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1¡¢ Introduction to PCCP pipeline
Prestressed concrete cylinder pipe (PCCP) is a new type of composite pipe, which is composed of steel plate, prestressed steel wire, concrete and cement mortar, after forming steel cylinder, pouring concrete, applying prestress control technology and spraying protective layer.
It is a kind of water pipe which is made by winding hoop prestressed steel wire on the high strength concrete pipe core with steel cylinder and spraying dense cement mortar protective layer on it. It is a composite pipe composed of thin steel plate, high strength steel wire and concrete. It gives full play to the tensile strength and easy sealing of steel and the compression and corrosion resistance of concrete. It has the characteristics of high sealing, high strength and high impermeability.
The production and application of prestressed concrete cylinder pipe has a history of more than 70 years. In 1939, the French Bonner pipeline company first designed and manufactured prestressed concrete cylinder pipe (PCCP). In the 1940s, Europe and the United States competed to develop PCCP. The United States is a country that produces and uses PCCP. Up to now, the United States has used 28 000 km PCCP with a large diameter of 7600 mm. In addition to the United States, PCCP has been widely used in more than ten countries in the Americas, Europe, Africa and Asia. In recent years, the most frequently used PCCP is Libya in Africa. The development and production of PCCP in China started relatively late, and it began in 1980s. Although the history of PCCP production and use in China is only more than 20 years, due to the favorable opportunity of rapid development of national economy and acceleration of urbanization process, through independent research and development, introduction of technology and equipment digestion, the products can be completely localized.
According to the statistical analysis of "2013-2017 China prestressed concrete cylinder pipe (PCCP) industry market outlook and investment strategic planning analysis report", the different positions of steel cylinder in the pipe core can be divided into two types: lined prestressed concrete cylinder pipe (PCCPL) and embedded prestressed concrete cylinder pipe (pccpe).
2¡¢ Characteristics of PCCP pipeline
PCCP pipe is a kind of high strength concrete pipe core with steel cylinder, wrapped with prestressed steel wire, sprayed with cement mortar protective layer, steel socket and spigot are welded together with steel cylinder. The socket has grooves and aprons to form a flexible joint of sliding rubber ring. It is a composite structure composed of steel plate, concrete, high strength steel wire and cement mortar, which has the respective characteristics of steel and concrete ¡£ It is suitable for large-scale water transfer projects between cross regional water sources, water supply and distribution network of water supply, industrial and agricultural irrigation systems, circulating water pipes of power plants, various municipal pressure sewage main pipes and inverted siphons, etc., which are widely used in the world.
Prestressed concrete cylinder pipe (PCCP) has the characteristics of reasonable composite structure, high internal and external pressure, good joint sealing, strong seismic capacity, convenient construction, good anticorrosion performance and convenient maintenance. It is widely used in long interval water supply trunk line, pressure inverted siphon, urban water supply project, industrial pressure water pipeline and power plant circulating water project Pipeline, pressure sewage main pipe, etc. Compared with the previous pipes, PCCP has the advantages of wide application range, long economic life, good seismic performance, convenient installation, low operation cost, and basically no water leakage.
3¡¢ Anti corrosion requirements of PCCP pipeline
It can be seen from the PCCP pipe structure that the inner and outer walls of the pipeline are made of concrete. Because the concrete is alkaline, it is not resistant to acid corrosion and chlorine dissociation corrosion, and the microorganism in the soil layer can also damage the concrete. Therefore, the PCCP pipeline must be treated with anti-corrosion before it is buried in the ground. The anti-corrosion coating must have the following characteristics to meet the anti-corrosion requirements of PCCP pipeline:
1.Due to the lack of compactness and impermeability of common coating, the corrosion medium will corrode the substrate through the coating in the process of use.
2. Aging resistance and durability
Because PCCP pipeline is usually used as buried pipeline, it has a long service life and is inconvenient to repair. Therefore, the anti-corrosion coating must have excellent weather resistance and aging resistance.
3. Resistance to chloride penetration and corrosion
Due to its small volume and high activity, chloride ion is easy to pass through the common coating and corrode the substrate. At the same time, chloride ions can catalyze some organic compounds and accelerate their aging process.
4. Conductivity
Electrochemical corrosion is one of the most important reasons for corrosion of buried pipelines. Now the cathodic protection method is usually used to prevent electrochemical corrosion. It is required that the coating has a certain conductivity to eliminate the electrochemical corrosion caused by corrosive medium.
5.Expansion coefficient
The expansion coefficient of the anticorrosive coating should be close to that of the substrate, so that the coating will not fall off from the substrate during the thermal expansion and cold contraction. This is a factor that must be considered when investigating the durability of anticorrosive coating.
6. Adhesion
The adhesion between anticorrosive coating and substrate should be strong, so that the coating will not fall off during long-term use.
Shandong Linyi Bosi conductive materials Co., Ltd. is a high-tech enterprise specializing in the production of MMO flexible anode, conductive polymer flexible anode and titanium coated anode, mainly providing corrosion protection, cathodic protection, engineering design, installation and technical services.