Embrittlement dangers

Refinery management, 524-525 Refinery metallurgy, 415-429 metals used in refinery service, 415-416 stainless steel nomenclature, 416-418 corrosion resistance, 417, 419—426 embrittlement dangers, 426 rigorous service, 426-427 heat-exchanger tube fouling, 428 troubleshooting problems, 428... 

The electrode material is economically important in electrochemical synthesis and an attempt is made to reduce to a minimum the use of expensive noble metals, which are regularly used in small quantities in academic investigations. Of course, the principal danger in using less stable materials is that they themselves will be oxidized or embrittled in use, respectively, as anode or cathode. 

A rchaeological excavations at pre-Columbian sites have yielded espe-cially rich collections of textile artifacts. These materials often reveal information of considerable anthropological and art historical significance. The difficulties of restoration, maintenance, and exhibition for archaeological textiles are well known to conservators and art historians (1). These materials are frequently recovered in a severe state of deterioration ranging from dangerous embrittlement to extreme friability. The... 

Up until now, there has been little interest in electrolytic deposition of iron metals and chromium from nonaqueous solutions, because such deposits are easily obtained from aqueous electrolytes. On the other hand, adhesive layers can be applied to reactive metals like titanium, beryllium, and magnesium, for example through nickel deposition from nonaqueous solutions. By depositing such metals out of nonaqueous solutions, hydrogen sensitive materials, such as low-alloy high-strength steel, can be coated without danger of embrittlement. Materials coated in this way with a compact poreless metal layer can be further coated in an aqueous electrolyte. 

This model is considered to be useful to improve the knowledge of the role played by the factor of hydrogen accumulation in prospective rupture sites by stress-assisted diffusion, one of the key items in hydrogen embrittlement, a very dangerous phenomenon that frequently accompanies structural metals and alloys in service. 

A number of techniques using similar concepts were developed over the years to treat leathers that had already deteriorated. Aqueous solutions of potassium lactate were routinely applied to the surface of bookbindings and other leather objects. Unfortunately, in many cases, the deleterious effects of the liquid water solvent on acidic leathers took place before the buffer salt neutralised the acid, resulting in dark, seriously embrittled leather. In order to avoid the effects of aqueous solutions, methods were tried employing ammonia vapour. The object was placed in an enclosed chamber over an open dish of ammonium hydroxide solution. However, ammonia vapour is a strong alkali and there is a danger that even with the use of dilute solutions, leathers that were too acidic would be transformed into ones which were too alkaline. Another alternative was to use an organic base such as imidazole in a non-aqueous solvent. However, this was also liable to result in leathers that were too alkaline. 

The total cost of material fracture is about 4% of gross domestic product in the United States and Europe (88,89). Fracture modes included in the cost estimates were stress-induced failures (tension, compression, flexure, and shear), overload, deformation, and time-dependent modes, such as fatigue, creep, SCC, and embrittlement. The environmentally assisted corrosion problem is very much involved in the maintenance of the safety and reliability of potentially dangerous engineering systems, such as nuclear power plants, fossil fuel power plants, oil and gas pipelines, oil production platforms, aircraft and aerospace technologies, chemical plants, and so on. Losses because of environmentally assisted cracking (EAC) of materials amount to many billions of dollars annually and is on the increase globally (87). 

Adequate operational procedures may also contribute to reducing the probability of generating a PIE. Examples include the prevention of excessive thermal stresses in metal pressure vessels and the monitoring of vessel material for radiation embrittlement the limitation of plant transients by the use of pressure relief valves and safety features activated by the protection system prohibitions or restrictions during the conduct of dangerous operations the use of seismic instruments to provide data for the assessment of the condition of the plant for continued operation following an earthquake and the control of... 

Brazing of CoCr-alloys can be performed either in a hydrogen atmosphere or in vacuum. As filler metals Ni- or Co-base alloys or Au-Pd-alloys can be used. In order to achieve a better wetting by the filler metals an electroplating or flashing with Ni is performed. Copper filler metals should be avoided because of the danger of an embrittlement of the seam. Table lb.8 shows the compositions of a typical Co-base filler metal. 

Carbon Steel. Carbon steel is commonly used without danger of SCC up to 50% NaOH and 54°C. At high NaOH concentrations and temperatures, welds and stressed zones are prone to failure unless stresses are relieved. Figs. 14.29 and 14.30 show the caustic embrittling characteristics of steels and nickel alloys [33,34]. 

It is clear, therefore, that both styles of major hazard regulation would have averted the accident, had they been in place. A safety case regime would have mandated a systematic hazard identification procedure which would have identified and controlled the hazard of cold temperature embrittlement. An incident report system which required the reporting and investigation of abnormal temperature events and leaks would also have resulted the discovery and control of the danger of embrittlement. 

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