Bow-tie diagrams are emerging as a very useful tool to depict and maintain an up-to-date, real-time, working risk management system embedded in daily operations. They are a proven concept in the worldwide offshore industry. These diagrams provide a pictorial representation of the risk assessment process. This article introduces the bow-tie concept to the downstream and chemical process industries in the United States. The authors believe that bow-tie diagrams can be a resourceful method in the safety and risk practitioner's toolkit to improve performance of the hazard identification and risk assessment process and to demonstrate that major hazards are identified and managed to as low as reasonably practicable. Because of their graphical nature, the biggest advantage of bow-tie diagrams is the ease to understanding of risk management by upper management and operations groups. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Based on the thermal balance between quenching and heating potentials of each component (fuel/oxygen/diluent), a method of computing flame temperature is proposed. This method can be used to find the critical flame temperature at lower flammable limits or estimate the lower flammable limits with an assumed critical flame temperature. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Numerous research activities are conducted all over the world to study biological treatment of H₂S in laboratory-scale bioreactors. Important hazards associated with these bioreactor systems include the escape of H₂S gas and leakage of chemical/biological liquids, which have severe adverse effects on the involved labors, equipment, and materials. The objective of this article is to present a quantitative safety analysis of a laboratory-scale continuous bioreactor system for H₂S gas biotreatment using the fault tree analysis approach. Three unwanted top events were determined as the most hazardous events, being H₂S leakage inside the laboratory, H₂S leakage to outdoor from bioreactor outlet, and leakage of liquid chemical/biological solutions. The minimal cut sets and the probability of the occurrence of each top event were determined. The importance of cut sets and basic events were calculated, and priorities for control measures were determined. The analysis allows better decision on priority of control measures, and maintenance or replacement schemes of the system components in an endeavor to minimize the probability of failure or hazard occurrence. The presented analysis proves the usefulness of fault tree analysis in making quantitative risk assessment and safety analysis, which are important elements in laboratory safety management system. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

This article describes the new offshore safety management rule that is often referred to as SEMS II. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

This article provides an overview of combustible dust. A summary of recent combustible dust incidents and the variety of types of materials that can represent a combustible dust hazard when present in a particulate form are provided. Fundamentals of combustible dust are covered, comparing and contrasting combustible dust to flammable gases and vapors. Test methods used to characterize the hazards of combustible dust are reviewed. Relevant standards and regulations are described. Finally, guidance on the primary methods to prevent and mitigate combustible dust incidents is summarized. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

The principle that the risks for a facility should be reduced to As Low As Reasonably Practicable (ALARP) increasingly is embraced around the world. This article describes how the principle can be used to establish both individual and group risk tolerance criteria that are needed for risk analysis studies using techniques such as Layers of Protection Analysis. The consideration of uncertainties in risk estimates in the ALARP context and the use of the precautionary principle are also described, and the use of cost–benefit analysis in applying the ALARP principle is discussed. Other related principles used in risk management are described. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

An explosion in an atmospheric storage tank initiated additional tank explosions and a pool fire at a tank facility in Norway. The tank farm had been operated as a purification plant for a petroleum product called coker gasoline. The process entailed extraction of malodorous sulfur containing components, in particular thiols (mercaptans). After several tanker loads of coker gasoline had been treated with a solution of sodium hydroxide and water, the efficiency of the sweetening process declined as precipitated waste accumulated in the tanks and the alkaline solution became increasingly saturated with impurities. The approach adopted for handling the accumulated waste included the addition of hydrochloric acid to neutralize the spent caustic. The explosion occurred when about 80% of the scheduled amount of acid had been added to the solution in the tank. There were no fatalities in the accident, but at least two people received medical treatment for injuries sustained during the course of events. The investigation concluded that the accident was caused by a chemical explosion in the tank. Several factors point toward thiols as the predominant constituents in the fuel–air mixture, but vapors from other volatile substances may also have played a decisive role. The ignition source was most likely a hot surface, resulting from adsorption of volatile organic compounds on activated carbon in the air filter and subsequent self-heating and glowing combustion in the carbon bed. The article summarizes the main results from the accident investigation and lists various measures that can be taken to prevent similar accidents in the future. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

