TestOil - Oil Analysis Blog

The first and often the obvious option is to have an on-site oil analysis lab to process all oil samples collected.  There are many pros to this option.  Turnaround time for results can be controlled in house.  There is no dependence on an outside resource.  Testing packages can be altered easily, etc.  However there are also cons to this option.  Expensive equipment must be purchased and maintained.  Testing supplies must be inventoried and purchased on a routine basis.  Lab technicians must be trained for each test procedure.  At least one lab analyst must be trained to interpret test results.  This alone requires a technical skill that often takes years to acquire and refine.

Another option for testing samples would be to bargain with the lube vendor supplying the plant.  Who knows better what is in the oil and what it should look like – especially if there are any formulation changes?  Often lube suppliers will offer to perform oil analysis for “free” if the company will purchase all their lubes from said company.  It has been said that letting the vendor make all the decisions around oil analysis is like “Letting the fox guard the henhouse”.  One must consider if it is better to pay extra for an oil analysis program or to turn the program over to a vendor and then have limited control on most decisions.  Remember, lube manufacturers are in business to sell lubes, not oil analysis.  Also remember that the supplier has little to gain by offering poor results.  If they tell you it’s good and your machine fails, it will be on their head.  If we tell you the oil is bad so you’ll change it and you find out otherwise, you will completely lose trust in them.

If it is determined that contracting an outside lab is the best course for your oil analysis program, care must be taken to insure that the lab is a good fit for your company.  As previously stated, there are as many different approaches to oil analysis as there are types of cars.  This is not saying that any one approach is better or worse than another.  It simply means that it is important to match a lab with the predictive maintenance strategies that your plant employs.

It should also be understood that many labs serve specialty industries.  Some cater to the transportation industry while others are primarily power, petrochemical, etc.  While a particular oil analysis lab may not specialize in the industry you work in, if you give them a call they will still agree to perform your testing for you.  The question that must be answered is “will I receive the correct tests and does the lab have the experience required to be my oil analysis provider?”

There are several other considerations that must be taken into account.  Some of them might be:

What is turnaround time on samples?

What does pricing include?  Shipping cost/site visits from lab, training, rush samples, sampling, supplies, lube audits, re-tests, etc.?

Will technical help be available? Does it cost extra?

 How long will the contract last?  What would it cost to “drop” the contract?

Report distribution

Management reports and online access to program data

Earlier this year, TESTOIL modified our FTIR analysis for turbine oil and began reporting new, enhanced parameters.  We improved the data interpretation to generate these new parameters which provide our customers a more detailed oil analysis of the health of their turbine oil.

New parameters include:

Thermal Event Acid – A degradation mechanism of the fluid caused by micro dieseling or spark.

Acid – Final oxidation mode of the lubricant. Could be oxidation in the presence of  water.

Amine Antioxidants – Measurement of amine antioxidants in the lubricant.

Aromatic Additive – Measurement of aromatic additives in the oil.

Base Oil Aromatic – Measurement of the aromatics contained in the base oil.

Oxidation Ester – Measurement of oxidation in the absence of water.

Phenolic Antioxidants – Measurement of phenolic antioxidants in the lubricant.

  Important Note

In order to perform the enhanced FTIR Turbine oil analysis we will need you to supply us with a 3 oz Virgin Sample of your turbine oil to keep on file.  It is critical to receive the reference sample in order to accurately measure the new FTIR parameters.  Pleaseuse the label below to submit your Virgin Sample.

Questions?

In order to create and maintain a world-class oil analysis program you need to have the support and dedication of your lab.  The analysts at TESTOIL are available at any time to discuss concerns about your equipment or overall program.

In today’s culture of looking for high returns on investments, there are not many that can compare to a comprehensive lubrication program. Tremendous financial savings can be enjoyed by eliminating poor lubrication practices from an organization. Numerous financial losses are attributable to poor and inadequate lubrication programs and techniques, and most of the losses are not going to jump out at you. This is why it is important to think of every aspect of lubrication. Just working on one area will not yield the financial results you desire. It is all or nothing. This article will offer valuable guidance as to why and how to look at the big picture when updating your lubrication program.

