Tagged: steam turbines

Varnish Badges of Honour

Varnish Badges_honour

Varnish is widely known as a primary culprit of equipment failure. This sticky enemy effectively finds its way into most of our equipment and causes operators, maintenance personnel and plant managers a series of nightmares. From unplanned shutdowns costing millions of dollars to sticking of servo valves on startup, or increases in bearing temperature, varnish usually announces its arrival. Once it has been found, there is typically a cause for panic but perhaps it just needs to be understood rather than feared?

 

The ICML VPR & VIM Badges

Recently (August, 2021), the International Council for Machinery Lubrication launched two new badges. These badges are, VIM (Varnish & Deposit Identification and Measurement) & VPR (Varnish & Deposit Prevention & Removal). These were created after the culmination of 3 years of work from the global varnish test development committee. It has been designed for those involved in all aspects of managing or advising lubricant programs especially those with the responsibility of recommending, selling or installing appropriate deposit control equipment or other mitigation strategies.

Most of the readers will already be familiar with my enthusiasm for understanding lubricant degradation. Thus, when these badges came out, I knew I had to secure them! While the requirements for taking the test suggest the possession of the MLT I or MLA I certification or 1 year of experience, I figured that my MLE certification would be an asset (as I haven’t gotten my MLT I certification yet, it’s on the list!). However, I wanted to make sure that I covered all of the elements in the BoK for both the VIM & VPR badges, so naturally I turned to the varnish guru himself, Greg Livingstone!

 

Fluid Learning – All the way!

Greg is the CIO at Fluitec but he’s also the facilitator for the ICML VPR & VIM badges. What a treat! If you’ve never heard the name Greg Livingstone then you’re obviously not in the lubrication field. Greg has penned hundreds of papers on varnish and can be thought of as the varnish guru since he has extensive experience in this area. It’s a no brainer that I chose Fluid Learning to get me up to speed on what I needed to know for these exams!

Greg was an amazing facilitator and not only covered information relevant to the BoK for the exams but gave students a full overview about everything you needed to know about varnish. These on demand sessions kept me scribbling notes and nodding to myself and saying, “Oh that’s what really happens!” He presents the information clearly and adds some much needed humour into the sessions. It was an absolute privilege having him as my tutor for these badges.

 

VPR & VIM- What you need to know!

Varnish Badges_need-to-know

VPR - Varnish & Deposit Prevention and Removal

The VPR badge ensures that candidates understand proactive methods and technologies which can be employed to reduce the degree of degradation. It is also designed to confirm that they can sufficiently evaluate combinations of technologies to prevent and remove varnish including the proper steps to set up and implement an effective varnish removal system.

The topics covered in the VPR include:

  • Problems associated with Varnish & Deposits (20%)
  • Factors affecting Breakdown (28%)
  • Proactive Methods that can be used to minimize oil breakdown (16%)
  • Methods / Technologies that can be used to remove oil breakdown products and/or prevent deposits (36%)

The complete BoK for the VPR badge can be found here.

 

VIM (Varnish & Deposit Identification & Measurement)

The VIM badge on the other hand is more ideally suited for personnel responsible for recommending suitable oil analysis tests and mitigation efforts related to the deposit tendencies of various in-service fluids (application dependent). They would also be responsible for monitoring and adjusting these strategies accordingly.

The topics covered in VIM include:

  • Problems associated with Varnish and Deposits (20%)
  • Varnish and Deposit Composition (24%)
  • How Breakdown Products / Contaminants become Deposits (24%)
  • Oil Analysis Techniques that can be used to gauge Breakdown and Propensity towards Deposit Formation (32%)

The complete BoK for the VIM badge can be found here.

 

Exam tips!

Varnish Badges_exam_tips

The actual exams for both the VPR & VIM are set at 45 minutes with 25 multiple choice questions. Candidates must achieve 70% grade to attain the badges. Currently, the fee for the exam is USD75. Since there were overlaps of the content and the exam durations weren’t that long, I decided to sit both exams in one day. I will only advise this for those who are comfortable with doing this as exam anxiety and all that comes along with it can be stressful!

Here are a couple tips for taking these exams:

  • Log into the system 30 minutes prior to your scheduled exam time. This allows you to clear your mind, settle yourself and gives you an extra 15 minutes to figure out where the email is with your credentials! If you can’t remember your password to login to the system, this also gives you enough time to get that reset and sorted before the actual exam time.
  • The session only opens 15 minutes before the appointed time. During this time, you will converse with the moderator as they do the checks of the room and your National Identification. The moderators will engage with you and ensure that you are sitting the correct exam.
  • Ensure you have your National Identification on hand (your passport can be used as well). As long as it has your picture and the expiration date on the same side, it will be acceptable. For the Trinidadians, do not use your National ID card as we have our pictures on the front with the information on the back (I used my Driver’s permit).
  • Candidates have the option of “Flagging” questions to come back to them later. This is a great tool to help you to mark those questions you want to return to or double check.
  • There is a timer in the screen layout which helps you to keep track of your time. 45 minutes passes very quickly when you’re running through the questions!
  • Exam results for these badges come back very quickly as much as within a few hours or one day depending on the time of your exam.

Why do you need these badges?

Varnish Badges_need-badges

As long as you work within the lubrication sector or interface with machines requiring lubrication, then you need to get these badges! Oil degradation occurs throughout the life of the lubricant whether it’s a small or large operation. By understanding how it degrades and ways to mitigate that degradation, you can save your equipment and avoid unwanted downtime. These badges were designed for the personnel in the field to allow them to make decisions regarding the lubricant and to empower them in taking steps to avoid degradation or mitigate it should the need arise. Consider it as getting your passport stamped by the ICML!

The courses offered by Fluid Learning are perfect for those seeking to understand lubrication deposits, what causes them and how they can be mitigated. While the content covered during these sessions align with the ICML VPR & VIM badges, they also add to a more holistic approach to varnish and deposits. Fluid Learning is an official ICML Training Partner and is currently the only one (of which I am aware) offering training prep for these badges. I highly recommend them for anyone seeking to learn more about or avoid sticky varnish situations. 

At the moment of writing this article, there are only 8 people globally who have acquired these badges from ICML. I am the first female in the world to attain these badges but I will not be the only female for very long. Varnish is an issue which affects us all and we need to understand it, so we can prevent it and keep our equipment safe. I hope to see many more candidates with these badges in the near future!

Additives and their properties

Properties of Additives in Lubricants

add_calcium

Each lubricant has a varying percentage of additives as not all lubricants are created equally. Lubricants are designed based on their application or use within the industry. For instance, an engine oil is typically composed of 30% additives, 70% base oil while turbine oils comprise 1% additives and 99% base oil.

Therefore, particular attention must be paid to getting the additive compositions to be just right for the application and ensuring that the additives can perform their functions.

Each additive has a particular function and is used as per the application of the lubricant. We have adapted the following from Analysts Inc – Basic Oil Analysis which describes the purpose of some of the most commonly used additives in lubricants.

additives

Used Oil Analysis Tips

oil_sample

“When should an oil sample really be taken?”

In used oil analysis, oil samples can be taken at any time, but one should always consider the insight that they are trying to gain before testing the sample. This is crucial in deciding the type of tests and the intervals at which they should be performed.

 

For instance, if we are testing the quality of the oil or we want to compare a fresh batch to a used one, then we can take a sample directly from the drum.

If we are trying to decide the rate at which the additives are being depleted or wear being accumulated then we can take a sample at different operating hours to trend the data. This method can work if we are trying to determine the most appropriate run time for a lubricant in particular conditions.

However, if we are trying to track the health of the components on a regular basis as part of our PM program then taking a sample at the end of the scheduled maintenance interval is desired.

Taking an oil sample from a component is like performing a blood test by the doctor. It helps us to understand what’s really happening. It can show us if there is excessive wear, contamination or lubricant degradation which allows us to identify its “health”. However, the correct tests need to be carried out to determine these conditions.

There must be a reason behind taking the oil sample, not just a random act. When trying to establish a trend regarding a particular aspect of the oil, this should guide your choice of tests otherwise we can end up paying for tests that do not add value.

Always ensure sound reasoning behind testing rather than just checking the box!

While taking an oil sample at the end of the scheduled operating hours is very convenient, is it truly efficient?

When a piece of equipment is scheduled for maintenance, it is usually taken out of service for a couple of hours to perform the assigned
maintenance tasks.

However, if an oil sample is taken a couple days in advance of the scheduled maintenance, then when the results return the maintenance team can be on the lookout for issues highlighted by the results.

For instance, if the value for iron was significant or rising then they can perform inspections for areas which may cause this type of wear and address this challenge while the equipment is offline.

The graphic on the side can be used as a quick guide to determining when to take a sample.

Remember to always evaluate the reason behind establishing the sampling frequency before scheduling sampling.

sampling_freq

Microdieseling

microdieseling

What is Microdieseling?

Microdieseling is also called Compressive Heating and is a form of pressure induced thermal degradation.

The oil goes through 4 stages in this degradation process:

1. There is a transition of entrained air from a low pressure to a high pressure zone

2. This produces localized temperatures in excess of 1000°C

3. The Bubble interface becomes carbonized

4. The oil darkens rapidly and produces carbon deposits due to oxidation

The conditions required for microdieseling can be either:

  • Low flashpoint with LOW implosion pressure
  • Low flashpoint with HIGH implosion pressure

For a low flashpoint with a HIGH implosion pressure, this constitutes to ignition products of incomplete combustion such as soots, tars and sludge

However, for a low flashpoint with a LOW implosion pressure, adiabatic compressive thermal heating degradation occurs to produce varnish from carbon insolubles such as coke, tars and resin.

stages_MD

Electrostatic Spark Discharge

ESD

What is Electrostatic Spark Discharge?

Electrostatic Spark Discharge is real and extremely common for turbine users!

Static electricity at a molecular level is generated when dry oil passes through tight clearances.

It is believed that the static electricity can build up to a point whereby it produces a spark.

There are three stages of ESD.

1. Static Electricity builds up to produce a spark – Temperatures exceed 10,000°C and the lubricant begins to degrade significantly.

2. Free radicals form – These contribute to the polymerisation of the lubricant

3. Uncontrolled polymerisation – Varnish and sludge produced (some may remain in solution or deposit on surfaces) which can also result in elevated fluid degradation and the presence of insoluble materials.

How can a lubricant fail?

How can a lubricant fail?

This question has caused many sleepless nights and initiated countless discussions within the industrial and even transportation sectors. Before examining the causes for lubrication failure, one must first consider the definition of lubricant failure.

lubricant_fails

The composition of a liquid lubricant can be described as a combination of base oil and additives (Menezes, Reeves and Lovell 2013, 295). These two components work in tandem to define particular characteristics of the lubricant to perform its functions. According to Menezes, Reeves and Lovell (2013, 296) the five functions of a lubricant include;

  • the reduction of friction
  • minimization of wear
  • distribution of heat
  • removal of contaminants and
  • improvement of efficiency.

As such, lubrication failure can then be described as the failure of a lubricant to adequately perform any or a combination of its five functions as a result of the degradation of any of its two components; namely the base oil or additive package. Thus, it can be deduced that lubrication failure is as a result of lubricant degradation.

Now that we understand that a lubricant fails when it undergoes degradation which by extension results in the lubricant not being able to perform any of its functions properly, we need to explore further on the types of degradation that exist. Only then can we really answer the question of how a lubricant can fail.

Barnes (2003, 1536) focuses on three main mechanisms of lubricant degradation namely;

  • Thermal Degradation
  • Oxidation and
  • Compressive Heating (Microdieseling).

One may argue that these three types form the basis of all mechanisms of lubricant degradation.

ldm
6deg_mech

However, Livingstone, Wooton and Thompson (2007, 36) identify six main mechanisms of degradation namely;

  • Oxidation
  • Thermal Breakdown
  • Microdieseling
  • Additive Depletion
  • Electrostatic Spark Discharge and 
  • Contamination.

In this instance, the six identified mechanisms all produce varying identifiable characteristics which lend to these six forming the foundation of identification of lubricant degradation mechanisms. With these six in mind, one would need to be able to determine which degradation mechanism is at work in their facility. Afterwards, methods to treat with these mechanisms must be administered. Firstly, let’s understand each mechanism.

Oxidation

This mechanism involves the reaction of oxygen with the lubricant. According to Livingstone, Wooton and Thompson (2007, 36) oxidation can result in the formation of varnish, sludge, increase in viscosity, base oil breakdown, additive depletion and loss in antifoaming properties of the lubricant.

Barnes (2003, 1536) refers to this phenomenon as the addition of oxygen to the base oil to form:

  • Aldehydes
  • Ketones
  • Hydroperoxides and
  • Carboxylic Acids.
What is Oxidation_
Stages of Oxidation

On the other hand, Wooton (2007, 32) explains that there are three main stages of oxidation namely initiation, propagation and termination. Fitch (2015, 41) explains that:

  • Initiation entails the production of a free radical via the lubricant and a catalyst.
  • Propagation involves the production of more free radicals via additional reactions.
  • Finally, termination entails either the continuation of the oxidation process after the antioxidants have been depleted or the antioxidant stopping the oxidation process.

Microdieseling

Livingstone, Wooton and Thompson (2007, 36) have characterized Microdieseling as a form of pressure induced thermal degradation. They describe it as the transition of entrained air from a low pressure to a high pressure zone which results in the adiabatic compression.

This type of compression results in localized temperatures almost on excess of 1000°C.As such, the lubricant undergoes dramatic degradation. Wright (2012, 14) explains that because of these high temperatures, the bubble interface becomes carbonized. As such, carbon by products are produced and the oil undergoes oxidation.

microdieseling
Stages_ESD

Electrostatic Spark Discharge

Livingstone, Wooton and Thompson (2007, 36) describe this phenomenon as the generation of static electricity at a molecular level when dry oil passes through tight clearances. It is believed that the static electricity can build up to a point whereby it produces a spark. This spark can induce localized temperatures in excess of 10,000°C which can significantly degrade the lubricant at an accelerated rate.

Van Rensselar (2016, 30) also advocates that Electrostatic Discharge contributes to the formation of free radicals in the lubricant which subsequently results in uncontrolled polymerization. This polymerization of the lubricant gives rise to the formation of varnish and sludge which may deposit on the surface of the equipment or remain in solution. Van Rensselar (2016, 32) indicates that the most common result of Electrostatic Discharge is an elevated rate of fluid degradation and the presence of insoluble materials.

Thermal Breakdown

This mechanism is largely dependent on temperature as one of its contributory factors even though dissipation of heat was highlighted above as one of the functions of a lubricant. However, during the operation of machinery particular components tend to develop increasing temperatures.

As described by Livingstone, Wooton and Thompson (2007, 36) once this temperature exceeds the thermal stability point of a lubricant, the consequences can include shearing of the molecules. This phenomenon is also called the thermal cracking of the lubricant which can result in the production of unwanted by products, polymerization and decrease in viscosity.

Subsequently, Barnes (2003, 1536) explains that thermal degradation usually occurs when the lubricant experiences temperatures in excess of 200°C. He also states that the by-products of thermal degradation differ from that of oxidation.

Wooton and Livingstone (2013) state that there are two main actions that can occur once a lubricant is thermally degraded.

  • Either the small molecules will become cleaved off and volatize from the lubricant. This does not leave any deposit in the lubricant.
  • On the other hand, there is the condensation of the remainder of the molecule in the absence of air thus dehydrogenation also occurs. Consequently, coke is formed as the final deposit with numerous types of deposits forming between the start of the condensation to its final deposit of coke.

The main contributing factor for thermal degradation can therefore be linked to dramatic increases in temperature or constant high temperatures.

Additive Depletion

Wooton and Livingstone (2013) indicate that additive depletion can result in either organic or inorganic deposits. The nature of the deposit is dependent on the type of additive that has been depleted and its reaction with other components in the oil.

For instance, if the rust and oxidation additives drop out of the oil, they typically react to form primary antioxidant species thus producing organic deposits. However, as Wooton and Livingstone (2013) explain, inorganic deposits can also be formed from additives that have dropped out of the oil but did not react with anything. This unresponsive reaction is typical of ZDDP (Zinc dithiophosphate) which is an additive that assists with reducing wear in the lubricant.

In cases of additive depletion, the FTIR test seeks to identify spectra relating to the reacted or unreacted additive packages for the lubricant in use (Wooton and Livingstone, 2013).

Contamination

This mechanism of degradation can include foreign material entering the lubricant and being used as catalysts for degradation mechanisms listed above. Contaminants can include a variety of foreign material, however Livingstone, Wooton and Thompson (2007, 36) have narrowed the list to metals, water and air. These main contaminants can significantly contribute to the degradation of the lubricant by oxidation, thermal degradation or compressive heating.

From the above, we can summarize these lubricant degradation mechanisms into the following table:

From this summary, we can now assess the methods in which a lubricant can fail. While this article may serve as a guide in determining various lubricant degradation mechanisms, each mechanism must be treated differently depending on the conditions (environmental and operational) that exist during the lubricant failure. A proper root cause analysis should always be done when investigating any type of failure.

References

1 Livingstone, Greg, Dave Wooton, and Brian Thompson. 2007. “Finding the Root Causes of Oil Degradation.” Practicing Oil Analysis, Jan – Feb.

2 Barnes, M. 2003. “The Lowdown on Oil Breakdown.” Practicing Oil Analysis Magazine, May-June.

3 Livingstone, Greg and David Oakton. 2010. “The Emerging Problem of Lubricant Varnish.” Maintenance & Asset Management, Jul/Aug.

4 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.

5 Van Rensselar, Jeanna. 2016. “The unvarnished truth about varnish”. Tribology & Lubrication Technology, November 11.