The Use of Fuller’s Earth in the Regeneration of Contaminated Transformer OilOil Regeneration machine Contemporary approaches to the regeneration of used/contaminated transformer oil will be examined in this article. It has been shown through research and real world field experience, that mobile oil reclamation equipment of the CMM-R type, manufactured by GlobeCore, is perfectly suited for this purpose. The GlobeCore CMM-R units utilize a Fuller’s Earth sorbent filter process that autmoatically reacivates the sorbent material after every regeneration cycle. This advanced and environmentally friendly process restores transformer oil back to its orginal new like condition. With an optional “Inhibitor Injection” system, the GlobeCore CMM-R units can even improve the oil to better than new condition.
This unique unit has 12-columns of sorbent materials that can process 4000 liters/1056 U. S. Gals. of used oil per hour. The unit filters oil with reuseable/reactivatable Fuller’s Earth sorbent materials and is controlled by GlobeCore’s automatic system with remote interface and operation.
INTRODUCTIONTransformer oil is a liquid dielectric that provides up to 80% of the dielectric strength of a typical electric power transformer. Additionally, oil plays the important role of maintaining the transformer operating temperature through heat transfer known as cooling. During normal operating conditions, transformer oil will undergo changes to its chemical and electrical properties under the influence of various factors like temperature, electric field, and molecular oxygen interaction with the materials of the electrical equipment. This is especially true in the case of transformers that were constructed using low-quality insulating materials and paints lacking resistance to oil. The influence of these factors on the insulating oil leads to the clouding of oils and yields products with low resistence to oxidation as well as an increase in dielectric loss. As the level of oxidation rises, there is a good possibility that colloidal particles and sludge will form inside the transformer. In comparison with ions, colloidal particles have a lower mobility that leads to charge and increases the inhomogeneity of the electric field. The result is a reduction in the dielectric strength of the transformer oil. The sludge, along with other insoluble aging materials and particles, that seep into the oil from outside sources, (emulsion water, the fibers and metal particles), form a finely dispersed solution. This process also increases the heterogeneity of the electric field in transformer oil, significantly reduces the breakdown voltage and increases the tangent dielectric loss. The most dangerous contaminates are the impurities ranging between 2 to 10 µm. Additionally, moisture and water, even in small volumes, are capable of reducing transformer oil electrical resistance and result in high dielectric loss. The worst case scenario is an accident resulting in the catastrophic loss of your electrical equipment and electric service interuptions for your customers. To prevent undesirable effects caused by changes in the chemical and the physical properties of the insulating oil, it is necessary to carry out measures aimed at regeneration (recovery) of transformer oils as part of a comprehensive preventive maintenance program. The GlobeCore.com “Service Life Extension Program” utilizing the GlobeCore Process has become an intregal part of transformer maintenance in the industry today.
Preserving Precious ResourcesIn countries such as Germany, Italy and Belgium more than 50% of the used transformer waste oil is sent to oil recovery plants. This is despite the cost effectiveness and feasibility of oil regeneration pocresses that save the oil and return all the oil back to the transformer. European countries however, recover larger volumes of oil than Commonwealth Independent States (CIS countries such as Russia and other former Soviet republics and/or Warsaw Pact nations). For example, Russia simply wastes 40-48% of used petroleum oils. Only 14-15% of oils are regenerated and saved, while 26-33% are used as fuel or burned. The re-using of transformer oil after regeneration preserves precious resources and protecs the environment. The GlobeCore Process is the best way to accomplsh that goal.
THEORICAL BACKGROUNDRegeneration of used transformer oil is based on physical, physico-chemical and chemical processes. The particular sequence of these methods is as follows:
- Mechanical (sedimentation, filtration, separation, washing with water, distilling the fuel, cleaning under a force field);
- Thermo-physical (evaporation, vacuum distillation);
- Physic-chemical (coagulation, adsorption, ion exchange purification, selective treatment);
- Chemicals (sulfuric acid cleaning, alkaline cleaning, hydro treating, application of sodium and its compounds).
