Manufacturing Process

1.1.1 Melting equipment: Two coreless-type furnaces and three coreless-type furnaces with volume of ten tons each, capacity is 50T/H.

1.1.2 Qualified molten iron, pig iron, scrap steel, alloy and rejected pipes are used to put into the furnace as per an exact proportion. Contents will be adjusted to be proper.

1.2.3 Temperature will be made up to 1460-1520°c

1.4 Molten iron complying with specifications will be spheroidized, with spheroidization agent being put into the hollow at the bottom of ladle before molten iron being poured in.

Qualified spheroidized molten iron will be covered with pearlite and then transported to casting platform by crane.

1.2.1 Centrifugal casting equipment includes four water cooling metallic centrifugal casting machines that are: two machines for DN80-300mm, one machine for DN400-700mm machine for DN800-1200mm.

1.2.2 Molten iron will be poured into a volumetric tilting ladle, entered the mold spinning at high speed with water cooling through a long trough, and solidified to be a pipe. The pipe will be extracted by an extractor and then transmitted to annealing furnace.

1.3.1 Core making equipment includes four core-making jets with hot core boxes, two are type of dual workstations and two are type of single workstation, and also includes two manual core-making jets.

1.3.2  The material for core making includes silicon sand, solidifying agent and resin. They will be mixed per a specified proportion and rolled fully and then conveyed into the hopper of the machine. The material will be jetted into core box and cores will be made after heated and solidified.

1.3.3 Cores will be tested to be qualified, marked with numbers and then conveyed to casting.

1.4.1 The main equipment includes the three machines for mold welding, four machines for grinding and peening and two latches, all the molds are homemade.

1.4.2 After a mold is used for casting for a shift, it must be replaced to maintain. Its internal surface will be first ground with sand wheel to remove rust, and then dotted with peening head to strengthen its crack resistance and adhersion for molten iron.

1.4.3 Cracks on the internal surface of the mold must be removed by turning. The area turned will be welded, and then the excessive metal will be turned again. Finally grinding and peening will be done.

1.5.1 Annealing equipment is a horizontal chain style furnace of type of continuous annealing. It is 52 meters long, made up of heating section, heat holding section, slow cooling section and fast cooling section.

1.5.2 Cast ductile iron pipes, after entering the furnace, will be pushed rolling forward by claws on chains driven by a speed regulating DC motor. Meters will control the temperature automatically.

1.5.3 Annealing curve:

 

1.6.1 Zinc coating machine will produce electric arc to melt zinc and apply it to external surface of pipes.

1.6.2 Zinc layer must even and adhesive.

1.7.1 After annealing, bell and spigot end, internal and external surface of ductile iron pipes will be finished to remove fins and so on, and then checked for their dimensions.

1.7.2 After finishing, ductile iron pipes will be tested for water pressure one by one. The requirements are 5MPa for DN100-300, 4MPa for DN350-600 and 3.5MPa for DN700. Testing pressure will be kept for 10 seconds.

1.7.3 Qualified ductile iron pipes may be given cement mortar lining, zinc coating and bitumen coating at customers’ request.

1.8.1 Cement lining machine has treble working-stations.

1.8.2 Cement, sand and water will be mixed as per specified proportion and stirred thoroughly, then pumped through a lance into a pipe spinning at low speed. The pipe will be moved to the high-speed station then to discharge excessive water and deposit cement mortar densely.

1.8.3 Cement lining will be given a natural cure. It will be smoothed with a grinder after being dry and solid.

1.9.1 Anti-corrosive bitumen layer will be applied to external surface of pipes and internal surface of socket.

1.9.2 The Bitumen layer must be even without trace of dripping or flowing.

1.10.1 Installation mark at spigot end and trade mark, if any, will be painted on

1.10.2 Pipes will be packed in bundles with thick pieces of wood and steel belts to be ready for shipment at customas’ request.

 

Standard of Quality