Breakdown of Causes

Experts who study accidents often do a breakdown or analysis of the causes. They analyze them at three different levels  

Direct causes (unplanned release of energy or hazardous material) 

Indirect causes (unsafe acts and unsafe conditions) 

Basic causes (management safety policies and decisions, and personal factors) See diagram at the beginning of this chapter.) 

Most accidents are caused by the unplanned or unwanted release of large amounts of energy, or of hazardous materials. In a breakdown of accident causes, the direct cause is the energy or hazardous material released at the time of the accident. Accident investigators are interested in finding out what the direct cause of an accident is because this information can be used to help prevent other accidents, or to reduce the injuries associated with them. 

Now that direct causes have been discussed, let us move one step down from there and discuss indirect causes, or symptoms, that may be considered contributing factors. In most cases, the release of excessive amounts of energy or hazardous materials is caused by unsafe acts or unsafe conditions. Put another way Unsafe acts and unsafe conditions trigger the release of large amounts of energy or hazardous 

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Table 2.1 lists the Great Kanto Earthquake and other major earthquakes in Japan, with the numbers of fires and a breakdown of causes for each. 

TABLE 5.3 Breakdown of Causes of Landing Failures as a Function of the Failure Mechanism... 

The practical importance of the higher sulfanes relates to their formation in sour-gas wells from sulfur and hydrogen sulfide under pressure and their subsequent decomposition which causes well plugging (134). The formation of high sulfanes in the recovery of sulfur by the Claus process also may lead to persistance of traces of hydrogen sulfide in the sulfur thus produced (100). Quantitative deteanination of H2S and H2S in Claus process sulfur requires the use of a catalyst, eg, PbS, to accelerate the breakdown of H2S (135). 

Lubrication of sheet and strip is necessary for aU operations. Although for special operations vegetable and mineral oUs maybe employed, a mixture of paraffin and taUow oU is normally preferred in rough rolling. Requirements for finish-roll lubricant are more strict because of staining caused by breakdown of the oU or reaction with the zinc. Strip zinc is usuaUy finish-rolled with cotton seed or mineral oU. 

An especially insidious type of corrosion is localized corrosion (1—3,5) which occurs at distinct sites on the surface of a metal while the remainder of the metal is either not attacked or attacked much more slowly. Localized corrosion is usually seen on metals that are passivated, ie, protected from corrosion by oxide films, and occurs as a result of the breakdown of the oxide film. Generally the oxide film breakdown requires the presence of an aggressive anion, the most common of which is chloride. Localized corrosion can cause considerable damage to a metal stmcture without the metal exhibiting any appreciable loss in weight. Localized corrosion occurs on a number of technologically important materials such as stainless steels, nickel-base alloys, aluminum, titanium, and copper (see Aluminumand ALUMINUM ALLOYS Nickel AND nickel alloys Steel and Titaniumand titanium alloys). 

Cullinan presented an extension of Cussler s cluster diffusion the-oiy. His method accurately accounts for composition and temperature dependence of diffusivity. It is novel in that it contains no adjustable constants, and it relates transport properties and solution thermodynamics. This equation has been tested for six very different mixtures by Rollins and Knaebel, and it was found to agree remarkably well with data for most conditions, considering the absence of adjustable parameters. In the dilute region (of either A or B), there are systematic errors probably caused by the breakdown of certain implicit assumptions (that nevertheless appear to be generally vahd at higher concentrations). 

Table 1.1 Breakdown of U.K. fires causing more than 50 000 damage in 1997 ...

Weathering. This generally occurs as a result of the combined effect of water absorption and exposure to ultra-violet radiation (u-v). Absorption of water can have a plasticizing action on plastics which increases flexibility but ultimately (on elimination of the water) results in embrittlement, while u-v causes breakdown of the bonds in the polymer chain. The result is general deterioration of physical properties. A loss of colour or clarity (or both) may also occur. Absorption of water reduces dimensional stability of moulded articles. Most thermoplastics, in particular cellulose derivatives, are affected, and also polyethylene, PVC, and nylons. 

An increase of the capture airflow rate normally results in increased capture efficiency, but the relationship between these quantities is not linear. A case-by-case evaluation is necessary to establish this relationship. In every case an increase of the airflow rate causes an increase of the operating costs. Analogously, a decrease in airflow rate leads to a decrease in capture efficiency and in some cases, a total breakdown of the capture effect (e.g., capture dev ices working with the vortex principle require minimum airflow rates). 

Back corona is caused by the electrical breakdown of gas in the dust layer. This breakdown produces positive ions, which drift toward the negative discharge electrode. The presence of ions with opposite polarity causes a reduction in the particle-charge and -collection efficiency. To avoid this problem, several methods are used. These include... 

The venoms of poisonous snakes contain (among other things) a class of enzymes known as phospholipases, enzymes that cause the breakdown of phospholipids. For example, the venoms of the eastern diamondback rattlesnake (Crotalus adamanteus) and the Indian cobra Naja naja) both contain phospholipase Ag, which catalyzes the hydrolysis of fatty acids at the C-2 position of glyc-erophospholipids. 

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