This International Standard provides guidance for flushing of lubricating oil systems, and grading of the resultant cleanliness. The flushing process is twofold: ⎯ to remove dirt from the erection and installation, and ⎯ to demonstrate that the pipes and the system as a whole is sufficiently clean. Crankcase and, where applicable, gearbox etc. are cleaned separately before flushing, and requirements relating to this are also specified in this International Standard. Similar considerations apply to the system tank and other components of the system. For this International Standard, the cleaning process is considered as “washing through” when the Reynolds number, Re, is u 3 000, and “flushing” when the Re W 3 000