Iron, pipeline

Although iron pipes suffer from the same corrosion risk as steel pipelines, associated with the generation of a galvanic cell with a small anode and a large cathode, the risk is mitigated for iron pipelines because the electrical continuity is broken at every pipe joint. For this reason long-line currents are uncommon in iron lines and cathodic protection is rarely necessary. It also accounts for the ability to protect iron lines by the application of nonadherent polyethylene sleeving . 

A 3-in Schedule 40 iron pipeline carries steam at 6 atm gauge. The line is uninsulated and is 70 m long. The surrounding air is at 25°C. The emissivity of the pipe wall is 0.70. How many kilograms of steam will condense per hour What percentage of the heat loss is from conduction-convection ... 

Comply with requirements of insurance companies regarding fire fighting facilities to be provided on the premises, e.g. cast iron pipelines, dedicated water pumps of special design for fire fighting, separate power supply feeders/DG set, CO2 cylinders, sand buckets, dry chemical powder-type fire extinguishers, long hose reels smoke detectors, and sprinklers must be installed and maintained. 

Fig. 2. Relationship between generalized Reynolds number Re and friction coefficient X, cast iron pipeline 250 mm, ...

Explain why msting of underground iron pipelines can be prevented by sacrificial protection 77.27 21.06 -0.66 -0.11... 

Cast iron pipelines have in some cases lasted for decades transporting seawater or salt solutions [91, 92]. 

Table 3 Ductile cast-iron pipeline system for the transportation of waste water in drinking-water protection zones II [23]...

The most common units are mm year (mpy). As an example, consider the corrosion of an iron pipeline by an acid liquor. If the steady corrosion current density is 0.1 mAcm" ... 

Solids materials that are insoluble in hydrocarbon or water can be entrained in the crude. These are called bottom sediments and comprise fine particles of sand, drilling mud, rock such as feldspar and gypsum, metals in the form of minerals or in their free state such as iron, copper, lead, nickel, and vanadium. The latter can come from pipeline erosion, storage tanks, valves and piping systems, etc. whatever comes in contact with the crude oil. 

Shale oil contains large quantities of olefinic hydrocarbons (see Table 8), which cause gumming and constitute an increased hydrogen requirement for upgrading. Properties for cmde shale oil are compared with petroleum cmde in Table 10. High pour points prevent pipeline transportation of the cmde shale oil (see Pipelines). Arsenic and iron can cause catalyst poisoning. 

The most significant chemical property of zinc is its high reduction potential. Zinc, which is above iron in the electromotive series, displaces iron ions from solution and prevents dissolution of the iron. For this reason, zinc is used extensively in coating steel, eg, by galvanizing and in zinc dust paints, and as a sacrificial anode in protecting pipelines, ship hulls, etc. 

The buildup of carbonaceous materials in the sulfuric acid presents one of the most serious problems of acid concentration (76—80). Acid concentration also presents a corrosion problem. The vessels are mild steel lined with lead or brick the steam heating elements are composed of siUcon, iron, or tantalum, and pipelines are generally constmcted of lead (81). 

Note also that graphitic corrosion may occur preferentially in poorly accessible areas, such as the bottom of pipelines. Trouble-free service of cast iron components does not necessarily indicate that all is well, since components suffering severe graphitic corrosion may continue to operate until an inadvertent or intentional (e.g., pressuretesting) shock load is applied. At this point massive, catastrophic failures can occur. 

We now examine three real corrosion problems the protection of pipelines, the selection of a material for a factory roof, and materials for car exhaust systems. The rusting of iron appears in all three case studies, but the best way of overcoming it differs in each. Sometimes the best thing is to change to a new material which does not rust but often economics prevent this, and ways must be found to slow down or stop the rusting reaction. 

If scratches and breaks occur in the zinc layers by accidental damage - which is certain to occur when the sheets are erected - then the zinc will cathodically protect the iron (see Fig. 24.4) in exactly the way that pipelines are protected using zinc anodes. This explains the long postponement of rusting. But the coating is only about 0.15 mm thick, so after about 30 years most of the zinc has gone, rusting suddenly becomes chronic, and the roof fails. 

With the fall of the Roman Empire, the ancient water supplies petered out. In early medieval times, people were content to conduct local water in wooden pipes to public cisterns. The first wooden pipelines for water were laid at Liibeck about 1293 and in 1365 at Nuremberg. In 1412 the Augsburg master builder Leopold Karg first used wrought-iron pipes in conjunction with wooden pipes to supply water. Because of their propensity to corrosion, they seem to have proved a failure and a few years later they were exchanged for wooden, lead, and cast-iron pipes. 

The first anode installation for the cathodic protection of gas pipelines in New Orleans consisted of a 5-m-long horizontal cast-iron tube. Later old tramway lines were used. Since in downtown New Orleans there was no suitable place to install impressed current anodes and to avoid detrimental effects on other pipelines, Kuhn recommended the use of deep anodes which were first installed in 1952 at a depth... 

Cement coatings are usually applied as linings for water pipes and water tanks, but occasionally also for external protection of pipelines [7]. Cement is not impervious to water, so electrochemical reactions can take place on the surface of the object to be protected. Because of the similar processes occurring at the interface of cement and object and reinforcing steel and concrete, data on the system iron/ cement mortar are dealt with in this chapter taking into account the action of electrolytes with and without electrochemical polarization. To ensure corrosion protection, certain requirements must be met (see Section 5.3 and Chapter 19). 

For pipelines, so-called bracelets are used (see Section 16.6). They consist of groups of plate anodes of more or less large breadth, partly curved, which are secured near to one another on an iron band support like links of a bracelet and laid around pipelines. With the same objective, half-shells are used which are fixed in pairs under stress around the pipe and then welded. 

Distribution networks in towns have been built over periods of deeades with various phases of pipeline teehnology. Networks ean eonsist of welded steel pipes, steel pipes with lead soekets, different types of east iron and plastie pipes. 

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