elements within the oil. The two most common types of atomic emission spectroscopy are rotating disc electrode (RDE) and inductively coupled plasma (ICP).

Both of these methods have limitations in analyzing particle sizes, with RDE limited to particles less than 8 to 10 microns and ICP limited to particles less than 3 microns. Still, they are useful for providing trend data. Possible sources of many common elements are shown in the table below.

The best way to monitor this type of data is to first determine what is expected to be in the oil. An effective oil analysis report will provide reference data for the new oil so any amounts of additive elements can be easily distinguished from those of contaminants. Also, because many types of elements should be expected at some level (even contaminants in certain environments), it is better to analyse trends rather than focus on any specific measurement of elemental analysis data.

Particle Counting

Particle counting measures the size and quantity of particles in the oil. Many techniques can be used to assess this data, which is reported based on ISO 4406:99. This standard designates three numbers separated by a forward slash providing a range number that correlates to the particle counts of particles greater than 4, 6 and 14 microns. Here’s an illustration of how different particle counts are assigned specific ISO codes.

Moisture Analysis

Moisture content within an oil sample is often measured with the Karl Fischer titration test. This test reports results in parts per million (ppm), although data is often shown in percentages. It can find water in all three forms: dissolved, emulsified and free. The crackle test and hot-plate test are non-instrument moisture tests for screening before the Karl Fischer method is used. Possible reasons for a moisture reading being too high or too low would include water ingression from open hatches or breathers, internal condensation during temperature swings or seal leaks.


Interpreting Oil Analysis Reports

The first thing to check on an oil analysis report is the information about the customer, originating piece of equipment and lubricant (see Section A of the sample report below). Including these details is the customer’s responsibility. Without this information, the effectiveness of the report will be diminished.

Knowing which piece of equipment the oil was sampled from affects the ability to identify potential sources of the measured parameters, especially wear particles. For example, the originating piece of equipment can help associate reported wear particles with certain internal components.

The lubricant information can provide a baseline for several parameters, such as the expected viscosity grade, active additives and acid/base number levels. These details may seem straightforward but are often forgotten or illegible on the oil sample identification label or request form.


What Is an Oil Analysis Kit?

An oil analysis sampling kit should include everything required to obtain a representative sample from a piece of equipment. Generally, the lab performing the analysis will offer this kit with their service. It should contain disposable tubing, a sample label, a vessel for mailing back the sample and a sample bottle.

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What is Turbine Oil Analysis?

What is Turbine Oil Analysis?

For an asset as valuable as a Gas or Steam Turbine, you’ll be thinking that all regular maintenance activities are carried out on time and correctly; but whilst vibration levels along with temperatures and pressures are monitored routinely to look for any signs of performance degradation or untoward changes that could affect the continued operation, wouldn’t it be beneficial to know just how well the Lubrication system is performing? In this article, I will be explaining all you need to know about what Turbine Oil Analysis is.

Why Should You Undertake Turbine Oil Analysis?

what is turbine oil analysisChanging the oil in your turbine is expensive, monitoring the performance and additive levels are not. This data will give you a trend that allows you to schedule and budget for the costly oil change.  

What parameters for the lubrication system are checked, other than ensuring the reservoir content is sufficient and oil pressure and temperature are within the expected limitsThe presence of Chip detectors and filter DPI gauges provide an indication that there is a build-up of debris. 

Would it be beneficial to know how the oil is performing in relation to the design standard?  You could say that temperature and pressure values are sufficient to satisfy this requirement.  However, those aspects do not show the chemical changes which are occurring in the circulation system content. 

How much longer will your oil continue to provide the key functions of cooling, lubricating, and protecting.  The expense involved in changing out the oil for these assets is not something that can be taken lightly, so carrying out a premature change to be on the ‘safe side’ brings that forward, but at significant cost. Also if you have no analysis how do you know if your change is premature or too late? 

