Showing papers in "Process Safety Progress in 2004"

Integrated inherent safety index (I2SI): A tool for inherent safety evaluation

Abstract: Inherent safety is a proactive approach for loss prevention and risk management. Considering the lifetime costs of a process and its operation, an inherent safety approach can lead to a cost-optimal option. Inherent safety may be achieved at any stage of process design; however, its application at the early stages of process design yields the best results. Despite being an attractive and cost-effective approach, the inherent safety methodology is not widely used. Many reasons have been attributed to this lack of widespread use; the nonavailability of systematic tools for the application of inherent safety principles is perhaps the most important reason. This paper presents a conceptual framework of an integrated inherent safety index (I2SI). It is called an integrated index because the procedure, when fully developed, is intended to consider the life cycle of the process with economic evaluation and hazard potential identification for each option. The I2SI is composed of subindices which account for hazard potential, inherent safety potential, and add-on control requirements. An application of the I2SI is also discussed. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 136–148, 2004

A review of estimation methods for flash points and flammability limits

Abstract: INTRODUCTION Flash point measurements of various types are used as one measure of the flammability of liquid materials. The flash point is also related to the lower flammability limit, which is the minimum content of the combustible in a combustible–air mixture that will propagate flame [1]. Many manufacturing processes involve flammable chemicals; therefore, flash points and flammability limits are essential to maximize safety in process design and operational procedures. Flammability is an important factor in the development of safe practices for handling and storage of liquid mixtures. Regulatory authorities use flash point determinations made from small-scale test apparatus to classify flammable and combustible liquids. These determinations are based mainly on the use of the closed cup flash point temperature as the key property for classifying liquids according to their degree of flammability. Based on these classifications, regulators then specify or provide guidance on the appropriate methods for transporting, handling, packaging, storing, dispensing, and protecting these materials [2]. Also, federal regulations require that the mixture flash point be provided as part of materials safety data information. Industry works with mixtures under different conditions of temperature, pressure, and oxygen concentrations according to the process involved. The flash point can be used to determine the level of risk in different stages of a process because it is the temperature at which sufficient vapor is generated to bring the concentration of flammable vapor above the lower flammability limit. One question that must be answered to ensure a safe level of operation in a certain process is “What is the minimum oxygen concentration requirement for flame propagation?” Or, in terms more directly applicable to process operations, “What is the minimum amount of inerts required to prevent flame propagation?” The quantity of air that is required to decrease the combustible vapor concentration to a safe level in a particular process carried out at a specific temperature should be based on flammability measurements at that temperature. Knowledge of flammable limits at elevated temperatures and pressures is needed for safe and economical operation of some chemical processes. This information may be needed in order to start up a reactor without passing through a flammable range, to operate the reactor safely and economically, or to store or ship the product safely [3]. Flash points are available for most pure liquids, but the information for mixtures is very limited and is usually at ambient pressures. For mixtures of flammable liquids, or more importantly, liquid mixtures containing both flammable and nonflammable constituents, the precise level of risk is more difficult to predict. Mixtures of flammable and nonflammable constituents are especially significant because the vapor phase composition differs from the liquid composition, and it can change from nonflammable to flammable as the mixtures evaporates or its temperatures changes. Flammability limits obtained experimentally under conditions similar to those found in practice are most reliable for designing installations that are safe and assessing potential gas-explosion hazards. Predictive theoretical methods are needed to estimate the flash point of mixtures when experimental data are unavailable. Flash point determinations for mixtures generally are based on the Le Chatelier equation together with a vapor–liquid equilibrium model calculation of the vapor composition when liquids are involved. Most existing predictive methods are appli© 2004 American Institute of Chemical Engineers

Risk-based maintenance (RBM): A new approach for process plant inspection and maintenance†

Abstract: This paper discusses recently proposed methodology for the design of an optimum maintenance management program. The methodology is based on integrating a reliability approach and a risk assessment strategy to obtain an optimum maintenance schedule. The method is called risk-based maintenance (RBM). First, the likely equipment failure scenarios are formulated. Out of the many likely failure scenarios, the ones that are most credible are subjected to a detailed study. Detailed consequence analysis is done for the selected scenarios. Subsequently, a fault tree analysis is performed to determine the probability of failure. Finally, risk is computed by combining the consequence analysis and the probability analysis results. The calculated risk is compared against known acceptable criteria. The frequency of maintenance tasks is obtained by minimizing the estimated risk. The proposed methodology is used to answer two questions: Which equipment should be included in a scheduled maintenance program? When should the maintenance be scheduled? Offshore oil and gas process facilities involve hazardous chemicals (highly flammable and toxic) at extreme conditions of temperature and pressure. Proper maintenance of process equipment is one of the important activities to ensure safe and continuous operation of the facility. RBM methodology has been used to develop a detailed maintenance plan for safe and fault free operation of the facility. © 2004 American Institute of Chemical Engineers Process Saf Prog, 2004

