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The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience (2012)

Chapter: 4 The Concepts of Inherently Safer Processes and Assessment

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Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
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4


The Concepts of Inherently Safer Processes
and Assessment

INTRODUCTION

The committee was asked to consider the processes used by Bayer Crop-Science to manufacture methyl isocyanate (MIC) and carbamate pesticides in Institute, West Virginia, and compare its analysis to “the inherently safer process assessments conducted by Bayer and previous owners of the Institute site.” Whereas the preceding chapter provided an overview of the plant and its history to provide background on the development of the processes, this chapter provides an overview to the concept of inherently safer processes (ISPs) and describes the role of ISPs in a process safety management (PSM) system as background for the analysis of the decisions made during those developments. Chapter 5 contains the analysis of alternative methods for production of MIC and the carbamate pesticides produced in Institute, including consideration of ISPs. This chapter also provides an introduction to the role that ISP analyses can play in decision-making. More information about the broader context in which companies manage decision making, and a suggested framework for approaching that process in complex scenarios, is presented in Chapter 6.

THE ISP CONCEPT

ISP is best described as a philosophy for engineering design of material processing plants, rather than a specific set of technologies or processes. The ISP philosophy can be applied at all stages in the life cycle of a manufacturing plant, from early process invention and research, through development, plant design, operation, and eventual shutdown and demolition, and at all levels of design detail.

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

It is an approach that encourages the designer to attempt to eliminate or minimize hazards (physical, inhalational, etc.) identified at each stage in the process life cycle, and at every level of process and plant design, rather than accepting the existence of the hazards and designing safety systems to control those hazards. It may not always be feasible to eliminate or reduce hazards, but the ISP philosophy requires that this be attempted before moving on to specification of risk management equipment and procedures. Note that describing a process as “inherently safer” can only be done in the context of specific hazard or subset of hazards and that management of all liazards must be considered in order to design a safer process. Thus, a substitution (inherent) might eliminate one type of hazard but require the development of new standard operating procedures (procedural) to manage a different one.

The terms “inherently safer processes” (ISPs),1 and variations such as “inherently safer technology” (IST) and “inherently safer design” (ISD) were first used in discussions about PSM in the 1970s after serious process industry incidents around that time.2 These incidents focused industry, government, and public attention on PSM, and resulted in the initial development of many of the PSM techniques and regulations that are in common use throughout the world today.

The ISP philosophy was first fully articulated in 1977 by Trevor Kletz, a senior safety advisor for Imperial Chemical Industries (ICI). That year Kletz presented the Jubilee Lectufre to the Society of Chemical Industry in Widnes, England, which he titled “What you don’t have, can’t leak.” In his talk, Kletz challenged the practice of storing large quantities of flammable or toxic materials at manufacturing plants and questioned the need for the use of elevated temperatures and pressures in processing (Kletz, 1978). He also suggested that risk management efforts should aim at elimination of hazards where feasible, instead of using safety systems and procedures to manage the risk. This should be accomplished, for example, by reducing the amounts of hazardous material used in processes, using less-hazardous materials, or developing technology that allows for processes to proceed under milder conditions. Kletz described this as “inherently safer.”3

In subsequent years, a set of principles for ISPs were established within the chemical community, an effort supported by Kletz (1984, 1985, 1991, 1998) and others in the chemical industry (Puranik et al., 1990; Ashford, 1993; Windhorst, 1995; Mannan, 2005; See also additional references at the end of this chapter). As

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1 The term “inherently safer processes” is used here in accordance with the language of the statement of task.

2 These included a 1974 explosion at a chemical plant in Flixborough, England that resulted in the deaths of 28 and injuries to another 36 individuals and a 1976 chemical release at Seveso in Milan, Italy that sickened many in the surrounding area.

3 In his 1977 lecture, Kletz used the term “intrinsically safer.” This was later changed to “inherently safer” to avoid confusion with the use of “intrinsically safe” to describe electrical equipment designed to meet specific hazardous area classification requirements.

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

the principles spread and were adopted, many examples of their implementation emerged. The Center for Chemical Process Safety (CCPS) aggregated this information in the book Inherently Safer Chemical Processes: (Bollinger et al., 1996; CCPS, 2008b). The early versions focused primarily on general concepts, but as acceptance of ISPs by the professional community has grown, the later versions extended the scope to provide more specific guidance on application of those concepts to process design. Today there are a number of working definitions of ISPs, some of which are presented in Box 4.1. In general, these definitions are quite consistent and reflect a consensus of the engineering community on what ISP means.

BOX 4.1
Definitions of Inherently Safer Processes

CCPS (2008b, p. 11). “Inherent safety is a concept, an approach to safety that focuses on eliminating or reducing the hazards associated with a set of conditions. A chemical manufacturing process is inherently safer if it reduces or eliminates the hazards associated with materials and operations used in the process and this reduction or elimination is permanent and inseparable. The process of identifying and implementing inherent safety in a specific context is called inherently safer design. A process with reduced hazards is described as inherently safer compared to a process with only passive, active, and procedural controls. An inherently safer process should not, however, be considered ’inherently safe.’ or ’absolutely safe..’ While implementing inherent safety concepts will move a process in the direction of reduced risk, it will not remove all risks. No chemical process is without risk, but all chemical processes can be made safer by applying inherently safer concepts.”

