Embrittlement insulation

Excessive vibrations according to international codes can cause mechtinieal failure in the insulation by loosening wedges, overhangs, blocks and other supports that hold the stator and the rotor windings or rotor bars in their slots. Vibrations also tend to harden and embrittle copper windings and may eventually break them when they become loose (see also Sections 1 1.4.6 and I 1.4.7). 

Where waterside deposits are evident, they provide a heat insulating effect and also permit under-deposit contaminant concentration. Under conditions of high pressure, heat flux, or stress, this combination of factors may lead to the development of embrittlement corrosion or stress corrosion cracking (SCC). 

Aluminum is not embrittled by low temperatures and is not subject to external corrosion when exposed to normal atmospheres. At 200°C (400°F) its strength is less than half that at room temperature. It is attacked by alkahes, by traces of copper, nickel, mercury, and other heavy-metal ions, and by prolonged contact with wet insulation. It suffers from galvanic corrosion when coupled to copper, nickel, or lead-base alloys but not when coupled to galvanized iron. 

The consequences of oxydative and thermal breakdown of a polymer are discolouration, surface roughening, embrittlement, etc. for rubbers tackiness, followed by embrittlement. For electrical applications oxidation goes accompanied by a strong increase in the dielectric losses, and a decrease in insulation resistance and breakdown strength. 

Although the refrigeration of a hazardous process fluid will provide the benefits listed above, this technique does necessitate the insulation of the process equipment and piping. This makes it more difficult to inspect the equipment for external corrosion and embrittlement problems, unless there is an aggressive inspection program in place or noncorroding materials of construction are employed. 

Elemental sulfur is an inexpensive material available in high purity and large quantities, and has repeatedly been suggested for new uses in the civil engineering field. It is used as an extension to asphalt in road pavements and as an insulating material, but use as a construction material requires modification with additives designed to stop the embrittlement that occurs with pure elemental sulfur. If pure liquid sulfur is cooled to ambient temperature, monoclinic octasulfur (/S-Sg) is instantaneously formed, which then slowly converts to orthorhombic a-Sg. Because of the difference in densities between a- and )3-Sg, a brittle material results. Many additives have been proposed to modify elemental sulfur, nearly... 

The maximum use temperature is a term coined by the US organization. The Underwriters Laboratory, and it is the maximum temperature at which a polymer can be used continuously, under low stress conditions, with the loss of no more than 50% of the original useful properties (tensile and impact strength, for example, or dielectric strength in the case of cable insulation). For the engineer unfamiliar with plastics, the low values of typical maximum use temperatures can come as a shock. For example, glass-filled nylon 6,6 has a heat distortion temperature of 252°C, but the resin can embrittle as a result of thermal oxidation within 2 h at 250°C. Even at 70°C, embrittlement will still occur within two years [1]. 

Standard Test Method for Evaluating the Influence of Thermal Insulations on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel Standard Test Method for Electronic Measurement for Hydrogen Embrittlement fi-om Cadmium-Electroplating Processes... 

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