Improving Machine Performance and Service Life with Oil Dehydrators/Purifiers and Conditioners

Regular maintenance of industrial machinery is crucial to maximizing performance and service life. One essential aspect of an effective maintenance program is effectively purifying and conditioning lube and hydraulic oils used in the machinery. This blog post will explore the significance of oil dehydrators/purifiers and conditioners and how they improve machine performance and prolong equipment life.

Understanding Oil Dehydrators/Purifiers and Conditioners

Oil dehydrators/purifiers and conditioners are specialized systems designed to remove contaminants and maintain the quality of various oils used in industrial applications. These oils play a vital role in powering and lubricating machinery.  They also reduce friction and dissipate heat, preventing wear and tear. However, over time, contaminants such as particulate, moisture, air and other gases accumulate in the oil.  This leads to costly issues affecting machinery productivity, reliability, and service life.

The Role of an Oil Purifier

An oil purifier is a system with an oil dehydrator and particulate filter.  Dehydration removes free, entrained, and dissolved water and unwanted gases.  The particulate filter removes solid particles such as dust, soot, metallic corrosion products and carbon.  These purifiers often utilize a low-watt density heater to raise the temperature of the oil to facilitate efficient dehydration.  By employing a combination of heat, vacuum dehydration and particulate filtration, an oil purifier maintains clean, dry oil and keeps lubricated and hydraulic-powered equipment productive and reliable.

Benefits of Using an Oil Dehydrator/Purifier

• Improved Lubrication: Clean oil ensures better lubrication, reducing friction and wear between machine parts. This results in improved efficiency and reduced energy consumption.
• Enhanced Equipment Performance: By maintaining the oil’s recommended cleanliness level, oil purifiers help machinery operate at peak performance levels, maximizing productivity and reliability.
• Extended Equipment Lifespan: Continuous online oil purification minimizes the risk of mechanical breakdowns and extends the lifespan of expensive industrial equipment.
• Cost Savings: Investing in an oil purifier can lead to long-term cost savings by reducing the need for frequent oil changes and preventing expensive repairs.
• Maintaining clean, dry oil in hydraulic systems prevents safety issues related to sluggish responses and equipment failures.

Oil Conditioners

Some machinery operates in wet environments or utilizes steam that may condense and leak into the lubrication system.  If a leak suddenly occurs, it may demand rapid removal of a large volume of water, exceeding what a standard oil dehydrator/purifier can handle. 

Oil conditioners are oil purification systems designed for applications requiring bulk water removal.  In addition to a common oil dehydrator/purifier, they incorporate a special coalescing filter to knock out large amounts of water rapidly.  The coalescing filter can be used intermittently when water ingression overwhelms the oil dehydrator or continuously.

Benefits of Using Oil Conditioners

• Removes a large volume of water from oil quickly.
• Minimizes equipment damage when lubrication or hydraulic power systems are subjected to sudden, unexpected episodes of water ingression from steam seal leaks, environmental or other conditions.
• Prevents or minimizes downtime that would otherwise result from water ingression.
• Reduces waste because wet oil is dehydrated instead of being changed.

Conclusion

Oil dehydrators/purifiers and conditioners play a vital role in ensuring industrial machinery’s efficient, reliable operation. These devices improve machine performance and extend equipment lifespan by effectively removing contaminants and stabilizing oil properties. Investing in oil purification optimizes machinery operations and leads to significant cost savings in the long run.

Consider incorporating oil dehydrators/purifiers or oil conditioners into your maintenance routine to improve your equipment’s performance and reduce maintenance costs. By doing so, you can experience the benefits of cleaner oil and reap the rewards of prolonged equipment life, reduced oil waste and increased productivity.

Remember, maintaining clean and well-conditioned oil is a proactive approach to safeguarding your valuable investments in industrial machinery. Start exploring the options available in the market to find the best oil dehydrators/purifiers and conditioners that suit your specific needs and requirements.

Understanding and Evaluating Lube and Hydraulic Oil Purification Systems

Lubrication and hydraulic fluids for industrial machinery will most often suffer from water contamination. AMPTIAC Quarterly reports that, 75% of hydraulic system failures result from fluid contamination. Water is second only to particulate as a source of major contamination of machine oils. Rotating equipment is especially vulnerable. For example, as the water content in turbine lube oil gradually increases, the machine begins to develop multiple failure points. These include bearings, bushings, seals, shafts and more.

While other forms of contamination must be mitigated, water contamination presents unique challenges. Free and emulsified water are easily identifiable. Free water accumulates and stratifies, while emulsions typically appear as cloudiness or rag layers. Dissolved water is invisible but just as toxic as the other forms. According to NORIA, “Depending on the oil type and temperature, a bearing can lose 75% of its life due to water contamination before the oil becomes cloudy.” Reducing water content well below the saturation level is obviously desirable. This prevents the liberation of free water in oil coolers, while curtailing additive depletion and degradation of critical oil properties such as viscosity, lubricity, and film strength.  “Oil Purification Systems,” aka “Oil Purifiers” utilizing vacuum dehydration were designed for these challenges.

As defined here, their primary function is to remove ALL forms of water from the oil. Most, also remove free and dissolved gases, as well as particulate contamination. Hence, as used here, the term “Purifier” or “Purification System,” alludes to the removal of free and dissolved water and gases, oil/water emulsions, and particulate. Though often advertised to the contrary, most oil/water separation technologies do not purposefully remove dissolved water nor any gases. This is where systems that utilize vacuum dehydration are distinguished from those employing coalescing filters, water absorption media, corrugated plates and centrifuges. Application of an Oil Purification System utilizing vacuum dehydration is necessary when total water content starts to increase in lube or hydraulic fluid systems.

