Industrial Lubrication｜Development and Application of Synthetic Industrial Gear Oil
February 19, 2022
Summary: With the development of industrial gear equipment and the evolution of industrial Gear Oil specifications, the requirements for gear lubrication continue to increase, and the advantages of synthetic industrial gear oils are increasingly apparent. This paper analyzes the development status, performance characteristics and typical applications of synthetic industrial gear oil, and points out that the application of synthetic industrial gear oil will become more and more extensive in the future. Industrial gear oil is widely used in closed gear devices in metallurgy, mining, metal processing and other industries. With the development of science and technology and industrial production, gear transmission is developing in the direction of small size, light weight, high speed and heavy load and high power. For this reason, the oil used in gears is required to have a wider operating temperature, better extreme pressure and anti-wear properties, better anti-friction and energy-saving properties and longer service life. Synthetic industrial gear oils blended with base oils such as polyalphaolefin (PAO), synthetic ester, and polyether (PAG) can just meet these requirements and have been widely used in steel, cement, wind power and other industries. This paper briefly introduces the development status, performance characteristics and applications of synthetic industrial gear oils. 01 The development trend of industrial gear oil The improvement of gear box manufacturing technology and the evolution of industrial gear oil specifications are the two major factors affecting the development trend of industrial gear oil. 1.1 Development of Industrial Gear Equipment With the rapid development of the gear industry, industrial gearboxes are developing in the direction of greater power, higher load and smaller volume, and the working environment is humid. The increase in the load increases the contact pressure of the tooth surface and the wear and pitting between the metal and the metal; the smaller volume of the gearbox means that less oil is used to lubricate the gears and bearings, which will cause the oil temperature to increase. Elevation accelerates the oxidation of oil products, and the sludge produced by the oxidation process will shorten the service life of oil products and gearbox components; wet working conditions will lead to increased bearing corrosion, resulting in increased equipment maintenance and replacement costs. As an important part of gear design, industrial gear oil has also put forward higher requirements in terms of anti-wear performance, bearing capacity, anti-pitting performance and oxidation stability with the development of gear equipment. Traditional CKC and CKD series can no longer be used. However, synthetic industrial gear oils have received extensive attention due to their good viscosity-temperature characteristics, excellent oxidation stability, excellent friction characteristics and long oil drain intervals. At the same time, with the development of industrial gear equipment, the specifications of oil products have also changed.
1.2 Evolution of Industrial Gear Oil Specifications The AIST 224 standard of American Steel Corporation has always represented the highest specification of industrial gear oil. The quality of L-CKD gear oil in the national standard "GB 5903-2011 Industrial Closed Gear Oil" formulated by my country has reached this standard. In addition, the commonly used industrial gear oil specifications include the national standard ISO 12925, the North American AGMA 9005-E02 EP, and the European DIN51517-3. The extreme pressure properties, rust and corrosion resistance, anti-emulsification properties and oxidation stability of industrial gear oils are the common requirements of these specifications. In addition to the above specifications, an important trend in the development of industrial gear oils is the increasing influence of OEMs on changes in gear oil specifications. Generally speaking, these OEM specifications often require certification, and the certified oil can be recommended by the OEM manufacturer. Oil specifications proposed by important foreign OEMs (including bearing manufacturers, gearbox manufacturers and equipment manufacturers) include Flender specifications from SIEMENS; David Brown S1.53.101 specifications from David Brown; Cincinnati Milacron specifications from Cincin-nati Machine, etc. Among them, the most influential is the Flender specification, which requires the oil to pass the FZG micropitting corrosion test, the Flender anti-foaming test, the coating material compatibility test, and the phase of the liquid sealing material on the basis of meeting DIN51517-3. Capacitive Test, Shaft Seal Rubber Compatibility Test and Flender Filtration Test. Flender specifications are generally considered the most demanding in the wind power industry, and most wind turbine OEMs want to use Flender-certified oils. 1.3 Status Quo of Synthetic Industrial Gear Oil Judging from the development of the above-mentioned industrial gear manufacturing and industrial gear oil specifications, in addition to good tribological properties, the future industrial gear oil should also meet the requirements of energy saving, environmental protection and safety as much as possible. Table 2 lists a comparison of synthetic industrial gear oil products from major lubricant companies. From the perspective of Base Oil types, the synthetic industrial gear oils introduced by major companies are the most widely used synthetic base oils such as poly-alpha-olefin (PAO), synthetic ester, and polyether (PAG). Type industrial gear oil is mostly used in severe working conditions such as high load, extremely high temperature or extremely low temperature. It has excellent lubricating properties and can provide optimal protection for gears.
