1、 Identification of moisture content in hydraulic oil
(1) Visual inspection method: If the oil is milky white and cloudy, it indicates that the oil contains a large amount of water.
(2) Combustion method: Dip a small amount of the oil to be tested with clean and dry cotton yarn or cotton paper, and then ignite it with fire. If a cracking sound or flashing phenomenon is found, it indicates that the oil contains a lot of water.
2、 Identification of impurity content in hydraulic oil
(1) Sensory identification: There are obvious metal particle suspensions in the oil, and the presence of small particles can be directly felt when pinched with fingers; Under illumination, if there are reflective flash points, it indicates that the hydraulic components have been severely worn; If there is a large amount of metal debris settling at the bottom of the fuel tank, it indicates that the main oil pump or motor has been severely worn.
(2) Heating identification: For hydraulic oils with lower viscosity, they can be directly placed in clean and dry test tubes for heating. If sediment or suspension is found in the oil in the test tube, it indicates that the oil already contains mechanical impurities.
(3) Filter paper identification: For hydraulic oil with high viscosity, pure gasoline can be diluted and then filtered with clean filter paper. If a large amount of mechanical impurities (metal powder) are found on the filter paper, it indicates that the hydraulic components have been severely worn.
(4) Sound identification: if the whole hydraulic system has large and intermittent noise and vibration, and the hydraulic oil pump makes a "buzzing" sound, or even the piston rod "crawls", then observe the oil tank level, the oil pipe outlet or the transparent level gauge, you will find a lot of foam. This situation indicates that the hydraulic oil has been immersed in a large amount of air.
3、 Identification of viscosity changes in hydraulic oil
(1) Glass plate tilting method: Take a clean glass plate, place it horizontally, and drop one drop of the tested hydraulic oil onto the glass. At the same time, drop another drop of standard hydraulic oil next to it. Then tilt the glass plate and observe carefully: if the flow rate and flow distance of the tested oil are both higher than the standard oil, it indicates that its viscosity is lower than the standard oil; otherwise, it indicates that its viscosity is higher than the standard oil.
(2) Inverted glass bottle method: Place the measured hydraulic oil and standard oil in two transparent glass bottles of the same size and length (do not fill them too full), and plug the bottle mouth with a stopper. Then quickly invert at the same time. If the bubbles of the tested hydraulic oil in the bottle rise faster than those of the standard oil in the bottle, it indicates that the viscosity of the oil is lower than that of the standard oil. Otherwise, it indicates that the viscosity of the oil is higher than that of the standard oil.
4、 Identification of changes in hydraulic oil quality
(1) Identification of oil pump fluid: Take a small amount of the tested oil from the oil pump. If it is found to be milky white and cloudy (sometimes like light yellow milk), and when using the combustion method for identification, it is found to contain a large amount of water. If the viscosity is lost by hand, it indicates that the oil has completely emulsified and deteriorated. The manufacturer of Dalan Hydraulic recommends that it should not be used again.
(2) Identification of fuel tank oil: Take a small amount of the tested oil from the tank and filter it with filter paper. If there is black residue and a pungent odor on the filter paper, it indicates that the oil has oxidized and deteriorated.
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