Ductile Iron Pipe

Why Ductile Iron Pipe

        Why would you choose ductile iron pipe rather than other pipe materials? The reasons are obvious for that not only ductile iron pipe possesses the inherent strength and flexibility of ductile iron, combined with proven corrosion protection systems, but also the cost savings can be achieved from design to installation and commissioning.

        Ductile iron is produced by treating molten low-sulfur base iron with magnesium under closed controlled conditions. In ductile iron, the graphite exists in the form of spheroidal shape, which has little influence on weakening the matrix and resulting in centralizing strain, so ductile iron possesses good flexible property. While, in grey iron, the graphite is present in flake form, which has the effect of cutting the iron matrix and making it become brittle and easy to crack.

Remarkable Mechanical Properties of ductile iron
        The mechanical properties of ductile iron are markedly superior to those of grey iron and approaching the properties of steel. Ductile iron possesses the nature of iron and properties of steel. The much improved properties were recognized to be of particular benefit in the centrifugal pipe industry and as such most of the pipe production now in ductile iron.

        Documents relevant to earthquakes show that the damage rate per kilometer for ductile iron pipe mains is one quarter of that for grey iron and one thirteenth of some other materials of pipes.

Advantages of Ductile Iron Pipe

♦  Ductile iron pipe possesses excellent mechanical properties. It has the tensile strength, yield strength and    module of elasticity that are comparable with steel pipe.

♦  Ductile iron pipe has high corrosion resistance. Ductile iron pipes are lined with cement or resins, and coated with bitumen paints, which solves the problems of internal and external corrosion that grey iron pipes and steel pipes can not solve. Therefore, the users don’t have to take any anti-corrosive measures. It also prevents secondary pollution to the water quality.

♦  The joints are flexible and have good adaptability. The connections of ductile iron pipes are push-on joints or gland mechanical joints with rubber gaskets, and have good leak tightness and ductility. No welding is required. The designed deflection is 3~5 °, so the number of fittings required can be reduced. The joints can absorb the stress caused by foundation settlement and prevent pipe rupture.

♦  Easy to assembly. Ductile iron pipe installation is convenient and not  subject to weather conditions. The installation does not need sophisticated equipments and workers do not have to be highly professional.

♦  The pipes satisfy the highest hygienic standards. Drinking water and ground water are protected by pipe walls which seal against diffusion. The pipes are resistant to extremely high internal pressure.

♦  The service time is up to 50 years, with the material properties unaffected.

♦  High load-bearing capacity.

♦  Ductile iron pipes are environmentally-friendly. Pipes are sustainable and recyclable, and the materials used are inorganic.

♦  Both deep and shallow top covers are possible. The pipes are suitable for all soils and laying methods.

Economic advantages.

No need for change of soils or additional bedding for the pipes, and the soils excavated can be re-used.

Major savings of time and money, because the soil excavated does not have to be taken away.

Anti-Electrolytic Performance

General Principle of Electrolytic Corrosion
Corrosion can occur due to differences in the electrolyte. These differences   may be in soil resistivity, oxygen concentrations, moisture contents and various ion concentrations. The variations produce current flow from one location, through the electrolyte, to another portion of the same metallic structure. In the case of electrolytic corrosion, the external man-made current generates corrosion.

Anti-Electrolytic Corrosion of Ductile Iron Pipes
Due to the large electric resistance, ductile iron pipes are not easily subject to electrolytic corrosion. The gaskets for ductile iron pipes with mechanical joint are insulated; therefore it is no need to worry about the electrolytic corrosion. The electric resistance of ductile iron and steel are as follows: