OILKLEEN electrostatic oil cleaners have been delivering amazing results to our customers all over the world. Recently, the OILKLEEN electrostatic oil filters were used to remove varnish and contamination from a 10,000 gallon (38,000 liters) steam turbine. Due the size of the system 2 GREEN MACHEEN 500 units were piped in parallel and run on the system for 60 days. Then after the 60 days a single GREEN MACHEEN 500 unit was left on the system to operate 24/7 and maintain the varnish free system.

Here are pictures of the OILKLEEN filters BEFORE and AFTER the 60 days.

Filter Element NEW and OILKLEEN Filter after 60 days of service on this system. Over 15 pounds of internal varnish were measured in each filter element after only 60 days. The FILTER LIFE rating on the computer had dropped from 100% to 74% when this picture was taken. The OILKLEEN filter still had 3/4 of its life left when we removed it for this inspection.

This is a picture of the internal system filters before OILKLEEN and after 60 days of having the GREEN MACHEEN electrostatic oil cleaner on the system. These results are truly amazing.

Internal filter elements BEFORE and AFTER 60 days of using the OILKLEEN electrostatic oil cleaning system. As you can see this system had severe internal varnish build up and the OILKLEEN electrostatic oil cleaners were able to strip and remove these varnish deposits in a very short time.

Technorati : electrstatic oi cleaners OILKLEEN filters varnish removal

The Israel Electric Company is one of the largest industrial companies in Israel. For the year ended December 31, 2007, the Company had total revenues of U.S $5 billion, net loss of U.S. $26.3 million and total assets of U.S. $17.9 billion.

As of December 31, 2007, the Company maintains and operates 17 power stations sites (including 5 sites for steam driven power stations) with an aggregate installed generating capacity of 11,323 MW (Including 26 MW which generating by independent private producer under the Company dispatch). In 2007, the Company sold 49,323 GWh, of electricity.

In the ten years from 1997 through to 2007, the aggregate demand for electricity in the State of Israel grew at an average annual rate of 4.8%, exceeding the average annual rate of growth of the State of Israel's gross domestic product ("GDP") rate during the same period which was 3.8%.

OILKLEEN® was selected as the electrostatic oil cleaner for the Israel Electric Company and prove our superior technology we conducted a 1 month trial on a GE FRAME 9FA gas turbine. The lubricant in the system was approximately 6200 gallons (approx 23,500 liters) and was approximately 5 years in service. Particle count drops were amazing, dropping the cleanliness levels by up to 12 times cleaner in just 1 month of service with an OILKLEEN® GREEN MACHEEN 300 electrostatic oil cleaner.

The before and after varnish potential colorimetric patch test showed a significant drop from an approximate VPR of 95-100 range for the BEFORE sample to a VPR of 10-20 ranger for the AFTER 1 month of OILKLEEN®.

Iceland is a country rich in geothermal resources. Because of the mid-Atlantic ridge, there is constant, volcanic activity beneath the surface in various parts of the country. As a result, there are huge amounts of hot water reservoirs in the ground.

Orkuveita Reykjavíkur provides electricity, geothermal water for heating, and cold water for consumption and fire fighting. They service an area that extends to 20 communities, covering 67% of the Icelandic population. They harness hot water from geothermal fields in Reykjavík and distribute to various customers. In addition, they operate geothermal plants at Hellisheiði and Nesjavellir where they heat groundwater and distribute to the district heating. Orkuveita Reykjavíkur produces electricity by using geothermal, high-pressure steam at plants located at Hellisheiði and Nesjavellir.

The OILKLEEN GREEN MACHEEN 300 WATER-X electrostatic oil cleaner with molecular sieve water removal technology built into 1 compact system was used to remove varnish and contamination from the large Steam Turbines used at this Geothermal facility.

The OILKLEEN® GREEN MACHEEN is the first ever electrostatic oil cleaner with a stacked electrode filter design in a stainless steel tank. Only OILKLEEN® gives you 18 electrostatic fields with 15,000 volts of field strength in each and the rugged durability of stainless steel tanks. The OILKLEEN® GREEN MACHEEN also has an optional oil chiller to cool the oil before the oil goes through the 18 elecrostatic fields. This causes the free radical molcules that are soluble do to the higher operating temperatures, to turn insoluble and then be removed though the OILKLEEN® electrostatic cartridge.

"The results were amazing, and the OILKLEEN® GREEN MACHEEN was very fast and effective in lowering our QSA values in a short amount of time..."
- GE FRAME 7 Plant Engineer comment

The OILKLEEN® electrostatic filter cartridge is the first of it's kind and actually has varnish indicators located on the filter. When the filter in new the filter element is white and once the filter collects varnish the filter will turn black. For the first time you can actually see what was removed from your oil.

OILKLEEN® has 18 electrostatic fields versus only 1 from any other electrostatic filter company in the world.

We have just signed an agreement with Chevron Products Company to become the newest member of the ISOCLEAN service provider network. OILKLEEN® will provide high speed electrostatic oil cleaning services, onsite colorimetric varnish testing, and be the supplier for CHEVRON end user customers and Chevron Marketers for varnish removal services.

CHEVRON has developed a solution offering to provide fluid conditioning services and other CHEVRON services to various industrial customers for purposes of improving equipment reliability of such customers, the ISOCLEAN Solutions Program.

This unique partnership will allow the OILKLEEN® technology to play a vital role in total system cleanliness and overall solutions for varnish and contamination related issues at Chevron end user accounts.

With OILKLEEN® and Chevron partnered up under the ISOCLEAN Solutions Program, OILKLEEN® will help develop the Chevron Brand, and too also help Chevron lubrication marketers' customers and Chevron's customers realize the value of doing business with Chevron and OILKLEEN®

Today we launched our new website - featuring new case studies, articles, PDFs, high quality photographs of our products and more. We are still working on the site and will be continually updating and improving the site as new developments occur in the world of oil filtration technology.

We now have a feed for our news, so those who would like to stay up to date with the latest developments in electrostatic oil filtration can subscribe here.

Thanks for visitng our site and feel free to use our contact form to notify us of any issues or suggestions you have while browsing our site. Of course, if you'd like a quotation or information regarding our oil cleaners, we're standing by.

We have just signed a contract with Shell Oil Products US to manufacture and private label, the Shell Servoshield electrostatic oil cleaner. Shell will market and sell the Shell Servoshield 800 and the Shell Servoshield 400 in the United States.

By combining the patented OILKLEEN® technology with the high performance quality of the Shell brand of Industrial lubricants, customers can have a complete turn key solution for fluid contamination.

The McDowell Mountain Business Center (located in beautiful north Scottsdale, Arizona) is about to become the new home of OILKLEEN®. This state of the art facility will serve as the main corporate headquaters, research and development of new technologies, on-site lab, and manufacturing complex for the worlds fastest electrostatic oil cleaners.

The above photo shows our new head office. You can get the new contact details by clicking the contact link below.

The intent of this article is to present in layman's terms what we consider important information regarding a new high speed electrostatic 'kidney-loop" system, which is designed to remove sub-micron particles and other foreign matter (varnish) from lubricating fluids. Over 30 years of R&D, on-site beta testing, and trial and error resulted in seven electrostatic filter patents and valuable information that we are passing on to you.

Electrostatic Oil Cleaners

There is a lot of hype these days promoting electrostatic filtration. Some of the information is good, but some of the hype borders on deception and marketing tactics. The problem stems from the lack of a complete understanding of electrostatic principles. It's a very complicated subject that encompasses a combination of physics, chemistry and math. So without going into lengthy math formulas and a realm of chemistry terms lets see if we can explain the principles of electrostatics in layman's terms.

Electrostatic Laws

Electrostatics is the branch of physics that deals with a phenomena arising due to the existence of electric charges, they do not move, they are static. There are a number of laws associated with electrostatics; one of the most important is Coulomb's Law, which describes the force between charged objects. Charge is a basic property of matter. Every constituent of matter has an electric charge with a value that can be positive, negative or zero. For example, electrons are negatively charged and atomic nuclei are positively charged. Most bulk matter has an equal amount of positive and negative charge and thus has zero net charge. The principle of Coulomb's Law is a fundamental law of nature.

Keys to a Successful Electrostatic Oil Cleaner

The key to an efficient and effective electrostatic oil filtration system is the product of several coordinated essentials, electric field strength, and the number of electrostatic fields, flow rate, electrode surface area, and chargeable contamination collection media. Then the most important is dialing in all the essentials for optimal performance and results, and making them work perfectly together. Now let's explain how these essential keys work.

