Category Archives: Transformer oil filtration

GlobeCore: Oil Purifier Protects Power Transformer and Extends Its Life by 20 Years

Globecore GmbH, a German company, manufactures oil purifier which  extends power transformer service life by 20 years.

Globecore protects and saves millions of dollars of investments in power transformers. This is achieved by transformer oil purification, which can be performed on site, with the transformer energized. Old oil is reused. Transformer oil is used in power and instrument transformers, as well as oil-filled switchgear. The oil insulates energized parts of the equipment, dissipates heat and extinguishes the arc in switches.

Transformer oil is used in power and instrument transformers, as well as oil-filled switchgear. The oil insulates energized parts of the equipment, dissipates heat and extinguishes arcs in switches.

What are the hazards of transformer oil contamination?

The transformer lives as long as its insulation system. Transformer gradually accumulates oxidation products, contaminants and other impurities over time when used. Oxygen and water in the insulating fluid provokes oxidation even under ideal operating conditions. Particles originating from the construction materials of the transformer are also a problem.

The process of oxidation results in formation of acids, which act on carbon and metals, forming aldehydes, alcohols and soap metals. These substances deposit on solid insulation. Contaminants increase oil viscosity, hampering circulation and cooling.

Therefore, aging of transformer oil is a consequence of combined effects of high temperature, oxygen, and electric field in the presence of the transformer construction materials. Important operational parameters of the insulating fluid (acidity, dissipation factor and dielectric strength) are very sensitive to its aging. The higher the intensity of the process, the sooner they reach critical levels, and the oil becomes impossible to use. Using such oil is also dangerous to the transformer: the risk of failures and power outages increases significantly.

What to do with used transformer oil?

Accumulation of waste transformer oil is a serious environmental concern. Consider this: over 40% of waterways in the world are contaminated and covered with a film of waste oil. One liter of waste oil makes a million liters of groundwater unusable! Plants and animals die due to massive pollution with oil products. Besides, waste oil contains carcinogenic substances. Dumping of waste oil into the environment is entirely unacceptable. So what is the solution and how to preserve the planet for future generations?

There is a solution: restoration of transformer oil to its initial condition and reusing the oil. Beside the pronounced environmental benefits, this solution allows to save on purchasing new and disposing of used oil, as well as to extend transformer lifetime by 20 years or more. At this time, the cost of one power transformer reaches, on average, hundreds of thousand US dollars. The number can easily reach into the millions, if the costs of disassembling the oil unit, transporting and installing a new transformer are factored in.

Transformer Oil Filtration Unit Globecore CMM-12R at electricity substation.

Transformer Oil Filtration Unit Globecore CMM-12R at electricity substation.


Methods of transformer oil purification

Let us consider several techniques used in filtration of used transformer oil.

Centrifuges. These devices are large drums in sealed cases. The drum consists of a number of conical plates with orifices. Centrifuges are used for removal of moisture and solid particles. At one time centrifuges were widely used in oil processing facilities despite their limitations, such as low capacity, complex design, intensive mixing of the processed oil with air and large footprint. With time, compact mobile units for oil treatment were developed, and the number of centrifuges operated is now on decline.

Electric purification. Electric purification is based on the uneven influence of the electromagnetic field on contaminants in transformer oil, which causes the impurities to settle on electrodes. The biggest limitation of this method is the complexity of cleaning the deposits from the electrodes. Also, electric purification cannot remove water. Due to these reasons, this approach has not been widely implemented  

Adsorption. This technique involves percolation of oil through a layer of adsorbent (silica gel in most cases), loaded into a vertical cylinder. Silica gel is produced by a series of chemical reactions, making the material rather expensive. Besides, there is a problem of silica gel disposal, since oil-contaminated materials must not be released into the environment.

The alternative is purification of transformer oil with Fuller’s earth, a natural adsorbent. Due to its porous structure, this material has good adsorptive qualities and can be used both for continuous regeneration of transformer oil from dehydrating breather filters, and also for restoration of oil drained from a transformer.

Generally, Fuller’s earth must somehow be disposed of, just like silica gel. However, GlobeCore process allows to reactivate and reuse the sorbent for transformer oil purification many times over.

Transformer Oil Degassing Cart. Oil Purifier.

Transformer Oil Degassing Cart

Thermovacuum dehydration and high vacuum degassing. The GlobeCore process using heat and high vacuum ensures the best parameters of transformer oil. Operation of these units is environmentally safe and does not involve special disposal or storage.    

