WATER PIPE Subject

Failure of cooling water piping in sequence 17 was dominated by soil consolidation lailure of underground piping. The pipe is subject to non-ductile cracking during extremely cold w eather. 

The preparation of foams of PCHE and copolymers has also been claimed [79]. A combination of a low-boiling hydrocarbon (butane) foaming agent and a higher boiling hydrocarbon plasticizer (toluene) were used to prepare foams. The increased heat distortion temperature of PCHE has been proposed to lead to utility in insulating foams for hot water pipes and similar applications. In addition, the superior weatherability of this material would allow use in applications in which the product was subjected to UV exposure. 

That mystery often surrounds the process of corrosion is probably because of the hard-to-recognize forms that the electrochemical cell takes. Persons accustomed to the laboratory will visualize an electrochemical cell as a beaker containing electrolyte in which to pieces of metal are immersed and joined externally with a wire. It is difficult to make the translation between this situation and that of a water pipe running through alternate marshy and sandy patches of soil, yet both are electrochemical cells—and both will be subject to the reactions that go to make up corrosion. 

If a plastic is subjected to a constant high creep stress for a long time, the creep rupture failure that occurs may be by yielding, or by crazing and crack growth. Creep rupture is important for the design of gas or water pipes (Chapter 14), where the cylindrical shape is stable during creep. It is less important for products that are bent or twisted, where excessive deflection is likely before any rupture process starts. 

Plastic pipe and fittings, particularly PVC-P and to some extent PE, are overwhelmingly being used in construction as a big competitor of metallics. APME s report [52] demonstrates that plastics use in gas, sewage and water piping has tripled in the EU. Health hazards in PVC-P pipes and fittings, are subject to emission of the plasticisers used. Polyacetals are also used for sanitary ware and plumbing. 

Potable water is transported to consumers through a network of pipes which consists of mains pipes with a range of sizes and connections to consumer premises by smaller service pipes. In the older industrial cities of Europe, much of the pipeline infrastructure is around 100 years old and iron water pipes and gas pipes are subject to decay by corrosion. Water pipes suffer additionally from internal build up of deposits lining the pipes which eventually interfere excessively with flow capacity. 

Cables are not subjected to condensation dripping from metal sinks, cold water pipes and tanks or made wet from leaks. 

Most people are familiar with corrosion in some form or another, particularly the rusting of an iron fence and the degradation of steel pilings or boats and boat fixtures. Piping is another major type of equipment subject to corrosion. This includes water pipes in the home, where corrosion attacks mostly from the inside, as well as the underground water, gas, and oil pipelines that crisscross our land. Thus, it would appear safe to say that almost everyone is at least somewhat familiar with corrosion, which is defined in general terms as the degradation of a material, usually a metal, or its properties because of a reaction with its environment. 

Certain types of equipment are specifically excluded from the scope of the directive. It is self-evident that equipment which is already regulated at Union level with respect to the pressure risk by other directives had to be excluded. That is the case with simple pressure vessels, transportable pressure equipment, aerosols and motor vehicles. Other equipment, such as carbonated drink containers or radiators and piping for hot water systems are excluded from the scope because of the limited risk involved. Also excluded are products which are subject to a minor pressure risk which are covered by the directives on machinery, lifts, low voltage, medical devices, gas appliances and on explosive atmospheres. A further and last group of exclusions refers to equipment which presents a significant pressure risk, but for which neither the free circulation aspect nor the safety aspect necessitated their inclusion. 

Waters While MIC-causing bacteria may arrive at the surface of their corrosion worksite by almost any transportation system, there is always water present to allow them to become ac tive and cause MIC to occur. There are plenty of examples of even superpure waters having sufficient microorganisms present to feed, divide, and multiply when even the smallest trace of a viable food-stuff is present (e.g., the so-called watei for injection in the pharmaceutical industiy has been the observed subject of extensive corrosion of pohshed stainless steel tanks, piping, and so on). 

Equipment in which water flow is slow or intermittent is subject to deposition and associated corrosion. Hence, service water-system components that operate intermittently frequently suffer attack. Deposits accumulate in narrow orifices, screens, long horizontal pipe runs, sumps, or at regions of constricted flow. 

Carbon steel heat exchangers, cast iron water boxes, screens, pump components, service water system piping, standpipes, fire protection systems, galvanized steel, engine components, and virtually all non-stainless ferrous components are subject to significant corrosion in oxygenated water. 

Pipe used for low-pressure applications such as transporting air, steam, gas, water, oil, etc. Employed in machinery, buildings, sprinkler and irrigation systems, and water wells but not in utility distribution systems can transport fluids at elevated temperatures and pressures not subjected to external heat applications. Fabricated in standard diameters and wall thicknesses to ASTM specifications, its diameters range from Vs to 42 in. o.d. 

In de-aerated conditions, for instance in most central heating systems, little if any attack on copper occurs . As far as drinking waters are concerned, copper is not classified as a toxic substance or hazardous to health. To avoid any difficulties due to unpalatability, the maximum continuous copper content should not exceed 10 p.p.m., with a limit of 3 p.p.m. in water after standing overnight in copper pipes. A review of the subject by Grunau makes reference to 394 published papers. 

General corrosion damage was the cause of failure of an A1 alloy welded pipe assembly in an aircraft bowser which was attacked by a deicing-fluid — water mixture at small weld defects . Selective attack has been reported in welded cupro-nickel subjected to estuarine and seawater environments . It was the consequence of the combination of alloy element segregation in the weld metal and the action of sulphate reducing bacteria (SRB). Sulphide-coated Cu-enriched areas were cathodic relative to the adjacent Ni-rich areas where, in the latter, the sulphides were being continuously removed by the turbulence. Sulphite ions seemed to act as a mild inhibitor. 

The cathodically protected primary structures may be the hulls of ships, jetties, pipes, etc. immersed in water, or pipes, cables, tanks, etc. buried in the soil. The nearby unprotected secondary structures subjected to interaction may be the hulls of adjacent ships, unbonded parts of a ship s hull such as the propeller blades, or pipes and cables laid close to the primary structure or to the cathodic-protection anode system or groundbed. 

Water is flowing at 5 m/s in a 50 mm diameter pipe which incorporates a 90° bend, as shown in Figure 2.8. What is the additional force to which a retaining bracket will be subjected, as a result of the momentum changes in the liquid, if it is arranged symmetrically in the pipe bend ... 

Before adopting this method at the ordnance plant, sections of pipelines were chosen for test samples, to determine if the swab and pig method would satisfactorily clean these contaminated pipes. One half the sections were cleaned by this method and the other half was thoroughly flushed with water. They were allowed to dry and then were subjected to initiation by fires. The sections that had been flushed with water ignited and burned vigorously. The sections that had been subjected to cleaning with the swab and pig had no product remaining that would support combustion. 

Plastic piping should only be used as specified by the manufacturers and listed by UL or equivalent. New water lines should be subjected to a hydrostatic test of 150% of design pressure for at least 2 hours (NFPA 24). Leaks should be repaired and tests repeated as necessary before lines are covered. 

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