The record of low temperature filter transformer oil purchased by ZYA-500 double vacuum oil filter in 2009 is as follows: 60 t transformer oil is filtered without heating (the user is a transformer oil manufacturer, the crude oil temperature before filtering is 38 º C, and the water content is 19 PPM), the filtering speed is 500 L/min, 60 t transformer oil is filtered in 3 hours, and the water content in the filtered oil is 8 PPM.