1. Benchmarking To understand where your lubrication program needs to be, you must first find out where it currently stands. In order to accomplish this, an in-depth benchmarking process must be performed to compare your current program to industry best practices in key areas of lubrication. Without having a metric to compare your program to, it becomes the blind leading the blind. All successful programs start with a clear picture of how much work they need to do to become world class and what they need to do to get there. Transitioning a lubrication program is not like turning on a light. It takes understanding, clear vision, dedication, champions, time and financial resources to make it happen.

2. Design and Engineering During the design and engineering phase, look at every lubrication point and determine what actions need to be put into place. These actions can range from equipment modifications and routine inspections to one-off inspections, etc. They are usually dependent upon the equipment type, criticality, reliability needs, financial benefit, safety consequences and other factors that affect the bottom line. Based on these factors, you should create clear, concise and specialized procedures for each lubrication point. These procedures will be used to modify equipment for contamination control, provide standards for oil analysis and coach the lubrication technician on proper lubrication techniques (i.e., top-ups, drains, filtration and oil sampling).

During this phase, you also should make sure the correct lubricant is being used in each lubrication point. This process involves checking the OEM recommendations for a baseline and then performing certain calculations for proper viscosity selection, lubricant type, performance properties, re-lubrication volumes, re-lubrication frequencies, etc. Re-lubrication volumes and frequencies often are left out of procedures, and a “shoot-from-the-hip” method is used. Not understanding how much and how frequently the lubricant should be supplied to an application, especially grease-lubricated bearings, can cause frequent lubrication-related failures.

3. Lubricant Consolidation Many times, as a byproduct of the design and engineering phase, lubricant consolidation occurs. This is important on many levels, as it allows for a clearer picture of what products need to be purchased, which reduces purchasing costs, eliminates unnecessary or unused products from inventory, decreases the likelihood of lubricant cross-contamination and helps the lubrication team understand which products they need and why. As the specialized procedures are created during the design and engineering phase, each lubrication activity should have the correct lubricant specified. This will help ensure that the technician is using the right product in the right place.

4. Storage and Handling Once all of the necessary lubricants are identified, it is time to think about your storage and handling practices. Proper storage and handling techniques are essential in developing a successful lubrication program. You can perform all of the equipment modifications for contamination control, but if you can’t get the lubricant from the storage room to the application without introducing contamination, all of those modification efforts were in vain. This is why it is so critical to have a proper lube room with dedicated receiving filtration, storage systems, filter carts, stored filtration, dispensing equipment and a safe and clean environment for the lubricants to be stored.

Lubricant labeling is another frequently missed opportunity. Labeling should be a high priority when thinking of execution. Lubricant-specific labels should be created and placed on stored lubricants, top-up containers, grease guns, filter carts and the equipment. This makes lubrication tasks much more efficient and reduces the likelihood of the wrong lubricant being used in the wrong application. If technicians can clearly see the label on the equipment, go back to the lube room and find the matching label on the filter cart, top-up container or grease gun, their jobs become much easier and safer.

5. Implementation After designing and engineering a lubrication program, the next step is to implement what you have developed. Many times this is where organizations fail to execute and never see the value of all their previous efforts. Implementation is not a one- or two-day exercise but a multi-month commitment based on available resources. Complex types of equipment such as hydraulic systems will necessitate multiple modifications in order to be considered best practice, requiring a substantial financial commitment. The modifications can include breathers, sight glasses, dedicated sampling ports, quick-connects for periodic decontamination, filters, etc. This is where all the time spent developing the specialized procedures from the design and engineering phase pays off.

Every modification activity for each piece of equipment should have its own dedicated specialized procedure to instruct the labor force on how to perform the modification correctly. Other less complex types of equipment such as grease-lubricated bearings may not have any modification procedures but only routine lubrication procedures. These applications do not require as much of a financial or labor commitment to implement, and once the specialized procedure is written, the technician can start with the needed tasks immediately.

