Pollution and harm of hydraulic oil

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Pollution and harm of hydraulic oil

I. water mixed in the oil

1 The way of water entering the oil

(1) the water in the air condenses into droplets and falls into the oil due to the alternation of cold and heat in the oil tank cover

(2) the seal of cooler or heat exchanger is damaged or the cooling pipe is broken, so that water leaks into the oil

(3) the moist air entering the system through the loose sealing of the piston rod of the hydraulic cylinder condenses into water droplets

(4) when using oil, it carries human water and water absorbed by the affinity between oil and water when exposed to humid environment

2. The harm of mixing water in the oil

(1) after mixing a certain amount of water in the oil, the hydraulic oil will be emulsified in a white and turbid state. If the anti emulsifying ability of the hydraulic oil itself is poor, the water can not be separated from the oil after standing still for a period of time, so that the oil is always in a white and turbid state. This white emulsified oil enters the hydraulic system, which not only rusts the inside of the hydraulic components, but also reduces its lubrication performance, intensifies the wear of parts and reduces the efficiency of the system

(2) after the iron series metal in the hydraulic system is rusted, the peeled rust flows in the pipes and hydraulic components of the hydraulic system, spreads and spreads, which will lead to rust in the whole system and produce more peeled rust and oxides

(3) water will also interact with some additives in the oil to produce pollutants such as precipitation and colloid, which will accelerate the deterioration of the oil

(4) sulfuric acid and hydrochloric acid are produced by the interaction of sulfur and chlorine in water and oil, which aggravates the abrasion and wear of components, accelerates the oxidative deterioration of oil, and even produces a lot of oil sludge

(5) these water pollutants and oxidation products immediately become catalysts for further oxidation, which eventually leads to the blockage or jamming of hydraulic components, resulting in a series of faults such as action failure of hydraulic system, blockage of oil distribution pipe, reduction of cooler efficiency and 320kg plug of oil filter

(6) in addition, the "microbubble structure" of the wood itself suffers from different degrees of damage. At low temperature, the water condenses into small ice particles, which is also easy to block the gap and dead mouth of the control element

II. Various impurity particles are mixed in the oil

the solid pollutants in the oil mainly exist in granular form. Some of these impurities are residual in the process of component processing and assembly, some are generated by hydraulic components in the working process, and some are caused by the intrusion of external impurities. The harm is:

1 Various particulate impurities in the oil will cause harm to the pump and motor. When the impurity particles enter the gear end face of the gear pump or gear motor and the side plates of the covers at both ends, the tooth top and the shell, or when the impurity particles enter the blade and blade groove of the vane pump or vane motor, the rotor end face and the oil distribution plate, the stator and the rotor (blade top), or when the impurity particles enter the plunger and plunger cylinder hole of the plunger pump or plunger motor, the rotor and oil distribution plate, sliding shoes and inclined plate Between the sliding pairs of variable mechanism, it may cause jamming failure. Even if it does not cause jamming failure, it will aggravate the wear. The heat-resistant temperature of impurity particle polymer material refers to that the oil inlet filter in front of the pump may be blocked under 1 constant load, resulting in cavitation of the pump or multiple concurrent faults

2. Various particulate impurities in the oil will cause harm to the hydraulic cylinder. Particulate impurities will cause strain and wear between piston and cylinder block, piston rod and cylinder head hole and sealing elements, increase oil discharge and reduce volumetric efficiency and effective thrust (tension). If particulate impurities jam piston or piston rod, the oil cylinder will not act

3. The contaminated particles in the oil will cause harm to various valve components. The contaminated particles may cause the slide valve to be stuck or the throttle 121 to be blocked, resulting in the valve action failure. Even if there is no stuck or blocked fault, the contaminated particles will also cause the moving pair of valve elements to wear prematurely, increase the matching clearance and deteriorate the performance

4. Pollutants breed bacteria, aggravate oil aging, make oil black and smelly, and further produce pollution. Such a vicious cycle may have the following consequences:

(1) pollutants block the oil filter, resulting in empty oil pump and vibration and noise

(2) pollutants increase the friction of oil cylinder or motor, resulting in crawling

(3) pollutants make servo valves and other components with poor anti pollution ability completely lose their functions

(4) pollutants block the channel of the pressure gauge, so that the pressure cannot be transmitted and reacted correctly

III. air intrusion in oil

the air in the oil mainly comes from loose pipe joints, loose element joint surfaces, oil pipes exposed to the oil surface and seal failure. The oil exposed to the atmosphere will also dissolve the air. In addition, when the amount of oil in the oil tank is small, the circulation of hydraulic oil is accelerated, making it difficult to eliminate bubbles. At the same time, the insufficient depth of "oil eating" of the oil pump suction pipe also makes it easy for air to enter

the air mixed into the hydraulic system is usually suspended in the hydraulic oil in a bubble state with a diameter of 0.05 ~ 0.50mm, which has a serious impact on the bulk elastic modulus and viscosity of the hydraulic oil in the hydraulic system. With the increase of the pressure of the hydraulic system, part of the air is mixed into the hydraulic oil, and the rest still exists in gas phase. When the amount of air mixed increases, the volumetric elasticity coefficient of hydraulic oil decreases sharply, the propagation speed of pressure wave in hydraulic oil slows down, and the dynamic viscosity of oil increases linearly. The air suspended in the oil and hydraulic oil combine to form a mixed liquid. The stability of this oil depends on the size of bubbles and has a significant impact on the hydraulic system. There may be faults such as vibration, noise, pressure fluctuation, instability of hydraulic components, crawling and reversing impact of moving parts, inaccurate positioning or disordered action. At the same time, it also increases the power consumption, accelerates the oxidation of oil and reduces the lubrication performance of oil. (end)


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