This article explores new process safety metrics for measuring process safety performance in the chemical processing industry. While Process Safety Management enables an operation to optimize their process safety programs and organizational risks, there is an emerging need to evaluate process safety implementation across an organization through measurement of key indicators. Lagging metrics utilize process safety incidents as the numerator and divide it by an appropriate process-related denominator or “normalization factor.” Currently, work hours is used extensively as a normalization factor to evaluate safety performance in the process industries. However, this lagging metric does not directly reflect process safety information and may not accurately reflect the safety performance of the process. Modified denominators are explored in this study and compared with the existing time-based denominator to validate the effectiveness and applicability of the new metrics. Each proposed normalization factor was validated using available industry data. A statistical unitization method has been used to convert incident rates of different ranges for the convenience of comparison. Results show that some proposed process-related metrics have potential as alternatives, used along with the time-based metric, to evaluate process safety performance within organizations. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Technicians in laboratories and factories need the instruments and equipment which they use to be reliable, available, maintainable, and safe. In addition, sometimes an apparatus is also required to be foolproof. This article deals with the question of how the concept of foolproofness may be defined and tested. To clarify its meaning, the term “foolproofness” is compared with a similar concept—that of inherent safety. The article proposes a criterion describing acceptable foolproofness of an instrument, and a procedure which may be used to test whether the apparatus is acceptably foolproof. An example illustrates how the procedure to examine foolproofness may be applied. Selected parts of a case study show that the procedure is applicable to the analysis of scientific apparatus under development, and that it is able to provide the designer with reasonable results. It helps reveal the areas where the design of apparatus could be improved. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Due to the extremely corrosive environments inside many exhaust ducts fabricated from combustible materials, the mechanical integrity of fire sprinkler system components is often prematurely compromised, leaving the system unable to protect against fires originating within these ducts [FM Global Loss Prevention Data Sheet, 7–78, Industrial Exhaust System, 2011; Understanding the Hazard, Fire in Industrial Exhaust Systems, FM Global, Johnston, RI, 2006]. Pilot testing of a new fire sprinkler system was conducted to protect the fiber-reinforced plastic duct at a nitric/hydrofluoric (HF/HNO₃) mixed acid pickling operation. Based on previous laboratory and field tests [Su and Doerr, Process Saf Prog 29 (2010) 70–78], this fire sprinkler system was composed of corrosion resistant sprinkler nozzles, a linear heat detector, flexible mounting connections, sprinkler piping, and controls. Pilot testing results have led to development and recommendation of a new fire protection system capable of protecting combustible exhaust ducts from fire in extremely corrosive environments. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

The April 2010 Deepwater Horizon tragedy and release from the Macondo Well resulted in a re-examination of the existing regulatory framework, significant modifications to the structure and function of key regulatory agencies, and the application of new safety management system (SMS) requirements to offshore facilities in United States waters. Late-2010 witnessed the evolution of both prescriptive and performance-based regulations designed to address the direct and underlying causes of this tragedy. The objective of this article is to briefly review these new regulatory requirements and illustrate how they are related to the application of other SMSs, for both offshore and onshore facilities. The common themes, objectives, and overlaps of specific onshore and offshore SMS elements was examined, and tips on how these overlaps can be used to more effectively (and sensibly) implement these programs is discussed. This article also outlined successful SMS programs that are being applied by various state agencies to onshore and offshore coastal facilities, and derived lessons-learned from these programs that may assist in the implementation of related federal programs. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

The determination of safety integrity levels (SILs) for safety instrumented functions requires the comparison of calculated risk with risk tolerance criteria. The IEC 61511/ISA 84 standard on safety instrumented systems specifies the use of risk tolerance criteria for hazardous events but does not provide any guidance on the type or form of criteria that should be used. Industry guidance on appropriate risk tolerance criteria for SIL determination is also lacking. This article discusses the type and form of criteria that should be employed and their use in SIL determination is described. ©2013 American Institute of Chemical Engineers Process Saf Prog, 2013

The Safety and Chemical Engineering Education (SAChE) program, initiated in 1992, is a cooperative effort between the Center for Chemical Process Safety (CCPS) of the American Institute of Chemical Engineers (AIChE) and engineering schools to provide teaching materials and programs that bring elements of process safety into the education of undergraduate and graduate students studying chemical and biochemical products and processes. The SAChE Committee is comprised of representatives from academe and industry in addition to AIChE and CCPS staff with the objective of developing and distributing teaching materials on chemical process safety. In addition to providing a brief history of SAChE, this article summarizes the current major efforts of the Committee including SAChE Products (materials suitable for classroom adaptation distributed through its web site http://www.sache.org), SAChE Faculty Workshops (to introduce faculty to the practice of chemical process safety in an industrial setting), and SAChE Student Safety Certificate Program (materials suitable for self-study currently available through the AIChE eLearning web site http://aiche.learn.com). © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Excellent safety performance is our goal. But safety is not bankable. Long periods of time without significant incidents may in some cases create an unwarranted sense of complacency and relaxation of discipline. We must encourage a healthy respect for process industries chemicals, equipment, processes, procedures, and all the things we do for process safety management. Continuous incident-free operations may result in a slackening up of our well-established practices and procedures. Perhaps, incident-free safety performance tolerates a wink and a nod at proven methods allowing questionable shortcuts to flourish. This article offers some suggestions on raising the awareness by sharing focused examples of past mistakes and some catastrophic blunders. A number of resources are listed that identify easy-to-use, thought provoking case histories. Some are available at no cost. If employees share a sense of vulnerability within their process, there will probably be less deviation from time tested protective operations and maintenance activities. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

