Created on:2022-04-06 09:11

Function and precautions of hydraulic oil during the use of concrete transfer pump

Function and precautions of hydraulic oil during the use of concrete transfer pump

Hydraulic oil is used as an intermediate medium in the hydraulic transmission system of concrete pump to transfer and convert energy. At the same time, it also plays the role of lubrication, anti-corrosion, cooling and flushing of various parts in the hydraulic system. Improper selection of hydraulic components will cause accidents or even reduce the safety of the whole hydraulic system.

1. Select high-quality hydraulic oil

The use of high-quality hydraulic oil is the key to ensure the normal operation of the system. The selection of hydraulic oil should be strictly controlled from the following aspects.

(1) Good wear resistance and lubricity. A large number of moving parts of the hydraulic system need lubrication to prevent the wear of the relative moving surface, good anti-wear and lubrication, reduce mechanical friction and ensure the service life of the main oil pump and motor. In particular, the pressure of concrete pump system is up to 32Mpa, which requires higher anti-wear performance of hydraulic oil. We choose the brand of anti-wear hydraulic oil yb-46.

(2) Good oxidation resistance. The temperature of hydraulic oil of concrete pump is required to be controlled at 30 ~ 60 ℃, and any higher temperature will greatly reduce the service life of hydraulic oil. When the temperature is too high, the oxidation process of hydraulic oil is accelerated, and the viscosity will increase after oxidation; With the extension of time, the formation of oxides increases, precipitates and blocks the filter, especially the plunger of the main oil pump, resulting in abnormal operation of the hydraulic system.

(3) Proper kinematic viscosity. Kinematic viscosity is an index of oil flow performance. Appropriate kinematic viscosity is the first factor to consider when selecting hydraulic oil. Under the same working pressure, if the viscosity is too high, the motion resistance of hydraulic components increases, the temperature rises faster, the self-priming capacity of hydraulic pump decreases, and the pipeline pressure drop and power loss increase; If the viscosity is too low, the oil film of sliding parts becomes thinner and the support capacity decreases, which can not guarantee the good lubrication conditions of mechanical parts, aggravate the wear of parts, and the system leakage increases, resulting in the decline of pump volumetric efficiency. After our long-term practical experience, yb-46 is generally selected as the hydraulic system of concrete pump, and the kinematic viscosity of hydraulic oil is 41.4 ~ 50.6 at 40 ℃.

(4) Good viscosity temperature characteristics. Viscosity temperature property refers to the degree that the viscosity of oil changes with the rise and fall of temperature, which is usually expressed by viscosity temperature index. The larger the viscosity temperature index, the smaller the decrease of oil viscosity with the increase of temperature, so that the internal leakage of the system will not be too large.

The working condition of the concrete pump is relatively bad. During the operation, the oil temperature of the system changes with the load and ambient temperature, so the viscosity temperature index shall not be less than 95.

(5) It has good compatibility with sealing materials and environment. Hydraulic oil will swell, soften and harden the sealing elements in contact with it, so that the sealing material will lose its sealing function. Hydraulic oil flows out of the hydraulic system due to leakage, seal failure and other reasons. If the hydraulic oil is incompatible with the environment, it will pollute the environment. Therefore, it is required that the hydraulic oil and sealing materials can adapt to each other.

(6) Good flame resistance. Hydraulic oil with good flame resistance shall have high flash point, ignition point and spontaneous combustion point.

(7) Good shear stability. During the operation of concrete pump, the change-over valve is changed frequently, and the main oil pump works continuously. When the hydraulic oil passes through the pump and change-over valve, it is subjected to severe shear, resulting in the breaking of some macromolecular polymers in the oil, such as the molecules of tackifier, into small molecules, reducing the viscosity. When the viscosity is reduced to a certain extent, the hydraulic oil cannot be used.

(8) Good demulsibility and hydrolysis stability. During the use of hydraulic oil, it is inevitable to contact with water and air. The oxidation of hydraulic oil produces corrosive acid, which destroys all hydraulic components and affects the normal operation of hydraulic system.

2. Judgment of hydraulic oil quality

After a period of use, the hydraulic oil may be polluted and the quality will change. Continued use will cause adverse damage to the system. Therefore, the hydraulic oil should be checked regularly. Whether the hydraulic oil is polluted can be judged by watching, smelling and simple test.

(1) Check whether the hydraulic oil is polluted. Drop a drop of hydraulic oil on the filter paper, the hydraulic oil diffuses rapidly, and there is no sediment in the middle, indicating that the oil quality is normal; If the diffusion is slow and there is sediment in the middle, it indicates that the hydraulic oil has been polluted and the oil quality has deteriorated; Take a thin metal sheet, heat it and drop a drop of hydraulic oil. If there is a burst phenomenon, it indicates that the hydraulic oil contains water. This method can test that the water content in the oil is more than 0.2%; Take a clean cotton ball, dip it in a little hydraulic oil, and then ignite it. If there is a "pop" sound, it indicates that there is water in the hydraulic oil.

(2) Judge by smell. Pungent smell indicates that the hydraulic oil is oxidized at high temperature; If the fuel is not clear, it indicates that fuel may be mixed.

(3) Judge by observing the color. The hydraulic oil is milky white and turbid, indicating that the hydraulic oil has been flooded; The hydraulic oil is dark brown, indicating that the hydraulic oil is oxidized at high temperature.

(4) Simple judgment of viscosity. Take a drop of two different hydraulic oils and drop them on an inclined clean glass to see which one flows faster, and its viscosity is lower.

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