Flow Rate

If your flow rate is too fast you could lose efficiency, and vice-versa if your flow rate is too slow you might not remove oxidation and foreign contamination material as fast as the lubrication system will create it. It's a simple formula; if your electrostatic oil cleaner is removing insoluble foreign material faster than your lubrication system is making it, then you have a clean system. If not, then your lube oil will oxidize as if there was no electrostatic oil cleaner there, and you will experience problems.

Electric Field Strength

In order to remove contamination particles and oxidation by-product molecules from oil you must have a very strong electric field. This electric field is what will charge the contamination particles and pull them out of the oil and to the collection media and bond them to the sharp edges of that media. Once again if your electric field is too low your electrostatic oil cleaner will not remove the contamination particles before the oil has left the electrostatic field. This means the particle was not removed and your system just pumped the contamination back into your lube oil reservoir. This is an example of bad efficiency or phenomenon we like to call, "pushing particles". If charged particles are not removed by a collection media that exists in the electrostatic field then, by the laws of electrostatics, that particle now carries a charge inside your oil and will attract and agglomerate with other opposite charged particles. In the laws of physics, this means that you have contamination particles in your system that will grow throughout your lubrication system equally. These particles will eventually get large enough that they will lodge in the tight tolerances of your system components. It is very important to note, that your electric field strength has to be high enough to draw the contamination particles from viscous oil while in the electrostatic field. All the foreign contamination removal in true electrostatic oil cleaners will happen in the electrostatic field and the contamination will be removed by the collection media.

Electrostatic Field

When two objects in each other's vicinity have different electrical charges, an electrostatic field exists between them. An object is negatively charged (-) if it has an excess of electrons relative to its surroundings. An object is positively charged (+) if it is deficient in electrons with respect to its surroundings. This is important because the foreign material and contamination particles which form varnish are very small. So small, that they are actually an insoluble molecule. The reason electrostatic oil cleaners can remove oxidation by-products and sub-micron contamination, is that even a molecule can take an electric charge in the electrostatic field and then be bonded to the collection media. Inside true electrostatic oil cleaner, everything happens inside the electrostatic field. This means that every insoluble foreign contamination particle is removed inside this field and there is no particle being charged and released back to the oil.

Number of Electrostatic Fields

If you're like me then you want everything bigger, faster, and stronger. Hey, it's a product of our environment, and with things like Monster Garage, NASCAR, Super Sized Fries, and Orange County Chopper, we just want everything better. Well, for once in the laws of electrostatic principles this reins true. If you have 16 electrostatic fields versus 1 electrostatic field, then the higher number will remove more sub-micron foreign contamination particles. This one is easy to explain; if I was a molecule and I had to run through one electrostatic field, without getting caught in the collection media, I might make it with enough force or velocity. However, even with increased force and velocity my chances are cut to 1/16th, if I had to run through 16 electrostatic fields without getting caught.

Electrode Surface Area

Electrode surface area is critical in electrostatic oil cleaners because this is how you can make the electrostatic field larger. This is very simple; if you have large high voltage and negative plates you will have a large electrostatic field. If you just have two points much like a spark plug then you have a very small electrostatic field. So in this case size matters, the larger the electrode surface area the larger your electrostatic field is.

Chargeable Contamination Collection Media

You have heard us talk about the chargeable contamination collection media and how it is in the electrostatic field. If electrostatic oil cleaner had no collection media it would just charge particles and then put them back into the reservoir. There would be no noticeable removal of fluid contamination. Now that we know all the laws of physics regarding electrostatic principles, you can see why the collection media is so important. You must have a durable collection media to withstand the chemistry of lubrication oil and the contamination particles, which must have very many sharp edges, millions and millions of sharp edges. These sharp edges are what the charged molecules look for once excited inside the electrostatic field. If you increase the sharp edges, then you can increase the amount of collected material, thus making your electrostatic oil cleaner very efficient. Unlike mechanical filters where a brand new out of the box filter has the highest efficiency it will every have, electrostatic oil cleaners actually become more efficient as they collect material. The material will actually make the collection media take on a charge and attract more and more contamination. The contamination in the oil will aggressively keep attracting and bonding on the media until there is enough collected material to increase the electrical current high enough to alarm the system out. Once the system alarms out, all you have to do is replace the removable collection cartridge and the process starts all over. This is important because in this situation your electrostatic oil cleaner actually becomes more efficient the longer it runs. As long as your voltage will stay the same, and you keep the electric field strength the same. If you're increasing the collected material and your voltage drops off then you are losing efficiency with your electrostatic oil cleaner.

New Kidney-Loop Fluid Purification System

Electrostatic filtration is not a newly discovered technology, for years its been used to remove airborne contaminants. A limited number of oil electrostatic filter designs have been developed, but some only fulfill limited requirements. Removing sub-micron particles and other foreign matter from oil is extremely difficult. Years of electrostatic R&D, on-site field test, and experimentation with different oils provided us with large amounts of useful information.

Case Study #1

We gathered real time situation data from an OILKLEEN electrostatic unit that was under test at a paper mill for 10 months. In one fifteen day period (24/7) this unit collected over 7-pounds of contamination and foreign matter from a 1,000-gallon hydraulic system. A majority of the material was oxidation by-products (varnish). The 7-pounds of contamination was contained in a single foreign matter collection cartridge. ISO codes during the testing period continually remained below 10/04/00. At the end of these 10-months it was discovered that this method of electrostatic charging had actually gleaned the interior surfaces of the system of oxidation and varnish.

Case Study #2

Information from a GE Frame 7EA field study was collected to show how varnish and oxidation levels were removed in under 7 days. OILKLEEN 250 electrostatic oil cleaner was put on the reservoir in a kidney loop configuration. The gas turbine customer had an independent lab perform a varnish potential rating for them where they it was an 85 VPR and had a high ISO particle count of 20/19/17. After 7 days with the OILKLEEN 250 electrostatic oil cleaner this VPR rating was a 3VPR and the ISO particle count was an amazing 9/5/1. Also, we performed a microscopic photo analysis to show the amazing particle count reduction with before and after photos.

Varnish and Oxidation levels dropped in 7 days with the OILKLEEN system

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Before ISO Code 20/19/17 After ISO Code 9/5/1

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Electrostatic Oil Cleaner Summary

Introducing new technology is very difficult, as most of us are reluctant to change. These new electrostatic filter claims of efficiency had to be proven beyond a reasonable doubt and highly educated scientists and engineers constantly questioned their own lab reports.

We understand their concerns; IF - for years your lab reports never showed any thing below an ISO code 14/12/09, then one day a test reveals a 09/04/00, would we have your attention? Good then we hope to have it now.

Routine oil analysis doesn't give you the full picture. You could be overlooking varnish problems in your system. OILKLEEN® makes use of Quantitative Spectrophotometric Analysis (QSA) varnish potential tests to find varnish problems routine analysis can't.

How did Analysts Inc develop QSA?

QSA combines a number of varying approaches to determine the sludge and varnish potential of lubricants. Led by Brian Thompson from our Louisville, Kentucky laboratory, Analysts has independently researched this problem for a number of years. Over time we identified other organizations including oil companies, filtration companies and many end users that were also concerned about the problems of varnish build-up and the inability to identify its presence with traditional laboratory testing. These companies, including Clarus Technologies, Shell Oil, ChevronTexaco, Kleentek, and a number of plastics manufacturers and power producers were very helpful in our developmental work on QSA.

What makes QSA testing different?

QSA testing protocol was purposely designed to isolate, identify and measure the specific degradation by-products responsible for the formation of sludge and varnish, there is no other commercial technology like QSA offered in the marketplace. QSA does not use traditional oil analysis methods or instruments. Through field research, we developed the Varnish Potential Rating (VPRSM), in which severity levels are application specific. Until QSA was developed, there never was a VPR.

Why is it so difficult to detect varnish potential with traditional fluid analysis techniques?

Let's start with a brief explanation of what varnish is made of and how it forms. Varnish deposits are made up of lubricant degradation by-products. Lubricant degradation occurs from oxidative, thermal or chemical attack on the building blocks of the lubricant - the hydrocarbon molecule. Hydrocarbon degradation is a complex process where normal oil molecules transform into a wide variety of harmful intermediaries. These intermediaries are highly reactive and easily transform into new compounds. As these reactions continue or propagate, new polymers of increasing molecular weight form. Many of these compounds or by-products are insoluble. Simply put, varnish is composed of these organic polymers.