GlobeCore environmental solutions

For many years, GlobeCore has been developing and implementing technologies for restoration of used transformer oil.

The company has successful experience in servicing power transformers of land based and offshore wind farms. We offer a range of units specifically tailored for these purposes.

The UVM type units degas oil and remove particulate matter by a combination of heat, vacuum and filtration. This unit reduces moisture content to 5 ppm and gas content to 0.1% or less and increases dielectric strength to 70 kV.

The CMM-R oil purification plants extend transformer lifetime by restoring the dielectric strength and chemical composition of transformer oil. This equipment allows to maintenance oil directly in an energized transformer. Connecting a CMM-R to an operating transformer allows to remove sludge from the windings and extract it from the oil by the sorbent. These units are loaded with Fuller’s earth.

Adsorbent Fuller’s Earth for Industrial Oil Purifier

Adsorbent Fuller’s Earth for Industrial Oil Purifier


The GlobeCore oil purification process has the capability of continuous processing of transformer oil, saving on new oil and disposal of saturated sorbents. Fuller’s earth can be reactivated up to 300 times, the equivalent of 1.5 – 2 years of operation or purification of 1000 tons of oil.

Zeolite drying cabinet GlobeCore ZSC-15

Zeolite drying cabinet GlobeCore ZSC-15


GlobeCore also cares about environmental safety of other machines which use adsorbents. The SSZ-15 zeolite drying cabinet can pre-dry zeolite to improve adsorption and the quality of oil dehydration. The CMM-4RP, one of GlobeCore latest developments, allows reactivation of saturated sorbents used in transformer oil filtration systems. The technology can reactivate the same sorbent at least 10 times. The reactivated sorbents contain no residual oil and, if necessary, can be disposed of a regular household waste without harm to the environment.

GlobeCore CMM-4-RP unit restores waste absorbent

GlobeCore CMM-4-RP unit restores waste absorbent


Therefore, GlobeCore transformer oil filtration technologies allow to:

  • save on purchasing new and disposing of used oil;
  • significantly lower industrial load on the environment;
  • extend transformer life by at least 20 years.

In conclusion, we would like to show some numbers to emphasize the economic feasibility of used transformer oil restoration:

  • average market price of restoring one liter of transformer oil is $0.7-0.8;
  • average price of one liter of new transformer oil is $1.5-2.
Globecore Oil Purifier CMM-12R

Globecore Oil Purifier CMM-12R

About GlobeCore:

Globecore Service center in Germany. dielectric Oil purifiers

GlobeCore is a manufacturing company researching, developing and producing various oil and fluid processing systems for use in several different industries worldwide and is the developer of the Power Transformer Service Life Extension Program and the GlobeCore Oil Filtration Process for servicing oil filled electric power transformers.

Globecore Service center in USA. dielectric Oil filtration

Contact Information:

GlobeCore GmbH

Edewechter Landstraße 173, Oldenburg-Eversten, Deutschland, 26131

Oil purifier

Globecore: Transformer oil maintenance

Globecore: Transformer oil maintenance

Not So Small Point of Transformer Oil Filtration

Dielectric properties of transformer oil (e.g., voltage or dielectric loss factor) can be significantly improved by filtering, degassing and removal of moisture. Only  oil properly and adequately drained and filtered is suitable for transformer insulation. Often, even new transformer oil cannot be considered clean and safe for use in power systems as it accumulates pollutants during transportation.

During its use in the transformer, oil absorbs moisture, dirt particles, fibers, soot and other products of aging. Purification removes solids, free and dissolved water and dissolved gases from transformer oil. Purification also increases oil viscosity and dielectric loss tangent.

Purification is a complex procedure of removing the above contaminants to acceptable levels.

Research reveals the serious problems that arise with the contact of oil and moisture. Constant monitoring is required to identify and correct the issues in a timely manner. Analysis shows that 99% of poor dielectric strength indications are due to negligent sampling and test method selection.

Regarding the main issue of transformer oil purification, not so long ago, when diagnostics indicated high moisture content and other contamination, the following measures were taken:

  1. Subcontractors were selected to perform transformer oil purification
  2. Oil test results were submitted to the subcontractors
  3. A purification technique and process were selected, then a contract was signed with the subcontractor.

All of the above were not only time consuming, but also quite costly. At this time, the process of oil purification is no longer the sole area of specialized subcontracts, but can be performed by the customer onsite, using oil purification machinery.

