This portable vacuum oil purifier (single stage vacuum) is applicable to purify various kinds of electric insulating liquids such as transformer oil, silicone fluids etc. It can remove the free and soluble water, free and dissolved air and gases, other particulate matters etc and improve the oil dielectric strength. This system is designed for processing oils in workshops, oil storage tanks or directly in transformers (energized or de-energized transformers). It can used for on-site installation, maintenance and purifying new transformer oil or dirty used oil. This model is an ideal small size transformer oil purifier.