Sources of Water Contamination

There are several ways water enters lube and hydraulic fluid systems. These include:

1. Direct absorption from humid air in the headspace of the oil reservoir.
2. Rapid condensation in the headspace of the oil reservoir.
3. Rain and/or washdown water ingression through leaky hatches and seals.
4. Leakage from steam seals.
5. Leakage from oil coolers and heat exchangers.

Preventative measures for mitigating these ingression mechanisms should be in place.  However, it is very probably that water will find its way into these systems at some point.  This is when an Oil Purifier is convenient and often the most reasonable solution.

Process Technology Applied in Oil Purifiers

Before exploring the benefits of using Oil Purifiers, it is essential to understand how they work. Commonly, Oil Purifiers utilize vacuum dehydration technology for enhanced water removal performance. In some systems the oil may also be heated to optimize the dehydration process. Under vacuum, the required thermal input is reduced for the purpose of preventing thermal oxidative stress of the processed oil. Vacuum dehydration is the most efficient way to reduce water concentration levels below the threshold required to adequately protect vital machine components.

There are two commonly used vacuum dehydration processes, “vacuum mass transfer” and “flash distillation”. Vacuum mass transfer uses moderate vacuum levels (ࣘ≤22inHg) and heat (≤120 deg. F) in a process that accelerates moisture evaporation with minimal risks of oil degradation. Flash distillation uses deep vacuum (25-28 inHg) and high heat (150+ deg. F) to boil or flash water from the oil in a process carrying a higher risk of oil degradation. We only discuss vacuum mass transfer here.

Inside these dehydrators, the oil is distributed in a thin film over some form of media, such as packing rings. The increased surface area greatly improves the efficiency of the process. To achieve this,

• There is a vacuum chamber/tower in which oil flows from top to bottom, while dry air flows from bottom to top.
• There is a means of distributing the oil evenly over the inside cross section of the chamber/tower by creating an oil spray in the form of an umbrella.
• The oil passes from top to bottom through/over a media such as packing rings that expands the surface area and creates a thin, cascading film.

Dry air is continuously drawn across the oil surface, evaporating water and sweeping it out of the vacuum chamber along with any free and dissolved gases. Dehydrated oil exits the chamber and is typically routed through a particulate filter to achieve the desired level of cleanliness. This system could run as a batch or continuous process, but the latter tends to be more efficient.

Why Use Oil Purifiers

Before investing in an Oil Purification System, it is essential to consider the long term benefits.

Benefit #1: Improved safety

Safety is always number one. Particularly with respect to rotating equipment, mechanical failure and control issues can result in serious accidents. The average cost of a recordable injury is tens of thousands of dollars. A lost-time injury costs even more. By maintaining the purity of lube and hydraulic fluids, dangerous equipment failures such as broken shafts and hydraulic overspeed’s can be avoided. Prevention of a single injury will always justify the cost of an Oil Purifier.

Benefit #2: Less frequent oil changes

It is easy to see how stretching the useful life of lube and hydraulic fluids is economically beneficial. Factors like:

• Reducing the money spent on replacement fluid
• Lowering labor costs and freeing up time for other maintenance and repair projects
• Shrinking disposal fees

Have a significant impact on the return on this investment. Accordingly, extending the lifespan of the oil by several thousand hours makes a good case for investing in an Oil Purification System.

Benefit #3: Less unscheduled machine downtime

Often, machinery endures major wear and tear or massive and sudden breakdowns that can cause immense losses to a business. According to Forbes magazine “next to a safety or environmental mishap, unplanned/unscheduled downtime represents one of the costliest events at any industrial or manufacturing plant.”  Every event is different, but costs can run into millions of dollars. It is almost certain, when the downtime results from contaminated lube or hydraulic fluid, the costs will dwarf that of investing in an Oil Purifier. Machinery Lubrication published the following top reasons that unscheduled downtime is unwelcome:

• Production losses and schedule delays (business interruption)
• Lost revenue and profit (unhappy management/ownership)
• Promised delivery dates are missed (unhappy customers)
• The blame game and damaged relationships between operations and maintenance (morale issues)
• Hurried (botched) repairs cause future problems (cycle of despair)
• Lack of available replacement parts and skilled trades prolongs the downtime interval
• Repairs are at a “cost premium” due to rushed parts purchases, use of overtime labor and collateral damage
• Scheduled “proactive” tasks are replaced by chaotic reactive tasks (leads to future problems)
• Increased work pressure and job stress (job satisfaction issues)
• Safety risks due to rushed work, unskilled work, inferior parts, cutting corners, job stress, etc.

Alone, any of these demonstrates the value and ROI of an Oil Purifier.

Benefit #4: Better machine performance

The productivity of a company depends on how well equipment runs. When lube and hydraulic fluids are properly maintained, it elevates machine health. This results in better performance, higher availability and productivity. It also promotes a safer work environment and smaller environmental footprint.  On the other hand, contaminated lube and hydraulic fluids leads to derated capacity, sluggish operation, hydraulic control issues and other performance issues. Plant Services’ surveys indicate, one of the most important metrics used by the energy industry is “return on capital employed,” which correlates with the performance of rotating equipment. This suggests that if rotating equipment is underperforming due to contaminated lube or hydraulic fluid, investment in an Oil Purifier may have a significant and favorable impact on key business metrics.

These and other benefits unique to every plant offer extensive, quantifiable justification for capital investment in an Oil Purification System. If capital is tight, rental units are available that will protect machines through a budget cycle. There are many sizes and features for consideration, making it possible to find a system that suits any needs or budget.