Oil processing equipment producers offer a wide range of solutions for many applications, such as transformer oil filtration equipment, insulation oil regeneration systems, lube oil purification equipment, hydraulic oil filtration machines, turbine oil dehydration units etc.

In the last decade, such companies offer a complete systems and spare parts for transformer oil purification, available worldwide.

The process of transformer oil purification involves continuous circulation of oil through the purification system. The oil passes several coarse and fine filters, a vacuum drying and degassing section, adsorption to remove sludge and acids, etc. Besides, oil purification units are equipped with sensors to monitor oil quality at all times during purification.

Oil purification systems incorporate safety devices, such as transformer oil level sensors. These are required to automatically maintain the correct level of oil in an energized transformer when processing oil online. Oil heating is also managed automatically to prevent burning the oil, oil pressure is also controlled. The design of the units allows to perform oil processing so as not to pause or otherwise disrupt operation of power systems. Process rate is assessed by flow rate sensors.

The demand for oil purification units is growing, since increased loads on power transformer insulation systems require high quality and purity of the oil.

Industrial customers are only prepared to make a purchase, if the investment will pay off in the future in terms of finance and other resources. The extended service life of power systems and the oil makes in-house purification a popular and profitable solution.

Choosing The Right Oil Filtration System

Various factors affect a buying choice: client preference, salesperson skill, the weather, atmospheric pressure and the air in the store, etc.

In the industrial world, there are technical parameters and circumstances which form the opinion of the potential equipment owner.

Most systems for removal of solid particles from various petroleum based liquids, such as industrial, hydraulic and motor oils, use filtration.

Many manufacturers specialize in offering a wide range of solutions, producing many systems and units for filtration of transformer, hydraulic and turbine oil, complete oil reclamation systems and the like.

Purchasing equipment for used oil filtration saves on disposal and new oil purchase costs, along with offering an environmentally friendly solution to the waste oil problem. Besides, purification of oil extends the lifetime of oil filled equipment.

Here are some of points on filters worth noting:

  1. Physical filter size: this key component of a purification system must be relatively small to ensure rational unit design and, possibly, mobility.
  2. The results of filter testing: oil filters may be evaluated in many ways, but the most common method is the beta-ratio. This is the ratio of the number of larger particles entering the filter, and the number of the same particles downstream from the filter. If the beta-ratio is 10, it means that from 10 particles entering the filter, the filter fails to capture only 1.
  3. Pore size.
  4. Capacity, flow etc.

According to a General Motors research, published by the SAE, engine lifetime can be extended by a factor of 8 by going from the standard 40 micron filters to 5 micron.

It means that the process of developing new filtration solutions is not over and new products appear in the market very often.

Industrial users joke that oil is never a waste oil, it’s only dirty oil. At any rate, the reliability of various oil filled systems is ensured by the purity of the oil in them.

This leads to the conclusion that changing the oil is not always required, as long as the oil is kept clean. Oil purification systems remove acid, ash and sludge from the oil, as well as water and solved gases.

However, when selecting this kind of product, it should be treated very seriously. Not all filtration systems are created equal. Some advertizing materials are designed specifically to confuse the client. Leaflets and brochures seem nice, but can hardly be considered proof.

The client must make sure that the filtration system offers the right benefits to the facility. Asking the right questions when buying the unit and selecting a concept for its implementation before buying is always a good idea.

Using Oil Filtration Equipment From America to the Arctic

Oil filtration equipment removes contaminants from transformer oil, including water, particulate matter, air and other gases. Such systems commonly employ high vacuum and heat for oil treatment.

Oil filtration equipment is connected to the power transformers and the contaminated oil is supplied into the purification unit by pumps.Most of the filters used in such equipment can remove solid particles as small as 1 micron. To remove other contaminants, the oil is heated and passes through a vacuum chamber, where gas and water are removed from the surface of the oil.

The available range of oil processing equipment includes comprehensive systems, which are capable of performing multiple purification tasks.These units are used for preparation of fresh fluid for use in power systems, regeneration of transformer oil for further use and servicing of the power distribution facility in general.

Fresh oil must comply with purity and and quality standards, so it is degassed, dehydrated and filtered before being used in power systems.

If the oil already in use ages and demonstrates low flashpoint, high ash content, high cloud point, high dissipation factor, high acidity and low dielectric strength, the oil should be thoroughly  regenerated.

