Four Misunderstandings in Wind Turbine Gearbox Lubrication

August 6, 2015 Zhang Wei (Sea Xiaole)
In recent years, as the Chinese government has continuously strengthened its environmental remediation efforts, the investment in the wind power industry has continued to increase as a renewable energy source that replaces traditional high-energy, high-polluting coal-fired power generation. From 2009 to 2014, the average installed capacity of wind power increased by more than 17 million kilowatts per year, and the average number of newly added units was 10,798 units per year. By the end of 2014, the cumulative installed capacity of wind power in China had reached 141 million kilowatts, and the cumulative installed capacity reached 76,243 units. In the future, China's wind energy industry plans to increase the number of new units per year to about 10,000 units, and the newly added wind power installed capacity is about 20 million kilowatts. It can be said that the development is good and the situation is bright.
However, friends who often run the wind farm to maintain will find another situation. The operation stability of the newly installed domestic doubly-fed wind turbines in many wind farms across the country is not high, frequent failures, and high maintenance and maintenance costs. Among them, we have to pay attention to it as a misunderstanding of the mechanical failure of wind turbines. According to the 2014 American Gear Manufacturing Association AGMA, approximately 75% of the global industrial equipment failure rate is based on poor lubrication or faulty lubrication.
As shown in Figure 1 below, among the structures of mainstream gearbox wind turbines, the most important mechanical components requiring lubrication are as follows:

• main gearbox (speed increase box);
• Rotary spindle bearings;
• pitch bearings and drive reduction gearboxes;
• yaw slewing bearing and drive reduction gearbox;
• Coupling and brake parts;
• generator;
• Circulating hydraulic system; among them, the main gearbox has the largest amount of initial oil, and the initial gearing of different gear oils
From 200 liters to 800 liters, it is the most important part of lubrication and the most vulnerable part of lubrication failure. There are four misunderstandings that need to be corrected:
Misunderstanding 1. Passive oil bath lubrication is enough to meet the lubrication requirements of the main gearbox of the fan; traditional passive oil bath lubrication can only meet the lubrication requirements of the drive reduction gearbox with simple structure inside the fan, but it can not meet the more complicated structure. Lubrication requirements for a higher precision fan main speed increase gearbox. Therefore, it is necessary to gradually replace the traditional passive oil bath lubrication with active splash lubrication. Because active splash lubrication can effectively improve the permeability of the same type of gearbox oil and the heat dissipation effect of the transmission, the lubrication effect is better, and it is easier to wash away the frictional mechanical impurities on the gear meshing surfaces of each group and some corrosion after long-term operation. Sexual sticky gummy residue. However, this lubrication method needs to cooperate with a more efficient oil circulation system and a higher precision seal, otherwise it will easily cause gear oil leakage pollution.
Misunderstanding 2, the gear oil is full, neglecting the oil level ruler; if the gear is added to the main gearbox of the fan, if the filling is too full, in addition to the well-known oil body leakage pollution and gears caused by excessive lubrication The box is overheated, and more importantly, it will cause oil mist to be emitted under high temperature conditions, resulting in oil mist pollution inside the fan cabin with limited space. In addition, when the temperature in the cabin is lowered, the oil mist will settle on various mechanical and electrical components in the engine room, and when it encounters high temperature, it will easily cause electrical short circuit or even burning accident.
Misunderstanding 3, only pay attention to the viscosity index of the gear oil of the main gearbox of the wind turbine, but ignore the cleanliness index; because most of the wind farm has a large temperature difference, and the wind turbine works for a long time, many wind turbine manufacturers attach great importance to the wind turbine gear oil. The viscosity temperature index, in order to maintain good physical and chemical stability, viscosity and low temperature fluidity under high and low temperature conditions, thus achieving design lubrication requirements. However, many manufacturers have neglected the cleanliness index of the main gearbox gear oil. The cleanliness of the oil body can directly affect the amount of corrosive colloidal impurities produced by the oil under high temperature working conditions, and can also directly affect the clean dispersibility of the oil body under low temperature conditions, thereby indirectly affecting the oil body. Free acid and alkali and sludge production. At present, most of the gearbox oil supplier's fan main gearbox full synthetic gear oil NAS cleanliness is roughly in the range of 8~10, but this range is for oils with viscosity less than 100 (such as No. 46 anti-wear hydraulic oil) ) is effective, but for higher viscosity gear oils (such as No. 150, No. 220, No. 320 gear oil), this cleanliness range value does not effectively ensure that the fan gear oil does not clog in long-term maintenance-free applications. Therefore, increasing the NAS cleanliness range of the fan gear oil to 5-6 will effectively reduce the oil filter clogging alarm and the accumulation of sticky gelatinous impurities on the filter element and filter cartridge surface, and can also effectively improve the long-term oil product. The stability after use reduces the corrosion of corrosive sludge to the metal material inside the gearbox and the paint surface. All in all, oil cleanliness is not only an important indicator that affects the long-term use of oil, but also an important reference indicator that indirectly affects oil deterioration and viscosity.
Misunderstanding 4, is the clearer and transparentr the main gearbox oil after long-term use? Gearbox oil is like a blood circulation in the human body. The blood itself is a very effective body cleanser. From arterial blood circulation to venous blood, doctors will tell us that venous blood is generally darker than arterial blood. Because arterial blood is like gear oil that has just been loaded into the gearbox of the fan, it has high cleanliness and strong oxidation resistance. However, after circulation through the body, the venous blood contains many oxidizing substances and harmful impurities, which are filtered through liver and kidney. Detoxification of organs will remove harmful substances from the body. Gear oil also needs to have better cleaning ability. It can burn the mechanical impurities generated after long-term operation inside the gear box. Various oxides and chemical accumulations are washed out from the metal surfaces of the gears and bearings to prevent them from running on these friction pairs. Causes abnormal wear and corrosion. Therefore, if the gear oil sample after long-term use is very clear, it does not indicate that the oil has better performance. On the contrary, it may be that the oil has poor cleanability and lubricity. Therefore, it is better to combine the used acid pH and neutralize. The value and viscosity are more accurate than the relevant factory reference values for the new oil and the PQ impurity content.