Conventional laboratory test methods are not intended to identify these by-products. What conventional oil analysis does do is identify the end result of certain physical properties, contamination and component wear.

QSA focuses specifically on the chemical and physical signatures of the particular types of degradation by-products that have a high tendency to deposit on surfaces.

QSA, is concerned with elements in transition, degradation by-products that are on the way to becoming something else - varnish. Finding those elements in the oil is a complex and difficult task. One way to look at it is this is a natural evolution of the science of lubrication analysis and we are the laboratory at the leading edge of the research.

Does QSA replace the traditional used oil analysis programs?

No, not at all. QSA combined with a solid oil analysis program will broaden the spectrum of information that the users can utilize to make the most informed decisions from their analytical test programs. QSA focuses on lubricant properties that traditional oil analysis testing methodologies do not. QSA addresses sludge and varnish build-up. Proper routine oil analysis addresses component wear, sources of contamination and changes in the physical properties of the lubricant. Both are important players in the fight for increased equipment reliability.

How is the information reported?

Each client receives a customized report that includes the VPR, a severity scale that depicts where the result lies between normal and critical, a digital image of the separated contaminants, and a written interpretation of the laboratory results.

For a first time sampler, the easy-to-understand severity scale allows the user to quickly determine their risk for developing varnish related problems. We also include a historical graph of the VPR to assist in trending.

How was varnish detected prior to this technology?

Prior to the development of QSA, there was virtually no mechanism to provide an early warning of an impending varnish problem. Historically, the most common way of detecting varnish was by visual observation of easily viewed surfaces in the system. Unfortunately, dirty sight glasses and "bathtub rings" in lubricant reservoirs often do not show up until the contamination level has reached critical stage. All too often, unexpected varnish deposits were observed on internal components such as valves, bearings and gears during unscheduled and costly shutdowns or failures.

What kind of impact does this test have on overall plant and machinery reliability?

By monitoring those contaminants responsible for sludge and varnish, maintenance planners can properly schedule service and/or implement appropriate corrective actions before costly damage occurs and unnecessary downtime is experienced. QSA will develop into a useful tool in root cause analysis. By controlling factors that influence or promote lubricant degradation, machine reliability and availability increases. This has a significant impact on industry.

Do you find you have to educate potential customers as to how and why they might benefit from detecting varnish potential?

Not really. Varnish is a widespread problem that challenges many industries. We have found that almost everyone involved in maintenance, production, and reliability encounter some degree of problems associated with varnish. Most already understand the benefits of early detection.

Some of the most common problems related to sludge and varnish build-up that these professionals face are sticking servo control valves, elevated operating temperatures, accelerated wear and filter plugging. We have found that the marketplace is hungry for an effective predictive tool that can be used to monitor the otherwise missed varnish precursors in used lubricants.

What are your future plans and goals for this new test?

We officially introduced QSA to the marketplace at IMC 2004. Our immediate goal is to have our sales department actively introduce the technology directly to the industrial sector. Additionally our co-workers have written papers to present this technology at additional forums including the upcoming annual STLE meeting and other industry related conferences.

While the existing technology is solid and provides tremendous returns for our customers, we are continuing our research, particularly in areas such as contaminants versus lubricant performance.

What is the best success story you can share about detecting varnish potential?

QSA is now used extensively in the power generation and industrial hydraulic market. We have identified dangerous fluid conditions at numerous facilities during the past year. These alerts have allowed our clients to implement appropriate corrective actions and investigate root cause before an unscheduled shutdown or worse.

One specific case involved a base load power plant. The laboratory identified a very high VPR. Based on the QSA results, the plant initiated a corrective action utilizing electrostatic filtration as well as continued sampling. Over the course of the next few months QSA showed a gradual decrease in the VPR. When the plant shut down for planned maintenance the found the valves and filters were clean with no varnish related problems. The savings were in the tens of thousands of dollars.

Power plant owners have discovered that lubrication health plays a big role in keeping turbines running smoothly. Identifying varnish in turbine oils and getting rid of it are key to maintaining machinery reliability.

Mineral-based turbine oils lubricate most of the power generation industry's stationary gas and steam turbines. As gas turbine technology continues to improve, the stress on the turbine oil increases and requires improved base oils and additives to handle the higher temperatures and loads. Turbine oil manufacturers have responded by using Group II-finished products with improved additive characteristics. The new Group II turbine oils show much improved oxidation stability as measured by rotating pressure vessel oxidation test (RPVOT) and turbine oil stability test (TOST) over the older Group I formulated products that have been in place since World War II. Turbine manufacturers believe that oxidation stability is extremely important and have listed these two oxidation tests in their specifications along with tests that determine other properties including viscosity, water separability (especially for steam turbine oils), load carrying ability, corrosion protection, resistance to foam, air release and cleanliness levels.

However, now that Group II-based turbine oils have been in many turbine systems for more than 10 years, new challenges are arising regarding sludge, varnish and deposit formation for many gas and steam turbine operators. These contaminants are causing problems with turbine operations and, when left alone, can create operational issues with critical bearing and servo applications. These problems lead to reduced efficiency and production capability. Due to this new phenomenon, a better understanding of varnish is needed.

What is varnish?

Varnish is a thin, insoluble film deposit that is usually found on bearings and servo-valves. It is a high molecular weight substance that is insoluble in oil. Varnish insolubles are more than 75 percent soft contaminants that are less than 1 micron in size and are not measured by traditional particle counts. Insoluble compounds have polar affinities and, over time, begin to migrate from the body of the base oil to machine surfaces, based on system and oil conditions. Initially, the surfaces start to show a gold/tan color building to darker gum layers that develop into lacquer. The chemical compositions of these insoluble materials vary from case to case. For example, the composition of a varnish on a gas turbine servo valve may not be the same as a deposit found in a steam turbine oil system. Since insoluble compounds are less stable in Group II, III, and IV base oils due to their high purity, it is important to optimize the additive package with the base stocks and to maintain system cleanliness to retard varnish and sludge formation.

How is varnish formed?

Varnish formation is an operational and reliability issue. All turbine oils will create insoluble materials given severe and/or unusual operating conditions. These insolubles create lubricant imbalance due to factors such as oxidation, cross- and chemical-contamination, microdieseling and adiabatic compression. The tendency and speed at which turbine oils produce these products is greatly influenced by the formulation of the product, the stress on the oil and system contamination levels. Figure 1 shows the deposit tendency of commercial turbine oils. As illustrated, the synthetic turbine oil produced the second highest amount of insoluble materials mainly due to "mismatching" of additives with the synthetic base stocks. Synthetic base stocks are an excellent platform; however, if they are not properly formulated, optimum performance will not be achieved, resulting in increased varnish formation.

Harmful Effects of Varnish

The varnish deposits that form on machine surfaces cause numerous operational issues by interfering with the reliable performance of the fluid and the machine's mechanical movements. They can also contribute to wear and corrosion or simply just cling to surfaces. In severe cases, varnish build-up could prevent hydrodynamic lubrication of a bearing surface, resulting in bearing failure. Other potential problems include:

• Restriction and sticking in moving mechanical parts such as servo or directional valves
• Increased component wear due to varnish's propensity to attract dirt and solid particle contaminants
• Loss of heat transfer in heat exchangers due to varnish's insulation effect
• Catalytic deterioration of the lubricant
• Plugging of small oil flow orifices and oil strainers
• Increase of friction, heat and energy because varnish acts as a heat insulator
• Reduction in filter efficiency and potential filter plugging
• Damage to mechanical seals
• Journal-bearing failure
• Increased maintenance costs due to cleanup and discard of oil

Varnish detection

Varnish can occur in oils that appear healthy and clean, with no visible signs for concern through normal oil analysis. It cannot be identified by the typical in-service turbine oil tests. Low total acid number (TAN), a low ISO particle count and a high RPVOT does not guarantee that the lubricant is immune from varnish. However, varnish potential can be monitored by Fourier transform infrared spectroscopy (FTIR - nitration procedure), gravimetric analysis, color patch with spectrophotometer analysis (quantitative spectrophotometric analysis, QSA) and ultracentrifuge tests. Varnish potential may be monitored in the infrared spectrum of in-service oil. If the 1630 cm-1 peak in the infrared spectrum rises over time, this is an indication of higher varnish potential. Gravimetric analysis (similar to the procedure of ASTM D893) measures the weight of residual components. QSA utilizes gravimetric analysis and spectrophotometric analysis of the patch. A proprietary calculation gives the ultimate varnish potential rating. The ultracentrifuge test uses gravity to force oil sediment to the bottom of a test tube. This sediment is rated and given a numerical rating that corresponds to varnish tendency (Figure 2).

