Mechanical seal using a new type of tungsten carbide material, at the same time, the improvement of the double end seal, so that the long-term operation of the oil, can make the safe and continuous operation of the pump. The medium temperature is not more than 70, and the medium is 1-1.3k/dm3. Cast iron material of the use of medium pH value in the range of 5-9. 1Cr18Ni9Ti stainless steel material can be used with a variety of corrosive media.