Kletz and Amyotte (2010, p. 4). “Intensification, substitution, attenuation, and limitation of effects produce inherently safer design because they avoid hazards instead of controlling them by adding protective equipment. The term inherently safer implies that the process is safer because of its very nature and not because equipment has been added to make it safer. Note that we talk of inherently safer plants, not inherently safe ones, for we cannot remove all hazards.”

State of New Jersey and Contra Costa County, California. New Jersey, in its Toxic Catastrophe Prevention Act (TCPA) (NJDEP, 2009), and Contra Costa County, California, in its Industrial Safety Ordinance

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

(Contra Costa Health Services, 1999), require consideration of ISPs as part of their regulation of hazardous industrial facilities. Both regulations cite the 1996 CCPS definition of ISP (Bollinger et al., 1996) (the regulations were issued before publication of the second edition of the CCPS book), which is substantially the same as the 2008 definition above, although not as concisely stated.

U.S. Department of Homeland Security/CCPS. The U.S. Department of Homeland Security (DHS), concerned about the potential for intentional release of hazardous materials by terrorist attack, has been interested in ISP as an approach to chemical security. In 2010, the Chemical Security Analysis Center of DHS asked the CCPS to develop a scientific definition of IST (CCPS, 2010, p. Exec 1). A summary of that definition is:

Inherently Safer Technology (IST), also known as Inherently Safer Design (ISD), permanently eliminates or reduces hazards to avoid or reduce the consequences of incidents. IST is a philosophy, applied to the design and operation life cycle.… IST considers options, including eliminating a hazard, reducing a hazard, substituting less hazardous material, using less hazardous process conditions, and design a process to reduce the potential for, or consequences of, human error, equipment failure.… IST’s are relative. A technology can only be described as inherently safer when compared to a different technology, including a description of the hazard or set of hazards being considered, their location, and the potentially affected population.… IST’s are based on an informed decision process. Because an option may be inherently safer with regard to some hazards and inherently less safe with regard to others, decisions about the optimum strategy for managing risks from all hazards are required. The decision process must consider the entire life cycle, the full spectrum of hazards and risks, and the potential for transfer of risk from one impacted population to another.

HIERARCHY OF HAZARD CONTROL

PSM is an interactive, ongoing method for controlling hazards across a facility or organization, with the overall goal of reducing the frequency and/or consequence of an incident. As described in Chapter 2, within the United States, requirements for PSM exist under the Occupational Health and Safety Administration’s (OSHA) process safety management standard (OSHA, 29 CFR 1910.119). The PSM standard lists 14 mandatory elements ranging from employee training to process hazard analysis to change management. In practice, PSM is a system

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

that necessitates consideration of multiple options for achieving a safe process and the possible outcomes from each of those options. For example, when determining which hazard management strategy is the best option for a given situation, it is important to understand the effect that any one change in process design may have on all classes of hazard and how that change may affect the type of control strategy required to maintain a safe working environment.

One approach for acknowledging and addressing these trade-offs is to consider a hierarchy of hazard control. The hierciers, inherent, inherent passive, active, and procedural, which are described briefly below.4,5 Considering these possible hazard control methods in turn can help identify options for process design or modifications to improve process safety.

Inherent

The inherent approach to hazard control is to minimize or eliminate the hazard. Substituting water for a flammable solvent to eliminate the fire hazard is an example. CCPS identifies four ISP strategies to consider when designing or modifying a process (CCPS, 2008b). As adapted from that volume, one can:

Substitute—use materials, chemistry, and processes that are less hazardous;

Minimize—use the smallest quantity of hazardous materials feasible for the process, reduce the size of equipment operating under hazardous conditions, such as high temperature or pressure;

Moderate—reduce hazards by dilution, refrigeration, process alternatives that operate at less-hazardous conditions; reduce potential impact of an accident by siting hazardous facilities remotely from people and other property; or

Simplify—eliminate unnecessary complexity, design “user-friendly” plants.

Kletz and Amyotte (2010, pp. 16-17) use somewhat different terminology and identify more specific categories (which can be mapped into the four CCPS categories above), but the basic philosophy remains the same. As stated in that reference:

One person’s intensify may be another’s minimize. Someone’s attenuate may be someone else’s moderate. You may wish to consider segregate as a measure

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4 As with the terminology regarding inherent safety categories, these classifications fall along a spectrum of process safety approaches, and people may disagree about the category into which a particular design falls. For example, some might consider that a high pressure reactor design capable of containing a runaway reaction is an inherently safer design. Others would call this a passive strategy because the hazard—the high pressure from the runaway reaction—still exists, although it is robustly contained by a high pressure vessel.

5 Not that the use of these terms is not limited to chemical process safety but are also used in consideration of nuclear facility design and management.

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

segregate as a measure separate from inherent safety; your colleague may consider it a form of limitation of effects. …the characteristics of a user-friendly plant are sometimes not sharply divided and may merge into one another. Process design, like life, is seldom linear.

The following definitions will be familiar to many in the process industry. These have been summarized and adapted from the 2008 publication inherently Safer Chemical Processes: A Life Cycle Approach, 2nd Edition from the AIChE Center for Chemical Process Safety, and similar definitions can be found in many reference texts on process safety.

