Cast iron is the main material of the buried pipeline system used for transporting water in the fire protection system of nuclear power stations around the world. Why is cast iron popular in the nuclear power industry? Cast iron pipes have lots of benefits and advantages.
1. Excellent corrosion resistance
According to common sense, people will think that cast iron pipes will rust and have less corrosion resistance than plastic pipes, which is caused by misunderstanding and misleading propaganda. In fact, the corrosion resistance and aging resistance of cast iron drainage pipes are irreplaceable by other chemical pipes. Cast iron drainage pipe is made of gray cast iron. Gray cast iron is different from ordinary steel, and its carbon content is generally 2.5% – 4%, and all or most of the carbon exists in the structure of gray cast iron in the form of free graphite. The volume of this part of free graphite carbon accounts for about 10% of the gray cast iron. During the corrosion process, the iron element on the surface of the cast iron is corroded, and the insoluble graphite layer is left behind. This layer of graphite remains firmly attached, strong and dense, and becomes a protective layer against further corrosion on the surface of the casting. Ordinary steel has low carbon content and does not exist in the structure in the form of free graphite. It cannot form a graphite protective layer and has poor corrosion resistance, which is why gray cast iron drainage pipes have excellent corrosion resistance.
2. Excellent aging resistance
Unlike polymer chemical pipes, cast iron drainage pipes will not have material aging problems with the extension of service time, the change of temperature difference, and the exposure to sunlight, and have a long service life. At present, many building exterior wall rainwater pipes in China use plastic pipes, which will soon age and crack with the seasonal temperature difference and the sun exposure. Even if steel pipes are used, their corrosion resistance cannot meet the requirements. However, cast iron drainage pipes have unique advantages in aging resistance and corrosion resistance and are the best choice for exterior wall rainwater pipes.
3. Excellent strength and wear resistance
The tensile strength of cast iron drainage pipes is generally greater than 150MPa, 3-4 times the strength of PVC and other chemical drainage pipes. It has good compressive strength during the construction of buried pipes and can prevent the penetration of tree roots and the gnawing damage of rodents. The excellent strength and wear resistance of cast iron drainage pipes make them better able to resist the impact and abrasion of sediment, gravel, glass debris, ice particles, and food residues in sewage and rain, and ensure the reliability of the drainage system under various adverse conditions.
4. Excellent mute performance
As we all know, cast iron drainage pipes are excellent silent pipes. On the one hand, due to the dense structure of gray cast iron and its unique flaky graphite structure, it can effectively absorb the energy generated by vibration and greatly reduce the transmission of noise. On the other hand, at present, cast iron drainage pipes are mostly connected with rubber-sealing interfaces, which can effectively block the transmission of water flow and sound in the pipes. The research has proved that the efficiency of the flexible cast iron drainage pipe to block noise transmission is 7.5 times that of other chemical pipes, and the noise used in the drainage system is 6-10 decibels lower than that of PVC pipes. This is the reason why plastic drainage pipes often hear large water flow noise, while cast iron drainage pipes are very quiet when used for drainage.
5. Excellent fire resistance
Cast iron pipe system has many advantages over other alternative materials in terms of fire resistance structure. Cast iron pipe is non-combustible and has two obvious advantages in case of fire: first, it can prevent fire spread, then avoid the toxic gas generated by the burning of plastic pipes, which endangers the lives of residents and firefighters.