|Infobox on Cast-iron Pipes|
|Example of Cast-iron Pipes|
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|Risk factors||See text|
Cast iron pipe is a pipe which has had historic use as a pressure pipe for transmission of water, gas and sewage, and as a water drainage pipe during the 19th and 20th centuries. It comprises predominantly a grey cast iron tube and was frequently used uncoated, although later coatings and linings reduced corrosion and improve hydraulics. Cast iron pipe was superseded by ductile iron pipe, which is a direct development, with most existing manufacturing plants transitioning to the new material during the 1970's and 1980's.
Cast iron is an iron and carbon alloy containing between about 2% to 4% carbon and, similar to steel, it also contains small amounts of manganese, sulphur and phosphorus, but is higher in silicon content. Its high carbon content makes the metal very brittle so that it cannot be rolled or forged. Therefore, it is cast in moulds by pouring the molten metal. Cast iron is hard and durable, and some of the uses to which it is suited are the manufacture of pipes, iron baths, machine parts and stoves etc. This material rusts less easily than forged iron and steel.
Most of the old cast Iron pipes are cast vertically but this type has been largely superseded by spun iron type manufactured up to a diameter of 900 mm. Though the cast iron pipe has the disadvantages of heavy weight, and consequent high transport costs, short length, leading to higher laying and jointing cost, low tensile strength, liability to defect of inner surface, it is widely used because of its good lasting qualities. There are many examples of cast iron mains which continue to give satisfactory services even after a century of use. Due to its strength and corrosion resistance , C.I pipes can be used in soils and for water of slightly aggressive character. They are well suited for pressure mains and laterals where tapping are made for house connections. It is preferable to have coating inside and outside of the pipe.
Compared with plastic (PVC) pipes, cast iron pipe is more solid and durable. Furthermore, cast iron pipe has excellent noise suppression and fire resistant characteristics, and can be completely recycled.
Shipment / Storage / Risk Factors
Cast-iron pipes are usually unprotected.
Liable to breakage by rough handling. Pipes with a bell or flange end are most often broken or cracked on the straight or spigot end, and, when this occurs, the damaged portion may be cut off and sold as scrap while the remainder of the pipes may be salved as sound short lengths.
An investigation into the cause of unexplained hairline cracks in centrifugally spun cast-iron pipes showed that they were due to the cooling process. The pipes being laid on the open ground while still warm, and contact of one section of the pipe with the cold earth caused uneven cooling resulting in the hairline splitting observed at destination.
The pipe and fittings shall be inspected for defects and be rung with a light hammer, preferably while suspended, to detect cracks. Smearing the outside with chalk dust helps the location of cracks. If doubt persists further confirmation may be obtained by pouring a little kerosene on the inside of the pipe at the suspected spot. If a crack is present the kerosene seeps through and shows on the outer surface. Any pipe found unsuitable after inspection before laying shall be rejected.