A lot of people get confused when reading the ISO 4406 rating. The rating specifies a range of the number of particles of certain sizes that can pass through 3 particular sized filters namely; 4micron, 6 micron and 14 micron filters respectively.
For instance; a rating of 13/11/8 indicates:
13 represents 4000-6000 particles over the size of 4um
11 represents a range of 1000-2000 particles over the size of 6um and
8 represents a range of 130-250 particles over the size of 14um.
These values are actually the number of particles per milliliter. It does not mean that you have 13, 11 or 18 particles only in your oil, it's much more than that!
There are different ratings for different levels of cleanliness.
If your numbers are really high (25/22/19) then there’s definitely a high level of contamination!
Different components have different ISO cleanliness ratings. For instance, a roller bearing has a higher cleanliness target than a Variable Vane pump.
Understanding the ISO 4406 codes are crucial for determining the steps needed in “cleaning up” your system lubricants.
However, when we test for the cleanliness of an oil, there are a couple things that we need to consider:
When testing, we have exposed the oil to the elements (highly dependent on the method of sampling)
Results are not instantaneous (even with an onsite lab, there will be a timeframe between collecting the sample and processing it)
Since there are lag times involved, the value that is reported for the ISO4406 rating is never really truly representative of the oil. As such, when analysing the results of this test, it is important to consider that the actual value may potentially be higher than reported.
Quite often, when lubrication failures occur, the first recommended action is to change the lubricant. However, when the lubricant is changed, the real root cause of the lubricant failure has not been solved. As such, the cause of lubrication failure will continue to be present and may escalate further to develop other problems.
Essentially, this can cause catastrophic future failures simply because the root cause was not identified, addressed and eradicated. Moreover, the seemingly “quick fix” of changing the lubricant, is usually seen as the most “cost effective” option. On the contrary, this usually becomes the most expensive option as the lubricant is changed out whenever the issue arises which results in a larger stock of lubricant, loss in man hours and eventually, a larger failure which can cost the company at least a month or two of lost production.
In this article, we investigate lubricant failures in Ammonia plants and their possible causes. Some Ammonia plants have a developed a reputation for having their product come into contact with the lubricant and then having lubrication failures occur. As such, most Ammonia plant personnel accept that the process materials can come into contact with the lubricant and usually change out their lubricants when such issues occur. However, there are instances, where the ammonia is not the issue and plant personnel needed to perform a proper root cause analysis to determine the root cause and eradicate it. Here are a couple of examples of such instances.
Livingstone (1) defies the Lubrication Engineers Handbook in their description of ammonia as an inert and hydrocarbon gas that has no chemical effect on the oil, stating that this is incorrect. Instead, Livingstone (1) lists the number of ways that Ammonia can react with a lubricant under particular reactions such as;
ammonia being a base that can act as a nucleophile which can interact with any acidic components of the oil (such as rust/corrosion inhibitors)
reaction of ammonia with carboxylic acids (oil degradation products) to produce amides which cause reliability issues
transesterification of any ester containing compound to create alcohol and acids and the reaction of ammonia with oxygen to form NOx which is a free radical initiator that accelerates fluid degradation.
As such, one can firmly establish that ammonia influences the lubricant and can lead to lubrication failures should that be the cause of the lubricant failure.
The Use of Root Cause Analysis
Van Rensselar (2) quotes Zhou as saying the best method for the resolving varnish is to perform a root cause analysis. Wooton and Livingstone (3) also advocate for the use of root cause analysis to solve the issue of varnish. They go on to explain that the characterization of the deposit aids in determining the root cause of the lubricant degradation. As such, Wooton and Livingstone (3) have developed a chart to assist in deposit characterization as shown below.
Deposit Characterization graphic from Wooton and Livingstone (3)
Wooton and Livingstone (3) discussed that with the above figure, once the deposit can be characterized then the type of lubricant degradation can be more accurately identified. As such, the root cause for the lubricant degradation can now be firmly established thereby allowing solutions to be engineering to control and reduce / eliminate lubricant degradation in the future.
