Put the same brand of old and new jar oil in two tubes and compare the smell and color of the oil. If the old oil is dark and there is a big difference, the hydraulic oil should be replaced. If the color does not change too much, it means that it is turbid, indicating that water or other non-essential oils must be heated and evaporated in the oil before they can continue to be used. If the color of the oil changes and the resistance is still transparent, you should consider whether it is mixed into other oils. It can be used with little difference in viscosity.
As the viscosity of the oil rises, the speed of the bubbles is inversely proportional to the same brand of hydraulic oil, new and old. Note that there are two identical tubes, the hand at the nozzle, a small amount of air duct, and the rise of the bubbles is inverted Speed comparison of two test tubes. At the same speed. The results show that the viscosity difference is not large enough to be used. Because the bubbles in the old oil rise too fast, it means that the viscosity is too low to continue using.
In a bright environment, the human eye observes light in the same clean test tube, allowing foreign particles above 40 μm to be resolved. The more dispersed the impurities, it means that the oil is very dirty and can be used in static precipitation filtration. If the oil is darker, you can also filter the dowry with filter paper. The method is to drop a drop of stirring oil drops on the filter paper. After the oil, dark solid particles indicate that there are many impurities and should not be used.
Take a small amount of hydraulic oil sample and burn it on a steel plate. If the oil burns silently, it means that the oil is normal; if there is a crack during burning, it means that the water must be evaporated and then used.