Sizing of throttling device for gas/liquid two‐phase flow part 1: Safety valves

Abstract: The calculation of the mass flow rate through throttling devices is difficult when handling two-phase flow, especially when boiling liquids flow into these fittings. Safety valves are typically oversized by a significant extent, if sizing methods like the ω-method (originally developed by J. Leung), are used in case of low-quality inlet flow. Within this method the boiling delay of the liquid and the influence of the boiling delay on the mass flow rate are not considered. In this paper the HNE-DS model is proposed, where the compressibility coefficient ω is extended by adding a boiling delay coefficient. It includes the degree of thermodynamic nonequilibrium at the start of the nucleation of small mass fractions of vapor upstream of the fitting. In Part 1 the sizing of safety valves is described. Additionally, the derivation of the HNE-DS method is given in detail. Part 2 considers the mass flow rate through short nozzles, orifices, and control valves. The HNE-DS model can be used for all those fittings. A comparison with experimental results on safety valves with steam/water and air/water flow has emphasized the excellent accuracy of the new model. © 2004 American Institute of Chemical Engineers Process Saf Prog, 2004

Dust explosion prevention and the critical importance of housekeeping

Abstract: Two recent, tragic events remind us that the broad topic of high-energy release events encompasses more than vapor cloud explosions and reactive chemical incidents. Dust explosions also have potential for causing catastrophic harm to personnel and facilities. This paper describes recent, major dust explosions with a particular focus on learnings related to a commonly underconsidered aspect of facility operations—housekeeping. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 175–184, 2004

An inherent safety–based incident investigation methodology

Abstract: A methodology has been developed to enable the explicit use of the principles of inherent safety in an incident investigation protocol. The usefulness of this approach is demonstrated by application to the Westray coal mine explosion that occurred in Nova Scotia in 1992. This process-related disaster resulted in the deaths of 26 workers, destruction of the underground workings, and bankruptcy of the parent company. The purpose in presenting this case study is twofold: to validate the methodology and to identify the inherent safety considerations that could have prevented the incident. These findings have application beyond the realm of coal mining, extending well into the world of the chemical process industries. © 2004 American Institute of Chemical Engineers Process Saf Prog 23:197–205, 2004

The explosion at Concept Sciences: Hazards of hydroxylamine

Abstract: INTRODUCTION At 8:14 PM on February 19, 1999, a process vessel containing several hundred pounds of hydroxylamine (HA) exploded at the Concept Sciences, Inc. (CSI), production facility near Allentown, Pennsylvania. Employees were distilling an aqueous solution of HA and potassium sulfate, the first commercial batch to be processed at CSI’s new facility. After the distillation process was shut down, the HA in the process tank and associated piping explosively decomposed, most likely due to high concentration and temperature. Four CSI employees and a manager of an adjacent business were killed. Two CSI employees survived the blast with moderate to serious injuries. Four people in nearby buildings were injured. Six firefighters and two security guards suffered minor injuries during emergency response efforts. The production facility was extensively damaged. The explosion also caused significant damage to other buildings in the Lehigh Valley Industrial Park and shattered windows in several nearby homes. The U.S. Chemical Safety Board (CSB) examined physical evidence at the site and reviewed relevant documents, such as a report prepared by Hazards Research Corporation (HRC, [1]) for the Occupational Safety and Health Administration (OSHA). CSB also contracted with the U.S. Department of the Navy, Naval Sea Systems Command, Indian Head Naval Surface Warfare Center, for assistance in evaluating HA chemistry and processing. The center conducts research on energetic materials (explosives, propellants, etc.), including HA and its derivatives. HYDROXYLAMINE PROPERTIES AND APPLICATIONS HA is an oxygenated derivative of ammonia, represented by the chemical formula NH2OH. Table 1 lists its characteristic properties. HA is usually handled as an aqueous solution or as salts. The concentrated free base is susceptible to explosive decomposition. Only salts of HA were available until the 1980s, when Nissin Chemical Company, Ltd., of Japan commercialized aqueous free-base HA by adding a proprietary stabilizer to prevent decomposition. HA is commercially available in solutions up to 50 wt %. Over the past decade, the semiconductor manufacturing industry has used HA solutions in cleaning formulations to strip process residues from integrated circuit devices. HA and its derivatives are also used in the manufacture of nylon, inks, paints, pharmaceuticals, agrochemicals, and photographic developers. If not for the explosion, CSI would have been the first company in the United States to manufacture this product in commercial quantities. Nissin Chemical Company was the sole global supplier of HA up to that time. In early 1999, BASF Aktiengesellschaft started up a new production facility in Germany.

