Tag Archives: equipment for oil purification

Buying and Storing Transformer Oil

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Purchasing transformer oil is an important financial decision for your company.  It should be done very responsibly.

First, the buyer must a choose a brand of oil.  This requires careful consideration based on the type of equipment being used and the operating conditions the oil and the oil’s abilty to meet those conditions.

Second, the cost of the oil must be considered.  A small price difference in the cost of just one liter small can turn into a significant amount of money when purchasing a large volume of oil.

There are no universal recommendations for buying transformer oil. There are however, online services allowing buyers to compare transformer oil prices from various suppliers.  It is up to the buyer to research and choose a reliable wholesale distributor or retailer.

If you have already purchased transformer oil that meets the correct specifications and quality standards, then it is time to think about oil storage.

The practical way to store the oil is to use clean and dry, steel air tight vessels.  The tanks are usually coated with an oil resistant material inside.  The outside of the tanks should have anticorrosion and light reflecting coating.  The acceptable range of temperatures for storage of transformer oil is -40ºС to +60ºС/-40ºF to +140ºF.

The vessels should be equipped with valves for filling and draining as well as a manhole for cleaning, inspection and repairs.  Breathing systems must be equipped with silica gel or zeolite cartridges that can be monitored by special monitoring devices.

Three days after putting the oil into a storage tank, samples are normally taken for laboratory analysis.  Transformer oil in storage should be tested at least once a year for the following parameters:

  •  flashpoint;
  • dielectric strength at 90ºC/194ºF;
  • water extract reaction;
  • acid neutralization number;
  • particulate matter content in mircons; and
  • free water and moisture content.

It is also recommended to test the dissipation factor at 90ºС/194ºF at least once a year.

Each time the oil is tested for quality and purity, the results must comply with the parameters of fresh transformer oil regardless of the length of storage. Otherwise, the oil must be purified and regenerated to restore the oil to its new and clean condition.

GlobeCore offers a line of oil purification units under the CMM classification. These units improve color, remove acids, bases, and other aging products from any turbine, dielectric insulating oil, and industrial oils.

One of the advantages of the GlobeCore CMM line of units is their ability to regenerate oil on an energized transformer.  Another important advantage is the ability to reactive the fuller’s earth sorbent inside the unit many times over, reducing downtime for sorbent replacement and replenishment.

After the processing of transformer oil with GlobeCore equipment, transformer insulating oil is restored to an as good as new condition.

Purchasing a GlobeCore CMM unit gives you a modern efficient machine that is easy to operate and service.  The use of GlobeCore equipment and GlobeCore Process will extend the service life of the oil and the transformer significantly.

Oil filtration

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During operation, transformer oil accumulate contaminants, which can form various chemicals. These substances reduce the oil’s performance and are, of course, undesirable.

Operation of the transformer becomes unstable. To prevent this, transformer oil is filtered and purified. Some of the methods are discussed in more detail below.

The first stage of transformer oil purification is mechanical. This is a superficial treatment to remove particulate matter and water. The next step is deeper purification performed in vacuum with heating.

The first two stages are, in fact, preliminary. The main process involves various chemicals.

One of the methods is purification of oil with a 98% sulfuric acid solution.

In comparison to other chemical purification methods, the use of sulfuric acid has a significant drawback. Beside reacting with the contaminants, the acid also adversely influecnes the structure of the oil, making it somewhat unstable. Additional processes are required to resolve that problem.

The nature of selective purification is evident from the title. Speical solvents are introduced into the oil to remove specific impurities.

De-waxing is another widely accepted process. In this process, oil is treated with special solvents: acetone, toluene, bensol etc, to remove solid contaminants.

It should be noted that chemical methods influence oil’s stability, but extend the oil’s service life at the same time.

It should also be remembered that any purification process should end with finishing purification, closing the cycle of oil processing and filtration. This is usually done by contact method.

This means that the oil is mixed with special materials, usually clay or bleaching earth. The materials are then mixed and heated. Heating facilitates acviation of all sorbents in the clay.

These absorbents capture contaminants. Deep filtration separates oil from the clay. When selecting adsorbent, it is necessary to pay attention to the content of moisture. It should be suffucient to make production efficient and to make processed oil compliant with specifications.

The most interesting technology today involves the use of bleaching clays (Fuller’s earth). Globecore manufactures a range of CMM type units for filtration of various oils with the use of Fuller’s earth. The advantages of the design are the ability of multiple reactivation of the sorbent, mobility, simplicity of operation and high quality of the output product.

Downtime is significantly reduced by the ability to reactivate the sorbent without the need for frequent replacement, thus increasing process efficiency.