Passive

Passive safety systems are those that control hazards with process or equipment design features without additional, active functioning of any device. For example, a containment dike around a hazardous material storage tank limits a spill to an enclosed area because of the geometry and construction of the dike, and no action is required to provide this function.

Active

Active safety systems control hazards through controls and systems designed to monitor and maintain specific conditions or to be triggered by an event. Active systems include process controls, safety instrumented systems (SIS), and mitigation systems. A sprinkler system put in place to extinguish a fire is an example of an active system designed to minimize consequences. A control system that regulates solvent flow into a reactor vessel and prevents overflow is an example of a monitoring system.

Procedural

Procedural safety systems control hazards through personnel education and management. Such systems include standard operating procedures, safety rules and procedures, operator training, emergency response procedures, and management systems. For example, an operator may be trained to monitor the solvent level in a reactor vessel and to shut off the feeds to the tank if the volume exceeds a given quantity.

In general, inherent and passive strategies are the most robust and reliable, requiring the least monitoring or interaction to be effective, but incorporation of strategies from all tiers of the hierarchy should be considered and incorporated as needed for comprehensive PSM. Note that all process safety controls have the potential to reduce the probability or likelihood that a worst-case accident

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

occurs. However, the incorporation of ISP concepts into process design also has the potential to provide assurance that, should a worst-case release occur (i.e., the entire chemical inventory under worst meteorological conditions), an absolute upper bound to the magnitude of an offsite release exists, and that this upper bound is less severe than the worst-case accident resulting from conventional passive, active, and procedural controls.

When performing a process safety assessment, one should consider each level of this process safety “hierarchy” in turn. Quite logically, if the hazard can be controlled with a system that emphasizes inherent safety, active controls will not be necessary. However, since ISP is defined in the context of a specific hazard, the risk of introducing new hazards must be considered. For example, one can describe a process alternative as inherently safer with respect to the acute toxicity of a particular raw material when compared with another alternative. This statement does not say anything about the relative inherent safety characteristics of the two processes with respect to other hazards (fire, explosion, reactive chemistry, chronic toxicity, environmental impact, etc.). These hazards may be greater, reduced, or remain essentially unchanged between the two process alternatives, and the ISP for one hazard may also introduce new concerns.

Thus, it will always be necessary for process plant designers and operators to develop rigorous PSM systems incorporating the appropriate combination of inherent, passive, active, and procedural safety systems to manage all hazards. Some will be best managed using inherent methods, but others will inevitably remain and be effectively managed with other PSM systems. One must never assume that it is unnecessary to worry about all elements of PSM because one “inherently safer” process has been implemented.

INCORPORATING ISP INTO THE PROCESS LIFE CYCLE

The philosophy of ISP applies at all stages, but available options, or the feasibility of implementing those options, change over the course of a technology’s life cycle. Every life cycle begins with initial research and product/process conception, and then moves through process development, conceptual plant design, scaleup, engineering and detailed plant design, plant construction, startup, and ongoing operation and future modification (Hendershot, 2011a,b). In each of these phases, different kinds of choices and decisions are made by chemists, engineers, and other technologists. Both the second edition of the CCPS book, inherently Safer Chemical Processes: A Lifecycle Approach and the recent volume by Kletz and Amyotte contain examples of how such analyses can be incorporated into a process hazard analysis, including examples from industry, and each contains additional citations for more information. These descriptions will not be reproduced here. The purpose of this section is not to provide a step-by-step description of how such analyses can be done, but to provide the reader

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

with a broad overview of the elements of the analysis as context for the rest of the report.

There is potential synergy between process simulation and understanding ISP characteristics of a process. Process simulation is a mathematical representation of industrial chemical processes, often used in process design, control, and optimization. Simulations assist engineers in evaluating process alternatives and to identify possible options to, for example, reduce energy consumption, minimize waste, perform cost and benefit studies, and maximize profitability. These tools provide information about process operating conditions and inventory in-process equipment, both of which are important factors in understanding ISP. It may be possible to more explicitly incorporate ISP considerations into process simulation tools, e.g., the inventory of hazardous materials for different process options. Linking process simulation models to accident consequence and likelihood models would have the potential to facilitate the investigation of potential benefits of process alternatives being studied.

It is clear that the best opportunity for implementing ISP into a facility is early in the life cycle of a product or process. At that early stage, process technologies have not been chosen, facilities have not been built, and customers have not yet evaluated product samples or made commitments based on products with particular characteristics. As a product moves through its life cycle, these and other factors may limit options, make changes more difficult, or involve more people and organizations in the change. Development of an ISP, as with the development of any new process, requires extensive resources, including for example, expert personnel, laboratory facilities, pilot plant facilities, and significant financial expenditures, and modifications can become more costly when the process involves modification of an existing facility.

Some typical process life-cycle stages and some examples of ISP options that are best considered at an early stage include:

•   Selection of basic technology. Consider ISP options for the chemical synthesis route, raw material and chemical intermediate hazards, energetic reactions, etc.

•   Implementation of the selected technology. Consider how the chosen process chemistry will be implemented. Can hazardous operating conditions be minimized through better catalysts or other changes in operating conditions? Can impurities and by-products be avoided to eliminate purification steps? What specific unit operations are required? What is the order of processing steps?

•   Plant design. Consider ISP aspects of plant proximity to the surrounding population, in-plant occupied areas, and sensitive environmental areas; the general layout of the equipment on the selected plant site; and the number of parallel systems and size of those system (Hendershot, 2010a).