02 Application of three types of synthetic base oils in industrial gear oils
2.1 Application of PAO in Industrial Gear Oil The early PAOs were mainly used in the military industry, and it was not until the late 1980s that PAO lubricants began to gain large-scale applications with the significant growth in market demand and the advancement of civilian technology. In terms of preparation methods, foreign companies mainly obtain α-decane through ethylene copolymerization, and then obtain PAO base oils with different viscosities through catalytic oligomerization and hydrogenation saturation. Due to the high purity, high catalytic activity and selectivity of α-decene, and the process conditions are easy to strictly control, its product performance is better than that of PAO products prepared by wax decomposition, fractional distillation and repolymerization, mainly manifested as high viscosity index, Good low temperature performance and good thermal oxidation stability. In addition to the viscosity index of PAO is higher than that of class III base oil, its outstanding features are its low pour point and low temperature fluidity, which is much better than that of class III base oil. In addition, PAO has the advantages of excellent oxidative and hydrolytic stability, low volatility, and good compatibility with mineral oils. PAO-type synthetic industrial gear oil products, such as Kunlun KG/S fully synthetic heavy-duty industrial gear oil series, have achieved better performance in gear boxes under high load, extreme high and low temperature and severe corrosive environments in the paper, steel, cement and other industries. more and more applications. 2.2 Application of synthetic ester in industrial gear oil It advocates a deep understanding of students while teaching, with the aim of cultivating students to grow and become talents, and to teach students to be upright and moral, and to be confident. 2.3 Application of PAG in Industrial Gear Oil PAG is a linear polymer obtained by ring-opening homopolymerization and copolymerization of ethylene oxide, propylene oxide, butylene oxide and other raw materials under the action of a catalyst. PAG base oils have a very low coefficient of friction, excellent lubricity, very high viscosity index, excellent low temperature fluidity and excellent thermal and oxidative stability. However, PAG type lubricating oil is not compatible with mineral type lubricating oil, some paints and varnishes, it is necessary to clean the lubricating system during use, use fluororubber or nitrile rubber seals, and use epoxy resin paint or no coating inside the lubricating system. paint. Due to its low coefficient of friction, PAG-type industrial gear oils are suitable for the lubrication of gear pairs with many sliding forms, especially turbine and hyperbolic gears. Almost no residues, gums and other deposits are produced during the lubrication process, which can ensure the cleanliness of the lubrication system, reduce the blockage of the lubrication system pipelines and precision valves, and effectively prevent the equipment from low oil level or no oil caused by the above reasons. Equipment damage due to lubrication. PAG-type industrial gear oils, such as Kunlun Synthetic Elevator Oil, are designed for worm gears, especially for heavy duty, harsh operating environments. To sum up, the three types of synthetic base oils have different properties and different application ranges. Polyalphaolefin (PAO) is often used in gear lubrication under extreme working conditions because of its good oxidation stability and low temperature fluidity; synthetic esters are mostly used in biodegradable gear oils because of their good biodegradability; Polyether (PAG) is mostly used for the lubrication of worm gears due to its low coefficient of friction. 03 Application range of synthetic industrial gear oil At present, the use of synthetic industrial gear oils can be roughly divided into three categories. (1) Synthetic industrial gear oil must be used to meet harsh operating conditions, such as wind power gear oil. (2) The gear oil discharged after use is required to be biodegradable, such as marine gear oil. (3) In the case of harsh working conditions, although the use of traditional mineral gear oil can meet the requirements to a certain extent, if the use of synthetic industrial gear oil can immediately reflect the incomparable advantages of mineral gear oil, such as elevators, Gear oil for steel, cement, paper and other industries. 3.1 Oil used in wind power industry The operation of wind power equipment has different characteristics from the operation of other equipment. First of all, wind turbines are usually located in remote inland or coastal areas with abundant wind energy. The natural environment in these areas is relatively harsh, and the temperature difference between day and night is large. Wind turbines located in coastal or offshore areas are also affected by environmental factors such as humidity and seawater corrosion; Secondly, the operation of wind turbine gearboxes is characterized by low speed, high torque, and unstable load; thirdly, the main lubricating components of the wind turbine are located in the pods more than 30 meters above the ground. If the components are damaged due to lubrication failure, the Repairs and maintenance are very high; finally, the compatibility of the gear oil with the elements of the lubrication system such as paint, seals, etc. must be considered. Based on the equipment operating characteristics of wind turbines, wind turbine gear oils are mostly synthetic oils, and PAO-type synthetic gear oils are the main ones. 3.2 Marine degradable gear oil In March 2013, the US Environmental Protection Agency (EPA) mentioned in the latest revision of the VGP (vessel general permit) that from December 19, 2013 onwards, equipment that may come into contact with seawater on commercial ships sailing in US waters The oil products used must be environmentally friendly products, mainly involving industrial gear oil, hydraulic oil, etc. Currently, most of the base oils for biodegradable industrial gear oils on the market are synthetic esters. From the current development trend, synthetic esters are considered to be the most ideal base oils for biodegradable lubricating oils. This is because it has the following advantages: excellent lubricity; excellent high temperature stability and low temperature volatility; good viscosity-temperature properties; good biodegradability; good oxidation stability, etc. In addition, synthetic esters also have the advantages of being mutually miscible with mineral oils and most synthetic oils and additives. 3.3 Oil used in elevator industry For toothed elevators, the role of the traction machine lubricating oil is to reduce the heat generated by the gears during the transmission process, play a role in heat dissipation, ensure that the gears are fully lubricated, reduce friction, and achieve the purpose of improving the transmission effect and bearing capacity. In recent years, with the miniaturization of elevator traction machines, the continuous increase of extreme pressure loads and the continuous growth of high-speed elevators, elevator traction machines have been operating in a high temperature environment above 100 ℃ or even 130 ℃ for a long time. It is difficult to withstand long-term products, and the synthetic elevator traction machine lubricating oil uses chemically synthesized polymer compounds PAO and PAG as the base oil, which has a single molecular structure, neat, narrow distillation range, few impurities and good detergency. With special additives, it is of great help to improve the performance of elevator oil. The initial installation and designated oil of international brand elevators mostly use PAO type or PAG type synthetic gear oil. 04 Concluding Remarks In the future, the development of industrial gear oil will face many challenges, and meeting the comprehensive requirements of energy saving, environmental protection and long life will become the mainstream of gear oil development. With the advancement of synthetic lubricating oil technology, the advantages of synthetic industrial gear oil will become more and more obvious, and the application in various fields will be more extensive.