Varnish Removal

There are two general methods for removing insoluble materials in rotating equipment systems. The most common method is through electrostatic purification and the other (less common) is through chemical cleaning. The electrostatic filtration apparatus can be set up tank- or system-side and hooked up quite easily with limited impact on system operations. The unit itself places a small charge on the diverted oil stream. The small varnish precursors are charged and are sent through an ionic filter. The charged particles (positive and negative) are removed from the oil (Figure 3). As more varnish precursors are removed, the oil is able to absorb additional varnish molecules from those in the system that have already plated out and they begin the process of cleaning the system from varnish. The removal of varnish from system components is a long process. For electrostatic purification to work, it is critical for the lubricating oil to have a moisture content of less than 500 ppm water along with a low particle count. An important benefit of electrostatic filtration is that it helps remove particulates up to 2.5 microns, which helps improve system cleanliness and equipment reliability.

Chemical cleaning is another method for removing varnish. This method requires a significant amount of monitoring and often requires a system to be shut down. Cleaning chemicals are typically flushed through the system to dislodge varnish from components. These chemicals will soften and remove insoluble materials and the flushing action will remove them to fine filters. This process is usually performed for several hours to several days, depending on the size of the system and the extent of the varnish build-up on components. Once the flush and chemical treatment is complete, the system must be flushed again with an appropriate flush fluid to remove all residual chemicals and ensure no contamination finds its way into the new lubricating oil. Although this process is more intensive, it does allow for quicker removal of varnish versus the electrostatic method, especially with a large system. p

Authors

Leonard J. Badal, Jr. is a Business Solutions Specialist for ChevronTexaco and Mark Okazaki is a Product Specialist for Industrial Oils Technology at ChevronTexaco.

If the health community had a problem as large as turbine oil varnish it would be classed as an epidemic. Predicting and understanding lubricating oil degradation like human health, is not only an art but also a science. Numerous articles have been published revealing the various diseases within lubrication oil systems. The motivation for writing this paper is to deal with this highly published epidemic and prescribe a control for the disease.

As with human health, lubricating oil health should be looked upon and respected like the components that keep the body healthy. There are many analogies that relate to the human body and lubrication oil systems, heart (the pump), lungs, (system breathing), kidneys/liver (filters), veins (oil lines).

Machines are used to clean not cure body functions, such as kidney dialysis. A similar application is used to clean not cure lubrication oil functions, hot oil flushing/filtration. As with the human body various medications are used to control not cure health problems. The same holds true for lubrication oil systems, various additives are prescribed, and sometimes the side affects are worse than the problem.

As with the health of the human body there are a number of lubrication oil disease's that must be diagnosed; oxidation, varnish formation, peroxide, water, particle contamination additive depletion.

Oxidation is one of the most detrimental processes causing degradation of turbine oils during service. Oil oxidation leads to formation of acidic products, insoluble materials, and sludge, depletion of additives, loss of dispersancy, increase of viscosity, etc. All of these undesirable changes are, however, also affected by other concurrent processes occurring in an operating turbine oil system such as thermal degradation, mechanical, chemical reactions, metal catalysis, and interactions with other products, which result in nitration and hydrolysis. Contributions of such processes to degradation are the main reason that correlation of turbine oil test results with results of laboratory oxidation tests is not always successful.

Oxidation properties of a turbine oil are determined by its composition. In this respect, contributing factors are compositions of base oils, additives, and additive diluent oils. Particularly important are the presence and anti¬oxidant properties of synthetic antioxidant additives and of natural inhibitors in base and diluent oils. Conse¬quently, antioxidant capability is one of the most impor¬tant technological parameters determining the oxidation stability of turbine oils.

Turbine oil oxidation is initiated by free radicals, which are derived either from temperature or from decomposition of primary oxidation products such as hydroperoxides. These free radicals react with the oil, to abstract hydrogen and form alkyl radicals, which in the presence of oxygen form peroxy radicals. In the absence of antioxidants, peroxy radicals further react with additional oil to form hydroperoxides and alkyl radicals. This continues in a chain reaction process, which can result in the formation of a high concentration of hydroperoxides. Adding radical-trapping antioxidants to the oil can inhibit the chain reaction process.

Varnish

Varnish is a hard, sometimes brittle, veneer-like coating that covers metallic components inside lubrication systems. Varnish and sludge are terms that are interchangeable as they proliferate from the same degradation processes. To distinguish between the two, sludge is less dense than varnish and acts as a predecessor to varnish. Sludge will have higher water content, whereas varnish is moisture-free. Prolonged elevated temperatures will evaporate the moisture from the sludge increasing its density. Although they basically come from the same source, varnish as it forms on metal components, is a much more difficult problem to address. It's a sticky, gooey substance that can cause serious stiction and seizure problems in valves and other close tolerance system components. Combustion turbines in particular are very sensitive to varnish formation. Varnish with its sticky, gooey adhesive properties will combine with debris particles producing a slurry of oxidation wear contaminants.

The human health analogy to varnish is plaque that gradually builds-up in blood streams and attaches to the lining of veins and heart valves and varnish that attaches to the lining of piping and system valves. If not corrected both will eventually die. The human prescription to control or prevent this problem; medication, diet, exercise and other life style changes. The industry's prescription now used to control varnish that builds-up in lubrication oil streams; oil replacement and hot oil filtration/flushing.

Oxidation States

Before we go further in prescribing a cure for varnish, we must understand oxidation states. The oxidation state or oxidation number is defined as the sum of negative and positive charges in an atom, which indirectly indicates the number of electrons it has accepted or donated. The rules for oxidation states are in some ways arbitrary and unnatural, but need to be reviewed.

• All free (unattached) elements without a charge has the oxidation state of zero.
• All compounds have a net oxidation state of zero.
• The oxidation state of all of the atoms adds up to zero
• Polyatomic ions (radicals) have an oxidation states for the whole ion that is the charge on that ion.
• Oxygen has an oxidation state of minus two, except for oxygen as peroxide, which is minus one.
• Hydrogen has an oxidation state of plus one, except for hydrogen as hydride, which is minus one.
• Radicals or small covalent molecules, the element with the greatest electronegativity has its natural ion charge asits oxidation state.

In organic chemistry, oxidation of a hydrocarbon produces water and successively, an alcohol, an aldehyde or a ketone, carboxylic acid, and then a peroxide.

Oxygen will normally take in two electrons when it is not a free element therefore the combined form of oxygen (oxide) has an oxidation state of minus two. The exception of oxygen taking two electrons is peroxide.

Antioxidants

An antioxidant is any substance that retards or prevents deterioration, damage or destruction by oxidation. Free radicals act by oxidation. Oxidation is always damaging to whatever is oxidized, although often it is very useful-indeed, it is the source of all our energy, and our bodies could not work without it.

Chemists have known that free radical oxidation action can be controlled or even prevented by a range of antioxidant substances. It is, for instance, vital that lubricating oils should remain stable and liquid and should not dry up like paints. For this reason, such oils usually have small quantities of antioxidants, such as phenol or amine derivatives, added to them.

Peroxide

Peroxides are powerful oxidizers, and usually fairly unstable. Ionic peroxides react with water and diluted acids to form hydrogen peroxide. Organic compounds are oxidized to carbonates, even at normal temperatures. A peroxide ion contains two electrons more than an oxygen molecule and is diamagnetic (repelled by a magnet).

Diagnosing Lubricating Oil Problems

Oxidation is a chemical reaction promulgated by moisture, additive depletion. and lack of negative ions promoting the build-up of sludge. Varnish is a by-product.

Chain propagation and branching reactions in thermal failure produces organic, soluble compounds. The process continues until insoluble species are generated forming polymers and other compounds of high molecular weight. These insolubles have a sticky characteristic and easily bond to particles, depleted additives and water.