•   Detailed equipment design. Minimize the inventory of hazardous material in specific pieces of process equipment. Consider the impact of equipment

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

layout on the length and size of piping containing hazardous materials. Consider human factors in the design of equipment to minimize the potential for incorrect operation and human error (Hendershot, 2010a).

•   Operation. Use ISP principles on ongoing PSM activities such as management of change, incident investigation, pre-startup safety reviews, operating procedures, and training to identify new opportunities for ISP.

It is important to consider the entire footprint of a process when evaluating ISP options. Is risk actually reduced, or is it transferred somewhere else, perhaps increasing overall risk? One example used to demonstrate this concept relates to the balance of onsite storage versus increased deliveries of hazardous material (Hendershot, 2006; CCPS, 2010). If a plant reduces the size of a hazardous material storage tank, would the smaller tank size require a change from shipment of the material to the plant in railroad tank cars to much smaller trucks? Such a change could then result in a greater number of shipments overall to meet process requirements (one rail car can hold approximately an order of magnitude more material than a truck). With the additional shipments traveling by road instead of rail, the change in storage tank size could result in greater overall risk from release, depending on details of the transportation route.

It is also important to recognize that an ISP assessment is often not going to result in a clear, well-defined, and feasible path forward for a company. It is a useful philosophy that can help a company reduce its risk and provide structure for consideration of the full range of options in process design. The results of any analysis, however, have to be considered in context. For example, as already described, the inherent safety of one hazard may be reduced and another increased depending on size of a shipment or the mode of transportation of the shipment, or risk may shift from one community well equipped to respond to an emergency to one less able to do so. The cost to eliminate a hazard completely may be prohibitive, but introducing a well-designed passive control system may be feasible. Consideration of these and other, broader trade-offs (community perception, product quality requirements, etc.) should be factored into any final decision.

ADDITIONAL CONSIDERATIONS

As stated in Manuele (2003), “An organization’s culture consists of its values, beliefs, legends, rituals, mission, goals, performance measures, and sense of responsibility to its employees, to its customers, and to its community, all of which are translated into a system of expected behavior.” When the philosophy of ISP is incorporated into the culture of an organization, it becomes one of the cultural norms that guide behavior within that organization. Consideration of ISP can then be incorporated into all process and design activities rather than being considered an additional check-the-box exercise.

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

CCPS (2008) highlighted elements within organizations that can encourage successful adoption of ISP as part of the organizational culture. The first of these is integration of ISP into the PSM system. This should include consideration of ISP at all stages in the process life cycle, particularly at three key stages: product and process development, conceptual facility planning and early design, and during routine operation (including modifications and incident investigation). The second element is education and awareness. ISP is a philosophy of design; its application should extend beyond just engineering design to plant operation activities. Identifying opportunities to eliminate or reduce hazards should be part of the job for everyone involved in the design and operation of a process facility. This can only happen if there is a broad awareness and understanding of ISP concepts and principles, and these require that education and supporting documentation be made available to personnel.

RELATIONSHIP BETWEEN EMERGENCY PREPAREDNESS AND ISP

Emergency preparedness (EP is often considered to be an alternative to ISP strategies because EP is a procedural control). However, as is the case with active, passive, and other procedural controls (e.g., personnel training), EP can—and should—be implemented concurrently with ISP, e.g., where Horng et al. (2005) recommended combining source reduction with warning systems to reduce chlorine risks in Taiwan. A closer examination reveals that EP and ISP are closely linked because the latter can be used to reduce the magnitude of incident demands on the onsite and offsite emergency response organizations by reducing the size of the vulnerable zones (VZs) around chemical facilities. Specifically, applying ISP principles to the EPA (1987) procedure for calculating VZs shows that substitution decreases VZ size by reducing source toxicity (i.e., level of concern), whereas minimization achieves this objective by reducing the quantity available for release, and moderation reduces VZ size by decreasing the temperature and pressure of a release.

Smaller VZs reduce the demands on the emergency response organizations by reducing the size of the population at risk. Of particular importance is the fact that smaller VZs often mean that there are smaller special populations at risk—such as residents of schools, hospitals, nursing homes, jails, and athletic stadiums (see Lindell and Perry, 2006, Table 1, for a list of special facilities). Special populations generally have more logistical impediments to implementing population protection actions such as evacuation (Van Willigen et al., 2002) and, probably to a lesser extent, sheltering in-place (Sorensen et al., 2004).

Although the adoption of ISP strategies can have a positive effect on nearby offsite risks, it is important to recognize that they can have a negative effect on more remote offsite risks by transferring rather than reducing total risk (see CCPS, 2008b, p. 212). This risk transfer occurs when reducing onsite chemical inventory has the unintended consequence of increasing the number of shipments

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

and thus increasing the probability of releases on transportation routes. This can have an adverse impact on emergency response because releases from onsite sources, by their very nature, take place at locations where they are expected to occur and where there are (relatively) ample resources for emergency response. Releases during transportation, by contrast, take place at unexpected locations where there are likely to be fewer resources to support an emergency response. For example, the sites of transportation incidents will lack the detection and monitoring systems that are often installed around fixed-site facilities. Moreover, the primary responders to transportation incidents will be public sector hazardous materials response teams that are likely to have a relatively limited knowledge of any given chemical, given that hundreds of chemicals might pass through their jurisdictions. By contrast, facility personnel often handle only a few chemicals and thus usually have a deeper knowledge of these chemicals.’ characteristics and behavior.