When Should You Complete Turbine Oil Analysis? 

At regular intervals, samples should be sent away for analysis to assess several key aspects of the lubricant’s chemistry, examine the physical properties of the oil and identify any contamination. Monthly analysis should be carried out to keep trends relevant for the basic analysis suites. The full turbine suite to include the oxidative ability and remaining antioxidants should be carried out at a minimum every 6 months 

What Tests Are Completed As Part of Turbine Oil Analysis? 

A full turbine oil analysis suite should consist of the following:

TestTest MethodDescription
Rotating Pressure Vessel Oxidation Test (RPVOT) D2272-14aThis test evaluates the oxidative stability of the lubricant. The lubricants ability to resist oxidation and degradation under high temperatures, water contamination, oxygen, pressure, and a copper coil catalyst.
Remaining Useful Life Evaluation Routine (Ruler)D6971-09 + D6810This test monitors the % of remaining amine and phenol additives (which are primary antioxidants) compared to the new reference oil. These additives basically neutralise by-products of oxidation to stop the cycle of oxidation.
MPC Varnish PotentialD7843-18This test filters out the insoluble matter of turbine oil. The insoluble matter is then heated up and the colour is recorded using a spectrophotometer. This value is proportional to the lubricants potential to form harmful varnish and sludges.
Visual Inspectionn/aThe visual appearance of the oil and any particulates is noted to support the analytical results of the other tests.
Ferrous Wear Content (FW) D8184A total measure of ferrous particles in the sample irrelevant of size.
Elemental analysisD7303-12Measures several elements to identify wear issues, contaminant levels and chemical composition of the lubricant
Viscosity at 40°CD7279-14AA quality check to ensure the lubricant is still in the specification and therefore retaining its ability to lubricate.
ISO Particle countISO4406The particulates within the sample are analysed and counted to identify any particulate contamination issues.
Total Acid Number (TAN)D66411A + D974-14E02The total acid number allows the acidity of the lubricant to be analysed which gives us a trend and allows us to predict when oxidation is occurring.
PPM Water AnalysisD6304-07The CKF is used to determine the water content of the lubricant. This is compared to the reference oil to account for known additive interferences.
Fourier Transform Infrared (FTIR)E2412This allows the used lubricant result to be overlayed with the spectrum from the reference oil which will show changes to the chemical composition of the lubricant over time. Indicates oxidation, nitration, sulphation and contaminants.
BacteriaD6974-09R13E2Allows us to determine if any microbial growth is likely to occur in the oil tank due to steam, condensate or water contamination.

What Does A Turbine Oil Analysis Report Look Like?

A typical turbine oil analysis report is shown below. You can download our example turbine oil analysis report by clicking here.

What is Turbine Oil Analysis?

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Boundary Lubrication Issues

Boundary Lubrication IssuesLubrication Analysis

Adhesion is the result of two parts that drag across one another without adequate lubrication-film separation. This is also called Boundary Wear or Boundary Lubrication. The particles can be scuffed with striations from the dragging. The particles may show signs of melting due to the localised over-heating. Spherical particles are common when compete melting occurs.


Microdelamination is surface damage caused by steady state sliding and metal to metal contact at the microscopic asperity level. Damage occurs due to the plastic deformation at, or just below, the surface. The stress creates voids in the sub-surface belby layer initiating cracks. Cyclic motion causes the cracks to propagate resulting in particles which flake off.

Asperity Deformation

Asperity Deformation is caused by micro microscopic asperity contact that results in the asperities on the softer material plastically deforming, or smearing in the direction of movement. Repeated contact eventually leads to removal of the asperities at the weakest point.

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Types Of Wear

Types Of Wear

Abrasive wear particles are most commonly the result of dust or dirt in the oil. The dirt particles become wedged between two moving parts, embed in the softer surface, and cut into the harder one. The wear debris from this process appears to be miniature shavings from a machining operation.