Varnish forms when the solubility limit for the high molecular weight insolubles is exceeded. Temperature is a key factor in the solvency of a lubricant, and is a determinant for the creation of varnish. Studies have shown that insoluble compounds are more resistant to dropping out of solution at temperatures above 68°C. This explains why varnish will first start to form in cooler spots in the system, such as strainers and the splash area immediate above the fluid capacity in the reservoir. At extreme temperatures, thermal failure has the potential to produce black carbon particles, which can fall out of solution immediately.

The Varnish Detection Challenge

It is not possible to monitor thermal and oxidative degradation on the molecular level, but it is possible to observe the products formed at the termination of the degradation process. Employing oil analysis as a tool to monitor thermal and oxidative degradation to predict the formation of varnish can be a powerful addition to a predictive maintenance program. In many applications, routine oil analysis tests such as viscosity and acid number will alert the user of increases levels of thermal failure and oxidation. Measuring a fluid's resistance to oxidation (RPVOT - ASTM D2272) can also assess the health of a lubricant and indicate the fluid's potential to oxidize and produce varnish.

Once acid numbers become elevated, signifying thermal failure and oxidation, there exist sufficient levels of insolubles in the lubricant to justify varnishing concerns. Emptying reservoirs of thermally damaged lubricants will reveal sludge and varnish accumulation. Strainers will be covered in a brown, resinous material and sight-glasses may be hazy.

Ideally, detection of a fluid's varnish potential would occur when the thermal and oxidative degradation process initiates the production of soluble and quasi-soluble contaminants, well prior to the creation of varnish. Unfortunately, there are no known analytical procedures with the sensitivity to measure these minute organic compounds in this state. However, there are several oil analysis tests that have the ability to detect varnish pre-cursors and are suitable to be part of a predictive maintenance program.

High molecular weight by-products are the pre-cursor to varnish. They are polar in nature and have an inclination to precipitate out of the non-polar lubricant onto dipolar metallic surfaces. They can affect several of the lubricants properties including viscosity, foaming, demulsibility characteristics and cause interference with polar additives such as Extreme Pressure (EP), Anti Wear (A W) and corrosion inhibitors.

Thermal failure occurs in one or more of the following conditions. A hot spot in the system elevates the lubricant to a very high temperature causing localized thermal failure. Pressure-Induced Thermal Failure is a rapid adiabatic compression of air bubbles in a system that creates excessive high temperatures, causing thermal failure. Static electricity sometimes is generated between oil and mechanical filtration, creating high temperatures and free-radical generation.

Thermal Failure and Oxidation

Thermal failure and oxidation are similar lubricant destructive mechanisms involving free¬ radical chain proliferation. Thermal failure occurs in the absence of oxygen where as the process of oxidation uses an oxygen molecule as a catalyst to the reaction. Both degradation processes generate similar by-products. Analytical methods to measure thermal and oxidative degradation processes are also similar.

Following are some of the differences between thermal failure and oxidation: Thermal failure can occur in a lubricant prior to the anti-oxidants being depleted. Thermal failure can happen before elevations in acid number. Thermal failure can occur in new products I caused by improper storage practices.

Most lubricants are formulated with anti-oxidants designed to retard the thermal and oxidative process. Primary anti-oxidants are free-radicals scavengers, bringing an abrupt end to the self-accelerating degradation process. The key types of primary anti-oxidants are hindered phenols and aromatic amines. Secondary anti-oxidants decompose hydro-peroxides, another by-product in oxidation. Finally, oils are formulated with metal deactivators that render metallic oxidation catalysts inert.

Varnish Detection

When acid numbers become elevated, this is a signal that thermal failure and oxidation must be appraised for products of oxidation and varnish. Reservoirs bottoms and walls are a good source for discovery of sludge and varnish accumulation. Strainers may be coated in a brown, resinous material and sight-glasses may be also coated.

The challenge with combustion turbine applications and other sensitive applications is the amount of varnish that can cause serious consequences, in most cases it is extremely low. The formation of damaging varnish may be progressing well before typical routine oil analysis detects signs of degradation.

There are six tests that have the ability to detect varnish pre-cursors. These tests can help to trend the increase of insolubles and will indicate early detection of oxidation.

1. Colorimetric Analysis
2. Gravimetric Patch Test
3. Ultracentrifuge
4. Fourier Transform Infrared (FTIR)
5. Interfacial Tension
6. RULER™

Combining the test results will provide valuable information that positively correlates to the oils potential to produce varnish.

Oxidation-Reduction (REDOX)

The term redox comes from the two concepts of REDuction and OXidation. Oxidation describes the loss of an electron by a molecule, atom, or ion. It also means an increase in oxidation number. Reduction describes the uptake of an electron by a molecule, atom, or ion. It also means a decrease in oxidation number. These two terms go together, because in a chemical reaction, one cannot occur without the other; electrons lost by one compound must be gained by another. Reduction can also be considered to be the reducing of an atom's positive charge, and oxidation its opposite (gaining positive charge).

The logical starting point in the discussion of oxidation-reduction reactions is the atom, and the terms and conventions used by chemists in describing this phenomenon. All atoms are electrically neutral even though they are comprised of charged, subatomic particles.

Atoms and Subatomic Particles

Atoms can be visualized, as spherical, electrically neutral particles comprised of many subatomic particles. As far as the topic of oxidation-reduction is concerned, we shall consider only two of these particles, the proton and the electron. Protons are positively charged particles, which are always found in the dense core or nucleus of the atom. According to theory, the electrons, or negatively charged particle, are located somewhere outside of the nucleus and surrounding it in spherical fashion as shown in the sketch below.

Each proton is arbitrarily assigned a charge of "+1″; and each electron, a charge of "-1″. In every atom there is always the same number of protons (p) as there are electrons (e). Hence, every atom is electrically neutral, as the positive charges of the protons always cancel the negative charge of the electrons. In other words, the net electrical charge of any atom is always zero.

The terms, oxidation state or oxidation number, have been developed to describe this "electrical state" of the atom. The oxidation state or oxidation number of an atom is simply defined as the sum of the negative and positive charges in an atom. Since every atom contains equal numbers of positive and negative charges, the oxidation state or oxidation number of any atom is always zero.

Some Atoms attract electrons more strongly than others. This attraction for electrons shared in covalent bonds is called electronegativity. Strong attractions create electronegativity of the atom. When an electronegativity atom, such as oxygen, shares electrons with hydrogen to form water there is an unequal pull on the shared electrons. Oxygen pulls them harder than does hydrogen.

It is well known scientifically, that atoms and molecules are electrically neutral, and the number of negatively charged electrons is exactly equal to the number of positively charged protons. Much of the "normal matter" that we find around us is in this form. However, particularly when there are energy sources available, atoms or molecules can gain or loose electrons and acquire a net electrical charge. This process is called ionization. To use electrostatics and ionization energy (IE) to cure a disease, we must understand the importance of ionization.

Ionization

Ionization energy (IE) is the amount of energy required to remove one electron from an atom. It is measured by how strong the outermost electron is attached to the atom. Some atoms my have one or more ionization energies. If this is the case it's referred to as the "first ionization energy" or "i", second ionization energy" or "h" and so on. As stated earlier the ionization energy is the amount of energy it takes to detach one electron from a neutral atom. Ionization is endothermic meaning that the atom or molecule increases its internal energy (receiving energy from an outside source).

The ionization energy of an atom is equal to the amount of energy given off when an electron is added to an atom. Electrons added to an atom and the energy given off is called electron affinity (EA). For most atoms the initial electron affinity is exothermic meaning energy is given off. However when adding a second, third etc. electron you are working with a negative ion. Therefore it takes greater energy to add the extra electron.

Electrons

Electrons can be moved from atoms by heat, light, electric energy, or bombardment with high-energy particles. Electronegativity is a parameter, which describes, on a relative basis, the power of an atom to attract electrons. A free radical is a molecule fragment having one or more unpaired electrons, usually short-lived and highly reactive. They can be produced by proteolysis (hydrolytic breakdown) or pyrolysis (decomposition) in which a bond is broken without forming ions. Free radicals are known to be formed by ionizing radiation and thus play a part in deleterious degradation effects that occur in irradiated tissue. They also act as initiators or intermediates in oxidation, combustion, photolysis (chemical decomposition induced by light) and polymerization (bonding two or more monomers). Free radicals are highly reactive molecules or atoms with an unpaired electron.

