Failure vacuum generation

Mechanical failures occur when the part is exposed to some t5q)e of force that exceeds its capability. A part may be exposed to three different t5q)es of forces tensile, compression, and vacuum-generated stresses. Many processes require super- or subatmo-spheric pressure. In a fluoropol5mier-Iined vessel or a stand-alone vessel at elevated pressure, the walls are subjected to tensile stress. Compression stress develops in parts such as seals and gaskets where force is applied to the part, for instance, by placing it between bolted flanges. Vacuum can be a permanent or transient feature of a process and subjects a part to complex forces which could be a combination of tensile and compression. 

Brown et al. [36] attempted to approach pentalene (2) by a thermolytic ring-contraction-cyclization of 3-ethenylbenzyne 41, which, in turn, was generated by flash vacuum thermolysis of 3-ethenylphthalic anhydride 40. Indeed, the pentalene dimer 43 ( 50%) was formed along with phenylacetylene 44 ( 50%) in 80% overall yield (Scheme 6). The failure to detect monomeric pentalene (2) is in accord with the observation of de Mayo et al. that 1-methylpentalene (37) dimerizes above —140 °C [29]. The formation of phenylacetylene 44 was unexpected, and it is as yet unclear as to whether it arises by migration of two hydrogens in the aryne 41 or the intermediate carbene 42, or whether it is a secondary product formed from pentalene (2). 

Corrosion due to alkaline condensates may be controlled by selecting curing agents that do not generate ammonia and by vacuum baking assembled circuits at 125°C to 150°C for 16-96 hours to remove moisture prior to sealing. Arelated failure mechanism involving alkaline solutions is that of... 

The switchgear where PT was connected was of kind of metal-enclosed and was composed of 11 panels of 13.8 kV with a current capacity of 2,000 A. Nine of the panels were vacuum switches with their auxiliary equipment. One of the panels was used exclusively for measurement. The remaining panels, was empty because it could not be restored after the failure of one of the PT s occurred three years ago. One of the feeders of the switchgear was connected to one of the generators of the plant. 

Reactor pressure increase Several events may cause this e.g., inadvertent closure of one turbine control valve, pressure regulator downscale failure, generator load rejection, turbine trip MSIV closure, loss of condenser vacuum, loss of nonemergency AC power to station auxiliaries, loss of feedwater etc. All these have been analysed. Features are included in the instrumentation and control systems or redundancies to maintain reactor pressure through a combination of component automatic responses or operator actions, depending on the identified cause. 

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