This International Standard specifies the procedures for flushing from the hydraulic lines of larger hydraulic fluid power systems solid particulate contamination that can be introduced during the initial build of a new hydraulic system or after maintenance or modification of an existing system. This International Standard supplements, but does not replace, the requirements of the component supplier and customer, especially when those requirements are stricter than those specified by this International Standard. This International Standard is not applicable to a) the chemical cleaning and pickling of hydraulic tubes, or b) the cleaning of major system components (see ISO/TR 10949). Verification of the cleanliness of assembled systems is covered in ISO/TS 16431.