Polar Molecules

Chemical bonding is the result of elements sharing or taking electrons in the outer orbits of the element with which it is bonding. Normally, an atom has an even distribution of electrons in the orbits or shells, but if more end up on one side than the other in a molecule, there can be a resulting electrical field in that area. Water molecules are polar, with positive charges on one side and negative charges on the other side.

Polar Covalent bonds

A polar bond is a covalent bond (electrostatic force of attraction when one or more pairs of electrons are shared between atoms) in which there is a separation of charge between one end and the other, one end is slightly positive and the other end slightly negative.

Non Polar Molecules

Oil is a non-polar molecule, with electrons distributed more symmetrically, but do not have and abundance of charges at the opposite sides, thus canceling out each other.

Rule Polar and Non Polar Molecules

Polar molecules will mix to form solutions and non-polar molecules will mix to form solutions, but polar and non-polar combinations will not form a solution.

So far we have covered the basics of ionization energy. Now we need to look at the more advanced methods of discovery. Two characteristics of an atom that are very important to scientists are the Highest Occupied Molecular Orbital (HOMD) and the Lowest Unoccupied Molecular Orbital (LUMO). Together these two orbital are referred to as frontier orbitals. The HOMO can be found by locating the outer most orbital containing an electron. The LUMO is the first orbital that does not contain an electron. The frontier orbitals also give some insight into various aspects of the molecule such as hardness, aromatics and electronegativity.

Electronegativity

Electronegativity has an affinity for electrons and is a measure of the tendency of an atom to attract a bonding pair of electrons. If atoms are equally electronegative, both have the same tendency to attract the bonding pair of electrons, and so it will be found on average half way between the two atoms.

  •
  A+ B-
  •
 

To get a bond like this, A and B would usually have to be the same atom. This sort of bond could be thought of as being a "pure" covalent bond - where the electrons are shared evenly between the two atoms. If B is slightly more electronegative than A, B will attract the electron pair more than A. That means that the B end of the bond has more than its fair share of electron density and so becomes slightly negative. At the same time, the A end (rather short of electrons) becomes slightly positive.

  •
  A+ B-
  •

A redox reaction, also known as an oxidation-reduction reaction, is a type of chemical reaction where one of the reactants is oxidized and one of the reactants is reduced. Oxidation of a compound can be defined in several ways, one of which is that it is the gain of bonds to oxygen, another of which is that it is the loss of electrons. Similarly, two useful definitions of reduction, (the opposite of oxidation), are the gain of hydrogen or the gain of electrons.

The mnemonic OIL RIG can help you remember these definitions: Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).

Oxidation and reduction reactions always occur together, because the electrons that are donated from one compound, must be received by another compound. This is why redox reactions are said to be the product of two half reactions, the oxidation half reaction and the reduction half reaction. Each half reaction has a measurable reduction potential E0, which is a measure in volts of how easily the compound is reduced (how easily it gains electrons). Remember, the reduction potential is how much a species "wants" to get reduced, and the higher the number, the greater the potential.

Redox reactions play an important part in our lives. Combustion reactions that generate heat and electricity, such as the burning of natural gas, oil, gasoline or wood, are redox reactions, and in our bodies, redox reactions are needed to generate ATP to power our metabolism and our muscles.

Redox involves the transfer of electron density from one atom to another. For example, the electron density reaction of hydrogen and oxygen to produce water: The H2 and O2 both carry a charge of zero because they are nonpolar. But the product, water, is polar and hydrogen has a partial positive charge and the oxygen has a partial negative charge. During the reaction, the hydrogen atoms lose some electron density and the oxygen atoms gain. Many chemical reactions involve a shift of electron density and are called redox reactions. Reduction and oxidation always occur together. If one thing is reduced, another thing is oxidized. The reactant that is reduced is called the oxidizing agent and accepts electrons. The reactant that is oxidized is called the reducing agent and supplies electrons.

Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. This can be a simple redox process, such as the combustion of carbon to yield carbon dioxide, it could be the reduction of carbon by hydrogen to yield methane, or it could be the oxidation of sugar in the human body, through a series of very complex electron transfer processes.

One of the primary questions is: How can an object be charged and what effect does that charge have upon other objects in its vicinity? The answer to this question begins with an understanding of the structure of matter. Understanding charge as a fundamental quantity demands that we have an understanding of the structure of an atom.

One sure truth of this unit is that the protons and neutrons will remain within the nucleus of the atom; the movement of protons can never explain electrostatic phenomenon.

Nature of the Ionic Bond

An ionic bond is an electrical attraction between two oppositely charged atoms or groups of atoms. Normally, atoms are neutral and have no charge. However, in order to gain stability they will sacrifice their neutrality by either losing one or more of its outermost electrons thus becoming a positive ion (cation) or they will gain one or more electrons thus becoming a negative ion (anion). Elements that are described as "metallic" tend to lose electrons and elements that are described as "non-metallic" tend to gain electrons. Once this has happened the resulting charged atoms will attract each other. That electrical attraction between two oppositely charged ions is referred to as an ionic bond. Most salts are ionic. Any metal will combine chemically with any non-metal to form ionic bonds that hold the molecule together

Polarity of the Ionic Bond

Because the bonding electrons are literally under the domain of the non-metal in an ionic bond, the bond is said to be polar. Polar bonds generate a dipole moment. A dipole moment is an electrical force that is generated because of the unequal distribution of the bonding electrons between the two bonded atoms. In the case of an ionic bond that unequal distribution is extreme. The dipole moment that is generated is quite large compared to polar bonds of the co-valent bond.

A dipole moment is a vector measurement. A vector is a measurement that has a magnitude and a directional component. Any force (mechanical, electrical, magnetic, etc.) will be vector measurement. Examples would be velocity and forces. The other type of measurement is scalar measurement. These are measurements that have only a magnitude component but no directional one. Examples would be temperature, mass, speed, etc. Scalar measurements are handled differently than vector measurements when it comes to math operations. For example when you add or subtract scalar measurements you pay no attention to direction. With vector forces, you must pay attention to the direction and the angle between the vectors. Often the use of trigonometry is called for in order to resolve vectors.

Characteristics of Ionic Compounds

• Crystalline solids at room temperature
• Have higher melting points and boiling points compared to co-valent compounds
• Conduct electrical current in molten or solution state
• Are extremely polar bonds
• Most are soluble in water but not soluble in non-polar solvents

Controlling Turbine Oil Varnish

Controlling turbine oil varnish is analogous to controlling disease in the human body. One example, the substance that attaches to the lining of veins and heart valves and varnish that attaches to the lining of piping and system valves. If not corrected both will eventually die. The most efficient and effective means to control turbine oil varnish is with electrostatic charging of atoms and ions in combination with filtration. Electrostatic fundamentally is a phenomenon and must rely on theory in some cases. Therefore to help accomplish the task of controlling varnish requires some understanding of Electron Transfer Rules, Theory, Forces and Electrostatic Chemistry.

Electrostatic Chemistry

Bonding

The following are terms used to refer to bonding force between particles to remove solid particles and varnish:

Intermolecular

Force of attraction between atoms and molecules.

Ionic

Electrostatic force of attraction between two oppositely charged Ions.

Covalent

Electrostatic force of attraction when 1 or more pairs of electrons is shared between atoms.

Dative

1. A covalent bond in which the pairs of electrons involved in the bond is donated entirely from one of the atoms.
2. A bond in which both electrons come from a single donator atom.

Metallic

The attraction of free-floating valence electrons for the positively charged metal ions.

Hydrogen

Attractive forces in which hydrogen that is covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of an electronegative atom in the molecule or in a nearby molecule. The hydrogen bonding in water has about 5% of the strength of an average covalent bond.

Pi

In a pi bond, the bonding electrons are most likely to be found in sausage-shaped regions above and below the bond axis of the bonded atoms.

Sigma

A bond formed when two atomic orbitals combine to form a molecular orbital that is symmetrical along the axis connecting two atomic nuclei.

Bond Length

A measure of the distance between the centers of two bonded atoms.

Bond Enthalpy

The energy required to break a bond in standard conditions. (The condition of a substance at 25°C and 1 atm pressure).

Electrostatic Theory

VSEPRT (Valance Shell Electron Pair Repulsion) states that because electron pairs repel, molecules adjust their shapes so that the valance electron pairs are as far apart from possible.

Kinetic Theory

A theory stating that tiny particles in all forms of matter are in constant motion.