How to Evaluate Oil Purifiers

With many Oil Purifiers available in the market, it is important to understand the method of purification and how to evaluate them. The characteristics that are most important will determine whether this investment meets your expectations. Doing some homework and making an educated decision is vital.  The most important machine attributes relate to operational complexity, reliability, and oil processing performance. The best Oil Purification Systems will:

• Effectively remove all forms of water, gases, and particulate from oil with no oil degradation or additive depletion.
• Require minimal operator attendance to start, stop and run the unit.
• Offer adequate, simple and convenient monitoring and control.
• Require minimal scheduled or routine maintenance.
• Operate at full capacity over the entire range of application conditions, including oil temperatures, pressures and viscosities, piping configurations, and environmental conditions (including sound levels).
• Produce minimal environmental footprint.
• Operate with minimal energy and utility requirements.

The best way to evaluate these important qualities is to compare systems with a full-scale, onsite trial. Nothing beats a test drive. In this scenario, ensure that a knowledgeable factory or distributor representative is onsite during the trial to answer questions, train and assist the personnel conducting the test. It would also be beneficial to have the operations and maintenance staff participate and provide input in the evaluation. 

The next best alternative is to request a copy of the O&M manual. A thorough review of this document with the previously mentioned attributes in mind can provide useful information. For example, it will likely contain:

• A list of operational limits
• Important installation requirements
• Detailed start-up, running and shutdown procedures
• Component maintenance requirements
• Critical safety environmental and hazard information

Often, sales and marketing material omit much of this, but it can be found in technical documentation provided upon delivery of the machine. Do not be afraid to request additional documentation, data and drawings. Sales personnel should be able to help with this and provide valuable contextual information.

Conclusion

As you can see, an Oil Purification System can be very beneficial to any business that relies on lubricated or hydraulically operated machinery. Fluid health is critical to machine health. Industrial data suggests that the health and reliability of the machinery used by a business correlate to productivity, profit, safety and environmental metrics. Consider the impact that could be realized by making a wise investment in an Oil Purification System.

Start your research now and consider companies like PowerFlow Fluid systems, who offers decades of experience designing and building the best Oil Purification Systems.

PowerFlow Fluid Systems supports industrial sustainability with innovative and environmentally responsible solutions for optimizing performance of virtually all fluid systems throughout the plant.

Oil Purification Systems – Giving Power Generation Stations and Edge

The benefits of Oil Purification Systems are hard to ignore, especially in the current power generation industry.  Addressing the demand for maximum performance of all mechanical systems, these machines help minimize downtime of rotating equipment like steam turbines by keeping the lubrication and hydraulic oils clean and dry.  Oil Purification Systems remove free, dissolved, and emulsified water, as well as particulate and dissolved gases.  If not controlled, these contaminants will cause significant equipment damage, performance and safety issues.

PowerFlow’s XLP Series offers another advantage.  It is the easiest to operate and maintain out of all the Oil Purification Systems available.  Simply push the “Start” button.  The purifier will begin running and stabilize within a minute or two.  Check the gauges to make sure they are reading within the expected parameters.  If tower vacuum must be adjusted, this is accomplished by simply adjusting a needle valve.  Finally, vent air from the particulate filter housing by opening and closing the vent valve.  Done.  

From a maintenance standpoint you cannot beat PowerFlow’s Oil Purification Systems either.  Many of them have operated continuously for up to a year with no maintenance.  PowerFlow Fluid Systems’ XLP Series requires the least operator and maintenance attendance of any Oil Purification System.

High-end performance:

Unlike other systems, XLP Series do not require high heat nor deep vacuum.  The highly optimized vacuum mass transfer process employed by these units is very gently on the oil and very efficient.  They can also process oil up to 1000 cSt and pull oil from well below grade with no adjustments or adjunct equipment.  Oil foaming is not and issue in the least, as it is with most other vacuum dehydrator-based units.  

PowerFlow XLP Series Oil Purification Systems are simple, efficient and built to run.

In today’s power generation environment, any improvement, upgrade or optimization is significant.  Investing in an innovative lube and hydraulic Oil Purification System is certainly a value as it pertains to this reality.  Clean dry oil will help keep your generators running when the grid needs it the most.

 

Oil Purification Methods and Equipment

Oil purification can have many interpretations.  In lube and hydraulic fluid applications eliminating water, gases and solids from oil is critical for maintaining optimum system performance and oil service life.  

Oil gets contaminated during operation, maintenance and storage.  Contaminants come from various sources like:

• Leaking coolers
• Rust and corrosion
• Thermal oxidation and other fluid degradation mechanisms
• Environmental sources like air, rain, and dust
• Wear, break-in and damage of parts within the oil circuit
• Contaminated make-up oil

Contaminants from these sources are major catalysts in the cycle of wear; Contamination results in wear that results in contamination that results in more wear and so on.

Types of Contaminants Commonly Found in Oil

There are different types of contaminants found oil.  Some of these include:

• Solid and gelatinous particles
• Water, coolants and other liquids
• Air and other gases
• Paraffinic deposits and varnishes
• Acids
• Metals, salts and soaps

Oil purification equipment is used to control and/or eliminate these contaminants, improving the oil’s performance and service life. 

Oil Purification Methods

There are different methods used for purifying oil.  The type of oil and contaminants dictate the method used.  Following is a discussion of common methods.

Gravity Separation:

This form of oil purification involves an engineered system that exploits the differences in densities of solids, water and oil as a means of separation.  The equipment is simple, such as a settling tank, a weir-style oil/water separator or a drop leg.  Gravity separation can be very slow and is affected by many variables, making it an unreliable method in many applications.  It is most useful for bulk separation where time is not a major factor, and it may be followed by other purification steps.

