Safety incompatible chemicals

Process vents and drains, including emission control devices, are often overlooked but are important elements in the safety of batch systems. Inadequate attention to these items can result in incompatible chemical mixtures within the... 

The chemical industry generally handles business so well that it is difficult to find large numbers of recent incidents for examples. Many of the featured case histories in this book occurred over 20 years ago however, the lessons that can be learned will be appropriate into the twenty-first century. Tanks can fail from the effects of overpressure and underpressure in 2010 just as well as they failed in the 1980s. Incompatible chemicals are incompatible in any decade and humans can be forgetful at any time. Before we review a single case history, it is time to boast about the safety record of the chemical industry. 

Luckily for the laboratory chemist, many of these mishaps of yesteryear have been collated, most notably (and authoritatively) by Leslie Bretherick. Bretherick s Handbook of Reactive Chemical Hazards, which by 2006 had reached its 7th edition, details the predictable and the unexpected from the literature of reactive chemical hazards. In a review, published in Hazards in the Chemical Laboratory, 5th edn, ed. S.G. Luxon, Royal Society of Chemistry, Cambridge, 1992, Bretherick has also summarised some frequently encountered incompatible chemicals that present either a reactive hazard or a toxic hazard if combined. These two lists are reprinted here as Tables 11.4 and 11.5 by kind permission of the Royal Society of Chemistry. In addition, potentially explosive combinations of some commonly-encountered laboratory reagents are shown in Table 11.6 (reproduced with permission from Chemical Safety Matters, lUPAC-IPCS, Cambridge University Press, Cambridge, 1992). 

Occasionally, analysis may require that the sample be removed from the process completely but measured at line. This approach is necessary when, for example, there is incompatibility between the process and the analysis system. This could be for safety or chemical reasons (e.g. solvent or pH incompatibility). While the measurement in such cases can be made at the process site, the actual monitoring system can be essentially the same as that used for the on-line measurements. Only the sample introduction needs to be modified. 

Good laboratory safety practice requires that incompatible chemicals be stored, transported, and disposed of in ways that will prevent their coming together in the event of an accident. Tables 1 and 2 give some basic guidelines for the safe handling of acids, bases, reactive metals, and other chemicals. Neither of these tables is exhaustive, and additional information on incompatible chemicals can be found in the following references. 

The assumption underpinning the incident pyramid is that the causes for all types of event are the same. In fact, this assumption is only partially correct because the root causes of minor events are different from those that lead to process safety events. Therefore, improving day-to-day safety will not necessarily reduce the number of serious incidents. Minor events are typically caused by occupational problems such as trips and falls, lack of proper PPE, and improper use of machinery. Major events, however, are more often caused by process safety problems such as incorrect instrument settings, corrosion, or mixing of incompatible chemicals. Hence a program that leads to improvements in occupational safety will not necessarily help reduce the frequency of process-related events. Indeed, improvements in the occupational safety record may induce a false sense of confidence regarding the potential for a major event. (It is probable, however, that a poor performance in occupational safety will correlate positively with a poor performance in process safety.)... 

Facilities for storage of research materials in the laboratory should be selected with as much care as any other item of equipment. Many chemicals may be stored on ordinary shelves or cabinets, with only common sense safety provisions being necessary. Obviously, the shelves or cabinets must be sturdy enough to bear the weight of the chemicals. Storage should be such as to make it unlikely that the materials wUl be knocked off during the normal course of activities in the room. Shelves should not be overcrowded. It should not be necessary to strain to reach materials or to return them to their places. Incompatible chemicals should be stored well apart. Finally, the amount of storage should not be excessive, in order to restrict the amount of chemicals not in current use that would otherwise tend to accumulate within the facility. Periodically, one should weed the shelves of chemicals which have not been used for some time and for which no immediate use is foreseen. Older chemicals are rarely felt to be... 

Numerous physical hazards may be present in a CDL, one of which is armed suspects who may be under the influence of methamphetamine with its induced paranoia. Explosive vapors from the solvents used in the manufacturing process as well as incompatible chemicals (when mixed, these cause fire, toxic fumes, or explosion) are common in CDLs, as most operators are not trained chemists and have little regard for safety. 

American Industrial Hygiene Association. Laboratory Health and Safety Committee, Laboratory Safety Incidents, Glass Waste Bottle Ruptures https //www.aiha.org/get-involved/VolunteerGroups/LabHSCommittee/ Pages/Glass-Waste-Bottle-Ruptures%2c-Possible-Reaction-of-Incompatible-Chemical-Wastes.aspx, (Jan 2015). 

Good laboratory safety practice requires that incompatible chemicals be stored, transported, and disposed of in ways that will prevent their coming together in the event of an accident. Tables... 

Reverse Flow can create high-consequence hazards because it can lead to the mixing of incompatible chemicals or to the introduction of corrosive chemicals into equipment not designed for them. The cause of Reverse Flow is usually a pressure reversal — a high-pressure section of the process loses pressure process fluids then flow into that section back from low-pressure sections of the process. (The occurrence of reverse flow almost invariably imphes that a check valve and/ or safety instrumented system has failed to prevent the event)... 

Precaution Wear safety glasses, chemical goggles, impervious gloves combustible incompat. with strong oxidizers, alkalis NFPA Health 1, Flammability 1, Reactivity 0... 

Uses Emulsifier, dispersant for creams/lotions, bath oils Properties Yel. liq. mod. fatty ester odor flash pt. (COC) 548 F Precaution Wear safety goggles, chemical resistant rubber gloves incompat, with strong oxidizers... 

The process of formulation for any of the above is generically the same, beginning with some form of product specification and ending with one or more formulations that meet the requirements. Correct choice of additives or excipients is paramount in the provision of efficacy, stability, and safety. For instance, the excipients may be chemically or physically incompatible with the drug or they may exhibit batchwise variability to such an extent that at the extremes of their specification they may cause failure in achieving the desired drug release profile. In addition, some excipients, especially those that are hydroscopic, may be contraindicated if the formulation is to be manufactured in tropical countries. Flence formulators must work in a design space that is multidimensional in nature and virtually impossible to conceptualize. 

The chemical and physical compatibility of decontamination solutions or other decontamination materials must be determined before use. Any decontamination method that permeates, degrades, damages, or otherwise impairs the functioning of the personal protective equipment (PPE) is incompatible with such PPE and should not be used. If a decontamination method does pose a direct health hazard, measures must be taken to protect both decontamination personnel and the workers being decontaminated. Figure 16.22 presents a decision aid for the evaluation of health and safety aspects of decontamination methods. 

A detailed strategy for the approach to safety testing is provided in Chapter 2 (Figures 2.3, 2.4, and 2.5) and in Chapter 3 (Figure 3.4). These schemes are directed to the investigation of thermal instabilities, chemical incompatibilities, including acid, water, and oxygen incompatibility, and other factors important to potential unstable behavior. 

Safety aspects are considered in two phases (Fig. 11). In the rule based synthesis some safety related rules are applied in process concept selections. These include rules such as separate corrosive or hazardous components first or avoid using chemically incompatible substances in the same process. ... 

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