Van der Waals

The weakest of all attractions. Also known as Dispersion forces: generally thought to be caused by the motion of electrons, the strength of dispersion forces increases as the number of electrons in a molecule increases. As the electrons move about the molecule, temporary dipoles will be created that attracts the molecules to each other. Generally larger molecules exhibit larger Van der Waals forces.

Diffusion

The tendency of molecules and ions to move toward areas of lower concentration until the concentration is uniform throughout the system.

Brownian Motion

Brownian motion is the continuous random movement of small particles suspended in a fluid, which arise from collision with the fluid molecules. First observed when studying pollen particles. The effect is also visible in particles of smoke suspended in a still gas.

Laws

Coulomb's

The statement that force F between two electrical charges q1 and q2 separated by a distance r.

Force

Any two charged objects will create a force on each other. Opposite charges will produce an attractive force while similar charges will produce a repulsive force. The greater the electric charge the greater the force. The greater the distance between the two charges, the smaller the force.

Conservation of Charge

The Law of conservation of charge states that the net charge of an isolated system remains constant. If a system starts out with an equal number of positive and negative charges, there's nothing we can do to create an excess of one kind of charge in that system unless we bring in a charge from outside the system (or remove some charge from the system). Likewise, if something starts out with a certain net charge, say +100 e, it will always have +100 e unless it is allowed to interact with something external to it.

Charge can be created and destroyed, but only in positive-negative pairs.

Electrostatic Charging of Objects

Electrostatics

The study of electrostatic charges at rest:

There are two kinds of electrical charges, positive (+) and negative (-). Like charges repel and unlike charges attract. Thus, electrical charges exert a force on other electrical charges. This electrostatic force is directly proportional to the product of the charges and inversely proportional to the square of the distance of separation (another inverse square relationship).

Charged Object Created By The Separation Of Charges

• An atom is electrically neutral; it has the same number of protons (positive charges) as it does electrons (negative charges)
• Objects are charged by adding or removing electrons
• A positive charge occurs when there are fewer electrons than protons; its classical definition is the charge accumulated by a glass rod rubbed with silk or wool
• A negative charge occurs when there are more electrons than protons; it's classical definition is the charge accumulated by a hard, rubber rod rubbed with fur.

The choice of which name went with which charge was arbitrary. Benjamin Franklin set the convention. Franklin called the charge accumulation by the rubbed glass rod to be positive and that the rubber rod negative. Franklin also argued that whenever a certain amount of charge was produced on one-body in a process, an equal amount of the opposite charge was produced on another body. In any process, the net charge in the amount of charge produced is zero.

Electrostatic Field

When two objects in each other's vicinity have different electrical charges, an electrostatic field exists between them. An electrostatic field also forms around any single object that is electrically charged with respect to its environment. An object is negatively charged (-) if it has an excess of electrons relative to its surroundings. An object is positively charged (+) if it is deficient in electrons with respect to its surroundings.

Electrostatic fields bear some similarity to magnetic fields. Objects attract if their charges are opposite polarity (+/-); objects repel if their charges are of the same polarity (+/+ or -/-). The lines of electrostatic flux in the vicinity of a pair of oppositely charged objects are similar to lines of magnetic flux between and around a pair of opposite magnetic poles.

Conduction

A charged object touches another object; the amount of charge equally divides between the two objects; each object acquires the same sign charge.

Induction

A charged object is brought near, but not touching, another object; it attracts charges opposite to it and repels charges like it; when a ground is used, the opposite charge is acquired on the other object; it is thus charged without being touched. Of course, the net charge is still zero. Charges have merely been separated.

The idea by some that ions must be balanced to successfully remove debris from oil electrostatically is not a scientific fact. For example an electrostatic filtration system having one line that branches into two lines. With line A charged internally positive and line B charged internally negative, ion distribution in each line would have to be the same to balance the charge.

Electrostatic filtration the charging of atoms/ions has a distinct advantage over generic type mechanical filtration. Angstrom sized debris can be efficiently and effectively removed from turbine oil. The angstrom-sized particles are electrostatically attracted to one another forming large bundles of debris large enough to be captured in an open pore filter media.

Varnish Adhesive Theory

The basis of the electrostatic theory of adhesion is the difference in electonegativities of adhering materials. Adhesive force is attributed to the transfer of electrons across the interface creating positive and negative charges that attract one another. For example, when an organic polymer is brought into contact with metal, electrons are transferred from metal into the polymer, creating an attracting electrical double layer (EDL). The electrostatic theory tells us that these electrostatic forces at the interface (i.e. in the EDL), account for resistance to separation of the adhesive and the substrate.

A patented high-speed electrostatic oil cleaning and varnish removal system that can process oil at rates at 2500 gallons per hour has been developed by OILKLEEN. Water and damaging contaminants are also removed during the filtration process.

OILKLEEN's approach to electrostatic filtration is completely different that existing electrostatic filtration systems. The system provides a removable cartridge with filter media sandwiched between alternate positive and negative plates. During beta testing at a paper mill in Georgia a 420 gallon per hour unit removed over 7 pounds of debris from a 450 gallon operating hydraulic system with just one filter cartridge. Upon evaluating the debris it was found that a great portion of the debris was varnish.

OILKLEEN has taken GE Frame 7 gas turbines that had a QSA varnish potential rating of 90+ and removed the varnish from the system to deliver a QSA varnish potential rating of <7 in 3-4 days. The OILKLEEN high speed varnish removal service is th eonly solution to turbine oil varnishing issues.

OILKLEEN will be launching the OILKLEEN 250, OILKLEEN 500, and the OILKLEEN 1000 high speed electrostatic oil cleaning and varnish removal system at the May 15th NORIA, Lubrication Excellence Show. This will be the first time the public will be able to see the worlds fastest and most efficient electrostatic oil cleaning systems

Hydraulic and lube oil systems are critical to the safe, reliable operation of nearly all power plants. Steam turbine lubrication systems, generator sealing systems and boiler hydraulic devices are just a few of the many power plant components that rely on hydraulic and lubrication fluids. Insufficient attention to the cleanliness of these fluids can lead to increased component wear and increased operating and maintenance costs. This article examines the importance of fluid purity and describes the use of an electrostatic fluid cleaning device for power plant applications.

Component Damage

According to a study conducted by Dr. E. Rabinowicz at the Massachusetts Institute of Technology, surface deterioration was responsible for the loss of equipment usefulness in 70 percent of the instances observed. In the hydraulic and lubricating systems that were analyzed as part of this study, the majority of failures were due to mechanical wear and/or corrosion.

Abrasive wear is the primary wear mechanism in components associated with hydraulic and lubrication systems. Particles enter the clearance space between two moving surfaces, bury themselves in one of the surfaces, and act like cutting tools to remove material from the opposing surface. The size of particles causing the most damage are those equal to and slightly larger than the clearance space of the device. Most hydraulic components have operating (dynamic) clearances less than 5 microns. To protect opposing surfaces from abrasive wear and fatigue, particles of approximately this clearance size must be removed from the fluid.

According to a study conducted by Dr. E. Rabinowicz at the Massachusetts Institute of Technology, surface deterioration was responsible for the loss of equipment usefulness in 70 percent of the instances observed. In the hydraulic and lubricating systems that were analyzed as part of this study, the majority of failures were due to mechanical wear and/or corrosion.

Abrasive wear is the primary wear mechanism in components associated with hydraulic and lubrication systems. Particles enter the clearance space between two moving surfaces, bury themselves in one of the surfaces, and act like cutting tools to remove material from the opposing surface. The size of particles causing the most damage are those equal to and slightly larger than the clearance space of the device. Most hydraulic components have operating (dynamic) clearances less than 5 microns. To protect opposing surfaces from abrasive wear and fatigue, particles of approximately this clearance size must be removed from the fluid.

Abrasive wear brought about by particulate ingression has a significant impact on equipment operation. Wear can lead to dimensional changes, which modify fluid flows, leading to increased leakage and lower efficiency. In the case of a pump, for example, more power would be needed to generate the required flow and/or pressure, leading to higher operating costs. The particulate abrasion also begins a domino effect, as the abraded particles lead to more abrasion.