Case Studies
A case study from Wooton and Livingstone (3) was done with an Ammonia Compressor in Romania which experienced severe lubricant degradation. In this case study, they found that when the in-service lubricant was subjected to two standard tests namely MPC and RULER, both tests produced results within acceptable ranges. As such, there was no indication from these tests that the lubricant had undergone such drastic degradation as evidenced by substantial deposits within the compressor. Thus, it was determined that the deposits should be analysed as part of the root cause analysis.
For the deposits from the Ammonia compressor, Wooton and Livingstone (3) performed FTIR spectroscopy to discover that its composition consisted of mainly primary amides, carboxylic acids and ammonium salts. It was concluded that the carboxylic acids formed from the oxidation of fluid while in the presence of water.
In turn, the carboxylic acids reacted with the ammonia to produce the primary amides. These amides consisted of ammonium salts and phosphate. As such, the onset of carboxylic acids within the system eventually leads to the lubricant degradation. Thus, an FTIR analysisfor carboxylic acids was now introduced to this Ammonia plant as well as MPC testing to monitor the in-service lubricant.
Additionally, chemical filtration technology was implemented to remove carboxylic acids within the lubricant. These two measures allowed for the plant to be adequately prepared for lubricant degradation and avoid failures of this type in the future.
Another case study was done in Qatar with an ammonia refrigeration compressor which was experiencing heavy deposits due to lubrication degradation. For this Ammonia plant, high bearing temperatures and deposits were found on the bearing.
Upon investigation, it was realized that the lubricant had been contaminated externally and there was restricted oil flow to the bearings. After a FTIR was performed it was deduced that that the deposits were organic in nature and there were several foreign elements including high levels of carbon and primary amides.
From further root cause analysis, it was determined that the high temperatures observed were due to the lubricant starvation. Due to these high temperatures, oxidation initiated and with the high levels of contamination (mainly from ammonia within the process) this lead to degradation of the lubricant in the form of heavy deposits.
The bearing oil flow was increased and reduction in external contaminants were implemented. Oil analysis tests of Viscosity, Acid Number, Membrane Patch Calorimetry and Rotating Pressure Vessel Oxidation tests were also regularized in the preventive maintenance program. Thus, for this failure, some operational changes had to be made in addition to increased frequencies of testing. With these measures in place, there would be a reduced likelihood of future failures.
From the case studies mentioned, it can be concluded that ammonia systems have a higher possibility of undergoing lubricant degradation due to the contamination of the lubricant by ammonia gas / liquid due to its properties. However, it must also be noted that the ingression of ammonia into the lubrication system is not the only cause for lubrication failure.
Therefore, it is imperative that a proper root cause analysis be carried out to determine the varying causes for lubrication failure before the ingression of ammonia accepts full responsibility for any such failure.
References:
Livingstone, Greg (Chief Innovation Officer, Fluitech International, United States America). 2016. E-mail message to author, March, 08.
Van Rensselar, Jeanna. 2016. “The unvarnished truth about varnish”. Tribology & Lubrication Technology, November 11.
Wooton, Dave and Greg Livingstone. 2013. “Lubricant Deposit Characterization.” Paper presented at OilDoc Conference and Exhibition Lubricants Maintenance Tribology, OilDoc Academy, Brannenburg, Rosenheim, Germany, United Kingdom, January 22-24, 2013.
When failures occur in industrial plants, the first culprit to be suspected is usually the lubricant. However, should this be the first area that one looks at and what are the main causes of the lubricant failing? To understand this, I’ve taken a look at lubrication failures in industrial plants both globally and locally to understand the impact that they have on the sector.
Van Rensselar(1) explained that a recent study conducted by ExxonMobil Lubricants & Specialities of 192 US based power plants, 40% of these have reported issues of varnishing within their facilities. On the other hand; Livingstone, Prescott and Wooton(2) describe a study carried out by EPT Inc which document 44% lubrication failure of gas turbines (not including GE Frame 7FA & EA). It is therefore clear to see that there exists a prevalent issue of lubrication failure within the industry.
