The double lip seal is double duty: Seal the lubricating oil in the bearing cavity to ensure the formation of a continuous oil film (the oil film plays a bearing role and bears the weight of the roll and the working load of the rolling mill). Seal the external cooling water, rolling oil, iron filings, dust and other sundries to prevent them from infiltrating into the bearing cavity, avoid the contamination and failure of the lubricating oil in the cavity and cause the bearing to burn out, and maintain the normal operation of the bearing.