6. Re-benchmarking and Continuous Improvement After your newly revamped lubrication program has been up and running for a while, it is time to re-benchmark your program with industry best practices to see where your program is now compared to where it was during the initial benchmarking. This is where all of the hard work in the previous steps will show the financial rewards and re-enforce that the decision to develop a real lubrication program was worth the financial commitment.

As with any change of culture, management and workforce, a lubrication program needs constant refinement and continuous improvement. It is easy to slide back to the old ways of doing things if not careful, especially if the organization has a high turnover rate in the labor force. This is why it is so important to have developed the specialized procedures during the design and engineering phase, as they make it easier to train new members of the lubrication team and define how to do things correctly and accurately the first time, which promotes a sustainable culture change.

Featured in Machinery Lubrication (10/2011)

Any business that relies on heavy machinery to carry out their daily tasks also relies on things like oil analysis testing to actively monitor the condition of those machines. There are many industries that have to have some pretty expensive pieces of machinery running around the clock, and that machinery will get them nowhere without good oil. In order to ensure that those vital fluids stay at their optimal operating condition or to see what they can tell us about the interior conditions of the machine, they must be tested and analyzed on a regular basis.

The fluids located within each of these machines are generally necessary for normal operations, with many machines needing more than just a single type of fluid. Oils that are used to lubricate a machine do so by eliminating the resistance between moving parts that would generally cause a great deal of friction and results in excessive wear. In other machines they are critical to the operation because they are actually what operate the machine, like in a backhoe, which uses compressed oil to transport a hydraulic piston in and out to control the position of the machine’s digging arm.

Unless there is a highly skilled maintenance crew on standby around the clock, it is imperative that the fluids used to operate a machine not become contaminated and left untreated, because this will result in some costly problems. Contaminated fluids make up the vast majority of industrial maintenance issues that result in countless hours of downtime and some very expensive part replacements and repairs.

No matter how highly lubricated a machine’s inner parts are, they are sure to deteriorate a certain amount over time. When a machine part wears down, it leaves behind millions of small particles that get trapped in the fluids, making the fluids contaminated and no longer ideal for normal operations. Through proper analysis, the experts will discover the volume of particles that exist in the oil and where they came from, which will tell the maintenance personnel a lot of what they need to know about the machine’s various issues.

Oil analysis testing is one of many types of critical preventive maintenance that must be carried out in order to ensure that piece of industrial equipment is kept in optimal working order. Across every major industry, from farming to manufacturing, there are numerous types of machines and equipment that cannot function without the oil required to lubricate its moving parts and keep things in motion. In order to ensure that those vital fluids remain at their optimal operating condition or to see what they can tell us about the interior conditions of the machine, they must be tested and analyzed on a regular basis.

The fluids located within each of these machines are generally necessary for normal operations, with many machines needing more than just a single type of fluid. In some machines, they are required to properly lubricate and reduce the friction created by moving parts, which allows helps keep the machine at a safe working temperature. In order machines they are critical to the operation because they are actually what operate the machine, like in a backhoe, which uses compressed oil to transport a hydraulic piston in and out to control the position of the machine’s digging arm.

If any of these important fluids gets contaminated or lose their original properties over time, they will no longer be able to keep the machine running safely, which often leads to some very serious and costly malfunctions. It has been shown through a great deal of research that the majority of equipment failures are the result of none other than contaminated and poorly maintained fluids, so taking care of those fluids is the number one way to take care of the machines they are used in.

One thing about heavy machinery is the fact that there is no amount of maintenance that will prevent them from gradually wearing out over a certain number of years. As moving parts wear out, they are torn down into billions of tiny particles, which will be circulated through the oil until the oil is filled with tiny particles of whatever material the parts are created from. A maintenance crew can learn a lot about what is going wrong in a machine by analyzing the fluids and seeing what sort of contaminants are present and what materials they are made out of, which can then be matched with the parts that are wearing out.