When a lubrication failure occurs, it costs an estimate of USD100,000 per trip in a power plant(1). As such, lubrication failures are costly within the industry and methods to reduce issues relating to these types of failures should be explored. Van Rensselar(1) also interviewed Joe Z. Zhou senior research chemist for Chevron Lubricants in Richmond California who explained that one of the main causes of varnish is the primarily oxidized hydrocarbon molecules which undergo surface aggregation and further surface reaction to produce the varnish. However, Livingstone and Oakton(3) add to this description of the main causes of varnish as the oxidation of the oil whereby there is a loss of electrons from the molecules within the lubricant. They go on to state that hydrolysis and thermal degradation are also leading factors for the degradation of the lubricant.
Van Rensselar(1) explored the main cause of such increased volumes of varnish cases in recent times and found that due to changes in turbine designs to allow for reduced operating and capital costs, the clearances have become smaller, operations are now continuous and a common lubricant for both bearings and controls is now being used. With the reduced clearances, the lubricant can now heat up faster and allow for quicker oxidation occurrences thus leading to varnish. Additionally, with the use of a common lubricant for bearings and control functions, there are significantly different levels of filtration required. Bearings allow for at least a 200-micron filtration system whereas servo valves will accept nothing less than 3-micron filtration(1). As such, it has now become easier for servo valves to become clogged due to varnish as compared to instances in the past.
Case Studies
Johnson, Wooton, and Livingstone(4) describe a case study on a power plant in Arizona, USA where a failure occurred during a routine test. Upon inspection, soft varnish/sludge was found on the trip valve piston. The varnish/sludge was analysed using FTIR testing and its chemical properties suggested the presence of carboxylic acid, primary amide and methacrylate ester. Further investigations revealed that the varnish had accumulated in a uniformed fashion. However, MPC testing did not reveal significant varnish accumulation since these tests were conducted monthly and the varnish had accumulated significantlyduring that time. Upon performing a root cause analysis, it was discovered that a steam leak containing hydrazine gave rise to the presence of ammonia in the system which reacted with the carboxylic acids (produced from oxidation of turbine oils) to form varnish within the system. It was then decided that lower MPC levels were needed to manage the volume of varnish within the system and reduce the steam leaks into the oil. These actions were taken to ensure that the varnish levels could be managed such that there would be no future trips as a result of this issue.
Wooton and Livingstone(5) conducted another case study on a combined cycle power plant in the US which experienced a type of lubrication failure. The plant had been shut down during an outage and it was noticed that when the lubricant storage tank cooled past 32°C large black tar balls formed and floated at the surface of the tank. The filters appeared to contain the black tar when in a liquid form but when allowed to cool, the tar turned into a black / brown solid. FTIR testing on the deposit revealed decomposed amine antioxidant, an ester and an additive not characteristic of the lubricant in service. The non-characteristic additive was identified as a foam inhibitor which was not found in the lubricant in service. It was then concluded, that an incompatible fluid was mixed with the in-service lubricant. A quality control program was implemented to ensure that all the incoming fluids are compatible with the in-service lubricant. As such, for this case study, lubricant degradation occurred due to contamination.
Trinidad & Tobago
After conducting a lubrication survey with turbine users for the period 2014-2015 and it was found that within Trinidad & Tobago, turbine users can be classified into three main categories namely; Power generation, Oil & Gas and Petrochemical. It was found that internationally, there is a greater focus on the Power Generation sector in research regarding lubrication failures. However locally, Power Generation represents 40% of turbine users while Petrochemical represents 34%. On the contrary, it was found that the Petrochemical sector suffered more lubricant degradation issues as compared to the Power Generation sector from this study. Overall, the Petrochemical industry experienced the highest volume of lubricant failures.
Overall, it appears that while Power generation sector has a higher percentage of turbine users, locally the Petrochemical sector emerges as the larger shareholder of lubrication failures in the industrial sector. Given that most of the lubrication failures occurred via oxidation and contamination (both locally and internationally), one can only conclude that within the industrial sector a greater emphasis should be placed on the monitoring of the condition of the lubricants especially for critical equipment. When lubrication failures occur, they can be very costly, as such greater emphasis should be placed on the monitoring of these lubricants in service.