Additional information about the relationship between ISP and emergency response and emergency preparedness can be found in Appendix C.

OPTIONS FOR INCORPORATING ISP IN PSM

There are two common approaches to formal consideration of ISP: independent, stand-alone ISP reviews and incorporation of ISP into existing process safety review activities.

Independent ISP Reviews

An independent ISP review is conducted by a team that uses knowledge of chemistry, engineering, operation, process safety, and other relevant expertise to examine a process with the objective of understanding its hazards and finding ways to eliminate or reduce those hazards. The review can be done at any stage in the process life cycle from early product and process development through operating facilities. The more established the process, the more difficult and costly it becomes to take advantage of ISP opportunities involving the basic process technology. Thus, early consideration of ISP in product and process selection is important. Major renovation of established facilities also provides an opportunity to reevaluate the basic process technology from an ISP perspective.

The most important tool for an ISP review is an extensive checklist to help the team think about strategies and how they might apply to the process being considered. ISP reviews can draw upon any of the traditional process safety review techniques (e.g., HAZOP,6 What If, and Checklists) to identify hazards,

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6 HAZOP (Hazard and Operability Analysis) is a method of systematic evaluation of existing processes and operations developed for process hazard analysis and commonly used within the chemical industry.

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

and then use ISP checklists and principles to help identify opportunities to eliminate or reduce hazards. (See, CCPS, 2008b.) Some organizations have also incorporated incident consequence modeling into these reviews to help the review team understand the magnitude of a potential incident arising from the hazard and the potential benefit of ISP approaches to reducing the incident’s consequences. It is important to remember, however, that there are limitations to the use of checklists, and they should be considered only one element of the review and evaluation process.

Incorporation into Process Safety Reviews

Designers and operators of processing facilities use a series of health, safety, and environmental reviews at various stages in process design, development, and operation as a part of their PSM procedures. The goal is to identify hazards, and in many cases, the focus is on managing or mitigating the hazards through add-on safety devices and procedures once they have been identified.

To include ISP considerations, the protocols for conducting these reviews need to specifically require consideration of ISP opportunities as a part of these reviews. Additional, ISP-specific guide words can be added to guide word-based methodologies, such as HAZOP to encourage ISP consideration. ISP considerations also can be incorporated into all PSM activities, for example, management of change, incident investigation, pre-startup safety reviews, operating procedures, human factors reviews, and any other activities that generate lists of hazards and potential incidents. The important thing is to make sure that the participants in the activity are encouraged and trained to focus initially on eliminating and reducing hazards instead of managing and controlling hazards. This may not always be possible or feasible, but the participants should look for those opportunities rather than just assume that the hazards are present and design systems and procedures to control them.

These two approaches complement each other, and strong PSM programs incorporate both pieces.

MEASURING INHERENT SAFETY

When incorporating ISP into the PSM system, it would obviously be helpful to have a method for evaluating the inherent safety of any given approach. To that end, a relatively large number of ISP assessment tools exist for attempting to measure the degree of inherent safety of a given process or processing alternative, but there is no current consensus on ISP metrics. These techniques have been reviewed by, among others, Lees (Mannan, 2005, pp. 32.11-32.18), Khan and Amyotte (2003), Khan et al. (2003), and Kletz and Amyotte (2010). Most of these reviews have originated in the academic arena, and in general, these indices have not been applied in industry because they are in early stages of develop-

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

ment and their value has not been accepted. One potential problem is that many of the proposed indices consider many different kinds of process hazards—fire, explosion, acute toxicity, chronic toxicity, temperature, pressure, etc.—and use penalty factors to create an overall hazard index. This means that the creator of the index has applied some kind of evaluation of the relative importance of different hazards. If, as is often the case, the origin and justification for the relative importance are unclear, appropriate use of the index can be challenging.

One of the earliest efforts to develop an assessment tool was the approximately decade-old INSIDE (INherent SHE [Safety, Health, Environment] In DEsign) project conducted in Europe, and which resulted in INSET (INherent SHE Evaluation Tool), a toolkit “to identify inherently safer design options throughout the life of a process and to evaluate the options” (CCPS, 2008a). There are also well-known process safety methodologies such as checklist and what-if analyses that have been adapted for ISP consideration, primarily in terms of identifying hazards that could be addressed by the principles of inherent safety.

Well-established indexing methods such as the Dow Fire and Explosion Index (F&EI) (Dow Chemical Co., 1994b), the Dow Chemical Exposure Index (CEI) (Dow Chemical Co., 1994a), and the Mond Index (Doran and Greig, 1993) have numerous inherent safety aspects associated with their calculation procedures. The F&EI is a tool designed to help rank hazards in terms of relative physical damage in case of fire or explosion at a facility, and the CEI is a tool to aid in ranking the acute health hazard potentials of materials in the event of an airborne chemical release. The F&EI contains many elements related to ISP—for example, inventory of flammable or combustible material, high temperature, high pressure, exothermic reaction chemistry. However, the F&EI only considers fire and explosion hazards. The CEI was designed to consider material toxicity. Although these indexes have some value in characterizing the inherent safety of a plant, neither was developed with the intention of measuring inherent safety. The Mond Index is similar to the Dow F&EI, but is designed to address a wider range of materials and process and storage configurations.

