Heating differential: on the lower viscosity hydraulic oil can directly into the clean, dry test tube and heated. If you find oil liquid precipitation in tubes or suspension, it indicates that oil has been found in metal powders.
Filter identification: high viscosity of hydraulic oil, after dilution with pure gasoline, and then filter it with a clean filter. If lots of metal powder on filter paper, it indicates that the hydraulic components have badly worn.
Sensory identification: oil for hydraulic cylinder has obvious metallic particles in suspension, with pinched fingers can feel small particles; light, if you have reflective flashed, it indicates that the hydraulic components have badly worn; if the sediment at the bottom of the tank has a lot of scrap metal, it indicates that the primary pump or motor is badly worn.
Voice identification: If the hydraulic cylinder in operation during the entire hydraulic system is intermittent, loud noise and vibration, and main oil pump "hum" sound, even has a rod "creep" phenomenon, this time to observe the liquid in the tank, oil exports or transparent liquid level meter, you will find a large number of bubbles. If this occurs, it indicates that the hydraulic oil has plunged a lot of air.
In order to make the operation stability of hydraulic cutting machine, change the oil, best.