An overview of Doble TOPS


Insulating oils for general application, which are covered by this specification, are manufactured from predominantly naphthenic base crudes. Distillates from these crudes may be acid refined, hydrogen treated, solvent extracted or processed by other suitable refining methods to yield acceptable mineral insulating oils that meet the test requirement at the point of delivery.

Oils from paraffinic crudes may also be covered by this specification, with the exception of performance at low temperatures. Other requirements may be needed for these products to ensure proper function at low temperatures.


The use of all additives must be identified. An additive is a suitable chemical substance that is deliberately added to a mineral insulating oil to improve certain characteristics.

Oxidation stability

Uninhibited oils must be free of additives, natural or synthetic, that are used to improve oxidation stability. This includes (but is not limited to) 2,6 ditertiary-butyl phenol, 2,6 ditertiary-butyl cresol and metal deactivators such as benzotriazole and its derivatives.

Inhibited oils are insulating oils that have been supplemented with either 2,6 ditertiary-butyl phenol, 2,6 ditertiary-butyl cresol or any other specified and acceptable oxidation inhibitor. If an additive other than 2,6 ditertiary-butyl phenol or 2,6 ditertiary-butyl cresol is used, appropriate limit values for oxidation stability tests (those for Type I or Type II oils) should be agreed on by the purchaser and seller. If more than one additive is used, which warrants more stringent limits for oxidation stability, those for the Type II oils would apply.

Pour point depressants, gassing tendency improvers, additives for corrosive sulfur and static electrification (metal passivators), antifoaming agents and other additives:

All additives should be specifically identified or at a minimum identified by class of compounds (such as metal passivator), if the specific information is proprietary.


Insulating oils covered by this specification should be produced from proven crudes by suitable refining techniques, both of which should be approved by the purchaser. After such approval, no change in crude source, processing, or refining methods should be made that results in a substantial change in the product characteristics without the prior approval by the purchaser.

Shipping containers should be dedicated to new transformer oils. The shipping method and containers should be agreed upon by purchaser and seller and should not be changed without prior approval from the purchaser.

Doble Engineering Company

Doble Engineering Company