This article contains supporting materials and information that can be added to any safety course to improve the effectiveness of teaching in a university course or in an industrial seminar. These materials are primarily selected from a huge source of available materials by Safety and Chemical Engineering Education Committee (SAChE) and the U.S. Chemical Safety Board. The selection process is based on my own industrial and teaching experiences: (a) materials that I know emphasized the industrially important safety concepts and (b) materials and information that give the students and young professionals a positive safety culture; that is, the long lasting interest, knowledge, and motivation to prevent process accidents and injuries. The concepts described and stressed in this article include (a) motivation or reasons for studying process safety, (b) laboratory safety (including requirements for wearing safety glasses), (c) reactive chemicals, (d) boiling liquid expanding vapor explosions (BLEVEs), (e) hazards of dusts, (f) confined space entry, (g) nitrogen asphyxiation, (h) safety reviews and introduction to PSM, (i) Piper Alpha and details of PSM, and (j) continuing education. This article also identifies the source of existing and readily available process safety course lecture materials: the core materials that are enhanced with the supporting materials and information described in this article. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

As with any undergraduate engineering course, the selection of topics to include in a process safety course can benefit from a structured decision-making approach. Suggestions are offered in this article on the importance of considering the following entities/resources as educational determinants: accreditation bodies, professional practice regulatory bodies, technical societies, process safety and other literature, industry, and factors unique to a given institution. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

The authors were asked to assist a utility with a risk management decision. Specifically, the utility was considering whether they should maintain or decommission an 800,000 gallon propane storage sphere. The 30-year old sphere was the fuel storage vessel for a propane standby system. One of their major concerns was the shrinking buffer zone around their facility. Although the facility was originally located in a remote rural area, residential development had begun to encroach upon the facility's buffer zone.

This article describes a simple cost effective alternative to the United Nations tests for determining the Self Accelerating Decomposition Temperature (SADT) for transporting reactive chemicals. The proposed method uses simple calorimetry results together with well known heat loss models. Some detailed results and analysis are included that show (a) the proposed method gives essentially identical results as the United Nations H.1, H.2, and H.3 results, (b) the proposed method is not sensitive to the shape of the reactant, and (c) the proposed method can be easily used to determine results as a function of various conditions. This alternative method provides correct SADT of the substance as packaged for transport, and is, therefore, consistent with suggestions by the United Nations “Recommendation on the Transport of Dangerous Goods.” © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Management of change (MOC) is one of the more fundamental elements of process safety management (PSM) and one which is common to all PSM frameworks. It is also an activity that breeds frustration and difficulty in many organizations, and this may impede its effectiveness. To address, this concern it is necessary to fully understand the purpose and benefits of MOC, and the efforts required to make it work. This article highlights some of the principal barriers to an effective MOC initiative and suggests ways to streamline it so that it provides optimum benefit. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Several types of experiments are performed in laboratories at Fauske & Associates, LLC (FAI). Test equipment includes calorimeters to characterize reactive chemical systems and multiple instruments to characterize both combustible dust and gas/vapor explosions. It is a challenge to ensure that each project is completed safely, since a variety of chemicals are used and tested under extreme conditions. It is vital to ensure the safety of people, property, and the environment at all times. This requires first identifying the hazards (including rigorous review of material safety data sheets) and then implementing adequate engineering and administrative controls as necessary. This article will document best practices including management commitment, predicting and eliminating hazards during extreme test conditions, and implementing inherently safer design concepts to laboratory testing. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

It is well known in business improvement circles that good management does not necessarily equal good leadership. This applies to process safety management (PSM) as well. Effectively leading the translation of PSM to action for all whom it affects takes several concurrent actions beyond what is written in PSM regulations. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Process safety events (or near misses and incidents) are key indicators of a company's process safety performance. The goal in reporting and evaluating near misses is to improve operators’ hazards awareness by recognizing unsafe conditions and acting on less-severe Tier 3 near miss events before they escalate into more severe Tier 1 and Tier 2 type process safety incidents. Near miss analysis can also be used to identify themes and trends that a company should focus on to improve process safety risk management at their facilities.

