ISO 28521:2009规定了液压油管道系统的管道清洁和清洁级别。液压油管路系统中管路和部件的清洗对于液压系统的无故障运行至关重要。 它指出了实际执行清洗带有附属部件的液压系统特定部件的方法和设备。 清洁过程的目的是清除安装污垢，并检查管道和液压系统是否已充分清洁。 当雷诺数Re，u 3 000时，系统的清洗过程被认为是“冲洗”过程，当Re W 3 000时，系统的清洗过程被认为是冲洗过程。雷诺数是流体流被认为是层流还是湍流的指标。 ISO 28521:2009预先假定液压系统的管段已部分通过酸洗和部分通过机械清洁进行清洁。此外，假设来自系统供应商的动态和静态组件在交付时都足够清洁。 ISO 28521:2009中给出的质量标准是对各制造商规定的指南的补充，而不是替代。制造商的指南（如有）优先。

ISO 28521:2009 specifies pipe cleaning and cleaning levels of hydraulic oil pipe systems. The cleaning of pipes and components in hydraulic oil pipe systems is essential for the trouble-free operation of hydraulic systems. It indicates methods and equipment for the practical execution of the cleaning of specific parts of hydraulic systems with appurtenant components. The purpose of the cleaning process is to remove installation dirt and to check that the piping and hydraulic system have been adequately cleaned. The cleaning process of a system is considered a “washing through” process when the Reynolds number,R_e, u 3 000, and a flushing process when R_e W 3 000. The Reynolds number is an indicator of whether a fluid flow is considered laminar or turbulent. ISO 28521:2009 presupposes that the pipe sections of the hydraulic system have been cleaned partly by pickling and partly by mechanical cleaning. It is furthermore assumed that both dynamic and static components from system suppliers are adequately clean when delivered. The specifications given in ISO 28521:2009 are supplementary to, and not a replacement for, the guidelines specified by the various manufacturers. The manufacturer's guidelines, where available, take precedence.