Filtration:

This method is used when the primary contaminant is particulate matter.  Filters designed and constructed specifically for oil and hydraulic applications are used to remove trap contaminant particles.  These filters are typically cylindrical cartridges that fit in a sealed housing.  The cartridges contain a fibrous filter medium that the oil flows through trapping particles of a specified size.  As filters trap particles the pressure drop across the filter media will increase.  Once it reached a specified level that filter cartridge must be replaced or cleaned.

If the contaminant load is heavy, there may be a series of filtration steps beginning with course filters followed by finer filters.  There are specialized filter media for applications such as highly viscous fluids and fluids that tend to generate and discharge electrostatic energy.  Other specialty filters are designed to remove varnish precursors, soot, and gelatinous particles.  Filtration is a fundamental component of oil purification and may also serve as a stand-alone process or as a final guard from contamination that breaks through upstream processes.

ISO Cleanliness Levels are used to quantify particulate contamination.  Various organizations have evaluated tolerances and recommended ISO Cleanliness Levels for most lubricated machinery and hydraulic systems.  Many lube and hydraulic filters have rated removal efficiencies correlated to these for easy selection of the appropriate filter.

Filtration efficiency claims are often misunderstood.  Basically, filtration efficiency is a ratio of the number of particles of a specified size (commonly measured in microns) exiting a filter to the number of these particles entering the filter.  For filters in lube and hydraulic applications Beta Ratio is a common formula to express this.  The formula is:

ß(x)=[(Number of particles of size (x) upstream)/(Number of particles of size (x) downstream)]*100

This can be converted to percentage efficiency as follows:

Efficiency %=[(ß(x)-1)/(ß(x))] * 100

This is a scientific, quantifiable industry standard for measuring filtration efficiency.  Any absolute rated filter that is manufactured in a quality-controlled environment will have documentation of the filtration efficiency and the procedure used to measure it.

Hence, it is important to understand the difference between “absolute” and “nominal” ratings.  Absolute rated filters have particle removal efficiencies that are measured, repeatable and monitored by quality control.  Industry standards will be used and documented for measurements.  These filters tend to be manufactured to higher quality control standards and have efficiency ratings of at least 99% or ß(x)=100, although it could be any efficiency.  The key is that “absolute” means the efficiency is strictly defined and verifiable.

There is no industry standard for nominally rated filters.  At most there may be an understanding based on the manufacturer, media composition, experience and maybe some established empirical data that a particular filter has a specified nominal filtration efficiency within an acceptable level of variability.  However, according to the Cambridge Dictionary nominal means “in name or thought but not in fact or not as things really are.”  So bare that in mind and expect your filtration specialist to know how each of your filters is rated.

Finally, it is important to understand that every conventional filter media has a filtration efficiency for every particle size.  Particle removal efficiency for any filter media will follow a curve on an x-y chart.  The filtration rating is arbitrary.  Filtration manufacturers consider many factors, including industry, application and standards in deciding where on the efficiency curve to rate a particular series of filters.  Consider a filter marketed for compressor lube oil applications, and the industry filtration standard is 99.5% at 5 micron.  It would be reasonable for a filter manufacturer to design this filter to remove 99.5% of 5 micron particles.  This does not mean that it will not remove larger and smaller particles.  In fact, the manufacturer should have an x-y curve that specifies the filtration efficiency for a range of particles sizes.  The filter may remove 80% of 3 micron particles and 99.98% of 10 micron particles.  While this may be considered a 5-micron filter by definition, it could be used in an application that requires filtration of 99.98% at 10 micron or any other application fits its efficiency curve.  The question to ask is not “what is the filter rating?”  The correct question to ask is “what is the filtration efficiency” at a specified particle size.  Subtle but important.

Centrifugal Force:

This method could be considered enhanced gravity separation.  By imparting centrifugal force on the oil within a centrifuge or cyclonic separator.  The inertia of the heavier contaminants forces them out of the clean oil stream into a lower energy section of the device.  In this lower energy environment, gravity takes over and the contaminants fall into a collection area.  Finally, the contaminant can be manually or automatically discharged.

A centrifuge is the most common example in oil applications.  They work as follows:

• A drum filled with contaminated oil rotates
• The rotation imparts centrifugal force on the oil, sending contaminants heavier than oil to the edge of the drum
• The contaminants are removed by various manual and automatic mechanisms and are discarded as oily waste
• Clean oil is moved in the opposite direction toward the discharge

Centrifuges are effective for rapid removal of bulk, free water and particles down to 2.5-20 micron depending on many variables.  They are unable to remove dissolved water, emulsions and finer particles that form soot, sludges and varnishes.  They also require a significant investment in maintenance and operational resources.

Liquid/Liquid Coalescing:

Liquid/Liquid coalescing is the process of separating two immiscible liquids.  The bulk liquid is referred to as the continuous phase and the other liquid is the dispersed phase.  These devices work by promoting the coalescence and settling of droplets of the dispersed phase.

Coalescing occurs naturally but can be enhanced with the use of a fiber matrix, similar to a particle filter.  However, instead of permanently retaining the contaminant, the filter is designed to provide a quiescent zone where the following mechanism occurs:

• Droplets impact and cling to the media fibers
• As droplets accumulate, they contact and coalesce with other droplets
• The smaller droplets grow until they are larger enough for gravity to cause them to drain out of the coalescing media into a sump area
• The sump accumulates bulk liquid and is drained as needed

Coalescing filters are commonly used as a stand-alone system to periodically remove bulk free water from oil.  They are also commonly integrated into multi-step oil purification systems.  

Rapid removal of large amounts of free water contamination is often needed in lube and hydraulic system applications.  Coalescing filters work well for this.  However, their removal capabilities diminish sharply when the free water content drops to about 100-250 ppm(w), depending on many variables.  Simple physics suggests fewer droplets offer less probability of droplet/droplet interaction and coalescing.  Therefore, the law diminishing returns becomes evident.  Removal of free water below this threshold is not in the domain of coalescing filters.  Moreover, they are unable to remove dissolved water and most water-in-oil emulsions.  These forms of water contamination are handled best by flash distillation or vacuum mass transfer, also known as vacuum dehydration.

