Been taken to the precision parts of hydraulic systems with servo - parts internationally . and the cleanliness of the infused new oil should reach the requirement of grade 5 of nas1638 so as to ensure the system stability and running reliability 为此,国际上对液压系统中带有伺服机件等精密元件的油液清洁度采取严格的控制,对加入的新油清洁度要求达到美国宇航标准nasl638的5级,以确保系统稳定可靠运行。