A simple method for judging the quality of the hot

2022-08-08
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A simple method for judging the quality of hydraulic oil

the quality of hydraulic oil will not only affect the normal work of construction machinery, but also cause serious damage to hydraulic system parts. Combined with work practice, this paper summarizes several simple methods to identify the quality of hydraulic oil without special testing instruments

1 identification of water content of hydraulic oil

(1) visual inspection method: if the oil is milky white and turbid, it indicates that the oil contains a lot of water

(2) combustion method: dip a little oil to be tested with clean and dry cotton yarn or paper, and then ignite it with fire. If "crackling" cracking sound or flashing phenomenon is found, it indicates that the oil contains more water

2 identification of impurity content in hydraulic oil

(1) sensory identification: knowledge of friction and wear testing machine: there are obvious metal particle suspensions in the oil, and the existence of fine particles is directly felt when pinching with fingers; Under the light, if there is a reflective flash point, it indicates that the hydraulic components have been seriously worn; If a large amount of metal chips are deposited at the bottom of the oil tank, it indicates that the main oil pump or motor has been seriously worn

(2) heating identification: hydraulic oil with low viscosity can be directly put into a clean and dry test tube for heating. If sediment or suspension is found in the oil in the test tube, it indicates that the oil has contained mechanical impurities

(3) the pointer can be zeroed when the filter paper is full of thallium or thallium A: for hydraulic oil with high viscosity, dilute it with pure gasoline, and then filter it 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 seriously worn

(4) sound identification: if the whole hydraulic system has large, intermittent noise and vibration, and the main oil pump makes a "buzzing" sound, and even the piston rod "crawls", then observe the oil tank level, oil pipe outlet or transparent liquid level gauge, and a large amount of foam will be found. This indicates that the hydraulic oil has been immersed in a large amount of air

3 identification of viscosity change of hydraulic oil

(1) glass plate tilting method: take a clean glass plate, place it horizontally, and drop the measured hydraulic oil on the glass one by one, at the same time, drop a drop of standard hydraulic oil (new hydraulic oil of the same brand) next to it, then tilt the glass plate, and pay attention to observation: if the flow rate and flow distance of the measured oil are larger than the standard oil, it means that its viscosity is lower than the standard oil, otherwise, It means that its viscosity is higher than that of standard oil

(2) glass bottle inversion method: put the measured hydraulic oil and standard oil in two transparent glass bottles with the same size and length respectively (do not fill them too full), and then plug the mouths of the two bottles. Put the two bottles side by side, and then quickly turn them upside down at the same time. If the bubble of the measured hydraulic oil in the bottle rises faster than that 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; If the bubble rising speed of the two oils is similar, the viscosity is also similar

4 identification of hydraulic oil quality changes

(1) identification of oil pump oil: take a little oil measured from the oil pump. If it is found to be milky white and turbid (sometimes like light yellow milk), and when identified by combustion method, it is found that it contains a lot of water and feels that it has lost viscosity by hand, it indicates that the oil has been thoroughly emulsified and deteriorated and is not suitable for reuse

(2) identification of oil in the oil tank: take a small amount of tested oil from the oil tank and filter it with filter paper. If there is black residue on the filter paper and there is a pungent odor, it indicates that the oil has been oxidized and deteriorated. You can also directly take part of the precipitated sludge from the bottom of the oil tank. If you find that there are many asphalt and colloidal deposits in it, put it on your fingers and pinch it. If you feel that there are many colloids, it has strong adhesion, It means that the oil has been oxidized and deteriorated (1) water. The moisture content of water in oil shall be in accordance with the standard gb/t1118 After testing, the quality index of the technical standard should not be greater than the trace If the water in the oil exceeds the standard, it must be replaced; Otherwise, it will not only damage the bearing, but also rust the surface of the steel parts, which will emulsify, deteriorate and generate sediment of the hydraulic oil, hinder the heat conduction of the cooler, affect the operation of the valve, reduce the effective working area of the oil filter and increase the abrasion effect of the oil

(2) oxidation. Generally, the working temperature of mechanical hydraulic oil is ℃, and the service life of hydraulic oil is closely related to its working temperature. Experience tells us that when the working oil temperature exceeds 60 ℃, the service life of oil will be halved for every 8 ℃ increase, that is, if the added value is high at 90 ℃, it can only indicate that the service life of oil with high technical content is about 10% of that of 60 ℃, because the oil is oxidized. Oxygen reacts with hydrocarbons in the oil to slowly oxidize the oil, darken its color, and increase its viscosity. Finally, it may be so serious that the oxide cannot be dissolved in the oil, but deposited somewhere in the system with a brown viscous layer, which is very easy to block the control oil passage in the components, aggravate the wear of ball bearings, valve cores, pistons of hydraulic pumps, etc., and affect the normal operation of the system. Oxidation will also produce corrosion. Qee-tech equipment can quickly layer (upper left) etchant on the main structural strength components of the door module. The oxidation process starts slowly. When it reaches a certain stage, the oxidation speed will suddenly accelerate, and the viscosity will suddenly rise. As a result, the working oil temperature will rise, the oxidation process will be faster, and the accumulated sediment and acid will be more, and finally the oil can't be used again

(3) impurities. Impurities can not only wear all moving parts, but also affect the normal operation of the whole system and cause machine failure once they are stuck in the valve core or other moving pairs

(4) air. If the hydraulic oil circuit contains gas, when the bubble overflows, it will impact the pipe wall and components to form cavitation, which will make the system unable to work normally. A little longer time will also lead to component damage

(5) physical and chemical reactions. The cleaned paint in the oil tank will cause changes in the chemical properties of the oil

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