Ductile Iron Main

Two examples of cathodic protection are discussed protection of a ductile iron main protection of a cast-iron-lined main. 

In the valve system, bolts are generally the first to be affected by corrosion. In chambers, it is sometimes very clear as to the cause of the corrosion, and in the early stages corrective action can be taken. These chambers are generally filled with water and soil that run into the chambers from the road runoff. In addition water from the ditches and along the water main enters in openings where the main enters the manhole. Leaks can be reduced, but with the loading of traffic and shifting of the chamber in the frost 

Corrosion Prevention and Protection Practical Solutions V. S. Sastri, E. Ghali and M. Elboujdaini 2007 John Wiley Sons, Ltd 

Corrective action consists of replacing mild steel bolts with 304 stainless steel bolts. The bolts were coated with a wax-based primer to reduce the corrosion of the bolts in flooded chambers. 

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Selected Examples of Failure and Their Prevention Cathodic protection of water mains Here two examples of cathodic protection (i) ductile iron main and (ii) cast-iron-lined main are discussed. 

In the United States calcium carbide-based acetylene is mainly used in the oxyacetylene welding market although some continues to be used for production of such chemicals as vinyl ethers and acetylenic alcohols. Calcium carbide is used extensively as a desulfurizing reagent in steel and ductile iron production allowing steel mills to use high sulfur coke without the penalty of excessive sulfur in the resultant steel (see Sulfurremoval and recovery). Calcium cyanamide production continues in Canada and Europe (see Cyanamides). 

Distribution mains may be constructed of steel, ductile iron, polyethylene depending on operating pressure, etc. Recommendations are contained in the Institution of Gas Engineers publication TD/3, Distribution Mains. 

Deterioration of water pipe fittings such as service saddles contributes to water main failures. This type of failure may be due to galvanic corrosion since the pipe is cast or ductile iron, saddle is either bronze, steel or cast iron and the service line is made of copper. 

There are differences between North American and European pipe materials for certain applications, and very big differences in demand level. Consider new domestic hot water pipe. In 2002, North America used a total of 2.3 M tonnes of material, of which 46.7% was PVC, almost half was ductile iron, and less than 4% was polyethylene. Europe used only 625,000 tonnes, of which 25% was PVC and 45% was polyethylene, the remainder being mainly iron. European demand in this market is falling slowly. 

The water mains used to distribute drinking water have normally been constructed from cast-iron, ductile iron, asbestos cement and, more recently, from plastics (for example, MDPE medium density polyethylene). Leaching of lead from these materials does not normally occur. Very exceptionally, lead water mains have been used to distribute drinking water. The only known occurrences are in Ireland where their replacement has high priority (Devaney, 2009). 

Figure 7.21 Corrosion of a water main ductile iron adjacent to a copper fitting. (Courtesy of Drinking Water Services, City of Ottawa)...

The two main varieties of malleable iron arc ferritic and pcarlitic. the former more machinable and more ductile the latter stronger and harder. Carbon in malleable iron ranges between 2.30 and 2.65%. Ranges of other constituents are manganese, 0.30 to 0.40% silicon, 1.00 to 1.50% sulfur, 0.07 to 0.15% and phosphorus, 0.05 to 0.12%. 

The iron metals family of products may be classified into (1) the pure irons, such as ingot iron and wrought iron, which have only traces of carbon (see Table I) and other elements, and are very ductile (2) cast irons, which are alloys of iron and carbon, with or without other elements, and normally containing from 2.4 to 4.5% carbon (3) steels, which are alloys Df iron and carbon, with or without other elements, in which the carbon content seldom exceeds 1.7% (4) alloy steels whose properties mainly are attributed to the presence of one or more elements other than carbon. There are other groups and numerous subgroups in the total iron metals family. 

The major industrial use of vanadium is in alloy steels and cast iron, to which it lends ductility and shock resistance. Conunercial production is mainly as the iron alloy ferrovanadium, a tough, high-speed steel containing around 4-5% V. In ferrovanadium manufacture, vanadium pentoxide is reduced in an airtight electric furnace by ferrosilicon. ... 

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