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It has been a couple years now since the birth of my first child. I remember going to the doctor’s appointments with my wife where countless exams and tests were conducted to confirm that the pregnancy was progressing as it should. There were measurements, readings and occasionally blood tests. One of the blood tests was designed to look for genetic abnormalities. The literature on this test explained there was a chance for false positives as well as false negatives. Several samples were taken to ensure the test was performed accurately and the results could be verified.
Our son was born happy and healthy, but the memories of all the testing and the quest for accuracy with the results stayed with me. Similarly, when you receive medical advice that you don’t like or accept, you usually seek a second opinion from a different doctor or hospital. Although sometimes you may get better news or different results, oftentimes the same results come back, further substantiating the thoughts or recommendations of your doctors. This same logic can be applied to oil analysis laboratories.
How many times have you sent off an oil sample and had results come back that seemed odd or with information that you just couldn’t accept? While this isn’t the norm with oil analysis data, it does happen. Each result should be scrutinized and reviewed. Look for anything that seems out of the ordinary. At the end of the day, labs can make mistakes, so it is up to you to ensure the integrity of your data.
In the past, oil analysis services were offered in which quarterly samples would be taken from machines and the results analyzed, with the customer taking the corresponding action. The methodology was very pedestrian. If the results were labeled as green, nothing was done. If the results were marked as yellow, another sample would be taken in the coming weeks. If the sample was flagged as red, the oil and filters were changed. There was no in-depth analysis, and whatever data was presented on the lab reports was treated as absolute truth.
While this approach was overly simplistic, it yielded decent results for individuals in the field. However, if the lab made a mistake and reported a fluid property, wear or contamination parameter in a critical or red state, immediate action was taken, which normally meant dumping the oil charge and replacing the filters without ever taking a follow-up sample to confirm the evidence of an issue. If even one of those red reports had been a false positive, you could have avoided several man-hours of work and in some cases thousands of dollars in replacement parts. This could have easily paid for the secondary sample or follow-up action required to ensure the lab results were accurate.
When you receive less than desirable oil analysis results, the first step generally is to take a follow-up or confirming sample to send to the laboratory for more testing. Although this is an easy process to implement, it requires diligence on the part of the individual reviewing the data as well as the person taking the sample. If the original sample comes back in a critical alarm, taking another sample and sending it to the lab for immediate analysis must be pushed to the top of the priority list. This works well for most organizations that are willing to rely on the lab to have its own standards and policies for ensuring repeatability of the tests. Others would rather take this into their own hands and be the masters of their own data.
With many manufacturers of laboratory instruments now offering smaller and easier-to-use equipment for field applications, onsite oil analysis is becoming increasingly popular. These devices can perform a vast array of tests on used oil and provide useful data in nearly real time. Of course, the same consistency concerns that commercial laboratories must overcome also apply to onsite labs. These issues can be even more difficult for onsite laboratories due to the training and calibration requirements of much of the equipment. Still, these are fantastic tools for any oil analysis program.
Far too often when auditing lubrication programs, I see companies that have invested in testing equipment but do not properly maintain it or dedicate adequate personnel for its upkeep and use. Even for those who do make the proper investment in equipment and staff, the onsite lab should never replace sending periodic samples to an outside commercial laboratory. In most cases, the commercial lab will be able to perform more specialized tests than the onsite lab and can serve as a crucial check of your internal testing protocols and equipment accuracy.
One way to check the accuracy of any oil analysis laboratory is by using what is commonly referred to as a tracer sample. Think of this as a blind test to determine whether your sample preparation and results are what they should be. You can use the same fluid in multiple samples or change the fluid to see what the results will be.
The best practice is to utilize a reference sample of new oil, which you can then use to check for signs of additive depletion, viscosity changes or other physical property differences. Instead of extracting a single sample of new oil, you could take several. This will provide a bank of oil samples from the same batch of new oil. These now become your tracer samples.
Send the first tracer sample to the lab and have it tested against the normal test slate. The results should be archived. Several months later, send another tracer to the lab for analysis. Remember, oil ages, even inside a sample bottle, but the change is very slight. Therefore, the results of the additional tests should be in the same range. If the results vary widely, there is an issue with either the testing equipment or in the sample preparation. Ultimately, it will be up to the laboratory to determine the reason, but this merits a phone call to discuss the results. This process is equally effective for onsite labs. Just be sure they don’t know when a tracer sample is coming.
To check the accuracy of specific tests, such as elemental analysis or particle counting, you might choose to employ different fluids. For example, an ultra-clean lamp oil could be used to test a particle counter. If a sample of this type of oil is sent for particle counting, the results should be very low. If high particle counts are seen, it could be an indication that something is not working properly.
Turbine oil can be used for checking elemental analysis. Most oil analysis results for turbine oils appear as a blank slate in the elemental signature. Sending a sample of a known turbine oil and then analyzing the results in the elemental spectrum can provide good information on the repeatability and accuracy of a lab.
Some companies prefer to use multiple commercial laboratories to test the same sample of oil and then compare the results. This is quite common and encouraged for the utmost data accuracy. While this may not be feasible for every oil sample, it is good practice to periodically send the same sample from a critical machine to two different labs and run the same test slate just to ensure your data is trustworthy.
|25%||of lubrication professionals say they would not understand how to interpret an oil analysis report received from a commercial laboratory, based on a recent survey at MachineryLubrication.com|
Most oil analysis practitioners assume the data from their laboratory is accurate and irrefutable, but this may not always be the case. Routine checking of your lab is crucial. Fortunately, a system already exists for this practice, known as the ASTM Crosscheck Program. Although this program is voluntary, it can confirm when a lab is able to produce accurate, consistent results.
The program is based on different types of oil testing, but includes several common tests that would be performed on industrial fluids, such as viscosity, particle counting and elemental analysis. As with most programs like this, there are various subcommittees for different oil applications, such as automotive and turbines. Regardless of the oil type, the testing parameters should be consistent no matter which lab conducts the test.
The program is quite simple. Oil samples are sent to participating laboratories and tested. All the results are then gathered and analyzed to determine how accurate the labs are in achieving similar results from similar oil samples. This is important information to look for or request when using a commercial laboratory. Ask if the lab participates in the crosscheck program and if it has any other quality-control accreditations. Sometimes these questions alone are enough to shed light on a laboratory’s shortcomings.
If you plan to conduct your own crosscheck by utilizing the tracer method or employing multiple labs, make certain they all run the tests according to the same ASTM method. Even with some of the more common tests like elemental analysis, there are several ways in which they can be performed, with each producing slightly different results. To help minimize this risk, always ask or instruct the lab which ASTM standard of the test will be used. Also, be sure to select methods that can be crosschecked by either your onsite lab or another commercial laboratory.
If you suspect an issue with the testing, at the very least you should call the laboratory and ask for the test to be performed again. Most labs keep a small amount of each sample, commonly referred to as the retain. The retain can often be retested to confirm or potentially correct any error in the original sample. This practice is at the discretion of the laboratory, so it will require a conversation between you and your lab. This is more common among commercial laboratories and much harder for onsite labs to accommodate.
As you continue to refine your oil analysis program, keep in mind that the data from your laboratory may be incorrect. Use these recommendations and have an open conversation with your lab so you can rest easy knowing that the data you receive is as accurate as possible. And, as always, double-checking your lab is never a bad idea.