How do you diagnose internal leakage in hydraulic motors?

Internal leakage within a hydraulic motor is detected by measuring the flow of the case drain at load, looking for the possibility of a decrease in output speed or torque at constant pressure, and then comparing volumetric efficiency with the benchmark of the manufacturer. A flow test of the case can be the best way to test for determining excessive flow that is returning to the tank via the drain line of the case

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