Microbial Problems in Oils

Microbes can contaminate and grow in a wide range of mineral and synthetic oils over a surprisingly wide range of temperatures. Lubricating oils, Gear oils, Hydraulic oils, Preserving oils, Turbine oils, Stern tube oils and Transformer oils are just some of the oil types which can suffer problems of microbial attack.

The microbes grow in free water in the bottom of tanks and systems but also in water which is finely suspended in the oils. The microbes produce acids (causing increase in TAN/ reduction of TBN) and also, in the case of Sulphate Reducing Bacteria infection, sulphides. Oil additives are frequently destroyed by the microbes. The oils can become corrosive resulting in costly machinery failure for example when marine crankcase lubricants become infected. Microbial slimes cause filter plugging, a particular problem in hydraulic oils, but also in other oils. The microbes promote suspension of water in the oils and may cause viscosity changes.

Microbial slime in a ship’s stern tube lubricant