Transformer oil is a term that is applied to a broad range of products and manufacturers. For the perspective of this discussion, IET handles the typical mineral oil based product.
Oil Processing Policy–As a company we stay away from the less flammable products such as silicone fluids, high molecular weight products such as R temp, Askerals which are the PCB products that still remain in the electrical equipment population, chlorinated products such as WESCO SOL and to date the new FR liquids. Our goal is to maintain clean, uncontaminated processing equipment which keeps the equipment that we service uncontaminated as well. It is our policy to require oil sample results prior to processing. We look for PCB contamination levels and typically will not handle product with a PCB content of greater than 10ppm. In the event that we do get into a low level PCB issue, all of our equipment is drained, flushed, filters changed and sampled to insure there is no residual contamination prior to moving to the next unit or customer. Suspect units are also tested for dissolved silicone products. which can cause vacuum chamber foaming problems.
As you are aware, transformer oil is used in numerous types of electrical equipment and depending on the application has different degradation modes and degrees. Of the problems encountered, certain conditions are common among all equipment uses. IET has numerous ways of handling transformer oil.