Intensification

The best way to deal with a hazard in a flowsheet is to remove it completely. The provision of safety systems to control the hazard is much less satisfactory. One of the principal approaches to making a process inherently safe is to limit the inventory of hazardous material, called intensification of hazardous material. The inventories we wish to avoid most of all are flashing flammable liquids or flashing toxic liquids. 

Intensification of hazardous materials results in a safer process. In... 

So far the emphasis has been on substituting hazardous materials or using less, i.e., intensification. Let us now consider use of hazardous materials under less hazardous conditions, i.e. at less extreme temperatures or pressures or as a vapor rather than superheated liquid or diluted, in other words, attenuation. ... 

It is particularly in the serial inspection of castings, that radioscopy constitutes state-of-the-art when applied in conjunction with systems for image intensification, digital image processing and automatic image evaluation. For the examination of welds, however, standardization is still non-existent, thus rendering more difficult the application of this inspection technique.As a consequence the approval procedures of the respective supervisory or certification boards are often complicated and of necessity set up for each individual case. 

Demilitarization and Disposal of Explosive Material. An important consequence of international agreements to greatiy reduce the stockpiles of conventional and nuclear munitions is the intensification of a program to develop procedures to destroy, recycle, and/or reclaim explosives, propellants, and pyrotechnic material efficientiy and without significant environmental impact. 

Fracture Mechanics. Linear elastic fracture mechanics (qv) (LEFM) can be appHed only to the propagation and fracture stages of fatigue failure. LEFM is based on a definition of the stress close to a crack tip in terms of a stress intensification factor K, for which the simplest general relationship is... 

USP-grade anhydrous magnesium carbonate is used as a flavor impression intensification vehicle in the processed food industry (see Flavors and spices). Basic magnesium carbonates are used as free flowing agents in the manufacture of table salt, as a hulking agent in powder and tablet pharmaceutical formulations, as an antacid, and in a variety of personal care products (see Pharmaceuticals). 

Methyl- and dimethylnaphthalenes are contained in coke-oven tar and in certain petroleum fractions in significant amounts. A typical high temperature coke-oven coal tar, for example, contains ca 3 wt % of combined methyl- and dimethylnaphthalenes (6). In the United States, separation of individual isomers is seldom attempted instead a methylnaphtha1 ene-rich fraction is produced for commercial purposes. Such mixtures are used for solvents for pesticides, sulfur, and various aromatic compounds. They also can be used as low freezing, stable heat-transfer fluids. Mixtures that are rich in monomethyinaphthalene content have been used as dye carriers (qv) for color intensification in the dyeing of synthetic fibers, eg, polyester. They also are used as the feedstock to make naphthalene in dealkylation processes. PhthaUc anhydride also can be made from m ethyl n aph th al en e mixtures by an oxidation process that is similar to that used for naphthalene. 

The concepts behind the analysis are not difficult. The piping system is simply a stmcture composed of numerous straight and curved sections of pipe. Although, for straight pipe, elementary beam theory is sufficient for the solution of the problem, it is not adequate for curved pipe. However, by the iatroduction of a flexibiUty factor, to account for iacreased flexibiUty of curved pipe over straight pipe, and a stress intensification factor, /, to account for... 

Flexibility and Stress-Intensification Factors. The flexibihty factor k (>1.0) is defined as the ratio between the rotation per unit length of the part in question produced by a given moment to the rotation of a straight pipe (of the same size and schedule) produced by the same moment. A close approximation of the flexibiUty factor that agrees quite well with theory and experiment for bends is as follows ... 

The simplest method of reduciag stresses and reactions is to provide additional pipe ia the system ia the form of loops or offset-bonds. When physical limitations restrict the use of additional bends, a multiple arrangement of several small-size pipe mns may sometimes be used. Owiag to stress intensification, the maximum stress generally occurs at elbows, bends, and Ts. Thus, heavier-walled fittings may reduce the stress without significantly impairing flexibiUty. FiaaHy, effectively located restraints can reduce thermal effects on the equipment. 

In the absence of more direc tly applicable data, the flexibility factor k and stress-intensification factor i shown in Table 10-54 may be used in flexibihty calculations in Eq. (10-101). For piping components or attachments (such as valves, strainers, anchor rings, and bands) not covered in the table, suitable stress-intensification factors may be assumed by comparison of their significant geometry with that of the components shown. 

Comprehensive analysis shall take into account stress-intensification factors for any component other than straight pipe. Credit may be taken for the extra flexibility of such a component. 

TABLE 10-54 Flexibility Factor kand Stress-Intensification Factor i ... 

The flexibility factor k applies to bending in any plane. The flexibility factors k and stress intensification factors shall not be less than unity factors for torsion equal unity. Both factors apply over the effective arc length (shown by heavy centerlines in the sketches) for curved and miter bends and to the intersection point for tees. 

A single intensification factor equal to 0.9/h may be used for both and if desired. 

Acceptable comprehensive methods of analysis are analytical, model-test, and chart methods, which evaluate for the entire piping system under consideration the forces, moments, and stresses caused by bending and torsion from a simultaneous consideration of terminal and intermediate restraints to thermal expansion and include all external movements transmitted under thermal change to the piping by its terminal and intermediate attachments. Correction factors, as provided by the details of these rules, must be applied for the stress intensification of curved pipe and branch connections and may be applied for the increased flexibihty of such component parts. 

Openings are always required in pressure-vessel shells and heads. Stress intensification is created by the existence of a hole in an other-... 

Intensification is the preferred route to inherently safer design, as the plants, being smaller, are also cheaper. 

Substitution If intensification is not possible, then an alternative is to consider using a safer material in place of a hazardous one. Thus it may be possible to replace flammaole solvents, refrigerants, and heat-transfer media by nonflammable or less flammable (high-boiling) ones, hazardous products by safer ones, and processes which use hazardous raw materials or intermediates by processes which do not. As an example of the latter, the product manufactured at Bhopal (carbatyl) was made from three raw materials. Methyl isocyanate is formed as an intermediate. It is possible to react the same raw materials in a different order so that a different and less hazardous intermediate is formed. 

Attenuation Another alternative to intensification is attenuation, using a hazardous material under the least hazardous conditions. Thus large quantities of liquefied chlorine, ammonia, and petroleum gas can be stored as refrigerated liquids at atmospheric pressure instead of storing them under pressure at ambient temperature. (Leaks from the refrigeration eqmpment should also be considered, so there is probably no net gain in refrigerating quantities less than a few hundred tons.) Dyestuffs which form explosive dusts can be handled as slurries. 

Deficiency of natural AO in the organism brings to intensification of oxidizing processes in lipids and to occurrence in them of oxidation products in quantities that ar e above normal. 

The orientation of the cracks reveals that cyclic bending stresses or cyclic axial stresses were active. The intensification of these stresses at pits and intergranular corrosion sites produced the cracks observed. 

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