The potential for contamination of coalescing filters should be considered carefully.  By nature of their fiber matrix, they will filter particulate from oil but should not be used for this purpose.  A separate prefilter should be used.  Particulate contamination will degrade coalescing filter performance and service life.  Also, surfactants coat the fibers of common coalescing media, disarming it and severely degrading performance.   If surfactants are present in the oil a filtration specialist should be consulted.  Media is available that is not disarmed by surfactants and other chemicals.

Flash Distillation:

Flash distillation is one of two methods used to remove free, emulsified and dissolved water from lubricating and hydraulic fluids.  In this context flash distillation refers to the process of heating an oil/water mixture to the point that it will boil after being pumped into a vacuum chamber.  This process will yield a vapor and liquid phase in equilibrium.  The vapor will consist almost entirely of water since it has a higher vapor pressure than the base oil.  The water vapor is removed through the vacuum pump and condensed.  The dehydrated oil is pumped out of the bottom of the chamber.

This method also removes any gases and components that are volatile under the chamber pressure and temperature.  Removal of dissolved air and gases is beneficial.  However, this can also exacerbate foaming.  This is addition to temperature and vacuum level must be carefully controlled to minimize operational issues and limit the thermal degradation of the processed oil.

Vacuum Mass Transfer:

The term “vacuum mass transfer” is used in this context to refer to a process that essentially maximizes the transfer of water molecules from the oil to a counter current dry air stream without boiling.  This process was developed to address many concerns about flash distillation of oil.  These concerns include:

• Acceleration of oil degradation by deep vacuum and high heat
• Severe oil foaming that adds significant operational complexity
• High energy consumption
• Dialing back processing capacity to reduce operation complexities precented at the rated capacity

Vacuum mass transfer optimizes the vacuum dehydration process around three key variables, oil surface area, oil temperature and chamber vacuum level.  Using these variables, it is possible to promote a high rate of water mass transfer by dispersing the oil through an engineered packed column/chamber.  The very thin oil film and extensive surface area created by the special packing significantly improves the mass transfer efficiency under mild heat and vacuum level.

As water transfers from the oil to air stream it is carried out of the chamber through the vacuum pump, condensed and collected in a tank.

This process can remove 90% of free, dissolved and emulsified water and 80% of dissolved gases without imparting thermal or barometric stress to the oil.  The milder vacuum also reduces the foaming, energy consumption and operational complexity.  Vacuum mass transfer addresses all concerns raised by flash distillation.

Adsorption:

Adsorption is the physicochemical attachment of contaminants to the surface of a solid material by means intermolecular forces.  Adsorbents are typically solid materials with extremely high surface areas.  Generally, they are highly porous, providing a labyrinth of passages where the contaminant molecules come into close contact with the adsorbent surface and adhere.  These materials are generally used to remove or control trace contaminants at a molecular level.  This is often referred to as polishing or finishing.

There are several adsorbents commonly used in the lube and hydraulic oil applications.  These include:

• Lenticular filters made with cellulose media impregnated with activated carbon, diatomaceous earth and other activated materials that target specific contaminants.  These combine the advantages of depth filtration and selective adsorption in a high flow cartridge configuration.  While very convenient and effective for targeted contaminants, they are also the most versatile of the adsorbent category.  Still sources, sizes and sealing configurations vary by manufacturer with no industry standard.  This means you could start with one product and if your contamination issue changes you may have to purchase another complete lenticular filter assembly or other purification technology to address it.  One manufacturer does not necessarily have a complete range of lenticular solutions.
• Clay (Fuller’s Earth) is a fine mineral clay that has a generous adsorptive capacity for organic acidic contaminants that are common degradation biproducts in phosphate ester-based oils.  Clay is typically packaged in a disposable canister-style cartridge that is installed in a cylindrical housing.  While effective for acid control, Fuller’s Earth must be carefully monitored for performance and can require frequent replacement.  It also contains extractable metals that can contribute to oil degradation and can contaminate the oil with clay fines if a post-filter is not installed and properly operated and maintained.
• Activated alumina is aluminium oxide that is formulated (for our purposes) to adsorb organic acidic species.  Similar to Fuller’s Earth, this adsorbent can be an effective solution for acid control if properly monitored and maintained.  It has similar issues to Fullers Earth with extractable metals and fines.
• Ion exchange media is considered the state-of-the-art for lube and hydraulic oil polishing.  This media consists of highly porous resin or silica gel beads that can be functionalized for specific purposes.  The beads are packed in disposable cylindrical canisters forming a bed or column.  These are installed in a housing like a filter and oil percolates through the resin bed.  As oil fills the pores within the beads, contaminants adsorb and/or ionically bond to the surfaces.  The resins used are functionalized to control acid and conductivity of lube and hydraulic oil.  However, they also absorb a significant amount of water, posing some consideration in system design and operation.  On the other hand, some resins contain no extractable metals, and their hard plastic construction minimizes fines.

Electrostatic Varnish Precipitators:

Electrostatic precipitators are designed specifically for varnish mitigation.  They charge contaminant particles causing them to bond to rods, plates or other oppositely charged surfaces.  When properly operated and maintained, these devices can remove varnish precursors down to a submicronic level.  However, they rely on the conductivity of the processed fluid.  Since most lubrication and hydraulic oil systems experience periodic water ingression, fluid conductivity must be carefully monitored.