Oil Purification Equipment for Transformers

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The length of a transformer’s service life is determined by the service life of its insulation system.  If the insulation fails, the transformer fails.

Transformer insulation is made up of two components: (1) a liquid insulator known as transformer insulating oil; and (2) a solid insulator made up of Kraft paper and other cellulose material.  As much as 80% of a transformer’s insulation protection however, is provided by the insulating oil.  The insulating oil can be either changed, purified, or regenerated, but the solid insulation must last the entire service life of the transformer.  Transformer Preventive Maintenance therefore, is vitally important to the life of your transformer.

Industry statistics reveal that approximately 85% of  transformer failures are caused by insulation system malfunctions and failures.  Bad insulating oil will lead to degradation of the insulating paper and ultimately to catastrophic transformer failure.

Transformer oils are designed to maintain and increase the dielectric strength of the insulation material in the windings.  This is possible as a result of the permeation of oil into the solid insulation materials such as the paper, fabric, and cardboard that make up the solid insulation section of the transformer.

Due to its low viscosity, transformer oil is able to enter and flow through the solid insulation and also serves to dissipate excess heat by transferring the heat to the cooling system as it flows in and out of the solid insulation.

Degradation of transformer oil performance is caused by aging due in part to a process called oxidation.  This process occurs in transformer oil even in the most ideal of conditions.  As soon as oxygen and water enter the oil, the oxidation process begins and is unavoidable.  The insulating oil’s condition is also influenced by various solid particles known as particulate matter that enter into the transformer and become suspended in the oil.  Reactions between hydrocarbons, water and oxygen are significantly accelerated in higher temperatures which causes oil to decay or oxidize.  Oxidation cannot be stopped entirely, but it can be slowed significantly by oil treatment.

An annual oil check known as “Oil Analysis” is one the best tools for transformer preventive maintenance.  Special analysis of the oil will alert the operator to the condition of the oil and will tell him when to service the transformer.  Oil analysis can also indicate the overall health of the insulating paper.  A well organized oil analysis program provides the best way to monitor the acid number of the insulating oil and enable the operator to perform preventive maintenance before the contaminates in the oil become overly aggressive against the insulating paper.

A good preventive maintenance program should include purification and regeneration of transformer oil as opposed to merely changing the oil.  The main objective of preventive maintenance is the removal of oil aging products (contaminates) from the oil and the solid insulation before they cause damage to the insulation system.

When changing the transformer oil, it is usually replaced on site.  First, the transformer is dried, then its top part is rinsed by naphthenic or regenerated oil to remove dirt deposits. Only then the transformer is re-filled with new or restored oil.

The best and most cost effective way to service a transformer is with the GlobeCore Process.  Contaminated transformer oils are purified by the GlobeCore CMM-1A units.  The GlobeCore CMM-1A units are designed for the purification and drying of transformer oils.  The oil is dried by vacuum while the evaporating moisture is removed from the surface of the oil.  The oil’s viscosity should not exceed 70 cSt at 50ºС/122ºF.   GlobeCore’s CMM oil purification units offer purification of oil up to ISO4406 purity class 9.

Regeneration and purification of oil, using the GlobeCore Process, may be performed onsite and with the transformer energized or de-energized.  First the oil is pumped out and heated and then is passed through the GlobeCore unit.  The CMM unit degasses, filters and dries the oil and then returns the treated oil back into the transformer through the expansion tank.  The process is repeated until the composition of the oil meets industry standards.

Its time to get with the Process, The GlobeCore Process!

Transformer Oil Purification: Dewaxing

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Paraffin can be removed from transformer oil in several ways.  The most common methods are removal of solid crystals from the solution at low temperature and removal of n-paraffin hydrocarbons in combination with carbamide.

Dewaxing combines the treatment of oil with a special solvent (a mix of methyl ethyl cetone, benzene and toluene), heating the oil to 25-30 degrees (Celsius) higher than the oil’s cloud point (Wax Appearance Temperature or WAT), cooling to the required temperature and separation of solid hydrocarbons.

Acetone and methyl ethyl cetone solve some paraffin, but almost no oil.  Benzene is added to increase solvent capacity.

A mix of acetone (methyl ethyl cetone) with benzene can solve some paraffin and all liquid oil components at low temperatures.

An alternative way of dewaxing is the use of carbamide (urea) which forms a solid complex with paraffin.  The latter may be filtered and, after treatment with hot water, regenerate the carbamide. Filtered oil must also be treated with hot water to remove traces of urea.