Etowa et al. (2002) quantified the ISP features of both Dow indexes (F&EI and CEI) and demonstrated the beneficial impact of the principles of minimization, substitution, and moderation. The work of Edwards and coworkers at Loughborough University in the United Kingdom resulted in one of the first indexes designed specifically to address ISP opportunities—the prototype index of inherent safety, or PIIS (Edwards and Lawrence, 1993; Edwards et al., 1996).

Over the past decade there has been a proliferation of ISP indexing procedures and assessment methodologies appearing in the process safety literature. Table 4.1, adapted and updated from Kletz and Amyotte (2010) presents a summary of the literature in the area from 2002-2010.

Observations on the entries in Table 4.1 (again adapted from Kletz and Amyotte, 2010) include the following:

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

TABLE 4.1 Examples of Development of ISP Assessment Methodologies and Their Application and Extension, 2002-2010

Reference Contribution
Adu et al. (2008) Comparative evaluation of various methods for assessing EHS hazards in early phases of chemical process design.
Al-Mutairi et al. (2008) Linking of inherent safety and environmental concerns with optimization of process scheduling.
Carvalho et al. (2008) Method for identifying retrofit design alternatives of chemical processes. Uses Inherent Safety Index (ISI) developed by other researchers.
Cordella et al. (2009) Further development of procedure for decomposition product analysis (Cozzani et al., 2006) to account for acute and long-term harm to human health, ecosystem damage, and environmental media contamination.
Cozzani et al. (2006) Procedure for assessment of hazards arising from decomposition products formed due to loss of chemical process control. Applicable to consideration of substitution principle.
Gentile et al. (2003) Fuzzy-logic-based index for evaluation of inherently safer process alternatives with the aim of linking to process simulation.
Gupta and Edwards (2003) Graphical approach for evaluating inherent safety based on earlier developed Loughborough Prototype Index of Inherent Safety (PIIS).
Hassim and Hurme (2010a) An Inherent Occupational Health Index was developed to assess the health risk of process routes during the process research and development stage. The index can be used to compare process routes or to determine the level of inherent occupational health hazards.
Hassim and Hurme (2010b) The Health Quotient Index (HQI) was developed for assessment during the preliminary process design phase. This index quantifies a worker’s health risk from exposure to fugitive emissions by using data from process flow diagrams. This method can be used to quantify the level of risk from a process or to compare alternative processes.
Hassim and Hurme (2010c) The Occupational Health Index (OHI) was developed for assessment during the basic engineering stage. “This method relies on the information available in piping and instrumentation diagrams and the plot plan.” The health aspects considered are chronic and acute inhalation risks, and dermal/eye risk.
Hassim and Hurme (2010d) This method estimates inhalation exposures and risks and can be used early in the design stages by utilizing process flow diagrams. The risk of chemical exposure can be evaluated through either the “hazard quotient method or calculating the carcinogenic chemicals intake and the resulting risk of cancer.”
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Reference Contribution
Hassim and Edwards (2006) Process Route Healthiness Index (PRHI) for quantification of health hazards arising from alternative chemical process routes. Application is in early stages of chemical plant design.
Hurme and Rahman (2005) Discussion of implementation of inherent safety throughout process life-cycle phases. Use of ISI developed earlier.
Khan and Amyotte (2004) Integrated Inherent Safety Index (I2SI).
Khan and Amyotte (2005) Further development of I2SI to include cost model.
Kossoy et al. (2007) Use of nonlinear optimization method to select inherently safer operational parameters for given configuration of reactor equipment and materials. Primary concern is cooling failure.
Landucci et al. (2007) Procedure and indexes for evaluating inherent safety at preliminary process flow diagram (PFD) stage for hydrogen storage options.
Landucci et al. (2008) Further development of PFD method (Landucci et al., 2007) by use of quantitative key performance indicators (KPIs) to remove subjective judgment.
Leong and Shariff (2008) Further development of iRET (Shariff et al., 2006) to incorporate a quantitative inherent safety level (ISL), thus enabling integration of design simulation software with an Inherent Safety Index Module (ISIM). Application is again at the preliminary design stage.
Leong and Shariff (2009) Evolution of ISIM (Leong and Shariff, 2008) to a Process Route Index (PRI) for comparison and ranking of different routes to manufacture the same product based on hazard potential of routes.
Meel and Seider (2005) Use of game theory to achieve inherently safer operation of chemical reactors.
Palaniappan et al. (2002a) “Methodology for the integrated inherent safety and waste minimization analysis during process design.”
Palaniappan et al. (2002b) Indexing procedure for inherent safety analysis at process route selection stage.
Palaniappan et al. (2002c) Indexing procedure for inherent safety analysis at process flowsheet development stage. Discussion of iSafe, an expert system for automating procedures developed by Palaniappan et al. (2002b,c).
Rahman et al. (2005) Comparative evaluation of three ISIs with expert judgment at process concept phase.
Rusli and Shariff (2010) This paper presents the Qualitative Assessment for Inherently Safer Design (QAISP) method for application during preliminary design. This qualitative method combines hazard review techniques with inherently safer design concepts to generate inherently safer plant options/proactive measures.
Shah et al. (2003) SREST (substance, reactivity, equipment, and safety technology) layer assessment method for environment, health, and safety (EHS) aspects in early phases of chemical process design.
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Reference Contribution
Shariff and Leong (2009) This paper proposes a method of evaluating inherent risk within a process as a result of the chemicals used and the process conditions. Through integration with HYSYS, the method can be used as early as the initial design stages to determine the probability and consequence of possible risk due to major accidents.
Shariff and Zaini (2010) This paper reports on the development of Toxic Release Consequence Analysis Tool (TORCAT), a “tool for consequence analysis and design improvement via inherent safety principle by utilizing an integrated process design simulator with toxic release consequence analysis model.”
Shariff et al. (2006) Integrated Risk Estimation Tool (iRET) for inherent safety application at preliminary design stage. iRET links the design simulation software HYSYS with an explosion consequence model.
Srinivasan and Kraslawski (2006) Application of TRIZ methodology for creative problem solving to design of inherently safer chemical processes.
Srinivasan and Nhan (2008) Inherent Benign-ness Indicator (IBI), a statistical-analysis-based method for comparing alternative chemical process routes.
Tugnoli et al. (2009) A quantitative inherent safety assessment method is presented. This method utilizes process flow diagrams in early design stages. The result of the assessment is a quantification of the inherent safety of the process scheme by a set of key performance indicators.

