Oil Transformers

An oil transformer is essentially a transformer that uses mineral oil as a means of heat dissipation and electrical insulation. The oil helps cool the transformer. Transformer oil must remain stable at high temperatures for an extended period of time because the oil acts as electrical insulation between internal live parts. For larger transformers, external radiators may be placed on the transformer tank to improve cooling. The radiators helps the oil circulate and expel heat through natural convection.

Our larger oil transformers (usually for high voltage applications) often have to undergo a prolonged drying processes using a vacuum chamber and ovens. This is done to ensure that the transformer is completely free of water vapor before the cooling oil is brought together. This process helps prevent corona formation and subsequent electrical breakdown under load.

"The flash point (min) and pour point (max) are 140 °C and −6 °C respectively. The dielectric strength of new untreated oil is 12 MV/m (RMS) and after treatment it should be >24 MV/m (RMS)."

From http://en.wikipedia.org/wiki/Transformer_oil

Today, most transformers use a fluid that achieves a much higher performance level than standard naphthenic mineral oil, with far less risk. Mineral oils have issues with corrosive sulphur that can render them problematic in service and attempts to balance this with copper passivators are insufficient compared to readily-available and safer alternatives.

Pentaerythritol tetra fatty acid natural and synthetic esters are now a common mineral oil alternative. They counterbalance all the most prominent risks associated with mineral oil such as high flammability, environmental impact and poor moisture tolerance. Esters are also non-toxic to aquatic life, readily biodegradable and provide a lower volatility and higher flash point. Additionally, they have a high fire point of over 300°C. K-class fluids such as these are often used in high-risk instances, such as indoors or offshore applications. They also have a lower pour point, greater moisture tolerance and improved function at high temperatures.

"Well into the 1970s, polychlorinated biphenyls (PCBs) were often used as a dielectric fluid since they are not flammable. PCBs do not break down when released into the environment but accumulate in the tissues of plants and animals, where they can have hormone-like effects. When burned, PCBs can form highly toxic products, such as chlorinated dioxins and chlorinated dibenzofurans. Starting in the early 1970s, production and new uses of PCBs have been banned due to concerns about the accumulation of PCBs and toxicity of their byproducts. In many countries significant programs are in place to reclaim and safely destroy PCB contaminated equipment.

"Polychlorinated biphenyls were banned in 1979 in the US. Since PCB and transformer oil are miscible in all proportions, and since sometimes the same equipment (drums, pumps, hoses, and so on) was used for either type of liquid, contamination of oil-filled transformers is possible. Under present regulations, concentrations of PCBs exceeding 5 parts per million can cause an oil to be classified as hazardous waste in California (California Code of Regulations, Title 22, section 66261). Throughout the US, PCBs are regulated under the Toxic Substances Control Act. As a consequence, field and laboratory testing for PCB contamination is a common practice. Common brand names for PCB liquids include 'Askarel', 'Inerteen', 'Aroclor' and many others."

From http://en.wikipedia.org/wiki/Transformer_oil

Quality Transformer and Electronics does not produce oil transformers with PCBs. Furthermore, we will not accept repair jobs where PCBs were used.