The main advantage of carbamide dewaxing is that the whole process occurs at normal temperature and there is no need to purchase and install cooling systems.

Just like with any with other method however, this method also has its disadvantages.  The first disadvantage is the high melting temperature of isoparaffinic hydrocarbons that contain some methyl and ethyl groups.  Some naphthenic and aromatic hydrocarbons can melt at relatively low temperatures.

At the same time, carbamide treatment removes n-paraffin and isoparaffin hydrocarbons, but only if they contain one ethyl or methyl side chain.  Today the process is mostly used for the treatment of transformer oils made from acid-base oil refining.

The “Cold Dewaxing” process dominates the processing of transformer oils made by phenol purification of some crude oils.

Activated charcoal is different from silica gels, alumina gels and bleaching clays in the way that it can adsorb hydrocarbons with long chains.  It can adsorb just like solid paraffins of normal structure.  It has been suggested to utilize  activated charcoal for oil dewaxing, but this method has not been adopted by the industry or placed into widespread practice.

The main method of transformer oil distillate purification is adsorption.  It can also be the finishing operation in the final purification of oils produced by other methods.  Contact purification is also a possible method.

Oil Purification (Filtration)

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The main factor in determining the length of time to complete the purification process, is the degree or level of oil contamination.  The higher the “Acid Number” of the oil. the longer the process will take to complete.  In any case, the process should be controlled by special instruments.

Any new components installed into a hydraulic system must be just as clean or more clean as the ones already installed.  Component manufacturers are obligated to provide information on the purity of each component.  In case of hydraulic tank contamination, it must be cleaned during oil processing.  At the end of the process, the purity of oil will only be as clean as the cleanliness of the tank’s internal surfaces.  If hydraulic liquid is replaced by another, insoluble and not mixed with the original liquid, the time of purification increases drastically.

The Purification Process requires checking all filters and possibly replacing them as required.  The common misconception is that filters are a universal solution to maintain the cleanliness of oils and fluids.  Filters are not intended for the purification of heavily contaminated oil or fluids that may contain particles of metal, sand, small stones and other foreign objects.  Oil, water or air contaminated with such particles will remain contaminated after passing through the filters.  To ensure full system purification, it must be completely rinsed.  Oil and other fluids must be filtered thoroughly through an external filter.  This method however, has certain drawbacks, of which the most important one is the significant time required for external purification.  A good example of a long purification process is a large lifting machine which may take up to 15 hours to complete.

The only way to ensure the reliability and durability of hydraulic motors, pumps and other hydraulic components is efficient filtration (removal ) of solid particles and moisture from hydraulic fluid.  The existing national and international standards define the norms which the fluid must comply with. (16/14 class, ISO 4406)  Absolute filtration fineness is set at 3 microns.

Depending on the specific type of equipment, the purity requirements of the fluid may vary.  The versatility of purification and filtration systems therefore, becomes very important.  Versatile systems allow for operation with different types of fluids and ensure the required purity class regardless of original contamination.

This is just what GlobeCore offers. The GlobeCore UVR vacuum purification plants lighten and purify fluids, remove aromatics from turbine oil, industrial oil, and transformer oil as well as other petrochemical products, e.g. dark diesel fuel, HFO, gas condensate etc.

Transfromer Oil Purification Equipment by GlobeCore

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Application

CMM systems designed and manufactured by GlobeCore can perform the following functions: Degassing, dehydration and filtration of transformer oil, cable oil, turbine oil, and other industrial oils.  The CMM units remove gases, free and soluble water, and particulate matter from oils and fluids.  The CMM units are used in the installation, repair and operation of oil-filled high voltage equipment up to 1150 kV (power transformers, high-voltage switches etc.) as well as industrial turbines.

The GlobeCore CMM units perform the following services:

  • Purifying and drying of Transformer Oil
  • Vacuum filling of Transformers and Electrical apparatuses
  • Drying and Purifying of oil in transformers (on and off-line)
  • Vacuum Drying of Transformers
  • Degassing of Transformer Insulating Oil
  • Filtration of Transformer Insulating Oil

Technical Description

GlobeCore CMM units are designed as multipurpose Transformer Oil Conditioning units for field or factory use.  The units incorporate high capacity multi-stage electric oil heaters,  large capacity Vacuum Pumps with external connections for Vacuum filling work, three (3) stage particulate filtration systems, and connections for a large variety of service applications.

The Unit’s measuring devices include vacuum, pressure, and temperature meters.  The equipment can also be optionally supplied with a “water-in-oil” measuring device.  Installation of a water-in-oil measuring device allows in-line monitoring of water content.

