A simple method for identifying the quality of hydraulic oil in construction machinery

The quality of hydraulic oil not only affects the normal operation of construction machinery, but also causes serious damage to the components of the hydraulic system. Based on practical work experience, several simple methods for identifying the quality of hydraulic oil in the absence of dedicated testing instruments have been summarized.

Identification of moisture content in hydraulic oil

(1) Visual inspection method: If the oil appears milky white and turbid, it indicates that the oil contains a large amount of water.

(2) Combustion method: Dip a small amount of the oil to be tested in clean and dry cotton yarn or cotton paper, and then ignite it with fire. If you hear a "crackling" sound or a flashing phenomenon, it indicates that the oil contains a considerable amount of water.

Identification of impurity content in hydraulic oil

(1) Sensory identification: There are obvious suspended metal particles in the oil. When pinching with fingers, the presence of fine particles can be directly felt. Under light, if there are reflective flash points, it indicates that the hydraulic components have been severely worn. If there is a large amount of metal shavings settled 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 oil with lower viscosity, it can be directly placed in a clean and dry test tube and heated to increase the temperature. If sediment or suspended matter 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 higher viscosity, it can be diluted with pure gasoline and then filtered through clean filter paper. If a large amount of mechanical impurities (metal powder) remain on the filter paper, it indicates that the hydraulic components have been severely worn.

(4) Sound identification: If the entire hydraulic system has significant and intermittent noise and vibration, and the main oil pump emits a "buzzing" sound, or even the piston rod "crawles", at this time, when observing the oil level in the oil tank, the oil pipe outlet or the transparent liquid level gauge, a large amount of foam will be found. This situation indicates that the hydraulic oil has been immersed in a large amount of air.

Identification of viscosity changes in hydraulic oil

(1) Glass plate tilting method: Take a clean glass plate, place it horizontally, and drop a drop of the hydraulic oil to be tested on the glass. At the same time, drop another drop of standard hydraulic oil (new hydraulic oil of the same brand) beside it. Then tilt the glass plate and observe carefully If the flow rate and flow distance of the tested oil are both greater than those of the standard oil, it indicates that its viscosity is lower than that of the standard oil; conversely, it indicates that its viscosity is higher than that of the standard oil.

(2) Glass bottle inversion method: Place the hydraulic oil to be tested and the standard oil respectively in two transparent glass bottles of the same size and length (do not fill them too full), and then plug the mouths of both bottles with stoppers. Place the two bottles side by side and then quickly turn them upside down simultaneously. If the bubbles in the tested hydraulic oil in the bottle rise faster than those in the standard oil, it indicates that the viscosity of the oil is lower than that of the standard oil. Conversely, it indicates that the viscosity of the oil is higher than that of the standard oil. If the rising speeds of the bubbles in the two oils are close, it indicates that their viscosities are also similar.

Identification of quality changes in hydraulic oil

(1) Identification of oil in the oil pump: Take a small amount of the oil to be tested from the oil pump. If it is found to be milky white and turbid (sometimes like light yellow milk), and when identified by the combustion method, it is found to contain a large amount of water and has lost its viscosity when felt by hand, it indicates that the oil has been completely emulsified and deteriorated, and should no longer be used.

(2) Identification of oil in the fuel tank: Take a small amount of the oil to be tested from the fuel tank and filter it with filter paper. If there is black residue remaining on the filter paper and a pungent smell, it indicates that the oil has oxidized and deteriorated. You can also directly take out some of the settled oil sludge from the bottom of the fuel tank. If you find a lot of asphalt and gum sediment, place it on your fingers and pinch it. If you feel that there is a lot of gum and it has strong adhesion, This indicates that the oil has oxidized and deteriorated.