Metal Section

Ductile Iron, also known as Spheroidal Graphite (SG) iron or nodular iron is made by treating liquid iron of suitable composition with pure magnesium before casting. This promotes the participation of graphite in the form of discrete nodules instead of interconnected flakes. The nodular iron so formed has high ductility, allowing casting to be used for pipe making.

The hot metal tapped from induction furnace is transferred into the turning ladle. Pure magnesium is then charged into the reaction chamber through a charging mouth. The hydraulic system provided will tilt the turning table into vertical position, thus allowing molten iron to react with Magnesium. The reaction is allowed for 10 minutes. Once the reaction is complete, the hot metal is transferred to the pouring machine for casting the Ductile Iron Pipes.

Mould Section

Water – cooled metal mould process (De-Levoud Process) has been envisaged for centrifugal casting machines for production of Ductile Iron Pipes from DN 80 to DN 1200. After the spheroidization process, the SG iron is directed towards the centrifugal pouring-cum-casting machine. Molten SG iron is transferred to a quadrant type ladle and from its bottom into a rotating pipe mould with a water jacket inside the centrifugal casting machine.

Core Making Section

Head core made up of resin coated sand serves to seal the socket end of the mould and form the inside of the socket end of the pipe. As the mould rotates evenly, centrifugal force distributes the metal evenly, forming the pipe wall. Centrifugal casting machine containing the mould is mounted on a set of wheels, which move on a track.

Spining Section

Molten metal is poured into the spinning mould by the means of a pouring trough. As the spinning mould is retracted from the pouring trough, a uniform layer of metal is deposited on the mould. Hydraulically operated extraction devices are provided for easy removal of the moulded pipe. Water jacket is provided for circulating water continuously around the mould thus cooling it uniformly.

Heat Treatment Section

The cast pipes are heat treated in an annealing furnace to optimize the strength impulses and ductility of the pipes. The annealing furnace will be of a continuous chain type and will be LDO fired. Annealing furnace will have a pre-heating zone, soaking zone, fast cooling zone and controlled cooling zones. Pipes entering pre-heating zone at 600 ºC will be heated to 940 ºC. Pipes then enter the soaking zone, where they will be maintained at 940 ºC followed by cooling to 780 ºC in fast cooling zone. Pipes finally enter controlled cooling zone, where they are cooled to 600 ºC. Pipes will be moving inside AF on casting iron rails and pushed by fingers on closed dog type chain.

Zinc Coating Section

Zinc coating is done with a spray process with the help of Zinc spray guns which ensure smooth and uniform Zinc deposition. Zinc coating gives stable protective layer of insoluble zinc salt. It provides active protection due to the galvanizing effect, thus increasing corrosion resistance of the pipe in use. Prior to the application of zinc, the pipe surface is kept dry and free from rust or non-adhering particles or foreign matter such as oil or grease. The metallic zinc coating covers the external surface of the pipe and provides a dense, continuous and uniform layer. The uniformity of the coating can be checked by 2 inspection. The mass of zinc is not less than 130 g/m . The purity of zinc is at least 99.99%. The finishing layer uniformly covers the whole surface of the metallic zinc layer and remains free from defects such as bare patches or lack of adhesion. The thickness of the finishing layer remains 70 microns and the local minimum thickness not less than 50 microns. Special coating like extra zinc coating can also be provided.

Internal Grinding Section

Pipe grinding facilities are provided for cleaning the socket, spigot and the inner wall of the pipe. Spigot end cutting and chamfering is carried out during the grinding process.

Hydrostatic Pressure Testing Section

All the pipes are tested hydrostatically at a pressure depending on the size of Ductile Iron Pipe, as pressure depends on the class of the pipe. Pipes are filled with water until they are full and are then pressurized to a predetermined value of pressure for a fixed duration of time. To perform the test, pressure is applied internally and is steadily maintained for a period of 10 seconds. The pipes withstand the pressure test and shall not show any sign of leakage, sweating or defects of any other kind. The 3 total water in circulation is 30 m /hr. The water used for hydro-testing is re-circulated after settling at settling tank 3 provided in this section. About 29 m /hr of water is 3 reclaimed from the settling tank and 1 m /hr is required as make up water.

Cement Mortar Lining Section (CML)

All Ductile Iron Pipes are provided with internal cement mortar lining. The mortar shall contain at least 1 part of cement to 3.5 parts of sand by mass (i.e. S/C ≤ 3.5 by mass in the mortar). Lining thickness will be 3 mm for DN 80 – DN 300, 5 mm for DN 350 – DN 600 and 6 mm for DN 700 – DN 1200 pipes. Equipment required for cement lining of pipes consists of cement batching, mixing and material transfer equipment as well as cement and sand silos, cement lining machine along with traversing equipment etc. Internally lined Ductile Iron Pipe is cured in the curing oven. Special types of linings are also provided like CML with Bitumen Seal Coat and CML with Epoxy Coat. lined Ductile Iron Pipe is cured in the curing oven. Special types of linings are also provided like CML with Bitumen Seal Coat and CML with Epoxy Coat.

Steam Curing Section

Steam required for curing oven is drawn from the boiler envisaged exclusively for this purpose.

Internal Polishing Section

After steam curing, internal polishing of CML is done for a smoother surface which helps in maintaining higher flow rate and 'C' value which helps in saving pumping cost as well.

Bituminous Coating Section

The pipes are preheated in a hot chamber to dry any moisture from steam curing and to give better adherence to paint. Bituminous paint is applied by a spraying machine which ensures uniform coating of the Ductile Iron Pipe. Coating is applied on clean surface i.e. dry and free from dust. It must be smooth and tenacious and hard enough not to flow when exposed to a temperature of 65 ºC but not so brittle at a temperature of 0 ºC as to chip off when scribed with a penknife. The mean thickness of the coating shall not be less than 70 μm and the local minimum thickness shall not be less than 50 μm. For corrosive soils, excess bituminous coating can be provided.