Status Analysis and Interpretation of Wind Protection Coatings for Wind Power in China

At present, most of the blades use epoxy glass fiber reinforced plastic or unsaturated polyester fiberglass as the main film-forming materials. These organic glass steels have excellent mechanical properties. The experimental data accumulated by various manufacturers shows that the blade life can reach 20 years completely without external factors. Therefore, how to minimize external erosion will be the key factor in determining the actual service life of the blade.

The normal operation of the blade may be subject to the following types of external erosion: the first is from ultraviolet light on the resin; the second is the erosion of the substrate by wind sand, floating dust, and rain and fog. In the first case, it is chemical erosion; the second kind of erosion is mechanical, and it is much more difficult for the coatings industry than the first one. The tip speed during the normal operation of the blade can reach 80m/s, which is equivalent to the maximum speed of the F1 race car. Sand or water droplets contained in the wind will have a strong impact on the blade surface. If the blade coating is resistant to sand or rain erosion, the protective coating will lose significantly within a few years and will not last for 20 years. Most of the blades of a foreign famous main engine plant installed in Inner Mongolia Wind Farm in 2006 have been seriously worn out (see drawing) and must be repaired. The reason why this happens is because the paint protection adopted does not take into account the erosion of wind and sand. As we all know, modern large-scale wind blades mainly originate in the Baltic Sea and the low-lying countries near the North Sea in Central and North Europe. They are strongly affected by the North Atlantic warm current, and are mainly warm and humid temperate maritime monsoon climates. Their wind source characteristics are high water content and sand content. And the amount of dust is extremely low. Their blade coatings will naturally use rain erosion as the main testing standard for blade coatings, and the main representative is Simens' enterprise standard for rain erosion detection. The detection principle is as follows: The paint is applied to the propeller, and then it is run at high speed, and artificial vertical rainfall is used to check the breakdown time of the coating.

The resistance to sand erosion and rain erosion have similarities in mechanism, but they also differ. What they have in common is that the coating must withstand high-speed particle impact for a long time, and the coating must have a certain degree of elasticity. The difference is that the sand has a rough surface and high hardness, which makes it easier to scratch the coating. Therefore, the sand-resistant coating needs not only elasticity but also high mechanical strength. Elasticity and mechanical strength can be quantified using elongation and tensile strength, respectively. As long as the coating can ensure these two characteristics at any time, and then have enough thickness, it can effectively resist the wind and sand mist in the blade during the operation of the process. However, the elasticity of the coating often changes drastically with changes in temperature. Many coatings with good elasticity at room temperature will become rigid at low temperatures, thereby greatly reducing the impact resistance. As far as wind fields in northwest China are concerned, the strongest season for wind and sand is precisely in the winter, which is one of the reasons for the heavy loss of blade coating on a certain wind field in Inner Mongolia.

It must be pointed out that the resistance to sand or rain erosion and the wear resistance are two totally unrelated concepts. The former mainly tests the vertical direction, taking into account the loss in the horizontal direction, while the latter only considers the horizontal direction. In fact, coating damage is mainly caused by vertical impact. Many rigid coatings have perfect wear data, but their resistance to wind sand is extremely poor.

At present, there is no authoritative standard for the resistance to wind and sand in the coating of blade coatings at home and abroad. However, in view of the severe current wind and sand damage, GL, the Chinese Ministry of Science and Technology, and some host plants have already started some exploratory work. Some of these work have already been applied. In the selection of coating materials, such as the national project in 2009, it was proposed to meet the GB2423.37 sand dust test method; Simens' enterprise standard for rain erosion resistance detection; a domestic famous machine factory began to use the sandblasting test last year. The method was tested as a reference for material selection; a foreign paint company made reference to the method of GB2423.37 and a complete machine factory when testing in China, and formulated a relatively clear experimental method in the case of blade operation: Accelerating experiments based on experimental national standards are based on the shear speed of the wind turbine blade in the actual use environment, which increases the impact velocity of the dust and the measured object of the national standard and the particles of floating dust, and stipulates the sand dust. The particle size and other test conditions also give a clearer evaluation method.

Through the process of formulating the technical standards for the foreign paint industry and the methods developed, it is not difficult for us to see that their method is based on the fact that users have fully considered the various operating environments, and the users and paint companies have jointly studied and discussed. , so their approach gives people a better sense of the application's needs. If our mainstream Chinese host companies can take a forward-looking vision to learn about people's management methods, our wind power industry may have to take a lot of detours.