While safety instrumented systems (SISs) can be an essential element of process facility design to minimize the potential for process incidents, in some cases they can also be over-applied in the design phases of capital projects where the safety instrumented functions (SIFs) associated with the SIS are defined before the process hazards have been fully characterized. This approach may provide one mechanism for achieving a robust process control system design; however, the application of SIS also brings increased costs associated not only with the robust equipment needed to meet safety integrity level (SIL) requirements but also with the ongoing maintenance, testing, and procedures required throughout the SIS lifecycle. In order to balance the important safety benefits associated with the SIS with the increased capital costs it is critical to have a specific and comprehensive basis for decision-making. This article will illustrate the value engineering benefits of using the combined Hazard and Operability (HAZOP) Study and Layer of Protection Analysis (LOPA) methodology to comprehensively evaluate a design and provide a decision-making platform for determining whether protection for process hazards should be implemented using a SIF, a basic process control system (BPCS) feature, or alternate safeguard categories (e.g., relief valves, alarms, etc.) to ensure an adequate level of reliability without compromising safety. When the HAZOP/LOPA Study is performed following the value engineering session, the HAZOP/LOPA Study provides a critical cross-check to ensure safeguards are adequate and that changes made during the value engineering study do not introduce additional hazards. In contrast, when the HAZOP/LOPA Study is performed prior to the value engineering session, it provides a basis for decision making to remove SIFs or switch the function to the BPCS when the risk was determined to be low by the team (as defined by specific operating company criteria). © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

An article presented at the 8th Global Congress on process safety addressed the need to validate the adequacy of safeguards in order for them to be credited in process hazard analysis (PHA). Validation of safeguards is critical for process safety but its inclusion within PHA would cause a serious distraction from identifying hazard scenarios, which is the key objective of PHA. Furthermore, safeguard validation needs to be performed by qualified personnel with a different skill set than PHA team members using validation methods that are much different than PHA. Consequently, validation of safeguards, and other aspects of process safety that support PHA, should be performed before commencing PHA. The PHA team can then focus on the qualification ofsafeguards for specific hazard scenarios during the PHA. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

The identification, reporting, investigation, and subsequent elimination of the causes of process safety near miss (PSNM) events and the improvement of corresponding management systems will reduce or eliminate causes of process safety incidents before they occur. This article will focus on how The Dow Chemical Company is implementing a PSNM program at a global level. In addition, there will be several case studies demonstrating how the PSNM program has driven sustained improvements in facility management systems and unit operations. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Many companies collect and report process safety incidents. Some companies also collect process safety near misses. These safety near misses are sometimes quality deviations; for example, a process parameter that exceeds the safe operating limit, a critical safety system that is activated, or a minor release of hazardous material occurs. The intent of this article is to show how a quality incident can also be a process safety near-miss and what should be done to recognize its potential severity. Many of the causes of quality problems may be subtle, such as the fouling of cooling surfaces or a control valve that responds slowly. If these issues continue unchecked, the conditions will continue to persist and a more serious event occurs. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Process safety management (PSM) is often presented as technically complex, requiring a large staff of engineers and specialists with an array of tools and techniques that appear to grow in intricacy and sophistication year by year. Large companies are generally well positioned to operate in this arena—they have the resources to afford a staff of professionals and invest in system development, research specific problem areas, and construct elaborate PSM programs. Smaller enterprises can have similar risks, yet seldom have the internal resources and expertise to match the PSM efforts of the majors. The role of management can be over-simplified to employing the right expertise to take care of process safety.

By definition, process safety leading indicators are predictive in nature and therefore should have a direct correlation with actual process safety incidents. This article will present Six Sigma methodologies to map the process and analyze measurements, identify leading indicators and determine where statistical correlations exist among leading indicators and actual incidents, as well as how to differentiate normal variation from an actual shift from baseline performance. The methods presented are process mapping, statistical andgraphical analysis, chi-square test, and control charting. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

