Failure types chemical

Fig. 8.29 Causes of failure and failure types investigated by a large chemical company in the...

Hospitals and other health care facilities may further classify disasters as either internal or external. External disasters are those that do not affect the hospital infrastructure but do tax hospital resources due to numbers of patients or types of injuries (Cans, 2001). For example, a tornado that produced numerous injuries and deaths in a community would be considered an external disaster. Internal disasters cause disruption of normal hospital function due to injuries or deaths of hospital personnel or damage to the physical plant, as with a hospital fire, power failure, or chemical spill (Aghababian, Lewis, Cans, Curley, 1994). Unfortunately, one type of hospital disaster does not necessarily preclude the other, and features of both internal and external disasters may be present if a natural phenomenon affects both the community and the hospital. This was the case with Hurricane Andrew (1992), which caused significant destruction in hospitals, in clinics, and in the surrounding community when it struck south Florida (Sabatino, 1992), and Hurricane Katrina (2005) when it impacted the Gulf Coast, rupturing the levee in New Orleans (Berggren, 2005). 

It is a form of localized corrosion of a metal surface where small areas corrode preferentially leading to the formation of cavities or pits, and the bulk of the surface remains unattacked. Metals which form passive films, such as aluminum and steels, are more susceptible to this form of corrosion. It is the most insidious form of corrosion. It causes failure by penetration with only a small percent weight-loss of the entire structure. It is a major type of failure in chemical processing industry. The destructive nature of pitting is illustrated by the fact that usually the entire system must be replaced. 

A cause of sudden and catastrophic failure is chemical embrittlement. This occurs when the wrong chemical enters the vessel or pipe, and causes it to fail in a very short period of time. Examples of embrittlement include the effect of caustic on stainless steels and hydrogen on various types of steel. Chemical embrittlement is particularly serious because it can happen to new equipment as easily as old, and because it may give little or no warning that it is about to occur. 

Indicators can determine if uniform steam penetration has been achieved during a Bowie Dick-type test. Produced in the form of sheets (23 X 30 cm), chemical indicators are capable of uniform color change over their entire surface when exposed to pure saturated steam under test conditions. Nonuniform color development is an indication of failure of the test. U.S. and international stands for the performance and accuracy of chemical indicators have been pubHshed (13,14). 

Electrochemical corrosion is understood to include all corrosion processes that can be influenced electrically. This is the case for all the types of corrosion described in this handbook and means that data on corrosion velocities (e.g., removal rate, penetration rate in pitting corrosion, or rate of pit formation, time to failure of stressed specimens in stress corrosion) are dependent on the potential U [5]. Potential can be altered by chemical action (influence of a redox system) or by electrical factors (electric currents), thereby reducing or enhancing the corrosion. Thus exact knowledge of the dependence of corrosion on potential is the basic hypothesis for the concept of electrochemical corrosion protection processes. 

CCPS, 1989b, Process Equipment Reliability Data (Table 4.1-1) is a compilation of chemical and nuclear data. It assesses failure rates for 75 types of chemical process equipment. A taxonomic classification is established and data such as the mean, median, upper and lower (95% and 5%) values, source of information, failure by time and failure by demands are presented. 

This chapter overviews the techniques for incorporating external events into a PSA. The discussion was primarily aimed at nuclear power plants but is equally applicable to chemical process plants. The types of external events discussed were earthquakes, fires and floods. Notably absent were severe winds and tornados. Tornados are analyzed as missiles impacting the structures and causing common-cause failures of systems (EPRINP-768). Missile propagation and the resulting damage is a specialized subject usually solved with computer codes. 

Mosleh, Kazarians, and Gekler obtained a Bayesian estimate of the failure rate, Z, of a coolant recycle pump in llie hazard/risk study of a chemical plant. The estimate was based on evidence of no failures in 10 years of operation. Nuclear industry experience with pumps of similar types was used to establish tire prior distribution of Z. Tliis experience indicated tliat tire 5 and 95 percentiles of lire failure rate distribution developed for tliis category were 2.0 x 10" per hour (about one failure per 57 years of operation) and 98.3 x 10 per hour (about one failure per year). Extensive experience in other industries suggested the use of a log-nonnal distribution witli tlie 5 and 95 percentile values as llie prior distribution of Z, tlie failure rate of the coolant recycle pump. 

Only equivocal chemical evidence appears to be available for the unsubstituted aminoimidazoles. The failure of 2-aminoimidazole to undergo diazotization was originally interpreted to indicate that it existed in the imino form more recently, the 4-amino analog has been reported to behave as a normal aromatic amine. The infrared spectra of substituted aminoimidazoles of type 192 193 were con-... 

While lead of purity in excess of 99.99% is commercially available, it is very rarely used owing to its susceptibility to grain growth and fatigue failure by intercrystalline cracking, and indifferent mechanical properties. Because of its generally superior corrosion resistance, pure lead to BS 334 1982 type A, shown in Table4.13, is occasionally used in chemical plant, but only if there is no suitable alternative. 

CORROSION IN CHEMICAL AND PETROCHEMICAL PLANT 9 17 Table 9.3 Corrosion failures analysed by type (after du Pont (1%8 to 1971))... 

By a statistical model of a solution we mean a model which does not attempt to describe explicitly the nature of the interaction between solvent and solute species, but simply assumes some general characteristic for the interaction, and presents expressions for the thermodynamic functions of the solution in terms of an assumed interaction parameter. The quasi-chemical theory is of this type, and we have noted that a serious deficiency is its failure to consider the vibrational effects in the solution. It is of interest, therefore, to consider briefly the average-potential model which does include the effect of vibrations. 

Thermal reactions of the second type, which do not involve adding ligands toward formation of metal organic product compounds, are less widely recognized as chemical phenomena. There may be here a simple failure of reaction, as in Eq. (16), because (99) of the diffusion of CO from the reaction site there may be stabilization of an intermediate stage by scavenger action (26, 27, 56) ... 

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