SOURCE: Adapted from Kletz and Amyotte (2010) and supplemented with additional citations from the literature from late 2009-2010.

•  Many of the methods deal specifically with the early concept and route-selection stages of the design process.

•  Some of the approaches use sophisticated mathematical and problem-solving techniques such as fuzzy logic.

•  There has been a growing trend to link inherent safety with environmental and health issues in an effort to achieve an integrated approach.

•  There have been attempts to incorporate inherent safety assessment into process design simulators, and these efforts should be encouraged.

•  Some of the indexing methods have been in existence long enough for comparative evaluations to be made among them.

When commenting in 2005 on potential barriers to wider adoption of inherently safer design principles in the process industries, Edwards (2005) noted that the issue may not be the availability of ISP assessment tools but rather the limited use of these tools by industry. Reasons might include the subjective judgment

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

required by some of these tools and also their attendant complexity (Kletz and Amyotte, 2010). In 2011, it appears that the same availability of tools, yet limited uptake by industry, exists. Additional concerns surround the incorporation of ISP and PSM analysis into the business decisions a company must make. This is discussed in greater detail in Chapter 6.

Another approach that considers some important aspects of ISP, is consequence analysis of potential incidents. Estimates of the potential impact of an incident will include evaluation of the effect of inventory of hazardous material, flammable and toxic properties, plant operating temperatures and pressures, plant location, and other factors. Designers considering ISP alternatives for a process can model consequences associated with potential design options and understand whether the proposed ISP options have a significant impact on incident consequences. However, modeling and evaluating potential probabilities and impacts of system failures (worst-case accidents) can present their own challenges, especially with regards to modeling human behavior. This can lead to flawed evaluations in terms of emergency response and risk communication needs. This is described in greater detail in Box 4.2.

BOX 4.2
ISP and Probability Safety Analysis

Assessments about the safety of systems comprising conventional active, passive, and procedural controls are typically based on probabilistic safety analyses (PSAs) that estimate the probability of a worst-case accident from three inputs. These are (1) a probabilistic safety model (e.g., a mathematical model such as a fault tree or event tree) that identifies the events, such as process component and engineering safety feature (ESF) failure, that are required to produce a release; (2) the estimated probabilities of those events; and (3) the logical interrelationships among those events. The probabilistic safety model is used to combine the estimated probabilities of the individual events (component or ESF failure) to produce the estimated probability of the worst-case accident.

Once a probabilistic safety model has been developed, it can be used to compare the accident probabilities associated with different plant/process designs. Ultimately, the mathematical model is often used to determine when the probability of the worst-case accident has been decreased to a level that is acceptable to plant management. However, it is important to recognize that any mathematical model is a simplification of reality that ignores factors the analyst considers to have minimal effects on the probability of an offsite release. In addition, probabilistic

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

safety models sometimes ignore factors for which there are no available data or for which there is no established procedure for including them in the analysis.

One common problem in probabilistic safety models is that they are applied to systems composed of both people and technical systems but only the technical (equipment) components are modeled. This problem is being addressed in techniques that address human reliability (e.g., Swain and Guttman, 1983; Gertman et al., 2005; Spurgin, 2010) but human reliability is not always considered in plant PSAs.

Another common problem in probabilistic safety models is that the builders of the model often assume that the events in the model are independent. This assumption is violated when a common cause can fail multiple process components or ESFs, such as when an earthquake simultaneously fails a pipe carrying a toxic chemical, the secondary containment for that pipe, the flare tower, and the water curtain. Less obviously, the independence assumption is violated when a single operator fails to properly control multiple ESFs, a single maintenance person fails to properly maintain multiple ESFs, a single manager fails to properly supervise multiple operators or maintainers, or when an organizational unit’s safety culture tolerates inadequate performance. Such dependencies could be included in the model, but often this is not done.

