Corrosion protection of Lianzhong equipment wind power generation equipment

Wind power equipment is a large complex, its stable operation is restricted by many factors, among which the failure caused by corrosion needs special attention.

        The main part of wind power equipment is in open air environment, and the impact of environmental climate is significant. The types of environment climate they face are mainly divided into: coast; Offshore; Grassland; desert. The corrosion of salt is especially prominent in coastal and offshore offshore conditions, and the resulting faults may occur in any part of the equipment, including the base, tower, motor, transmission system, control system, transmission system, etc. The first large offshore wind farm in the world, hosweifu, began to have technical failure in some of the wind turbine transformers and generators shortly after it was put into operation. Through technical analysis, it is generally believed that offshore climate conditions and salt erosion in air are important factors. Because of the bad influence of corrosion environment, it has great influence on the stable operation of equipment, and also makes the operation and maintenance cost rise.

        When wind power equipment is installed in desert and grassland area, the outdoor part of the equipment may be attacked by sandstorm, and it will also bring serious corrosion problems (wear and erosion), which threaten the normal operation of the equipment.

        In addition, the influence of stress can not be ignored. During the operation of equipment, some parts of the equipment are affected by constant or alternating stresses from various sources. These stress factors may cooperate with the environment, which will cause stress corrosion and corrosion fatigue problems, which seriously threaten the safe operation of the equipment. The huge temperature difference between day and night will also bring a series of corrosion problems to the equipment, which will cause equipment failure (for example, corrosion caused by condensation in the inner cavity).

        Wind power equipment is composed of steel materials, especially the bearing part is mainly steel. Steel structure has been widely used in various projects due to its advantages of light weight, high bearing capacity, good seismic performance and convenient construction and installation. However, the corrosion caused by this is also very serious, and corrosion has become an important factor affecting the safety of the structure. The economic loss caused by corrosion is also an amazing number. Some people have found that the annual loss caused by corrosion accounts for 5% to 6% of the national economy through investigation and analysis of 5 domestic industries. Corrosion protection experts in various countries generally believe that if we can understand the corrosion mechanism correctly and use the corrosion protection technology reasonably, the economic loss caused by corrosion will be reduced by 25% - 30%. For wind power equipment, it can directly ensure its long-term safe operation.

        Because the steel structure is exposed to the atmosphere, the main corrosion is atmospheric corrosion. The corrosion of metal in the atmosphere is mainly due to the simultaneous action of electrolyte liquid film formed on the metal surface and depolarizer in the air. When there is liquid electrolyte membrane, the anodizing process dissolves the metal, and the cathode reaction is usually considered as the reduction of oxygen.

         The steel structure under atmospheric environment is affected by sunshine, wind sand, rain and snow, frost and dew, and the temperature and humidity change in the whole year. Oxygen and water in the atmosphere are the important factors that cause the corrosion of outdoor steel structure, which causes electrochemical corrosion.

        Industrial gas contains SO2, CO2, NO2, Cl2, H2S and NH3. Although the content of these components is very small, the corrosion damage to steel cannot be ignored, among which SO2 has the greatest impact, and Cl2 can destroy the passivation film on the metal surface. These gases dissolve in water and are acidic, forming acid rain and corroding metal facilities.

        The marine atmosphere is characterized by a large amount of salt, mainly NaCl, which is deposited on the metal surface. Because of its moisture absorption and the increase of the conductivity of the surface liquid film, cl- itself has strong erosiveness, which aggravates the corrosion of metal surface. The closer the steel structure is to the coast, the more serious the corrosion rate is, many times higher than that in the inland atmosphere.

        According to the main influencing factors of carbon steel corrosion in the atmosphere, some people put forward the empirical formula of corrosion rate: M = 0.484t + 0.701w + 0.075h + 8.202s-0.022y-52.67, where m-carbon steel corrosion in the atmosphere, mg/ (DM2 · d);

       T - regional temperature, ℃;

       W - regional humidity,%;

       H-sea salt particle size, mg/l;

       S-so2, mg/ (DM2 · d);

       Y - precipitation, mm

       From the above analysis, it can be seen that the corrosion related factors for steel structures exposed to air are temperature, humidity, sea salt particle quantity (mainly chloride ion corrosion) and SO2 quantity. The data of 8 years natural exposure test of carbon steel and weathering steel in different areas of China are as follows（ µ m/a）：

 