“A customer of ours is using an external engine oil filtration device designed to take out contaminants down to the 1- to 3-micron range while not affecting the additive package. The customer now believes he can extend the recommended oil change interval from 250 hours to 1,000 hours. However, if you take out all the normal wear particles, how can you determine or trend the wear in the engine.”

By sampling after the pump and before the filter, you can still see an increased rate of wear generation with oil analysis. By reducing the background level of wear particles (noise), it is comparatively easier to detect the abnormal generation of wear particles assuming, of course, that the sample is drawn after the pump but before the filter.

You will also need to set alarms carefully, using statistics to derive level limits and rate-of-change limits. The benefit of engine life extension associated with polishing the oil is considerable and will easily warrant some efforts to ensure that oil analysis can still the generation of abnormal wear.

I would advise your client to make sure that any decision to extend the oil drain interval is backed up by oil analysis (oil properties, contamination and wear debris monitoring). It is unwise to arbitrarily extend oil drains unless the decision is supported by data. Excessive particle contamination level is just one reason why we may change the oil.

The best way to tweak your oil change interval is to make actual assessments of its condition and remaining useful life. Unlike routine oil analysis, the types of tests you might want to select could be more similar to what you see on your lubricant’s spec sheet.

Begin by talking to your lubricant supplier about which performance properties would need to be evaluated. These could include oxidation stability, rust/corrosion protection, air release and foam stability, demulsibility, anti-wear protection, viscosity index (VI), silt particle concentration and other essential performance properties. Expect the cost of these tests to run several hundred dollars. However, you only have to run tests on samples from a few representative machines.

Obtain the sample just prior to the currently scheduled oil change. Send this sample along with a sample of the new lubricant (for baselining purposes) to a lab that can perform ASTM performance tests. You may need to obtain several hundred milliliters of fluid of each sample.

Once the tests are complete and an assessment made on remaining useful life, a decision can then be made on whether the oil change interval can be shortened or lengthened. A reasonable safety margin needs to be included in the decision. Once changes in the drain interval are made, monitor the oil carefully.

While fluid analysis is the best way to safely determine an optimal drain interval, the appropriate testing should be done by a reputable laboratory that uses reliable testing methods and produces quality results you can trust. Accredited laboratories are required to prove the accuracy of their results on an on-going basis or risk losing their accreditation.

“Do you have any rough estimations of oil analysis costs if performed onsite? I am trying to compare the costs of onsite versus sending to an outside lab.”

The question of the cost to analyze samples onsite versus offsite is a good one. Too many people are motivated to test samples in-house and completely dispense with offsite analysis based simply on cost.

The perception is that oil analysis costs can be significantly lowered by testing onsite. This is a somewhat misguided approach because by the time you buy the right equipment, maintain and calibrate it, maintain the lab, pay and train the staff to use the equipment (it typically takes a dedicated resource or full-time equivalent to run an onsite lab) and buy any consumables, the costs may be similar to or perhaps slightly higher to test onsite.

The value of onsite analysis is immediate feedback, the ability to retest on the spot and the message this sends to the organization as a whole. However, without considerable investment in instruments and people — equivalent to staffing a full-scale commercial lab — there will always be tests and expertise missing that need to be addressed through offsite analysis.

Onsite tools for oil analysis can provide a wealth of almost instant information on which you can make immediate maintenance decisions. However, keep in mind that even though onsite tools can produce results worthy of scheduling maintenance or some other action, you can’t accurately compare lab results to onsite results for the same test. Different methods will provide different results.

There are many other tests and kits available for use in the field and in the plant. Before you embark on the journey to onsite testing, you need to first ask yourself, “What will I do when I get this information?” In today’s tough economy, you must embrace technology that adds value. No matter if the oil analysis data you receive is from a field kit or a commercial lab, if you do not use it to make sound maintenance decisions (and just tuck the report away), then it really is a wasteful activity. Start by focusing on what information you need, then research the onsite options that are available.

