Filtration – is a process of removing particles of mechanical impurities and resinous compounds by passing oil through mesh or porous filters. There are a great number of different filtering materials: plastic and metal mesh, felt, fabric, paper, composite materials and ceramics. In practice, used transformer oils frequently contain impurities that are not retained by above mentioned filter materials. For this reason, many companies producing oil purification equipment in their installations increase the number of coarse filters and introduce a second stage of the process – fine cleaning of oil.
Oil has an ability to partially relieve itself of acidic products that concentrate in solid insulation of transformer. Further rapid growth of acidic number is characterized by formation of acid insoluble residue and water-soluble acids in oil.
The very same oxidation or aging of oil is influenced by different catalysts. One of them is oxygen, that can penetrate from outside and exist inside transformer.
To eliminate oil contact with atmospheric air, and thereby prevent contamination and oxidation of oil – is used nitric protection systems, in a form of low pressure (nitrogen pressure of not more than 3 kPa). The main elements of the system – is a expansion tank and a flexible reservoir, connected by oil line to transformer. The system is filled with nitrogen with pressure slightly higher than normal atmospheric pressure at all temperature changes. When transformer is heated the oil level in expansion tank rises and nitrogen from expansion tank spills into flexible reservoir, increasing its size. By lowering the level of oil in expansion tank nitrogen passes from the flexible container and its walls fall down. Gas-drying absorbs any moisture that may enter into gas system from oil or insulation or from gas bottle during feeding system with nitrogen.
Oxygen content in gas space of expansion tank must not exceed 1%. At higher oxygen content – nitrogen cushion for oil protection becomes ineffective. Oil should be degassed, that is, oxygen removed from oil with special vacuum systems. Saturation is done by blowing nitrogen. After 3-4 blowings, oxygen in oil is almost completely replaced by nitrogen.
Level of oil in expansion tank is controlled by a needle indicator, with lever based on film surface. Transformer with protection film is filled with degassed oil with mandatory regular control of its gas content.
As a rule the most popular installation are complex purification and recovery systems. It is not enough to remove oxygen and check nitrogen protection. Because oil does not only contact with air, it still comes in contact with moisture, temperature, harmful impurities etc.
Each treatment plant should be able to remove all oil pollutants, thus returning oil its original specifications. Otherwise, purification is considered ineffective.
CMM installations by GlobeCore are designed for complex cleaning of transformer oil. However, each of them has its own specifications and features. GlobeCore equipment ranges from high vacuum degassing units to transformer oil regeneration and purification systems with reactivation of sorbent. The choice of equipment depends on needs of the customer, the scale of the enterprise and industry it operates.
The aim of GlobeCore Company is to manufacture and supply modern equipment, which improves customer production.