Many precipitators must be manually cleaned.  This can be a messy and incessant task, possibly resulting in equipment neglect and performance issues.  Obtain references and do some research before investing in any equipment.  Electrostatic precipitators are no exception.

A note about varnish removal devices:

There is much said about varnish removal devices removing varnish from a fluid as well as machine components.  As with any substance, varnish particles have a solubility limit in fluids.  Consequently, removing these particles restores the fluid’s varnish solubility.  This promotes dissolution of varnish from machine components that contact with the fluid.  By this mechanism, any system that reduces a fluid’s concentration of varnish particles and precursors will also remove varnish from surfaces submerged in the processed fluid.

Fluid Purification/Conditioning Systems:

Throughout this article we have discussed the most common fluid purification methods.  The application of any single method is contingent upon understanding the fluid and contaminant characteristics.  In most lube and hydraulic oil system applications there will be multiple sources of contamination that may require different methods of purification.  For this purpose, multicomponent fluid purification/conditioning systems are common.

For example, steam turbine lube oil is often contaminated with ash and dust, degradation biproducts, water, acids, varnish and more.  Therefore, a turbine lube oil conditioner might contain a coalescing filter for rapid removal of bulk water, a vacuum mass transfer oil dehydration system for control of dissolved and emulsified water and dissolved gases and a particulate filter to maintain the recommended ISO Cleanliness Level.  Other components could be included as needed, such as a varnish removal pod, particle counters, water sensors, acid control modules and more.  Many OEM’s design and build custom systems that meet specific needs.

PowerFlow Fluid Systems supports industrial sustainability with innovative and environmentally responsible solutions for optimizing performance of virtually all fluid systems throughout the plant.  Check-out our products and services before deciding.  https://www.pwrfs.com/

GUIDELINES FOR EVALUATING OIL PURIFIERS

Maintaining the purity of lubricating oil is essential for optimal system performance and extended component life.  It is also relatively inexpensive and easy to do if you utilize the correct oil purification equipment.  

Water, particulate and gaseous contamination of lube oil is an unfortunate certainty and must be addressed. Failure to do so, will have a material impact on system operation, uptime and reliability.  Failure to continuously remove these contaminants is the number one reason for bearing failures that lead to machinery downtime and related costs.  “In a study by the Massachusetts Institute of Technology (MIT), it was estimated approximately $240 billion is lost annually (across US industries) due to downtime and repairs to manufacturing equipment damaged by poor lubrication” (Mowry 2).

Particulate contamination will result in equipment failures due to abrasive wear, erosive wear, adhesive wear and fatigue wear, varnishing, valve stiction, worn shaft seals, scoring on shafts, and premature loading of filter elements.  Therefore, it is paramount that it is monitored and controlled.  The gold standard for benchmarking particulate contamination is ISO 4406.  This standard establishes and defines a method of coding the concentration and sizes of particulates in a fluid.  This is the ISO Cleanliness Level and can be correlated to machinery service life.  Recommended oil cleanliness levels for some common machinery components are shown in Table 2.  Although these are good guidelines, actual application conditions and equipment characteristics should be considered before settling on an ISO Cleanliness Level. 

Machine/Element Target ISO Code
Roller Bearing	16/14/12
Journal Bearing	17/15/12
Industrial Gearbox	17/15/12
Steam Turbine	18/15/12

Table 2. Typical Base Target Cleanliness Levels (Particulate Contamination 5)

Whether dissolved, free, or emulsified, water contamination can be as much or more damaging than high particulate levels. Excessive water in lube oil leads to the following major issues:

• Premature component wear
• Depletion or alteration of the fluid’s additive package
• Formation of rust, emulsions, sludge, etc.
• Reduced hydrodynamic film thickness
• Formation of bacterial growth
• Accelerated metal surface fatigue
• Increased dew point in generator, resulting in increased windage losses/generator inefficiency
• Sticking/jamming valves
• Bearing wipes
• Potential icing at low temperatures
• Formation of acids

To get an idea of the magnitude of the damaging effects, consider that “as little as one percent water in oil can reduce the life expectancy of a journal bearing by as much as 90%” (Water).

According to Ametek Brookfield “acceptable levels of dissolved moisture typically range from 50-300 ppm (or 0.0050% – 0.0300%)” (Moisture in Oils).  There are three forms of water in oil, dissolved, emulsified, and free.  All forms should be controlled.  Free and emulsified water are directly related to equipment damage.  Dissolved water can react with oil additives causing degradation of its intended properties varnish precursors.  If water concentration is not kept well below the saturation point, there is a risk of formation of free and emulsified water during normal fluctuations in oil temperature.  Therefore, water concentration should be kept below the saturation point corresponding to the lowest expected oil temperature.

Gases exist in oil in four forms, free, entrained, dissolved and foam.  According to Noria, “Entrained air has the potential to impact the oil’s compressibility, heat transfer, film strength, oxidation, cavitation and varnishing (microdieseling)” (Fitch).  These issues result in shorter oil life, machinery damage and safety concerns.  Therefore, monitoring and control of gases in lube oils should be a standard part of lubricated equipment reliability programs.

Effectively managing contamination and the subsequent issues caused can be far less troublesome than you may imagine.  The answer is usually as simple as investing in the right oil purification system.  Oil purifiers are compact cart or skid mounted systems that filter, dehydrate and degas oil.  Oil purifiers like PowerFlow’s XLP Series will effectively and efficiently clean (ISO 14/12 or better), dry and degas mineral-based and synthetic oils. They will remove 100% of free water and gases and 90% (or more) of the dissolved water and gases from oils.

