it can remove water and gas in the insulating oil under high temperature and vacuity. it use more precise filter system to filter out impurities(filtering precision: 1-3um). It ia mainly used for purification of oil for transformer with voltage higher than 220kv. It can increase oil breakdown voltage by at least 40kv.They are suitable for oil treatment, vacuum oil injection, and cylic hot-oil drying in the installation and maintenance of big transformers.