This International Standard specifies a method for determining the resistance of a hydraulic filter element to flow fatigue when subjected to high viscosity fluid, using a uniformly varying flow rate up to a predetermined maximum differential pressure and a controlled waveform. It establishes a method for verifying the ability of a filter element to withstand the flexing caused by cyclic differential pressures induced by a variable flow rate. NOTE See the Introduction of this International Standard for information about its applicability.