Ageing and fitness regime of transformer oil
Mineral oil is used in transformers as liquid insulation and coolants. Owing to their function, the dielectric properties must be well maintained so that heat transfer and chemical stability is present throughout the operations.
Ageing of transformer oil
Ageing of the transformer denotes ageing of the entire insulation, especially the oil. Decrease of dielectric strength and premature failures owe themselves to the humidity and foreign particles which affect the interfacial tension of the oil.
A colour index close to 3 does not determine the quality of the oil, since more than two or three parameters confirm the oil degradation. Repeated and frequent oil sampling is required to avoid damages and repairs.
When the transformer oil is degraded, ageing occurs and performance suffers a setback. Heat, oxidation and moisture aggravate the ageing process and the used transformer oil must be replaced with new one.
Such replacement is not only costly but also drastically affects the ecosystem. The effectiveness of adsorbent technology using fuller’s earth and reclamation process is gaining popularity whose results are widely lauded. Even though the lifespan of a transformer is 20 to 30 years, a well-maintained transformer can last upto 50 to 60 years.
Reclamation of transformer oil
Reclamation is a process of restoring the “as good as new” value of transformer oil by removing acid, sludge and oxidation products and curbing the ageing rate of the oil. Though oxidation is the main reason for ageing, oil temperature, metals like copper and iron have a role in the aging process.
Reclamation is inevitable when neutralization number, interfacial tension and dissipation factor are far from the prescribed values. The soluble and insoluble contaminants are removed by combining chemical and physical processing which is an efficient and cost effective method to restore transformer oil.
Deposition rates of contaminants depend on the size of particles and difference of density between them. Centrifugation followed by dehydration reduces gas to water content and oil passes to the adsorbent treatment where oil is subjected to selective retention of contaminants.
Materials used for reclamation of transformer oil
Though activated bauxite is a low cost adsorbent used for reclamation, it leaves a large volume of wastes. Micro-particles of carbonated amorphous calcium phosphate (CACP), remove polar compounds in used mineral oil while biopolymers like chitosan polysaccharide bind CACP particles.
Bleaching is an important aspect of refining crude oil since it removes contaminants so that appearance and performance are enhanced. Adsorbent mineral polishing system improves colour and oxidation stability, removes odor, reduces sulphur content and organic acidity, offers higher yields and is environmentally friendly. Bentonite is successful in bleaching clays and removes impurities, suspended matter, sediments and contaminants successfully.
Advantage of Hering’s AMPS
Hering’s Adsorbent Mineral Polishing System improves colour, odour and chemical properties of the recycled oil by using lube-oil polishing treatment without presence of chemicals.The environment friendly Hering Phonix Green material is used in a physical process. The Phonix Green Clay can be used 500 times before being replaced and provides high quality group I and group II base oils. Hering AMPS can be used in flow rates from 50 liters per hour to 27,000 liters per hour and in non-cracking evaporator front end in Hering’s Waste Oil Recycling Plant or as add on in re-refining plants. It also removes sulphur from 2,000 PPM to 300 PPM in a single pass.
Highlights of AMPS include low operating costs, flexible operating modes, flexible layouts, minimized points of emission, available in global voltages and frequencies, low oil losses and waste which is standard industrial waste with low environmental costs.
Hering’s unbeatable German precision
Hering’s line of products for transformer maintenance includes transformer oil purification systems, regeneration systems, PCB removal systems, vacuum transformer drying ovens, waste oil recycling plants, reactivation clay polishing systems, TIDO series online transformer insulation drying and degassing systems and ISODRY series online transformer insulation drying systems.
Hering’s robust design is easy to operate and maintain and is custom-made. The modules can be shipped in a 40 ft container thus reducing shipping and handling costs. Hering is committed to fighting transformer oil deterioration and trains clients in online and offline oil processing and transformer drying activities. They customize the systems according to client requirements to optimize the benefits.