The neglect of human reliability and event dependence in probabilistic safety models leads to systematic underestimates of incident probabilities. However, such underestimates will not create significant problems when two system designs being compared that are very similar in their susceptibility to human error and common-cause failures. This is because in such cases comparison of similar system designs by subtraction of the failure probability of one system from the failure probability of the other yields the correct difference even if both of the absolute estimates are biased. For example, suppose the estimated failure probability for System 1 is PE1(which equals PT1- PB, where PT1is the true failure probability for System 1 and PB is the bias due to omitted error causes) and, similarly, the estimated failure probability for System 2 is PE2(which equals PT2-PB, where PT2is the true failure probability for System 2 and PB is again the bias due to omitted error causes). The difference between the estimated failure probabilities for the two systems is unbiased as long as the omitted error causes are the same in both systems because PE2- PE1= (PT2- PB)–(PT1- PB) = PT2- PT1.The difference between the estimated failure probabilities for the two systems is unbiased as long as the omitted error causes are the same in both systems because PE2- PE1= (PT2-Pε)–(PT1- Pε) = PT2- PT1. By contrast, the absolute esti-

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

mates of failure probability (i.e., the differences of PE2and PE1from zero) are biased to the extent that failure causes have been omitted from the probabilistic safety model. This illustration explains why it is so important to compare probabilistic safety analyses of (relatively) similar systems and to be very skeptical of estimates of absolute failure probabilities. Unless the failure modes for both systems are identical, the bias in each estimate may not be the same in which case the probability models may not be useful even for comparing alternative systems unless they are corrected to account for common-cause failures and human errors.

One consequence of underestimating the failure probability of a conventional system of active, passive, and procedural controls is that such underestimates make ISP strategies seem to be less advantageous than they would be if the failure probability of a conventional system of active, passive, and procedural controls were accurately estimated. If the magnitude of the underestimate were known to be small, then there would be little reason to be concerned about it. However, the magnitude of the underestimate is not known, but the evidence from published post-accident investigations suggests that it might be sufficiently large that conventional strategies of active, passive, and procedural controls are being chosen in situations where ISP strategies might produce significantly greater levels of safety at reasonable cost. To avoid this problem of underestimation, PSAs need to more carefully consider human reliability, common-cause errors and, in particular, organizational safety culture.

Another consequence of underestimating the failure probability of a conventional system of active, passive, and procedural controls is that such underestimates can lead to a neglect of offsite emergency response and emergency preparedness because of the belief that they are unnecessary. Consequently, plant personnel have insufficient familiarity with offsite agencies emergency plans and procedures to work effectively with them when emergencies occur. This can lead to major problems in the implementation of warning and protective actions (shelter in place or evacuation) of nearby residents.

Finally, underestimating the failure probability of a conventional system of active, passive, and procedural controls hinders risk communication with other stakeholders. In many cases, community groups focus on the worst-case accident and have relatively little interest about the estimated probability of that event. By contrast, plant personnel typically focus on the (estimated) low probability of a worst-case accident and believe that this justifies a low priority for what they consider to be only marginally greater safety at significantly greater cost. The disagreements are likely to be particularly acute if community groups mistrust plant management and, thus, have low confidence in the effectiveness of a conventional system of active, passive, and procedural controls.

Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×

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Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
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Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
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Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
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Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 61
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 62
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 63
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 64
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 65
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 66
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 67
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 68
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 69
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 70
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 71
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 72
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 73
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 74
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 75
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 76
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 77
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 78
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 79
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 80
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 81
Suggested Citation:"4 The Concepts of Inherently Safer Processes and Assessment." National Research Council. 2012. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience. Washington, DC: The National Academies Press. doi: 10.17226/13385.
×
Page 82
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The use of hazardous chemicals such as methyl isocyanate can be a significant concern to the residents of communities adjacent to chemical facilities, but is often an integral part of the chemical manufacturing process. In order to ensure that chemical manufacturing takes place in a manner that is safe for workers, members of the local community, and the environment, the philosophy of inherently safer processing can be used to identify opportunities to eliminate or reduce the hazards associated with chemical processing. However, the concepts of inherently safer process analysis have not yet been adopted in all chemical manufacturing plants. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience presents a possible framework to help plant managers choose between alternative processing options-considering factors such as environmental impact and product yield as well as safety- to develop a chemical manufacturing system.

In 2008, an explosion at the Bayer CropScience chemical production plant in Institute, West Virginia, resulted in the deaths of two employees, a fire within the production unit, and extensive damage to nearby structures. The accident drew renewed attention to the fact that the Bayer facility manufactured and stores methyl isocyanate, or MIC - a volatile, highly toxic chemical used in the production of carbamate pesticides and the agent responsible for thousands of death in Bhopal, India, in 1984. In the Institute accident, debris from the blast hit the shield surrounding a MIC storage tank, and although the container was not damaged, an investigation by the U.S. Chemical Safety and Hazard Investigation Board found that the debris could have struck a relief valve vent pipe and cause the release of MIC to the atmosphere.

The Board's investigation also highlighted a number of weaknesses in the Bayer facility's emergency response systems. In light of these concerns, the Board requested the National Research Council convene a committee of independent experts to write a report that examines the use and storage of MIC at the Bayer facility. The Use and Storage of Methyl Isocyanate (MIC) at Bayer CropScience also evaluates the analyses on alternative production methods for MIC and carbamate pesticides preformed by Bayer and the previous owners of the facility.

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