CHETAH program

The military explosives RDX and HMX are manufactured from the 3 components using the Bachman process. Some of the possible mixtures may lead to fires in open vessels and explosions under confinement, and the exothermic and other effects (some calculated by the CHETAH program) for a wide range of mixtures are presented as ternary diagrams. It was also found that acetic anhydride layered onto solutions of ammonium nitrate in nitric acid exploded, owing to formation of acetyl nitrate. 

FIGURE 2.10. Combination of Criteria 1 and 2 for Evaluating Explosibility in the CHETAH Program... 

The "Y" Criterion. The fourth criterion for hazard potential classification in the CHETAH program takes into account the number of atoms in a molecule of the substance involved, and is called the "Y" criterion. It is defined as follows ... 

Ducros, M. and H. Sannier, "Application du Programme CHETAH a l Etude de la Sensibilisation de Composes Oxygenes et a l Estimation des Limites Interfer-ieures dTnflammabilite" ("Application of the CHETAH Program for the Study of the Sensibility of Oxygen Containing Mixtures and the Estimation of the Lower Flammability Limits"), /. Haz. Mat., 19 (1988). 

Approximate heats of formation can be estimated by other methods, such as calculations that sum average bond energies. Computer programs such as the ASTM CHETAH program (Balaraju et al. 2002) use these types of calculations. Such programs may require expertise to understand and interpret. 

Other methods such as oxygen balance are available that point to chemicals likely to show self-reactivity. These methods are described in CCPS (1995b) and elsewhere. The ASTM CHETAH program (Balaraju et al. 2002) is useful for this purpose, if both the program and the expertise to use it are available to you. 

Chemical reactivity risk. See Risk assessment Chemical reactivity tests, 84-90 decision point, 90 deflagration screening tests, 85,87 reaction calorimetry, 88-90 screening data interpretation, 85, 86 small-scale screening tests, 87-88 Chemical structure and bonds, hazards identification, 80, 82 CHETAH program (ASTM), 79,82 Clean Air Act Amendments (CAAA) of 1990, 174... 

A general account of how the CHETAH program may be applied to estimation of chemical hazards in relation to process research and development has been given [10], Progressively enhanced and user-friendly versions of CHETAH, which give an overall hazard assessment and are capable of running on personal computers are available from ASTM [11], Comments critical of the criteria used for hazard evaluation in the 1994 CHETAH program [12] led to amendments and enhancements incorporated in the 1998 Windows version. The pure compound physical properties databank has since been expanded from 400 to 1500 compounds and the... 

The criteria defined by the CHETAH program (see COMPUTATION OF HAZARDS) were used to predict lower and upper flammable limits for various organic (C,H,0,N) compounds, results generally being in good agreement with experimental values [8]. 

D. J. Frurip, E. Freedman, and G. R. Hertel, in Proceedings of the International Symposium on Runaway Reactions, Cambridge, MA, March 7-9, 1989, pp. 39-51. A New Release of the ASTM CHETAH Program for Hazard Evaluation Versions for Mainframe and Personal Computer. 

A tabulation of theoretically hazardous halocarbon/aliuniruum combinations, and estimates of safe dilutions, calculated by the CHETAH program is reported [27]. See Bromomethane Metals... 

The CHETAH Program from ASTM Committee E-27 is also quite useful for theoretical calculations of enthalpy (decomposition, oxidation or combustion), oxygen balance, and potential energy release. Recent modifications of the program and updating of the data base make it even more useful. 

The CHETAH program assumes the gas phase but can also be used for evaluating condensed phases as well. When studying chemical reactions, if the assumption is made that the heat of vaporization of the reactants is equal to that of the products, the phase is irrelevant. This assumption is a reasonable one for fairly nonpolar materials. 

An example of where the CHETAH program was able to successfully be applied to the study of a condensed phase reaction is in the first step... 

In summary, we would like to emphasize the two current capabilities of the CHETAH program. The first is the estimation of gas phase thermodynamic data over the range of 25-1200°C, using Benson s second order group contribution method. The second capability of CHETAH is a hazard appraisal. This uses thermodynamic data to... 

Accelerating rate calorimeter (ARC), hazard evaluation process, 50 Accuracy, CHETAH program, 86 Addition... 

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