Since disposal of old oil and buying new oil are costly affairs, using the available equipment to purify oil and extract the sediment from the windings of the transformer is a very viable option, which saves on many costs, including the cost of repairing or even replacing a failed transformer.

Oil purification equipment is built for operation in various environments and climates. Stability and processing capacity of the machinery in high or low ambient temperatures, atmospheric pressure and elevation above sea level, makes the equipment usable by many clients the world over.

Bypass Oil Filtration: A Workaround?

Most users rarely think of the capabilities and difficulties of the equipment at their disposal.

This is equally true for regular consumers and large industrial users with large parks of various machinery and equipment.

This article focuses of bypass oil filters.

Filtration equipment of various models purifies and restores the quality of various fluids.

A reliable comprehensive purification system extends the service life of the oil and of the equipment the oil is used in.

The main components of such systems are vacuum chambers or adsorption columns, along with coarse and fine filters.

There are two types of fine filters: full-flow or bypass. The difference is that a full-flow filter takes the entire liquid flow, while a bypass filter is installed into the system in parallel and only takes 10% of the purified oil.

So, what do we know about oil filters, their capabilities and design? How does filter design influence filter efficiency?

Oil filters are used extensively for purification of motor, transmission, lube, hydraulic, turbine, transformer and other types of oil. The oil filter is an essential part of an automobile engine. First engine oil filters were quite simple, no more than a screen before the oil pump.

The first bypass filter was developed by American engineers in the beginning of the previous century. Most of the oil was supplied to the engine, while some oil was sent to the filter in parallel. With time, all oil was filtered. Oil from the filter returned to the sump.

Pure bypass filtration systems are not very common in the market, since such filter only processes 10-20% of oil circulating in the engine. However, the filtering media are usually rather effective in removing the smallest contaminant particles.

Actually, combined use of full-flow and bypass oil filters extend oil change intervals. This is because most of the oil is filtered by the full-flow filter, while the bypass filter removes the fine particles. As a result, the full-flow filter does not clog as fast.

Double-stream filters are also quite popular. These are designed around combining a full-filter and a bypass filter in one container. In such container, oil is divided in two streams, one of which goes through to the motor, while the other passes through a fine filter and goes back.

While looking for the optimal solution, the client should not only research all offers carefully, but also, maybe, participate in trials of such filtration systems and compare the efficiency of various filter solutions. There are many systems to chose from, bypass filter being only one of them.

A Practical Exercise In Transformer Oil Filtration

Transformer Oil Filtration

Purification, filtration and degassing plants are some of the most common systems for treatment or restoration of transformer oil, which has lost performance properties partially or even entirely. Due to the heavy loads on transformers and other oil filled electrical equipment, and also due to the influence of internal factors, such as moisture, and temperature, transformer oil degrades or ages during operation. With time, using such degraded oil becomes not only unreliable, but also harmful for the equipment.

The process of transformer oil treatment by filtration is rather simple and involves purification of heated oil, taken directly from the transformer tank, in various purification systems, such as vacuum, drying or adsorption. The end product of the process is clean transformer oil compliant with the requirements for the operation of oil filled equipment.

One example of such equipment is the CMM unit, which removes particulate matter, water and gas by heat and vacuum from transformer oil. Such purification systems are used for installation, servicing and operation of power transformers, high voltage switches etc.

This mobile unit is built around a single frame with metal sheet walls and lockable access doors. The unit features a spill tray in the bottom and can be installed on castor wheels or on trailers for transformer around the site or from one site to another.

The standard stock purification unit is equipped with a vacuum chamber of appropriate type (depends on unit model), a control system, oil pumps, a vacuum pump, piping and filters both for coarse and fine filtration. There also an oil heater, made of sheet metal, and equipped with heating elements, usually four, which operate at 1.2 kW power each.

The oil purification unit always includes various control sensors, such as temperature and level sensors, moisture sensor etc.

The process is controlled entirely from the control panel, which is installed on the lockable front door of the control cabinet. Connections and contact are installed inside the cabinet, indicator lights and control buttons are installed outside.

Various models of purification units differ by design, such as the number of filters, processing rate, power requirements, and the amount of liquid processed in one cycle. With the development of technologies, oil purification equipment becomes more perfect and accessible. Mobility and versatility of oil purification systems has become an international standard, and more improvements in the field are to be expected.