To make the most of your investment there are some very important characteristics to consider when evaluating oil purifiers:

Filtration Performance

An oil purifier should utilize highly efficient particulate filtration meeting a minimum particulate removal rating of Bx(c) = 1,000 per ISO 16889.  Many equipment manufacturers provide ISO Cleanliness Code targets for lubricated machine components.  The particulate filter should ultimately be able to achieve and maintain this level of cleanliness, while maintaining acceptable service life.  Incoming The air used in the dehydration/degasification process should also be filtered as it enters. Here we will focus on the oil filter.

There are a few characteristics about the filter element and housing that should not be overlooked.  Foremost, the filter housing and element should be specifically designed for lube and hydraulic applications.  This is very important because there are distinct differences from those that are designed for other applications, such as municipal water.  

The mechanical design of the housing should meet or exceed the maximum and minimum oil temperatures and pressures that could occur during any mode of operation or standby.  The housing, element or both should have an appropriately set bypass valve that will let oil bypass the filter during cold start-ups or other times when the pressure differential across the housing or element exceeds the limits of the system.  The filter housing should have a service indicator or pressure gauges that can be used to determine when the filter element needs to be changed.  The housing should be positioned with easy access and plenty of overhead room for changing the filter element(s).  The access port to the filter element should have a cover that is easy to operate and properly seal.

The filter elements should be absolute rated.  This means that the filter efficiency is tested and rated in accordance with a respected standard such as ISO 16889.  This also ensures the test results are reliable and repeatable.  Common absolute filter ratings will be stated as a beta ratio; for example, β(x)=1000, where ‘x’ is the particle size in microns at which the beta ratio is measured.  A nominally rated filter may not have a published filter efficiency and will not have a standard associated with it.  Many filter elements are also rated under cyclic stress conditions to provide a better estimate of performance in systems with pressure or flow cycles.  To get reliable, repeatable results always invest in absolute rated filter elements and consider cyclic ratings if available.

Other important features of lube and hydraulic filter elements are related to the design and construction of the cartridge and media pack.  When properly designed the collapse rating will be at least 150 psid.  They will employ a multi-layer media pack with inner and outer support layers and a filtration layer.  Often there will be other proprietary layers that enhance performance under stress or increase service life.  The most reliable filter elements will have an O-ring seal, positive pressure seal or a proprietary seal that is very precisely designed for ease of installation and zero bypass.  Flat gaskets are not recommended due to the propensity for sealing surface misalignments, hold down mechanisms that are prone to operator installation errors and adhesives that often fail.

More needs to be said about the most important component of the filter element, the media pack.  There are many designs and claims.  However, there are a few basic principles to keep in mind.  The media must be designed to maximize filtration capacity without unloading filtered particles, shedding fibers, compressing or bunching.  The most common absolute rated lube and hydraulic filter media material is microglass.  There is often an option for anti-static microglass media that helps prevent static discharge within the filter media.  This is a great choice if there is evidence of static discharge in your lube system.  Cellulose media is very common because it is inexpensive.  However, it is rarely absolute rated and has other drawbacks that can result in a higher cost of filtration.  For example, it absorbs water causing premature element changes and potential media failure.  The most reliable filter elements feature robust design and construction that will hold up to the application demands.  When selecting an element, consider the value of protecting your equipment investment with a filter element that has documented performance characteristics, compatibility with contaminants like water and lasts several times longer than cheaper paper/cellulose alternatives.

Oil purification starts with particulate control. Consider the technology and the design and construction quality of the particulate filter element and housing when evaluating oil purification systems.

The Dehydration and Degasification Process

Since much of the water and gas is dissolved in the oil the separation is usually accomplished with some variation of mass transfer optimized by temperature and pressure manipulation.  One of two common processes are used by most oil purifiers, flash distillation or vacuum mass transfer.  Flash distillation uses relatively high heat (150-160 deg F) and deep vacuum (25-29 inHg (v)) to “flash” or boil off water and gases from the oil, but there are known issues associated with that.  “The high temperature and vacuum employed in flash distillation devices can lead to loss of lower boiling base stock fractions and volatile additives and can result in thermo-oxidative fluid degradation” (Day).  Vacuum mass transfer is a more efficient process in which the oil is processed through an engineered packed column.  The packing creates an ultra-thin film and maximizes the oil surface area, releasing water and gas molecules through diffusion and convection.  The vacuum mass transfer process is highly efficient at lower temperatures and vacuum levels.

In both processes, ambient air is drawn into the vacuum chamber where it expands, reducing the relative humidity.  The dry air carries the water and gas vapors out through a vacuum pump and exhausts it to the atmosphere.

The bottom line is that the oil purifier should be able to remove 100% of the free water and gases and 90% (or more) of the dissolved water and gases from oils at no more than 120 deg F and 22 inHg vacuum.  This is accomplished easily and reliably with an expertly designed vacuum mass transfer process utilizing an engineered packed column.

The Oil Flow Control System

Oil purifiers are typically offline systems.  They are installed temporarily or permanently in a kidney loop recirculating on an oil reservoir.  Therefore, a means of pumping the oil through the purifier and back to the reservoir is required.  Some systems use pumps and others rely on the process vacuum to pull the oil into the vacuum chamber.  A pump draws the oil out of the chamber and returns it to the oil reservoir.  

There are pros and cons to the various oil feed systems outlined below.

Vacuum Assisted Oil Feed:

    Pros

• There may be reduced CAPEX, operating and maintenance cost because there is no oil feed pump; larger systems may require a booster pump.

    Cons

• This is a batch process requiring a more complicated control system that is sensitive to changes in the oil temperature, pressure and viscosity.  Due to this the system may require more operator attendance as oil conditions change that require machine adjustments.
• These systems tend to require deeper vacuum, creating more potential for foaming.  The foaming can result is process destabilization.  In many cases this requires more operator attendance, or the system is adjusted to process a smaller volume of oil that will result in less process upsets.  In effect, a larger system may be tuned down to the point of processing less oil than a smaller more efficient system
• Some system components such as control valves may be subject to high rates of repetition due to the nature batch processing.  These components may require frequent service or replacement.