The standard dust explosibility test is performed in a 20-L vessel with either one or two 5 kJ pyrotechnic igniters. The dust is deemed to be explosible if the ratio of the maximum deflagration pressure to the initial pressure exceeds some threshold value. This type of test is widely accepted and used. However, marginal dusts may be “over driven” in the 20-L standard test and yield a “false positive” result (i.e., indicate that the dust is explosible), even when such a dust is not capable of forming a dust cloud through which a flame would actually propagate any significant distance. This can be avoided by testing such dusts in a larger vessel, where the flame must propagate over a more reasonable distance in order to develop a maximum pressure sufficient to classify the dust as explosible. This article reports on urea dust testing where this type of result was obtained, but the approach taken in this work is applicable to other dusts as well. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Experiments were performed in order to measure evaporation rates of four different volatile organic compounds (VOC; 2-propanol, 1-hexene, acetone, propanal) and water. Evaporation mass flow rates and liquid temperatures where recorded. Different correlations were tested versus the experimental. Exponents and constant were recalculated to fit the experimental data. This new correlation was tested on an additional VOC experimentation (ethanol) and the accuracy of the correlation was satisfying. The correlation robustness was investigated versus temperature and wind velocity. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

A test was conducted which demonstrates that a detonation wave, once formed due to a deflagration to detonation transition (DDT) within a congested region, will propagate as a detonation from the congested region into an uncongested region. This is the expected behavior based on the general behavior of detonation waves as well as other tests reported in literature. The impact of a detonation wave propagating beyond the congested volume in which it is initiated on the resulting blast load was evaluated parametrically. As would be expected, the impact on the blast load is large for flammable clouds which extend well beyond the congested volume. The test rig was 16.5 m (54 ft) long with the first 9.1 m (30 ft) of the rig length comprised of a congested section 3.7 m (12 ft) in width and 1.8 m (6 ft) high. The congestion was made up of a regular array of vertical circular tubes [6 cm (2.375 in.) diameter, pitch-to-diameter ratio of 4.1, area and volume blockage ratios of 23% and 4.2%, respectively]. The last 7.3 m (24 ft) of the test rig length was completely uncongested. The test rig was configured without any confinement (i.e., no wall or roof sections). A near-stoichiometric ethylene-air mixture completely filled both the congested and uncongested portions of the test rig. Prior testing with a similar rig configuration had shown that this flammable mixture would undergo a DDT within the congested portion of the rig. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

This article summarizes the first part of a benchmark exercise comparing seven different commercial three dimensional codes used for dispersion modeling in the context of major accident risk assessments. The aim of this first stage was twofold: First, the project intended to better understand the potential magnitude of the variation in results for a relatively simple study case. The benchmark case confirmed that, just as with integral models, the use of different codes can cause significant variation in the dispersion results. Second, the study wanted to identify the key assumptions which had a predominant influence on the uncertainty of the results, with the intention of providing clear guidance in engineering specifications for the definition of the scope of work of a computational fluid dynamics dispersion study. This article summarizes the key drivers identified, to date, for the variation in results, and the work shows this variation can be reduced to an acceptable margin by clearly specifying these key assumptions. © 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

Hydrogen is a critical component in the production of cleaner fuels. Underground pipelines provide a safe, reliable supply of hydrogen to refineries and the petroleum industry. Proper assessment of the risks associated with underground hydrogen pipelines requires an accurate model of the jet fire consequence. This article will describe experimental and modeling work undertaken in order to define the appropriate methodology for utilizing DNV's PHAST software tool to represent the hydrogen jet fire from the rupture of underground hydrogen pipelines. Two experiments were conducted to measure the flow and radiation from an intentionally ignited rupture of a 6 in. diameter, 60 barg hydrogen pipeline buried 1 m underground. Adjustments to PHAST modeling parameters were required in order to obtain agreement between the measured and predicted radiation and flame length values. The modeling assumptions and parameter adjustments include:

• Velocity modification to account for interaction of the flow out of the two ends of the ruptured pipe and to model the subsequent discharge from the crater.
• Specification of the fraction of heat radiated.
• Specification of the angle of the release.

© 2013 American Institute of Chemical Engineers Process Saf Prog, 2013

The Macondo well blowout resulted in 11 fatalities and caused the largest nonintentional oil spill in history. The situation stemmed from a series of human errors through all stages of the project leading up to the blowout and subsequent explosion. These errors include faulty interpretation of signals indicating problems with well and safety system integrity, inappropriate modifications to safety systems, inadequate design of critical systems, failure to provide redundancy in the design stage, failure to adhere to administrative controls for the safe operation, failure to follow the American Petroleum Institute Recommended Practices 75 on drilling mud circulation, and others. Twenty five specific errors have been identified and classified into eight categories. The results show that the majority of the errors are latent errors and caused by poor leadership in the organization or management. In order to resolve these issues it is necessary to create a safety culture in which safety is paramount in operations and facilities. There are many lessons learned from this incident, but the most important lesson is that safety must be a way of life, beginning in the design stage and carrying through the project life cycle. © 2013 American Institute of Chemical Engineers Process Saf Prog 32: –, 2013