Criteria for Improvement of Industrial Filtration Equipment for Transformer Oils

Filtration Equipment

Purification essential oil uses

In practice, the industry is often confronted with the procedures filtration transformer oils that are used as the liquid insulation, protection and cooling systems of internal power systems.

Control processes and timely filtration and replacement of transformer oil are automated using a variety of devices and complex systems. Oil filtration is the process of removing particulate matter and resinous compounds by passing the fluid through a mesh or porous walls of filters. The filtration materials used are metal and plastic mesh, felt, fabric, paper, composites and ceramics and so on. The quality of the process is improved by increasing the number of coarse filters and introduction of the second stage: fine oil purification to improve existing filtration equipment for transformer oils.

The fact about industrial fluids is that even a brand new batch rarely complies with the purity requirements and usually cannot be used without treatment first. At the same time, transformer oil absorbs moisture, solid particles, fibers, ash and aging products during use.

Filtration systems remove particles, free and solved water and, in some cases, gas from transformer oil. If we present these processes as a mathematical curve, the increase of filtration equipment use causes improvement of oil, reducing dissipation factor and increasing the oil’s dielectric strength.

Purification essential oil uses

Transformer oil filtration equipment, apart from performing according to industry specifications, must also meet certain performance criteria, specifically:

  1. Purify the oil in one processing cycle.
  2. Substantially prolong transformer oil service life in the long run.
  3. Possess versatility to be used in various environments, both outdoors and indoors, and have the mobility to serve a variety of industrial parks.
  4. Be easy to maintain and operate.

Transformer oil has a tendency to shed acidic compounds, which then concentrate in cellulose insulation and damage it. Oil quality control and the timely use of filtration equipment are essential to consistent and reliable operation of power transformers.

Dielectric Oil Filtration

Dielectric oil serves as insulating material and cooling medium in transformers, oil circuit breakers, etc.

In operation oil is in constant contact with substances and elements of electrical equipment. This constant contact with metals accelerates oil’s oxidation process.   The most oxidation causes copper and its alloys. Also metal surfaces corroding accelerate oil oxidation further.

Exposure to high temperatures overheats transformer, leads to decomposition of oil resulting in sludge formation.  With temperature increasing – corrosion of metals increases too. The speed of corrosion depends on chemical composition of oil, moisture and oxygen.

With temperature rising proportionally giving off gases in oil, that also negatively affects the physicochemical properties of dielectric fluid. With time oil loses its dielectric strength. If appropriate measures are not taken – oil acquires black color.

Insulation of all kinds affects oil negatively. Sealing rubber has a similar effect.

Influence of electric fields has a negative impact on oil.  With increase of temperature electric fields intensify. A simultaneous impact of temperature and electric field leads to more intensive oil aging and increase the amount of sludge.

It is necessary to regularly monitor transformer oil and carry out filtration in order to avoid negative consequences like emergency situations as well as failures of costly electrical equipment.

GlobeCore manufactures and supplies equipment for purification of transformer, industrial, turbine and other types of oils.  GlobeCore oil recycling plants are convenient, practical and functional. Their operation is not accompanied by harmful emissions into atmosphere.  In addition, they consume minimal power, helping to save on expenses.

Vacuum Filtration of Oils

A two-level degassing unit is the basic element of systems designed for vacuum filtration of oils.  In fact, this is a sealed metal container divided into two parts (levels).  Special nozzles are arranged inside of the container and serve to provide a surface extention for the vacuum filtration of oil.  This function can be performed by cylindrical Raschig rings.  The main benefit of a Raschig rig is large surface ratio to the volume of flow and low oil flow resistance.

An oil pump feeds the oil that is being processed into the vacuum filtration system through a special mesh filter (coarse mesh filter).  After this, oil is heated to between 50-60ºC.  Then the oil is fed to the first level of the degassing sytem where it undergoes diffusion.  The oil flows down the surface of the Raschig rings in a thin layer under the influence of its own weight.  At the same time the space above oil in the first level is subjected to vacuum with a special vacuum pump.  Vapours of moisture and gases released during the procedure are pumped out through the zeolite tube and air filter.

The zeolite tube helps to absorb water vapor out of a steam-gas mixture. Once the necessary volume of transformer oil is treated by this device, it is necessary to let the zeolite in the tube dry.  The air filter is required to protect the vacuum pump from zeolite dust which can become airborne during the process of drying the zeolite.