Constant-Flow Oil Feed Pump:

    Pros

• Allows for a continuous process at constant flow reducing processing time.  This can result in quicker resolution of an oil contamination event.
• Less complex and more reliable process control.

    Cons

• Process control with a constant flow oil feed pump can require more operator attendance as changes in the oil temperature, pressure and viscosity will need to be addressed by manual tuning.  Another option would be to use a more complex control system.  In either case, the result may be less maximum oil processing capability under some conditions.
• Additional CAPEX, operating and maintenance required for the oil feed pump.

Oil Feed Pump with Variable Frequency Drive:

    Pros

• Allows for a continuous process at constant flow, reducing processing time.  This can result in quicker resolution of an oil contamination event.
• Improved process control.  The VFD can be programed to change the pump speed automatically to maintain a continuous flow rate as oil conditions fluctuate.
• Minimal operator attendance requirements.

    Cons

• Additional CAPEX, operating and maintenance required for the oil feed pump and VFD.

The bottom line is that a purifier with a variable speed oil feed pump will provide the most reliable processing with the least amount operator attendance.

The Oil Dispersion Process

Within an oil purifier’s vacuum chamber, the oil is exposed to dry air under vacuum.  The dissolved water and gasses transfer from the oil into the air as the vacuum source pulls it though the chamber and exhausts it to the surrounding atmosphere.  The rate of transfer of the water and gas molecules from the oil to the air is proportional to the surface area of the oil.  Therefore, the dispersion process and its effectiveness of maximizing the oil surface area is the most critical factor in oil purifier design.  It is often the most coveted also.  There are many designs.  Most use some form of dispersal media.

There are two common types, dispersal elements and packing rings.  Dispersal elements are cylindrical cartridge elements with a fiber matrix designed to create a thin film of oil within the media pack.  Packing rings are small metallic structures with geometries engineered for specific applications.  For oil purification the rings are designed to randomly stack in the vacuum chamber/tower with optimum fluid dynamics and mass transfer properties.

Dispersal elements are not the most efficient nor effective means of promoting mass transfer.  The fibers that make up the media are not specifically designed for maximizing mass transfer.  For a fiber matrix to be most effective the flow and distribution of oil through the element must be very precisely controlled to avoid flooding and optimize fiber utilization.  Considering the normal fluctuation in oil temperature, pressure and viscosity, cylindrical geometry of the elements, and the potential for media fouling, expect performance to be inconsistent at best.  Due to fouling and fiber damage the elements are considered consumables.  This is an undesirable maintenance burden and additional cost of ownership when compared with systems that use packing rings.

Packing rings used by some manufacturers are specifically engineered for their oil purifier vacuum chamber design.  For example, some manufacturers test various ring designs until they discover the size and geometry that provides the best performance in a specific purifier model.  This results in better mass transfer efficiency, lower energy demand, the elimination of the damaging effects of high heat and vacuum on the oil, and a lower cost of ownership because a properly design packing never needs to be replaced.

The bottom line is that a purifier that utilizes a column of packing rings for dispersal media will process oil more efficiently, will not harm the oil and will have fewer consumables to replace.

The Vacuum Pump

Both vacuum mass transfer and flash distillation units rely on vacuum pumps.  The pumps generate the vacuum needed for the dehydration process and pull a small amount of air through the process to sweep out the water and gas vapors.  There are three types of vacuum pumps commonly used.  These are liquid ring, oil sealed rotary vane and dry claw pumps.  Liquid ring pumps have a high utility cost primarily due to the need for a constant supply of sealing water.  The sealing water supply may also limit the installation and mobility of the purifier.  Oil sealed rotary vane pumps require a commitment to regular monitoring and service work.  They are also sensitive to water droplets that can be entrained in the exhaust gases, if not adequately removed upstream of the pump.  The dry claw style pump is the most suitable for the application.  “A claw pump is approximately 30% more efficient than a comparable rotary vane pump and uses less energy” (Dry).  They provide sufficient vacuum with very little utility cost, service or monitoring and less sensitive to liquid contamination.

The bottom line is that a purifier that uses a dry claw style vacuum pump is going to be more reliable, durable and have lower operating and maintenance costs.

We have covered some of the most important features to consider when evaluating oil purifiers.  Following these guidelines will help you make a good investment that will greatly extend service life, reduce downtime and lower the total cost of ownership of rotary equipment.  Keep our guidelines in mind will lead you to a purifier that will do all this while being very easy to operate and maintain.

Works Cited:

Fitch, Bennett, “Why You Should Be Measuring Air Contamination in Oil”, machinerylubrication.com, Noria Corporation, Dec 2014, Web, 19 April 2022

“Moisture in Oils: The Three-Headed Beast”, brookfieldengineering.com, Ametek Inc., 14 April 2014, Web, 19 April 2022

Mowry, Matt, “The True Cost of Bearing Lubrication”, toolbox.igus.com, IGUS Inc., Spring 2011, Web, 19 April 2022

“Particulate Contamination – Identifying, Eliminating and Removing it”, media.noria.com, Noria Corporation, n.d., Web, 19 April 2022

Day, Mike and Bauer, Christian, “Water Contamination in Hydraulic and Lube Systems”, machinerylubrication.com, Noria Corporation, September 2007, Web, 19 April 2022

“Dry Pumps: Claw Pumps”, vacaero.com, Vac Aero International, 23 March 2016, Web, 25 April 2022

“Water in Oil Contamination”, machinerylubrication.com, Noria Corporation, July 2001, Web, 19 April 2022