City	Beijing	Qingdao	Wuhan	Jiangjin	Guangzhou	Qionghai	Wanning
corrosion rate	7-12	12-63	7-14	15-56	10-27	11-110	12-216

   

It can be seen from the above table that the corrosion of marine atmospheric environment is much greater than that of inland environment, and that in the south is larger than that in the north. It is generally believed that humidity (wet time), SO2 and chloride pollution are the most important factors in atmospheric corrosion. According to the international organization for standardization, the corrosion types are classified into the following categories according to iso12944 standard:

         Iso12944 - corrosion definition and environment (typical environment in temperature climate for reference only):

 

Corrosion type	mild steel		external	internal
	mass loss (g.m-2)	Thickness loss (μm)
C1 Very low	≤10	≤1.3		Heating the interior of buildings, clean air, such as offices, shops, schools and hotels
C2  low	10－200	1.3－25	Air pollution is low, mostly in rural areas	Condensation may occur in unheated places (e.g. warehouses / gymnasiums)
C3  median	200－400	25－50	Urban and industrial atmosphere, moderate sulfur dioxide pollution, low salinity coastal areas	Production places with high humidity and some air pollution, such as food factory, laundry, distillery, milk factory, etc
C4   high	400－650	50－80	High salinity industrial and coastal areas	Chemical plant, swimming pool, seaside and shipyard, etc
C5  －I very high（industrial）	650－1500	80－200	Industrial areas with high salinity and harsh atmosphere	There are always buildings and places with condensation and high humidity
C5 －II very high（ocean）	650－1500	80－200	High salinity coastal and inshore areas	Always in high temperature and humidity buildings or other places

     

The environment of wind power generation equipment in coastal area belongs to C4 and C5 classification in the above table, which is seriously corroded environment.

       Although the steel structure is one of the most industrialized engineering structures, it can not be denied that there are still defects and hidden dangers in the steel structure. There are still a lot of research topics about the material problems of the steel itself, as well as the weatherability, fire resistance and corrosion resistance. At the same time, a large number of accidents show that due to the high strength of steel structure components, the section used is relatively small, and it is easy to lose stability. Some people have summed up that the three hidden dangers of steel structure are instability, corrosion and fire. When we use steel structure, we should always be vigilant and take corresponding measures. The instability is generally caused by load change and support condition; Fire reduces the mechanical properties of materials; Corrosion is a chronic disease. The corrosion resistance of ordinary steel is poor, especially in the environment of high humidity and corrosive medium, it will rust quickly and weaken the bearing capacity of components. For example, the average corrosion rate of steel roof truss in converter workshop is 0.10-0.16mm per year. According to statistics, 30% - 40% of the annual output of iron and steel in the world fail due to corrosion, and the net loss is about 10%. According to the accident statistics of reinforced concrete roof truss, wood roof truss, steel wood roof truss and steel roof truss in China, 38.62% of the steel roof truss collapsed, and the corrosion and lack of maintenance accounted for a large proportion. Wind power equipment has been exposed to the open air environment for a long time, so we must pay enough attention to the possible damage caused by corrosion.

        Offshore wind farms may be the development direction of China's wind power industry in the future. Take Denmark as an example. Denmark is a leader in the field of wind power generation. At present, Denmark has the largest offshore wind farm in the world. For the sake of environment, Denmark only cares about the capacity of remote areas with water depth between 5 and 11 meters. The reason is that the selected areas must be outside the National Ocean Park, shipping routes, microwave channels, military areas, etc., and 7 to 40 kilometers away from the coastline, so as to minimize the visual impact on the shore. Recently, in-depth research on fan foundation shows that it is more economical to install a fan at a depth of 15 meters. In general, the output of offshore wind turbine is 50% higher than that of wind turbine near land, so offshore wind turbine is more attractive. According to the experience of Denmark, the design life of the equipment is set at 50 years. With the lower tower, the fatigue load is relatively small, but the threat of sea waves and sea water mist increases, and the protection requirements for the generator increase. On the other hand, because it is far away from the coast, it is difficult for the maintenance personnel to get close to the fan in bad weather conditions, and the fan can not be repaired and maintained normally, which causes potential safety hazards. Therefore, it is particularly important to ensure the high reliability of offshore wind turbine, and the comprehensive anti-corrosion effect of equipment is an important factor to ensure the high reliability.