Field tests are some of the most overlooked, yet valuable tools that lubrication professionals can have in their arsenal. Most field tests are quick, inexpensive, simple to conduct and yield great information. One of my favorite field tests is odor.

Many characteristics and properties of an oil can be detected with our senses. We use our eyes to check level gauges, color, clarity, opacity, etc. We use our ears to determine conditions like cavitation, overloading, misalignments, etc. Why shouldn’t we utilize our noses more often?

Smell is a very direct sense. In order for you to smell something, molecules from that something must find their way to your nose. Therefore, everything you smell is releasing molecules. These molecules are mostly small, light, volatile chemicals that find their way into your nasal passages. Once in the nasal passages, these molecules come in contact with a special patch of neurons. These neurons have very small, hair-like projections called cilia that increase the surface area to capture more of the molecules. The molecules attach to the cilia and trigger the neurons to send a signal to your brain, which causes you to perceive a particular smell.

So which oil odors should you be trying to distinguish? Here are a few you should be able to recognize.

Oxidation

Oxidation has a sour or pungent odor, similar to rotten eggs. It occurs when the hydrocarbon constituents of lube oil combine chemically with oxygen. As with most chemical reactions, oil oxidation is accelerated by heat and pressure. It is no different than other commonly encountered oxidation reactions, such as rusting. Just like the effects that rusting and other corrosive processes have on metal substrates, oil oxidation results in a catastrophic and permanent chemical change to the base oil molecules. The net effect of prolonged oxidation is that the oil becomes acidic (chemically), causing corrosion, while an increase in viscosity occurs (physically).

Thermal Failure

Thermal failure has the smell of burned food. It typically occurs when the base oil comes in contact with hot surfaces within the oil-wetted path or due to a sudden and rapid increase in temperature associated with the adiabatic compression of entrained air bubbles in pumps, bearings and other pressurized lubrication environments. When this takes place, the layer of oil that comes in contact with the hot machine surface or compressed air bubble can change chemically.

Bacteria

Bacteria can produce a road-kill smell or stench. Once established, bacterial colonies will clog control systems, quickly degrade oil quality and performance, and generate corrosive byproducts. If not detected early, the problem will manifest itself into expensive repairs, extended downtime and a significant expenditure of scarce resources.

Contaminants

Contaminants such as solvents, refrigerants, degreasers, hydrogen sulfide, gasoline, diesel, kerosene and process chemicals all have a distinct smell of their own.

Sulfur Compounds

Sulfur compounds have a skunk-like odor. The various oxides of sulfur and water, both of which are combustion byproducts, react together to form sulphuric acid. This acid is neutralized by the basic reserve in the oil’s additive package (overbase detergent) and normally results in the formation of metallic sulfates.

Nitrogen Compounds

Nitrogen compounds have an almond-like scent. Nitration is another form of oxidation. It results from the reaction of oil components with nitrogen oxides (NO, NO2 and N2O4), which are produced from the oxidation of atmospheric nitrogen during the combustion process. In addition to causing oil thickening, nitration products are major contributors to the buildup of varnish.

Esters and Ketones

Esters and ketones have a perfume (fruity) odor. Esters are produced when carboxylic acids are heated with alcohols in the presence of an acid catalyst. Their odor is due to their volatile nature, which is caused by their chemical composition and conformations.

Although it’s not a cutting-edge science and there aren’t any cool handheld devices (yet), smell should be an essential part of your oil analysis program. It’s fast, cheap and easy. Very few things in the machinery reliability world offer all three of these attributes.

One of my favorite stories about using smell as a field test involved a client who sent me an oil analysis report that was very basic. It had the normal range of tests for an “economy” report. It showed an increasing viscosity, a darkening, the formation of some sludge and varnish, etc., all the telltale signs of an oxidative failure, yet the oil had not been in service very long.

Over the phone, I told the client to open the bottle and take a big whiff of it. I could tell by the awkward silence that he was making a face – you know the one you make when you think you’ve heard what someone has said but know it couldn’t be right. He repeated my request with a bit of sarcasm in his voice, to which I replied, “Just do it.” A few seconds later, I heard, “Wow! It smells like burnt oil!” That was our clue that the problem was thermal failure.

