From the aerospace field, aircraft design to mining, seabed oil field exploitation, the application range of hydraulic pressure is really wide and deep. The use of hydraulic pressure in construction machinery such as roller and excavator can complete the "vigorous work" which is beyond human power in high rescue and fast. Although machine tools and controllers at the Atomic Energy Research Institute can perform a certain level of power work, they still use hydraulic pressure to control work similar to the human nervous system. Although at present compared with mechanical, electrical and pneumatic machinery, hydraulic mechanism is expensive. However, more and more high power, special structure and cheap hydraulic mechanism. Generally speaking, the price of hydraulic mechanism is higher, but it has the advantages of easy use, low maintenance cost, good safety and so on. Large hatches are provided on the decks of cargo ships for easy loading and unloading. The hatch must be sealed by watertight, airtight doors in navigation. The closed device, the hatch cover, is usually 20t or 30t. Before the Second World War, it was time-consuming and difficult to lift and close hatchcovers by crane. Cargo ships now use hydraulic cylinders, hydraulic motors and hydraulic torque hinges to fully open and close the hatch doors.Equipped with hydraulic hatchcovers, ships need to be built 5% or 6% more expensive. However, given the savings in port and cargo costs, the extra cost of construction could be offset in a few years, and the crew's labor would be significantly reduced. So if equipped with a huge hatch cover, the first thing to consider is whether to use hydraulic lifting instead of a crane. This is an instance where hydraulic pressure has to be used. There are many similar applications on land and in mine-related enterprises. The higher the degree of need for hydraulic device, the faster and wider its application. If only "ease of use" is considered without in-depth consideration of equipment costs and maintenance costs, the hydraulic device used in this case is contrary to the example of hatch cover, which is difficult to popularize this kind of machinery and equipment.

