Current situation and development trend of hydraulic station oil

A hydraulic system is a complete set of devices that use oil as the working medium, transmit pressure through oil, and operate hydraulic actuators through control valves and other accessories. The hydraulic system is mainly composed of five parts, namely power components, actuating components, control components, auxiliary components, and hydraulic oil.

The power component refers to the oil pump in the hydraulic system, which can convert the mechanical energy of the prime mover into hydraulic pressure energy and provide power to the entire hydraulic system. The function of executing components, such as hydraulic cylinders and hydraulic motors, is to convert the pressure energy of liquids into mechanical energy, driving loads to perform linear reciprocating or rotary motion. Control components, namely various hydraulic valves, control and regulate the pressure, flow rate, and direction of fluids in hydraulic systems. Auxiliary components include oil tank, oil filter, oil pipe and pipe joint, sealing ring, quick change joint, high-pressure ball valve, rubber hose assembly, pressure measuring joint, pressure gauge, oil level gauge, oil temperature gauge, etc. Hydraulic oil is the working medium for transmitting energy in hydraulic systems, and currently commonly used types include mineral oil, emulsion, and synthetic hydraulic oil.

Hydraulic systems usually have the characteristics of small size and light weight, so the inertia force is small. When suddenly overloaded or stopped, there will be no significant impact; Capable of smoothly and automatically adjusting the traction speed within a given range, and can achieve infinite speed regulation; Easy to reverse direction, it can conveniently achieve the conversion between the rotation of the working mechanism and the linear reciprocating motion without changing the direction of motor rotation; The hydraulic pump and hydraulic motor are connected by oil pipes, and their spatial arrangement is not strictly limited to each other; Due to the use of oil as the working medium, the relative motion surfaces of the components can self lubricate, resulting in minimal wear and a long service life; Easy control and high degree of automation; Easy to implement overload protection.

However, during the operation of hydraulic systems, there are also the following issues: the use of hydraulic transmission requires high maintenance, and the working medium must always be kept clean; High precision is required for the manufacturing of hydraulic components, with complex processes and high costs; Hydraulic component maintenance is complex and requires a high level of technical expertise; Mineral oil working medium poses a fire hazard.

Hydraulic oil is the working medium that transfers energy, dissipates heat, lubricates, and inhibits corrosion, and is the "blood" of hydraulic systems. According to statistics, about 70% of hydraulic system failures are caused by hydraulic oil, which seriously affects normal production and work, resulting in significant economic losses. Therefore, it is particularly important to scientifically and effectively select, use, and maintain hydraulic oil. At present, there are various types of hydraulic oil, mainly divided into mineral oil type, emulsion type, and synthetic type according to their chemical composition.

Mineral oil hydraulic oil refers to hydraulic oil mainly composed of base oil extracted from petroleum through physical distillation method, with good lubrication and low price. However, mineral oil hydraulic oil is prone to combustion, has poor high-temperature performance, and low safety performance. Mineral oil has a high pour point and is not suitable for low-temperature operations due to the inability to remove impurities completely during the refining process. Mineral oil hydraulic oil has complex components, and its viscosity decreases and lubrication deteriorates at high temperatures, leading to the formation of sludge.

Emulsified hydraulic oil usually refers to water in oil or oil in water hydraulic oil. Due to the presence of water, it usually has a high flash point and ignition point. However, as water evaporates during use, its performance and quality will change accordingly.

Synthetic hydraulic oil is a hydraulic oil made by refining and processing compounds through chemical synthesis methods as the basic components, supplemented with various functional additives. Synthetic hydraulic oil has the following characteristics: it can meet the usage requirements that mineral oil or natural oil cannot meet, such as low temperature, high temperature, high load, high speed, strong oxidizing medium, and long life. Synthetic lubricating oil has a wide range of applications, and it can be said that any part that uses mineral oil can be replaced with synthetic oil. In addition, due to the special properties of synthetic oil that many mineral oils cannot match, some parts can only use synthetic lubricants.

As a type of synthetic hydraulic oil, synthetic ester hydraulic oil was developed in the mid-1930s. It is a lubricating oil prepared by organic synthesis methods and has a certain chemical structure and special properties. Synthetic esters have high flash point and ignition point, low evaporation loss, high viscosity index, strong corrosion resistance, good lubricity, and excellent adaptability to non-metallic materials. The organic biodegradation rate is 80% to 100% (according to CEC-L-33-AA) method, and the toxicity is extremely low. When replacing traditional mineral oil lubricants, there is no need to change the material of the system, which is harmless to human health and does not pollute the environment. It is a green lubricant that meets environmental protection requirements. Compared with mineral lubricants, it has a wide range of applications and can meet the increasingly stringent requirements of modern mechanical equipment for good lubrication, long oil change periods, and low energy consumption. Its price is higher than mineral lubricants, but it has excellent performance, long service life, and minimal mechanical wear. Therefore, synthetic esters have the most advantages as the base oil for mining lubricants.

At present, there are some synthetic ester hydraulic oil brands on the market, but there are still issues that need to be addressed regarding lubricity, stability, rubber compatibility, hydrolysis, and so on. To meet the requirements of modern industrial development for working media, as well as to meet performance requirements such as high temperature, high speed, high load, flame resistance, and environmental protection, it is particularly important to develop a new generation of synthetic ester hydraulic oils that are suitable for the national conditions. In the research process of synthesizing ester type hydraulic oil, how to further improve its flash point, ignition point, and high-temperature flame resistance performance is a topic of common concern among researchers. In addition, with the widespread use of lubricating oil, people will pay more and more attention to its impact on the environment, and researching environmentally friendly synthetic ester hydraulic oil will become an important development trend.