Fuel Dilution Test Upgrade

TESTOIL is committed to continually improving the methodologies and technologies used in our laboratory.  With that said, we are now using a Gas Chromatography (GC) method to measure fuel in engine oil.  The method is based on a proposed ASTM method (work item 24171) and is widely used in the industry.

In this method, the lubricating oil is injected directly into a gas chromatograph.  This will allow TESTOIL to produce data with better repeatability and less interference.

TestOil  is committed to continually improving the services and tools we provide to our customers.  With that said we would like to share with you some of the exciting new advancements we have made to our web-based reporting application, also known as DataSight.

DataSight is one of the most advanced web-based tools available in our industry.  It is a simple, organized, one-stop solution for program management that makes any oil analysis program more effective.

Our latest update to DataSight includes a new DASHBOARD which  comes bundled with a comprehensive suite of clever tools that provide our customers with a snapshot of their entire oil analysis program.  The dashboard has been specifically designed to help our customers streamline their oil analysis program management.

The new dashboard features:

A Monthly Scorecard, which is a snapshot view of the tests run for the month based on machine and lubricant, as well as the location where the sample was pulled.

Sample Trends is a overview of  sample volume completed over the past 18 months.

Exception Trend graphically depicts machine anomalies and lube anomalies also based on the past 18 months.

The Repeat Offenders table identifies specific problems with equipment and what problems you’re noticing

Lastly, Examples Due By Month is a table based on the schedule that you have already set up within your customer website.

Understand Elemental Spectroscopy

A wealth of information is available on your oil analysis report about wear behavior, contaminants entering the system, and the service needed.

As you read your oil analysis report, ask yourself what all the data means. Ask yourself other questions like: Where is contaminant debris coming from in this unit? What am I looking for that will help me see what is happening inside my machine? Am I looking at elemental levels that are from the additives, particles being picked up as the oil circulates, or from external contaminant ingression?

TESTOIL is committed to continually improving the methodologies and technologies used in our laboratory. With that said, we have upgraded our Varnish Potential Analysis adding some additional testing and upgrading our reports. In order to process the samples with the new reporting features we now require 16oz of oil compared to the previously required 8oz.

Click on image to view  new Varnish report

One significant change to our test process is related to reporting particle counts by two different methods. When there is a significant difference between the two methods (pore blockage/laser), this suggests the presence of soft contaminants. This additional test gives us another means of detecting the presence of soft insoluble products present in the sample.

Monitoring the additive levels provides information to ensure that the proper lubricant is being used for the application and for topping off.  Generally, four types of lubricants are used inmost industrial applications, and each has different additive levels.  Note that an oil’s level of additives measured by spectroscopy isn’t necessarily an indication of the oil’s quality, because the pressure of the element doesn’t indicate the functionality of the additive.

✓ Engine oils: They typically contain antiwear additives composed of zinc and phosphorus. Expect to see these elements present in about 1,000 ppm (plus or minus 200ppm). A detergent package should also be present, composed of some configuration of barium, magnesium, and calcium. These levels vary depending on the oil, but areusually above 1,000 ppm.

✓ Extreme pressure (EP) oils:  EP oils are typically for gear applications. You commonly see significant amounts of phosphorus.

✓ Anti-wear (AW) oils: AW oils include many bearing oils, some gear oils, and hydraulic fluids. These oils contain both zinc and phosphorus from 200 to 600 ppm. They may also have low levels of detergent (magnesium or calcium)present.

✓ Rust and oxidation inhibiting (R&O) oils: R&O oils are the easiest to identify. They include turbine oils, compressor oils, and some bearing and hydraulic oils. These oils have no additives that spectroscopy can measure, so they should have extremely low numbers for all additive metals.