References:
1 Van Rensselar, Jeanna. 2016. “The unvarnished truth about varnish”. Tribology & Lubrication Technology, November 11.
2 Livingstone, Greg, Jon Prescott, and Dave Wooton. 2007. “Detecting and Solving lube oil varnish problems”. Power Magazine, August 15.
3 Livingstone, Greg and David Oakton. 2010. “The Emerging Problem of Lubricant Varnish.” Maintenance & Asset Management, Jul/Aug.
4 Johnson, Bryan, Dave Wooton, and Greg Livingstone. 2013. “Root Cause Determination of an Unusual Chemical Deposit on a Key Oil Wetted Component.” Paper presented at OilDoc Conference and Exhibition Lubricants Maintenance Tribology, OilDoc Academy, Brannenburg, Rosenheim, Germany, United Kingdom, January 22-24, 2013.
5 Wooton, Dave and Greg Livingstone. 2013. “Lubricant Deposit Characterization.” Paper presented at OilDoc Conference and Exhibition Lubricants Maintenance Tribology, OilDoc Academy, Brannenburg, Rosenheim, Germany, United Kingdom, January 22-24, 2013.
Peter Horsburgh has essentially captured the 5 Habits of an Extraordinary Reliability Engineer in his book! His style of writing appeals to engineers as he keeps the content directly on point and provides case studies to each of his chapters. Most engineers aren’t big readers (except for manuals and when absolutely necessary) but the conversational tone in which Peter explains some of his revelations about the industry ideally captures the attention of reader. I couldn’t put the book down once I started reading it!
What I really love about this book is that it was holistically designed for engineers. The book is small allowing persons to carry it around anywhere and it isn’t too thick to daunt the reader into thinking that they need to allocate a couple of days to reading it. Peter has kept the chapters short, driving the various points home and has even provided summaries for each section of the book. This makes it super easy when trying to relate to an issue that he has discussed. Peter has also done an excellent job with the illustrations in the book to keep the reader’s attention and provide for some light amusement to keep the book as a guide that engineers want to return to time and time again
Additionally, an extra step was taken to ensure that the book has some durability built into it. The pages aren’t the ordinary soft paper, rather the pages have a bit of a card stock finish. This was my first light bulb moment after opening the book (there were tonnes more light bulb moments while reading it!). Obviously the pages had to be durable! This book was meant to be in the workshop with the engineers becoming part of their manuals! I can clearly see engineers rushing back to this book during the course of the day to get back to a particular chapter or case study that can assist them in some issue of the day.
I definitely enjoyed this book! Peter first introduces the reader to the 5 Don’ts of Reliability Engineering. I hadn’t realized until then that the “Don’ts” that were covered form critical parts of any Reliability Engineers’ day! The manner in which he introduces these stood out for me, as he brought in case studies to demonstrate instances where he dealt with some of these “Don’ts” or even performed them himself. It is with these case studies that I appreciated that some of the situations that I face daily may receive a “Don’t” when it shouldn’t. With Peter’s story telling ability, he was able to truly relate to the readers the practical examples of things that should and shouldn’t be done. Unlike other books, he demonstrates the impacts (and throws some financials in there as well, which helps us to actually quantify what we’re looking at) of particular “Don’ts”.
Right after the “Don’ts” section, he launches into the “5 Habits” which are each covered in their own Chapters. While he explains the habits in this section, he then further dedicates each Habit to a Section (not just a Chapter) where he mixes in his real life experiences as his Case Studies while providing introductory information on the habits and their impacts on the plant and its reliability. Quite skilfully, afterwards he dedicates a Section to “Applying the habits”. This is in keeping with the conciseness of the book!
I would highly recommend that all Reliability Engineers add this book to their library! It’s a book that gets all the lightbulbs blinking in your head from the moment that you begin reading it. However, it is not a book to be read just once, it needs to form part of your routine (either weekly or monthly). After reading this book, I can almost guarantee that the week that you spend in work afterwards will be nothing short of interesting as you may find yourself thinking… “Peter covered this in his book…let me just look back and verify if this can be dealt with in another way”. That being said, I believe that any engineer will make it part of their “consultation” guide especially during brainstorming sessions. It was indeed a pleasure reading this book!