Abrasive wear particles can be several hundred microns long. Hard metals tend to form smaller abrasive particles that may have a needle-like appearance.

The primary corrective action for abrasion is to filter the oil to remove the contaminants. It is also important to minimise the ingress of contaminants, especially dust.


Fatigue wear is the result of repeated cyclic loading of surfaces with compression and shear or compression and tension. This is most common in industrial bearings and gears.

The repeated loading of the same point on a gear or bearing causes micro-cracks to form and become interconnected. When the cracks intersect surfaces, spall occurs and flakes or chunks are released into the oil. These particles are commonly 10 to 30 microns at first and later grow to be 100 microns or more. Fatigue is often from one of the following root causes:

  • Improper assembly
  • Misalignment
  • Inbalance
  • Other conditions which concentrate loading in a non-uniform distribution.
 The corrective action for premature fatigue is typically to use another technology such as vibration analysis to find possible causes and minimise these. Fatigue will eventually require component replacement.

Corrosion and Lubrication Degradation

Corrosive problems are caused by water or other corrosive process media in oil, such as natural gas or sulphur.

Corrosion is especially a problem in refineries and crude oil processing facilities. Corrosive wear in industrial machinery is normally caused by contamination of the oil by water or other corrosive fluid.

Corrosive wear in engines can also be caused by degraded oil. Oxidation is a common way that oil gets degraded. Oxidation is caused when hydrocarbon oil molecules chemically react with oxygen from combustion gases, the atmosphere or moisture.

Long term high temperatures cause rapid oxidation. Measure the change in the dielectric constant, Total Acid Number or  Fourier Transform Infra-red (FT-IR) to give an indication of when to change the oil.

Also, look at the colour of the oil. If it is degraded, then it will be very dark in colour (brown to black). Keep in mind that it may be dark and still be perfectly good, but if it is bad due to oxidation or other chemical deterioration it should also be very dark. Dielectric increase of 0.1 usually means its time to change the oil.

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Wear Particle Analysis

No industrial oil analysis is complete without a comprehensive Wear Debris Analysis. Wear Debris Analysis (WDA) is a non-intrusive way to see inside complex machinery without taking it apart. Accurate identification of wear debris fragments can tell you which machine elements are damaged, and the nature of the problem which generated the debris.

Most (80%) of abnormal machine wear comes from one of four mechanisms:

  • Abrasion
  • Fatigue
  • Adhesion
  • Corrosion

Wear Debris Analysis tells you both the mechanisms and the severity. Armed with this knowledge, you can go after the corresponding route causes such as dust contamination, vibration faults, lubricant starvation or water contamination.

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Oil Storage And Handling

Oil Storage And Handling

Cleaning up your oil storage and using clean and correctly labelled storage containers is the first step in gaining control of your lubrication programme.

Care should be taken when handling lubricants. Incoming and used oils should be checked for contamination and to ensure that the correct oil is being used. Many problems may occur with wrong, mixed or contaminated oils throughout the plant.

At the least:

  • Label all your oils correctly with dielectric and viscosity.
  • Clean up.
  • Correctly label containers and equipment.
  • Accurately label sample bottles.
  • Store lubricants in a clean, dry location and use desiccating breathers.
  • Transfer lubricants using dedicated, tagged totes.

Contamination can best be controlled by learning what the contaminant is and identifying where it has come from. Contaminants may have many sources, including moisture, acquired when sampling oil. Dirty or hazardous environments such as coal handling or chemical refineries have their own problems, as do cement plants and wet environments.

Proper storage and handling of lubricants is a necessary first step, but this is often not enough. Exclusion technologies such as ensuring proper sealing of lubrication reservoirs on machinery is often the right solution. Filtration systems such as exclusion breather systems can greatly reduce contamination of particulates as well as moisture. Regardless of what solution is successful for your application, regular monitoring is necessary to maintain the integrity of your lubrication programme.

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