Contamination and hazards of hydraulic oil

1. Mix water into the oil

1. Ways to enter water in oil

(1) The oil tank cap condenses into water droplets and falls into oil due to the alternation of hot and cold.

(2) The seal of the cooler or heat exchanger is damaged or the cooling pipe is broken, causing the water to leak into the oil.

(3) The humid air entering the system through the unsealed sealing part of the hydraulic cylinder piston rod condenses into water droplets.

(4) Water that is brought by people when using oil and water absorbed by oil exposure to a humid environment.

2. The dangers of mixing moisture into oil

(1) After a certain amount of water is mixed into the oil, the hydraulic oil will be emulsified and turned into a white and turbid state. If the hydraulic oil itself has poor anti-emulsification ability, after being stationary for a period of time, the moisture cannot be separated from the oil, making the oil always in a white and turbid state. This white emulsified oil enters the hydraulic system, which not only causes rust inside the hydraulic components, but also reduces its lubricating performance, aggravate the wear of parts and reduces the efficiency of the system.

(2) After the iron metal in the hydraulic system rusts, the peeled rust flows in the hydraulic system pipelines and hydraulic components, spreading and spreading, which will cause rust inside the entire system and produce more peeled rust and oxides.

(3) Water will also interact with certain additives in the oil to produce precipitates and colloids, accelerating the deterioration of the oil.

(4) The interaction between water and sulfur and chlorine in the oil produces sulfuric acid and hydrochloric acid, which aggravates the abrasion and wear of the components, accelerates the oxidation and deterioration of the oil, and even produces a lot of oil sludge.

(5) These water pollutants and oxidation products will then become catalysts for further oxidation, which will eventually lead to blockage or jamming of the hydraulic components, causing a series of failures in the hydraulic system, blockage of the oil distribution pipe, reduced cooler efficiency, and blockage of the oil filter.

(6) In addition, at low temperatures, water condenses into tiny ice particles, which can easily block the gaps and dead mouths of the control elements.

2. Various impurity particles are mixed into the oil

Solid pollutants in oils mainly exist in granular form. Some of these impurities are residual during component processing and assembly, some are generated during working process, and some are caused by the invasion of external impurities. Their hazards are:

1. Various particle impurities in the oil can cause harm to the pump and motor. When impurity particles enter the gear end face of the gear pump or gear motor and the two end cover side plates, tooth tops and housing, or when impurity particles enter the blade and blade grooves of the blade pump or blade motor, the end face of the rotor and the oil distribution plate, the stator and the rotor (top of the blade), or when impurity particles enter the plunger and plunger cylinder holes of the plunger pump or plunger motor, the rotor and the oil distribution plate, the sliding pair of the variable mechanism, it may cause jamming failure. Even if it does not cause a jam, it will increase wear and tear. Impurity particles may also block the oil inlet filter in front of the pump, causing cavitation or causing multiple concurrent failures.

2. Various particle impurities in the oil can cause harm to the hydraulic cylinder. Particulate impurities will cause strain and wear of the piston and cylinder block, piston rod and cylinder head holes and sealing elements, increasing the amount of oil leakage, reducing the volume efficiency and effective thrust (tension force). If the particle impurities jammed the piston or piston rod, the oil cylinder would not move.

3. Contaminated particles in the oil can cause harm to various valve components. Polluted particles may cause the slide valve to get stuck or the throttling 121 to be blocked, causing the valve to fail. Even if there is no jam or blockage, the contaminated particles will cause the movement pair of the valve element to wear prematurely, increase the fitting gap, and deteriorate performance.

4. Pollutants reproduce bacteria, aggravate the aging of the oil, make the oil black and smelly, and further produce pollution.

Such a vicious cycle may have the following consequences:

(1) Pollutants block the oil filter, causing the oil pump to suck empty, causing vibration and noise.

(2) Pollutants increase the friction force of the oil cylinder or motor, causing crawling.

(3) Pollutants cause components such as servo valves that have poor anti-pollution ability to completely lose their function.

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

3. Oil invades air

The air in the oil mainly comes from loose pipe joints, intimate component joint surfaces, oil pipes exposed to oil surfaces and seal failure areas, and oil will also dissolve in the air when exposed to the atmosphere. 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 oil pump suction pipe 'eat oil' is not deep enough, which 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 to 0.50mm, which has a serious impact on the volumetric elastic modulus of the hydraulic oil in the hydraulic system and the viscosity of the hydraulic oil. As the pressure of the hydraulic system increases, part of it is mixed into the air-soluble hydraulic oil, and the rest still exists in the gas phase. When the amount of air mixed in increases, the volume elasticity coefficient of the hydraulic oil drops sharply, the propagation speed of the pressure wave in the hydraulic oil slows down, and the dynamic viscosity of the oil increases linearly. The air suspended in the oil combines with hydraulic oil to form a mixed liquid. The stability of this oil depends on the size of the bubbles and has a significant impact on the hydraulic system, etc. It may cause vibration, noise, pressure fluctuations, unstable hydraulic components, crawling, reversing impacts, inaccurate positioning or disordered movements, and it also increases power consumption, accelerates oil oxidation and reduces the lubricating performance of the oil.

Zhongshan Bada Machinery Manufacturing Co., Ltd. is one of the professional hydraulic machine manufacturers in my country. The company has key equipment such as large floor boring and milling machines, heavy lathes, milling machines and planing machines. It has advanced technology and equipment and can design and produce 2-12,000 tons of hydraulic machines.