Root Cause Analysis has always been dear to my heart. The procedure involved in finding the root causes and addressing them have intrigued me greatly as it involves using all your data gathering and cognitive skills. In the past, it was a bit difficult to properly perform RCAs since it usually meant jumping around different types of software. For instance, depending on the type of analysis that I wanted carry out, I would either use a Fish Bone Diagram or Cause and Effect Logic Tree. Depending on the type that I needed to use, I would have to switch programs just to get these generated. Then, there’s the issue of writing the final report and utilizing my expert copy and paste skills with Microsoft word while toggling excel worksheets to determine the costs attached to the failure.
Needless to say, I was very impressed when introduced to the PROACT software. It has an extremely friendly user interface (in some cases, I can even use drag and drop options!) which is very easy to navigate even for a beginner like me at the time. What I really love about the software is that it bridges the gaps and guides users (both for beginners and experts) on the RCA process. By allowing users to follow a step a by step processit ensures that users don’t forget vital pieces of information that are absolutely critical to the RCA.
If you are familiar with RCA, you will be aware that the basis of any RCA is properly establishing the Severity of the failures. As such, the first step when the user enters the software, is the assigning of the Severity of the failure with the Severity Calculator. This calculator can even be customized for varying applications! Afterwards, the profile of the failure is then defined. This profile allows the user to identify elements that may have been forgotten if the RCA was being done from scratch. The Severity Calculator also allows users todetermine the type of analysis that is fit for the severity index. Depending on the severity, the user can be guided to use either; 5 Whys, Fish Bone Diagrams or Cause and Effect Logic Trees. This is definitely one key advantage since it allows for different forms of analysis based on the severity.
Next the Critical Success Factors are inserted. The strategic placement for the input of these factors at this point in the analysis is purely genius! It forces the user to determine which factors directly impact them and these are usually placed on the final report. These CSFs start shaping the pending RCA into the mould that we need. Once these CSFs are established, then the objectives need to be defined. These help the analyst in guiding their RCA and ensuring that it is kept focused. It is easy to become distracted when performing these types of analyses since users are presented with an abundance of information. The definition of these aspects help the analyst to keep on track.
As with any RCA, there must be a team involved. The PROACT software allows users to delegate different tasks to different team members! It can even track the status of these events. Instead of sending long reminder emails (which tend to choke one’s inbox and can be easily missed), it is essentially easier to view the status of the assigned tasks using the PROACT software. This is a definite advantage of the software!
Now to the core of the software, the development of the RCA! Users are allowed to define the event that lead to the failure. Here’s where the software gets very interesting!!! Users can pull from existing templates dependent on the type of failure! This is the highlight of the PROACT software for a user like myself! It is very interesting to view templates (there are over 300 templates) of common failures and compare these to what the user has actually experienced. It allows the user to be able to access years of experience of a consultant at their fingertips! The team at Reliability Center Inc have definitely put a lot of work into developing these templates and have drawn upon their actual field experience for the past30+ years! This is the absolute game changer for the software!
During the building (or growing) of the Cause and Effect Tree, the user is allowed to authenticate their hypotheses and can attach pictures from the failure as verification for ruling out or accepting that mode as one of the root causes. These pictures can then be input into the final report without the need for cropping, cutting and pasting and all the exciting formatting issues that tend to occur when trying to include pictures in the final report.
PROACT also allows for users to input financial data. Another game changer for me! Users can define the costs associated with the downtime for particular failures, repair costs or even manpower costs. These all help to put a financial value on the cost of the failure being investigated. This neat trick is crucial for the review by upper management! Additionally, the final steps in any of the RCAs is to determine recommendations for the latent causes that were determined. These will be the courses of action to be taken to prevent failures of this nature from occurring in the future.
Overall, the PROACT software is indeed a time saver, keeps excellent track of the findings and collections of the investigation at hand and produces a very succinct, detailed report that anyone from upper management to the engineers can clearly understand. I love working with this software and my clients are always very impressed that this type of software actually exists and is so easy to use! I would highly recommend any user (novice or expert) in the reliability field to use the software in their everyday tasks and realize the impact that it has on increasing the efficiency of RCAs and their ROIs to their organizations.