(1) Appropriate viscosity and good viscosity-temperature characteristicsExcessive viscosity will lead to increased viscous resistance loss. Temperature rise; The suction of the pump can become worse, starting difficulties, and even cavitation; Control sensitivity decreases. Too low viscosity will increase leakage and reduce volumetric efficiency; Control accuracy decreases; The liquid lubrication film becomes thinner, and even can not form liquid lubrication and aggravate the wear.The viscosity index of hydraulic oil can be increased by adding the viscosity index additive to improve the viscositic-temperature characteristics. Such as polyisobutene, polymethacrylate, etc.(2) Good wear resistance (lubricity)Wear resistance is a property that reduces wear independent of viscosity by adding an additive to the oil to form an oil film on the dual surface of the friction pair. High viscosity does not necessarily have good lubrication performance, such as silicone oil, but if the viscosity is low, the liquid film is too thin to cover the surface roughness, and the wear resistance is not good, such as water.By adding oil additives (oleic acid, sulfide whale oil and sulfide olefin cotton oil, etc.) and extreme pressure anti-wear additives (containing phosphorus, sulfur, zinc and other substances, such as zinc dialkyldithiophosphate, molybdenum disulfide, etc., can be used at high temperature and heavy load), the hydraulic oil is formed on the metal surface of the physical or chemical adsorption film, this film is also called the boundary film, The boundary film forms the boundary lubrication between the friction pairs and prevents the matrix from contacting directly, which is conducive to reducing friction and wear.(3) Good oxidation stability and thermal stabilityOxidation stability refers to the ability of oil to resist oxidation. The oil is affected by heat, oxygen in the air, water and metal substances will oxidize and generate organic acids and polymers, the color of hydraulic oil becomes darker, the acid value increases, the viscosity changes and the formation of precipitating substances (tar), so the corrosion of hydraulic oil increases, the blockage of the small holes of hydraulic components and the intensification of wear.Thermal stability refers to the ability of oil to resist chemical reactions and decomposition at high temperatures. The high temperature of the oil will accelerate the cracking and polymerization, and the metal surface also acts as a catalyst. So the hydraulic oil must withstand a certain high temperature, while avoiding working at extremely high temperatures.The oxidation stability and thermal stability of hydraulic oil are generally improved by adding antioxidants.(4) Good emulsification resistance and hydrolysis stabilityThe ability of oil to resist mixing with water to form an emulsion is called anti-emulsification. The ability of oil to resist chemical reactions with water to decompose is called hydrolytic stability.Water is a pollutant in the hydraulic system. It is brought into the system by moist air from the breathing hole in the tank or by retracting the cylinder rod. Hydraulic fluid has water absorption, which depends on the properties of the base oil, additives and temperature. After intense agitation, the water in the oil is easy to precipitate and form emulsion with the oil. At this time, the water exists in the continuous phase of the oil in the form of tiny dispersed water droplets.Water can cause corrosion, accelerate oil deterioration, break oil film and reduce lubrication of hydraulic oil. Adding demulsifier (petroleum sulfonate, a surfactant) can improve the anti-emulsification property of hydraulic fluid.(5) Good bubble resistance and air releaseThe ability of hydraulic fluid to resist combining with air to form foam is called foam resistance. The ability of hydraulic fluid to release air dispersed within it is called air release.The elastic modulus of oil decreases due to air. Dynamic performance decreases; Cavitation, vibration and noise; Lubricating oil film fracture, aggravate friction and wear.Add defoaming agent (dimethyl silicone oil)(6) Good corrosion resistanceOxygen, water, various additives in the air of hydraulic oil and hydraulic oil oxidation and decomposition of acid substances may produce corrosion on the metal surface, aggravate wear.Add anti-rust agent (dodecene succinic acid, etc.)(7) Good shear stabilityThe ability of hydraulic fluids to resist shear and retain viscosity and viscomet-related properties. Through the small holes, gaps and other narrow channels in the hydraulic components, by strong shear action, so that the oil viscosity decreases.(8) Compatibility with sealing materialsThere is no mutual damage between the medium and the sealing material. It mainly refers to the contact between hydraulic oil and seals, without damaging the seals and reducing the sealing performance of the seals. The medium may cause the sealing material to swell, soften and harden. For example, the influence of mineral oil type hydraulic oil on polyurethane rubber is small, but the influence of water-based refractory liquid on polyurethane is great.(9) Compatibility with the environment and product (the weakness of mineral oil)(10) fire resistance (flash point, ignition point should be high, fire prevention, explosion-proof) such as aircraft, tanks, ships, steel rolling, smelting, mining and other fields.

First, how to check the pressure loss of the hydraulic station system.The pressure loss of hydraulic station system occurs in many places. It is necessary to check the total pressure loss of hydraulic station pipeline system.Two, the hydraulic station system heating temperature rise calculationHydraulic station system in the operation of a variety of mechanical losses, pressure losses and flow losses, these losses are mostly converted into heat energy, so that the hydraulic system heating, oil temperature rise, resulting in hydraulic system leakage increase, moving parts action failure and other adverse consequences.

Hydraulic station maintenance has several important points:1. Keep the hydraulic oil clean. Dirt in the hydraulic fluid can damage parts of the system.2. Keep the oil quantity in the hydraulic station. There is less oil in the hydraulic station, and air will enter, making the hydraulic system run abnormally.3. Pay attention to whether there is oil leakage in hydraulic equipment. Oil leakage indicates that the seal is broken, not to be replaced in time, not only costs oil, but also makes the output decline, serious do not act.4, familiar with the sound of hydraulic system operation. The sound of normal and faulty is different. When you hear the different sound of hydraulic equipment, you will know that there is something wrong. Remove it in time to avoid the small hairy lesions from eating large damage and causing large losses.5. Pay attention to check whether the tight parts are loose. Keep it effectively tight.Also note:1, hydraulic oil should pay attention to temperature, too high easy to reduce the service life2, but also pay attention to the filter of oil, clean the tank regularly and check the filter net3. Pay attention to exhaust the system when using the hydraulic station.