EHC Webinar Series Part I

EHC Fluid Basics & Testing Requirement

  In this webinar our presenters shared some basic knowledge of EHC system fluid and the potential problems that can arise due to poor maintenance and lack of vigilance.  They discussed fire-resistant fluids, phosphate ester pros & cons, compatibility, best practice oil sampling, testing requirements, condition monitoring, max. & min. limits, and report interpretation.

If you missed this webinar you still have a chance to view the recorded version.  Simply use the link provided below.

Fuze Meeting link:

https://www.fuzemeeting.com/replay_meeting/866e79b9/2555346

If a crackle test is positive, further testing is needed in the form of the Karl Fischer Water Test. The Karl Fischer coulometric moisture test is a series of chemical reactions discovered in 1935 by the German chemist Karl Fischer. This method analyzes water in the microgram or partper-million range. This test is very accurate, to .001 percent. Water determination by Karl Fischer is defined in ASTM D 6304.

For this test, a sample of oil is introduced into a titration vessel in known mass or volume. Any water present in the sample will react with iodine in the titration vessel.  Theamount of iodine required to react with the water and the known mass or volume of the sample are used to calculate the amount of water present in the sample.  Results can be clearly expressed in percent or parts per million.

An electric current passes through a generator containing a Karl Fischer solution.  Iodine is produced at the anode that consumes the water in the introduced sample. When an excess of iodine is detected, the analysis is complete. In choosing this method, make sure that test specimens are compatible with the chosen reagent and that no side reactions occur.  This method is typically used to analyze hydrocarbons, alcohols, and ethers.  Note: Analysis of ketones must employ a Karl Fischer solution that is specifically formulated for ketone analysis.

Low levels of water (less than 2 percent) are typically the result of condensation. Higher levels can indicate a source of water ingress.  Water can enter a system through seals, breathers, hatches, and fill caps.  Internal leaks from heat exchangers and water jackets are other potential sources.

“We have a 600-liter sump that supplies 150 liters per minute to eight turbine bearings from one reservoir. The oil flows from the reservoir by a single pump and filter, then separates to the eight bearings. We take the oil samples from the return lines before they join for the return to the reservoir. None of the samples show much wear. On the last sampling when there was a sign of bearing failure, the sample for that bearing showed only 4 ppm iron, 2 ppm tin, 1 ppm aluminum, 2 ppm silicon, 2 ppm sodium, 2 ppm magnesium, and everything else 0. Viscosity was 66.7 on Regal 68 at 1,000 hours (6,200 on the unit). Why would samples not show that there was a problem?”

The answer to your question can likely be summed up in one word — dilution! Assuming, as you state, that you are sampling on the return lines from each bearing, the reason for the low wear metal levels is likely due to the comparatively high oil volume in the return lines. In oil analysis, wear debris is measured in parts per million. When you state “2 ppm tin,” what you are actually saying is “2 mg of tin for every kilogram of oil.”

So the same amount of wear debris distributed in a large volume of oil, such as a circulating turbine, will generate a much lower ppm than the same amount of wear in a small wet sump system where the volume of oil is typically much smaller.

To minimize the effects, try to ensure the sample is taken as close to the bearings as possible. In addition, ensure that the sampling method is precisely controlled with the same method used every time, including flushing volumes. You might also need to tighten your alarms considerably to the extent where “normal” really means 0 ppm of tin (and other key elements), and any slight increase (even just 1 to 2 ppm) is considered “cautionary.”

Other possible causes of the low wear metal limits could be a failure mechanism, which really doesn’t generate significant amounts of wear debris, or one that creates larger sized particles (in excess of 5 microns), which do not show up in conventional elemental spectroscopy techniques. However, given the nature of this application, dilution is the most likely cause.

While most lubrication teams grasp the importance of good oil sampling, they are not exactly sure how to address the specifics. The good news is that instituting a quality oil sampling program in a plant is generally a relatively inexpensive exercise with high, short-term paybacks. If you haven’t instituted a world-class oil sampling program, now is a good time to start. If a sampling program is in place, maybe now is the right time to review it for compatibility with reliability goals. Don’t let a poor oil sampling program shoot your oil analysis program from the sky.