Flow rates are variable from 0 to >10,000 liters per hour (L/H) and heating from 24KW to 210 KW in four stages.  GlobeCore systems are designed for easy operation and maintenance.

The principal functions of transformer insulating oils are to serve as a dielectric medium and as a transformer coolant or heat transfer medium.  In order to perform these functions, transformer oil must have the necessary qualities at the time of initial impregnation and filling at the factory and later be able to maintain the same quality in normal operation.

High Vacuum Treatment improves insulating fluids that includes transformer oils and silicone fluids. GlobeCore transformer oil purification equipment was developed as a result of 30 years of experience in vacuum treatment of transformer oils.

Benefit

Every company dealing with oil-insulated high voltage equipment (transformers, high-voltage switches, turbines, etc.), shares the problem of having to change and dispose of contaminated oil and fluids.  The costs of changing and disposing of insulating oils are frequently very high and need a significant investment in time, labor, and money.  At GlobeCore, our equipment offers a practical, proven and economical method to purify oil so that it can be used again and again for your high voltage equipment.

Thermally accelerated Vacuum Dehydration and Degassing of Transformer Oil has gained wide acceptance as one of the most economical methods for the removal of dissolved water and gases.

On-Site Transformer Oil Purification is the most cost effective transformer maintenance service in existence today.  The GlobeCore CMM units not only purify the oil within the transformer, but actively regenerate the Transformer Insulating System by removing impurities that had become built up within the transformer over time.

Thermo-vacuum purification and degassing of transformer insulating oil, as performed by the GlobeCore Process, will result in the improvement of the condition of the entire insulating medium of your electric power transformers.

Here are some additional benefits of the GlobeCore Process:

  • Removal of dissolved moisture from transformer insulating oil
  • Reduction of combustible gases and oxygen
  • Improvement of insulating oil dielectric values
  • Improvement of transformer insulating oil power factor
  • Extension of oil service life
  • Extension of transformer service life and reliability

We at GlobeCore are committed to provide our customers with high quality products that satisfy technical and economic objectives.  We offer our vast experience in manufacturing, servicing and operation of transformer oil purification systems to your company.

Machines by GlobeCore come with a block of approved original equipment spare parts.  These spare parts meet all specifications required of the engineering process.  Over the years, optimal and high quality components have been carefully selected for our equipment.  GlobeCore guarantees the performance of our machines and the results of the oil treatment processes.  We have placed our equipment in more than 70 countries around the world and a reference list available upon request.

Short Process Description

Hot Filtration Mode

A gear type pump draws in the oil for processing via a valve and a strainer.  Processed oil is then pumped through the cartridge filter, the three-way valve and is then discharged to the processed oil vessel via a connecting line.

The above mode is also used for transformer core drying.  Transformer oil is circulated through the oil purification equipment.  After filtering the oil to remove the particles, the oil is heated up to max. temperature of 800C/1472F.  All residual gases are removed and the moisture is evaporated in the vacuum degassing chamber.  Residual moisture content can be reduced down to less than 3 parts per million (ppm).  Oil purification is a necessary maintenance process for oil-filled transformers and can be employed for removal of moisture from the transformer’s core and solid insulation. Heating of the transformer oil moves the moisture from paper to the oil and allows for its removal from the transformer.  The most common mistake made by operators of transformer oil purification equipment is to stop the drying process after reaching oil moisture content of less than 5 ppm.  After some time, when normal transformer operation conditions exist, the moisture content of the oil increases. It is essential to dry the transformer oil continuously throughout a long period.

Transformer Evacuation

Another required process is the immediate evacuation of the transformer after pumping the insulating oil out of the transformer tank.  The “Vacuum Effect” on the insulation surfaces greatly improves moisture content removal.  The process must be repeated several times before the desired effects will be achieved.

Hot Filtration and Thermo-Vacuum Drying

A gear type pump draws the oil in for processing via a strainer and cartridge filter.  It then directs the oil to the heat exchanger where the oil is heated by the heat conductor.  The oil is then fed to the vacuum drier’s sprayer after being heated to 60C/140F.  The Vacuum Pump maintains vacuum in the vacuum chamber.  a Vacuum can be regulated by valve(s) and monitored on the vacuum meter.  Filtered hot air comes into the chamber and removes gases and vapor from the oil’s surface effectively drying the oil.  The air is then discharged into the atmosphere via an oil separator by the vacuum pump.  A gear type pump then directs the oil into the processed oil vessel.  A programmable thermal regulator switch monitors the plant’s function continuously and maintains the pre-set temperature.