Reactions—Planned and Unplanned

Famous last words I didn t see an exotherm in the lab I only saw a little bit of foaming It goes a bit brown if you leave it in the oven for too long.  

Many accidents, particularly on batch plants, have been due to runaway reactions, that is, reactions that get out of control. The reaction becomes so rapid that the cooling system cannot prevent a rapid rise in temperature, and/or the relief valve or rupture disc cannot prevent a rapid rise in pressure, and the reactor ruptures. Examples are described in the chapter on human error (Sections 3.2.1 e and 3.2.8), although the incidents were really due to poor design, which left traps into which someone ultimately fell. 

The number of reactions that can run away is enormous, Bretherick s Handbook of Reactive Chemical Hazards [1] lists about 4,700 chemicals that have been involved in hazardous reactions of one sort or another, and there are more than 20,000 cross-references to entries involving more than one chemical. It is an essential work of reference for the chemist, the process engineer, and everyone involved in process safety. All I can do here is give a few examples to illustrate the reasons why runaways occur. 

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Identify all possible chemical reactions, both planned and unplanned... 

Identify all possible chemical reactions, both planned and unplanned Determine the inter-dependence of reaction rate and variables, establish the limiting values to prevent undesirable reactions, excessive heat development etc. 

THA helps in establishing guidelines for the sensitivity assessment of munitions. The purpose of an IM program is to increase the survivability of ships and aircraft by making munitions less sensitive to unplanned stimuli. MIL-STD-2105 provides a series of tests to assess the reaction of energetic materials to external stimuli representative of credible exposures in the life cycle of a weapon and requires the use of a THA in developing test plans. 

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