        In order to ensure the normal operation of wind power generation equipment, we must pay full attention to the corrosion of the equipment, and put the anti-corrosion concept throughout the whole process of design, manufacture, installation, use and maintenance, so as to minimize the maintenance demand and ensure the efficient operation of the equipment.

        Therefore, the corrosion types of wind power generation equipment should be concerned mainly come down to: corrosion problems caused by seawater and marine climate; Erosion and wear caused by sand and dust; Stress chemical corrosion caused by stress factors.

         Although people have accumulated considerable experience in corrosion protection of outdoor, coastal and offshore large and medium-sized semi permanent structures and equipment, it is still insufficient for wind power generation equipment. In this field, in addition to its unique needs, high efficiency, low cost, long-term maintenance free should be pursued. Therefore, relying on the simple transplantation of anti-corrosion technology can not solve the fundamental problem, it is necessary to research and develop its own characteristics of proprietary technology.

         Based on the above aspects and the characteristics of wind power generation equipment, this paper puts forward the key problems to be further studied

       1. The corrosion / erosion behavior and failure mechanism of key materials and structures (such as base, tower, pulp sheet, motor, bearing, circuit structure, etc.) in corresponding environmental media (such as sea water, sea wave, coastal atmosphere, sand and dust climate, high and low temperature drastic change, etc.) are revealed, and the corrosion model is established, and the efficient corrosion / erosion resistant surface is proposed.

       2. Study the stress corrosion and corrosion fatigue behavior of corresponding key materials and parts, obtain key data, clarify the correlation between corrosion behavior and corrosive medium, and provide effective anti-corrosion countermeasures;

        3. The contact corrosion law of contact interface between various related materials and dissimilar materials such as metal structure and the connecting parts between parts, the occurrence conditions, failure causes, influencing factors and characteristics of various failure forms (including fretting wear, stress corrosion, plastic deformation, shear failure, thermal failure, etc.) are studied, and the theoretical model of comprehensive influence of thermodynamics, mechanics and electrochemistry is established, The principle of structural design and the mechanism and strategy of surface strengthening are discussed;

        4. The development of advanced and efficient anti-corrosion coating and plating principles and corresponding technologies should have the long-term effect of protecting against environmental medium corrosion (for example, 20 years, which should match the service life of equipment); Advanced and efficient stress corrosion protection technology; High efficient erosion resistant surface coating and plating technology; Efficient long-term moisture-proof sealing and insulation technology for internal space of equipment.

        The first, second and third points above should be combined with the equipment design, so that the anti-corrosion concept and measures can be implemented from the beginning of the design, and the overall anti-corrosion effect of the equipment can be guaranteed from the source.

        Wind power generation is an important way for human to obtain power in the future. In recent years, China has invested a lot in wind power, but the humidity problem of wind power is very serious. Our company cooperates with the largest wind power enterprise in China to develop special dehumidifier for wind power. And run successfully!

Product parameters

 

 

Model	LZ-200M	LZ-400M	LZ-600M	LZ-800M	LZ-1000M	LZ-1200M	LZ-1500M
Voltage	220V/50Hz			380V/50Hz
Dehumidification capacity	0.6kg/h	2.5kg/h	3kg/h	4.5kg/h	7.5kg/h	8.5kg/h	10kg/h
Treatment air volume	220m3/h	420m3/h	580m3/h	850m3/h	1100m3/h	1250m3/h	1550m3/h
Regeneration air volume	60m3/h	130m3/h	200m3/h	260m3/h	400m3/h	450m3/h	580m3/h
Maximum power	1.5Kw	2.3Kw	4.5Kw	6 .0Kw	11Kw	13Kw	15Kw
Operating power	1.2Kw	2.0Kw	3.8Kw	5.5Kw	9Kw	11Kw	13Kw
Electric current	7A	10A	20A	12A	18A	22A	26A
Applicable area	10-20m2	20-30m2	30-50m2	50-80m2	80-100m2	100-130m2	130-170m2
Explain	The above applicable area, floor height of 3M, dehumidification capacity test conditions:T=200C，RH60%
Functional features	1. Professional humidity controller controls equipment operation 2. Current environment humidity digital display 3. The imported proflute runner from Sweden is adopted 4. Low temperature application: - 100C to + 700C 5. The minimum humidity can be controlled at 10% 6. Humidity control range can be programmed freely 7. The humidity of air outlet can be as low as rh5% 8. Test condition of dehumidification capacity: T = 200C, rh60%