Example 7-15 Blast Scaling

Compare two different explosive charge weights of the same material. For an observed overpressure of 40 psi from a specific charge using the scaling equation above, the scaled distance is Z = 5 ft/lb1/3. What is the distance for an overpressure of 40 psi with a charge of 500 lb  

Applied Process Design for Chemical and Petrochemical Plants 

The distance in which a 500 lb charge will develop a 40 psi overpressure is approximately 40 ft. 

An overpressure after an explosion is noted as 0.5 psi. The calculated scaled distance Z is 75 ft/ (lb)1/3. Thus for a one pound charge, windows are broken at a distance of 75 feet. How far will windows be broken for a 500 lb. charge  

In general, a reflected shock wave of 55 psi on a human for 400 milliseconds would be just about the tolerance limit [41] (see Table 7-25B). For a more detailed discussion of blast scaling and overpressure, see Ref [40]. 

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Blast scale was determined by use of dispersion calculations to estimate fuel quantity within flammability limits present in the cloud. Initial blast strength was determined by factors which have been found to be major factors affecting the process of turbulent, premixed combustion, for example, the fuel s nature and the existence within the cloud of partial confinement or obstacles. 

A few examples of pheromones will be shown to indicate the diversity of chemical structures. Many sex pheromones of Lepidoptera tend to be long-chain aliphatic aldehydes, acetates, or alcohols. The sex pheromone of a rice borer is Z 11 hexadecenal (11.29).153 The sex pheromone of the Israeli pine blast scale is shown in 11.30.154... 

Batch-type production processes, particularly those with small batch sizes, have less energy efficiency as compared to continuous processes. A typical example of a batch operation on a relatively small scale is the production of titanium in 1-ton batches of the metal. The energy efficiency of the process is much less than that of continuous methods such as iron being produced in a blast furnace, or even of large-scale batch methods such as basic oxygen steel-making. The heat losses per unit of production are much less in continuous and large-batch processes, and this also enables the waste heat from process streams to be used. 

Blasters can use this equation to estimate the peak particle velocity of a seismic wave or they can use the graph shown in Fig 2. For example Determine the typical peak particle velocity from a normally confined blast with a maximum charge-weight-per-delay-period of 400 lbs at a distance of 1000 ft from the receiving site. The scaled distance, R/W 4 = 1000/40044 = 50 corresponds to a peak particle velocity of 0.31 ips on the graph in Fig 2... 

The scale-up problems become much more difficult if the large scale reactor differs considerably from these ideal models. Notorious examples are fluidized bed reactors without internals, stirred tanks where the macro mixing is rate determining, and reactors filled with solid material where large temperature gradients exist, such as coke ovens and blast furnaces, and some catalytic gas-phase processes. 

Specify good-quality welds and avoid heat tint scales (use inert gas back-up procedures, for example). Remove the heat tint scale mechanically (grinding, electropolishing and/or abrasive blasting) and/or chemically (pickling). 

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