A large amount of water vapor and gases are vented in the first level of degassing system.  The oil then flows by gravity to the second level.  It undergoes the final drying and degassing process at the second level.  The desired level of degassing is achieved in the second reservoir due to a second vacuum pump which is joined in series with the main vacuum pump.

An electric pump supplies the dried and degassed oil from the second level of the vacuum filtration degassing system to a container for pure oil or back to the transformer after passing it through a fine mesh filter.

In most cases vacuum filtration systems designed for transformer oil treatment are called high vacuum degassing systems.  We recommend you to find out more about Globecore’s high vacuum degassing at

Oil Filtration: What Should You Know?

Almost every hydraulic and lubricating system contains some contaminants even at the beginning of its service life.  It may be metal particles originated during production or impurities that penetrated during initial assembly.  Then the number of particles only increases since they may get through vent holes, joinings or during corrective maintenance.

There have been cases when one liter of a working fluid contained 100 million particles with a size of more than 1 micron.  It has been established that about 80% of breakdowns of hydraulic and lubricating systems are caused by different contaminants that are formed as a result of jamming, bearing vibration, increased/extreme oil temperature or the absence of adequate hydraulic pressure.

It is therefore, necessary to ensure constant oil filtering by a coarse mesh filter and a superfine mesh filter.  The coarse mesh filters are able to retain particles  that are bigger than the size of the existing gaps.  Fine mesh filters remove contaminants with a size up to 5 microns reducing to zero the wear of the working surfaces. The number of unfiltered particles has also a great impact on the wear rate of the equipment.

The modern hydraulic equipment and fluid industry has established international standard ISO4406.  It is the internationally accepted standard used to rate the purity of oils and hydraulic fluids.  According to ISO4406, the amount of particles with a size of more than 5 microns and the amount of the particles with a size of more than 15 microns is determined by measuring 100 millilitres of the working fluid.

Coarse mesh filters usually retain contaminants with a size of more than 25 microns that reduces the service life of friction knots, working in a mode, determined by elastohydrodynamic lubrication.

Service life may be substantially extended by using filters with a filtration fineness of 10 microns.

In addition to removing particiulate matter through filtration, water and moisture must also be removed.  Water penetration should be also prevented since it is a dangerous impurity that can cause corrosion, favors cavitation and accelerates oil’s aging and degradation.  Additionally, water favors the sedimentation of additives, the reduction of lubricating film thickness, and the accelerated wear of the gear pump.

Peculiarities of Transformer Oil Servicing

Transformer oil is an petroleum product, used to insolate the active parts of transformers under voltage as well as cool and transfer heat during operation.

The performance characteristics of this oil product depend on its chemical composition that is determined from the raw material and methods uesed in its purification.  The commissioning of new electric power transformers requires only fresh oil that has not been previously in service.  Each batch of the product intended for transformer refilling should be certified by the supplier.  But, even fresh new oil delivered to the power facilities should be tested and, if necessary, cleaned of mechanical impurities, moisture and gases before being placed into the transformer.

Performance characteristics of transformer oil are evaluated by the following indicators:

  • dielectric strength;
  • loss tangent;
  • moisture content;
  • gas content; and
  • the presence of mechanical impurities.

Centrifuge processing of transformer oil refers to the classical methods.  Processing by centrifuge forces removes moisture and suspended mechanical particles from the oil.  Centrifugal treatment is applied when refilling power transformers with voltage up to 35 kV or used as a method of pre-treatment.  Long centrifugation is undesirable since it can lead to removal of antioxidant additives that can lead to the premature oxidation of the oil.

Transformer Oil Filtration

Filtration consists of transformer oil being passed through special porous partitions that retain unwanted impurities.

Absorption Treatment of Transformer Oil

The Absorption Treatment of transformer oil absorbs water and other impurities using special substances called “adsorbents.”  Adsorbents may include synthetic zeolites that intended to remove dissolved gasses and moisture from the oil.

Transformer Oil Treatment with Vacuum Units

Vacuum filtration systems provide for preheating of transformer oil up to between 50 to 60 ºС.  Then, the oil is sprayed in the first stage degasser and  flows down in a thin layer along the surface of a series of Rasching Rings.  Simultaneously, the first stage is vacummized by a vacuum pump.   Gas and moisture vapors are pumped through a zeolite cartridge and air filter.  The final drying and degassing of transformer oil is performed in the space of the second stage degasser.  Purified oil comes to the transformer or tank through a fine filter.