EXPERIMENT AND DATA COLLECTIONAt their headquarters in Oldenburg, Germany, GlobeCore has developed a line of equipment known the CMM-R series. The GlobeCore CMM-R units have been designed for the complex processing of used and contaminated transformer oils, hydrolic fluids, and fuels. We will examine the construction and operational features of the CMM-R units based on the very popular GlobeCore CMM-R12 model. It is composed of degassing, regeneration and inhibiting oil blocks. A diagram of how the CMM-R12 is connected to the transformer is shown in Fig. 1.
Fig. 1. Diagram of regeneration block, degassing and inhibition model CMM-R12 attached to the transformer for servicingModel CMM-R12 operates as follows: First the transformer oil is heated and filtered in the degassing block and is then fed through a regenerator. Second, the regenerated oil is returned to the column of a vacuum degassing unit to remove water and gasses by deep vacuum and heating as the final filtration step. Next, a detailed examination about the regeneration block. Transformer oil is passed through the Fuller’s Earth sorbent material, which has micro porous characteristics. This allows for filtration and removal of moisture, undesired impurities and decomposition products from the oil that are retained in the granular sorbent material. When the Fuller’s Earth reaches its maximum filtering capacity, the GlobeCore CMM-R unit will automatically begin to reactivate the sorbent material. The automatic reactivation mode is characterized by cleaning the micro pores of the Fuller’s Earth followed by removal of all harmful contaminants to the special container and carbon filter. The Fuller’s Earth sorbent therefore, can be repeatedly recovered over and over again to its original state. The automatic reactivation of the sorbnet makes it possible to carry out continuous treatment of transformer oil without unnecessary pauses or the need to continuously remove and dispose of spent sorbent materials. This significantly reduces the transformer maintenance processing time using the GlobeCore Process of sorbent reactivation as compared to the most common thermal desorption methods of sorbent reactivation that may take more than 30 hours to complete. After the Fuller’s Earth has been recovered and reactivated, it can be used again to filter and purify transformer oil. At the final stage of the GlobeCore Process, the oil runs through the “Inhibition Block.” An injection unit injects concentrates of ionol solution (DBPC-2.6) in to the oil in order to increase its resistance to oxidation. The oil is not only resotored to its original new like condition, but is significantly enhanced through the introduction of the inhibitor product. Regeneration of transformer “Insulating Oil” utilzing the GlobeCore CMM-R12 unit can be performed while the transformer is either energized or deenergized. The GlobeCore CMM-R12 model is controlled and setup through a microcontroller which uses a Touch Panel for ease of operation. Running the Regeneration Program requires only initial set up and performs the regereration process completely automatically. The operator is not required make any manual adjustments during the fully automatic process. For operator and environmental safety, the use of redundant sensors will alert the control modual to shut the system down in the event of any failure of the system and/or the connections to the transformer. The GlobeCore CMM-R12 unit was thoroughly tested in performing transformer oil regeneration. The test results of the physical and chemical analysis are shown in Table 1.
Table 1. The results of physicochemical analysis of transformer oil
|#||Parameter||Before reclamation||After reclamation||Norm||Norm according to IEC 60296|
|1||Appearance||Dull, dark brown||Clear, transparent||–||Clean, free of sediment and suspended solids|
|2||Acid number, mg KOH per 1 g of oil , not more than||0.63||0.01||0.01-0.05*||0.01|
|3||Sulfur corrosion||Presence||Lack of||–||Lack of|
|4||Moisture content ppm, no more than||170||5||–||30-40|
|5||Breakdown voltage, kV, more than||11||73||30-55**||30-70|
|6||Dissipation factor at 90°C/194°F, %, not more||4.0||0.001||0.5||0.005|
|7||Gas content, %||12||0,1||–||–|
|8||Surface tension at 25°C/77°F , mN/m||22||45||–||40|
|9||The size of mechanical impurities, um||50||0.2||Lack of||Lack of|
|10||Oxidation stability:- Acid number, mg KOH per 1 g of oil , not more than||–||0.2||0.15-0.35||1.2|
CONCLUSIONSBased on the results of laboratory studies of transformer oil regeneration, it is possible to draw the following conclusions:
- After the treatment by model CMM-R12 all of the measured parameters have been improved;
- The measured values exceed the requirements of international standards for the performance characteristics of transformer insulating oil;
- The technology used for reactivation of Fuller’s Earth sorbent reduces the time for processing oil;
- Oil maintenance will extend the effective service life of the transformer.