Abrasive wear has specific detrimental effects on power plant equipment. Silt contamination in spool valves, for example, can result in slow response and instability, spool jamming/stiction, surface erosion, solenoid burn-out and failure of safety systems. Silt contamination has similar effects on hydraulic actuators. Rod seal wear can lead to loss of oil through leakage, bronze bushing wear can lead to loss of rod alignment, piston seal wear can lead to loss of cylinder speed, and piston bearing wear can lead to a loss of holding characteristics and loss of alignment. Effective fluid cleaning is essential to minimize the possibility of oversize particles accelerating wear mechanisms.

Cylinder rod and seal systems are notorious contributors to contaminant ingression. Evidence points to higher ingression rates, with seal systems having the lowest leakage. This reinforces the need for effective silt filtration.

Bearing surfaces are subjected to failures as a result of repeated stressing caused by particles trapped by the two moving surfaces. In the beginning, the surfaces are dented and cracking is initiated. These cracks spread after repeated stressing by additional particles. Eventually the surface fails. Contamination reduces bearing life significantly through fatigue, abrasion, and roughening of operating surfaces.

The operating or dynamic clearance of a bearing is not equal to its machine clearance, but depends upon the load, speed and numerous other factors. Ideally, the rotor would be centered and there would be equal clearance around the device. In reality, the weight of the rotor imposes a load that creates the clearance pattern in. As motion is added, without lubricant, the rotor is off-center, but still impacts the bearing cavity. By adding a lubricating film between the two surfaces, a clearance is produced, but the clearance is not equal around the circumference because of the rotor weight. The variations in dynamic clearance shown by this example reinforce the importance of fluid cleaning.

Electrostatic Cleaning

Most hydraulic fluid systems in use at power plants incorporate in-line full flow mechanical filters to reduce particulate contamination. These mechanical filters are generally capable of successfully removing particulate down to 2-4 microns in size. Since the clearances of many of the hydraulic components are less than 1 micron, the long-term effect of component wear using only mechanical filters is increased.

Until recently, mechanical filters provided the only reliable method for successfully removing particulate from operating fluids. The decision-making process that guided filter sizing for a given system was greatly influenced by the equipment manufacturer's installed cost, which ignored long-term maintenance and reliability issues.

Further, the cost associated with using mechanical filters capable of removing fine particulate was very high. Not only did finer filters cost more, but they also had to be replaced more often because they plugged up more quickly.

Electrostatic particulate removal is not a new technology. Many industries, including injection molding, pulp and paper, steel, and automobile manufacturing, have been using electrostatic particulate removal for years to ensure proper fluid purity. Electrostatic fluid cleaning (EFC) has had little application in the power generation industry, however, primarily because of a lack of awareness.

Electrostatic fluid cleaning significantly differs from all of the current mechanical fluid cleaners by utilizing forces generated by an electrostatic field. All products not totally soluble within the fluid (contaminants) are capable of being removed. Additives, typically the anti-wear type, are not removed because they are totally soluble within the fluid.

In theory, EFC can remove all particulate contaminants from the fluid. In practice, it easily achieves NAS grades 3 or 4 (National Aerospace Standard 1638) and ISO standards 11/9 to 12/10 for fluid cleanliness. When used in conjunction with current in-line mechanical filters, the side-stream EFC is capable of maintaining an ultra-clean fluid system, thereby significantly reducing component wear and filter replacement costs.

The heart of an EFC unit is the collecting chamber, where contaminants are removed. The chamber consists of a circular reservoir of 10, 25, 50, 100 liters capacity, dependent upon machine size, in which plate electrodes are located approximately 30 mm apart. A set of pleated collectors made up of non-conducting material are placed between the electrodes (Figure 3). A high DC voltage (low current) is used to generate a force field between the electrodes. Fluid is supplied to the bottom of the collecting chamber by a small pump/motor assembly and passes the fluid via a diffuser vertically upwards and parallel to the collectors through the force field. The ultra-clean fluid then exits via the top of the collecting chamber, leaving the contaminant on the collectors retained by the electrostatic force.

Collectors

The collector design is important. Pleats configured at an acute angle are used to greatly multiply the potential collecting area. The collector surface area can hold up to ten pounds of contaminants, compared with about one-tenth of a pound for a conventional mechanical filter. Fluid naturally flows along the line of least resistance which is also closer to the strongest area of attraction. The force field is distorted due to the collectors and also the pattern of the contaminant build-up. Particles, depending on their composition, can be either negatively or positively charged. As a result, both sides of the collectors attract contaminant. The collector's acute pleating and unique surface finish, which is deliberately rough, enable it to hold contaminant on all the surfaces and not just in the bottom of the valley.

Due to the gravitational effect, there is a natural attraction between particles when they are very close or touching one another. This phenomena, together with the rough surface texture of collectors and the stickiness of much of the contaminant, ensures that contaminant build-up on the collector does not fall off once the electrostatic field is broken.

EFC Benefits

The electrostatic fluid cleaning process has been well proven on more than 30,000 units throughout the world. The end users enjoy many benefits from the certainty afforded with having an ultra-clean fluid:

• Fluid Conservation - Almost without exception, end users have not had to change the hydraulic fluid since the introduction of EFC. Normal wastage through leakage ensures that sufficient top-off fluid is made on a regular basis to replenish the additives which naturally deplete.
• Preventive Maintenance - As an off-line cleaning system, the EFC process is an ideal preventive maintenance tool and it is accepted that removal of all levels of contamination reduces wear greatly and extends the life of components such as pumps, valves, etc. In cases of sophisticated equipment such as servo valves, the reliability and integrity of the complete machine is greatly enhanced.
• Higher Productivity - Good preventive maintenance procedures bring the benefits of minimum downtime and the associated losses in production. With ever-increasing overhead costs, this is a major benefit.
• Restrictions - The majority of hydraulic systems still operate on mineral-based fluids, for which the EFC process is ideally suited. The process will not operate on any water-based fluids or fluids with an additive to improve conductivity such as Skydrol or Hy-Jet. However, the process will work on synthetic fluids such as phosphate ester, polyester, silicone oil and many industrial solvents.

EFC units cost from $7,000-$27,000 depending on the size of the associated fluid reservoir and the type of fluid being treated, phosphate ester or mineral oil. For a typical 600-gallon reservoir, the EFC unit will only draw about 500 W of power. The unit is also compact, measuring 28 inches in height.

Clean at La Cygne

Kansas City Power & Light's La Cygne Station is home to the first U.S. power plant application of EFC technology. Two EFC units are installed on the phosphate ester hydraulic fluid systems of the plant's 700 MW General Electric and 750 MW Westinghouse steam turbines. The EFC units draw 1.5 gpm from the turbines' fluid reservoir, clean it, and return it to the reservoir.

KCP&L initiated a fluid management review program about four years ago to identify and address various problems attributed to hydraulic fluid and lube oil contamination, including increased pump wear and noise, filter pluggage, and servo valve failures. The steam turbines' hydraulic fluid circulation systems, which were equipped with OEM filters, suffered from varnish build-up and high particulate loads. In a few instances, the severity of the fluid contamination had caused valves to stick, tripping the units.

A consultant recommended evaluation of electrostatic fluid cleaning. After careful consideration, KCP&L decided to install an EFC unit on one of the turbines to gauge its performance. About one year later, satisfied with the ability of the EFC to remove varnish and maintain effective cleanliness levels, KCP&L installed EFC on the second steam turbine. Since installation, both EFC units have been maintenance-free and La Cygne has not experienced a single unit trip attributable to high fluid contamination levels. Based on this success, La Cygne is evaluating the installation of EFC units on various other mineral oil lube systems over the next few years.

References

1 Rabinowicz, E., Friction and Wear of Materials, 2nd edition, John Wiley & Sons, July 1995.

2 Sasaki, A., et al. "The Use of Electrostatic Liquid Cleaning for Contamination Control of Hydraulic Oil," Lubrication Engineering, Vol. 44, No. 3, pp 251-256 (1988).

About the Author

Barry Sibul has been associated with the power generation industry for more than 30 years. He began his career with General Electric as a Field Engineer, Startup Engineer, Customer Trainer and Coordinator of Training. In 1981 he organized Lloyds Laboratories, the first non-OEM company to offer site-specific training for power plant personnel. Ten years later he co-founded NovaTech Corporation, which provides retrofit upgrade products on GE turbine control systems. In June of 1998, Sibul created Barry Sibul and Company, specializing in providing products and support services on power plant hydraulic fluid systems.

Power Engineering July, 2001

Author(s) : Barry Sibul