Minimum amount of flammable gas for explosion within a confined space

Abstract: Leaking of flammable gas in a confined space creates a flammable atmosphere, giving rise to a potential explosion. Accident analysis suggests that some explosions are caused by a quantity of gas significantly much less than the lower explosion limit amount required to fill the whole confined space, which might be attributed to inhomogeneous mixing of the leaked gas. The minimum amount of leaked gas for an explosion is highly dependent on the degree of mixing in the confined space. This paper proposes a method for estimating the minimum amount of flammable gas for explosion, referred to as the Gaussian distribution explosion model (GDEM). The GDEM assumes Gaussian distribution of flammable gas along the height of an enclosure, combustion of gas within flammable limits, and adiabatic mixing in the enclosure. The predicted gas volume for an explosion is tied to the explosion pressure that results in a given building damage level. The results can be applied to estimate the minimum amount of flammable gas and ventilation rate to mitigate the explosion hazard. The GDEM shows that only a very small amount of gas remaining in the confined space may result in a serious gas explosion accident. The results could be applied not only to set the leaking criteria for developing a gas safety appliance but also to determine the ventilation rate and investigate gas accidents under certain conditions. © 2004 American Institute of Chemical Engineers Process Saf Prog, 2004

Natural gas pipeline accident consequence analysis

Abstract: Industrial licensing activities require safety and environmental studies to enhance safety and environmental protection especially as applied to pipelines. After World War II, industrial activities increased and accident risk analyses are now routinely made to reduce hazards. Most common accidents such as toxic emissions, fires, and explosions must be avoided. The risk analysis technique is used to prevent these undesired events. In this paper, accident scenarios and consequence analysis are conducted to investigate events and consequences concerning a natural gas (NG) pipeline. We found that fatalities can occur within a 260-m radius if there is a gas pipeline collapse. At distances < 30 m, injuries can occur as a result of thermal radiation exposure to the jet fire. Secondary effects from gas explosions will also occur within these distances. These results demonstrate the importance of (1) routing pipelines away from populated areas and (2) preventive maintenance to prevent leaks. © 2004 American Institute of Chemical Engineers Process Saf Prog, 2004

An inherently safer process of cyclohexane oxidation using pure oxygen—An example of how better process safety leads to better productivity

Abstract: This paper discusses how detailed studies on flammability at elevated pressures and temperatures can be applied to liquid-phase oxidation of cyclohexane using air/oxygen and lead to an inherently safer process with better productivity. Flammability tests of cyclohexane/oxygen vapor and vapor bubbles under actual oxidation conditions were performed. The flammability of the vapor and vapor bubbles was found to be moderated by the addition of water into the cyclohexane liquid. The added water forms minimum boiling azeotrope with cyclohexane and its vapor renders the cyclohexane vapor and vapor bubble inflammable. Oxidations of the cyclohexane/water azeotrope utilizing pure oxygen were carried out and found to outperform the traditional air oxidation process by a factor of 2. This paper summarizes our work during the past few years toward a safer and better process development for the liquid-phase oxidation of cyclohexane. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 72–81, 2004

Vented gaseous deflagrations with inertial vent covers: State‐of‐the‐art and progress

Abstract: Previous studies on vented gaseous deflagrations with inertial vent covers and related regulatory aspects are examined. The model of turbulent deflagration dynamics, built on energy and mass conservation principles, is developed further to take into account the influence of vent cover inertia. An engineering formula for conservative estimation of the upper limit of vent cover inertia is presented. Similarity analysis has shown that the scaling relationship between the surface density of the cover, w, and the turbulence factor, χ, is wχ3 = const, indicating a significant interrelationship between vent cover inertia and venting-generated turbulence. Results confirm that turbulence gradually increases after vent opening begins, so that it is possible to increase vent cover inertia significantly. It is demonstrated that instead of widely accepted surface density limits of about 10 kg/m2, values of one/two orders higher, depending on the conditions, could be used for explosion protection with 100% efficiency for large-scale enclosures. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 29–36, 2004

The role of ASTM E27 methods in hazard assessment: Part I. Thermal stability, compatibility, and energy release estimation methods

Abstract: Accurate reactive chemicals data form the cornerstone of procedures used to assess the hazards associated with commercial chemical production and use. Since 1967, the ASTM E27 Committee on the Hazard Potential of Chemicals has issued numerous, widely used consensus standards dealing with diverse testing and predictive procedures used to obtain relevant chemical hazard properties. The decision to issue a standard rests solely with the membership, which consists of representatives from industry, government, consulting firms, and instrument suppliers. Consequently, the procedures are automatically relevant, timely, and widely applicable. The purpose of this paper is to highlight some of the widely used standards, complemented with hypothetical but relevant examples describing the testing strategy, interpretation, and application of the results. A further goal of this paper is to encourage participation in the standards development process. The paper is published in two parts. The first part deals with the E27 standards pertaining to thermodynamics, thermal stability, and chemical compatibility. The second part, to be published in the next issue of this journal, focuses on the flammability, ignitability, and explosibility of fuel/air mixtures. © 2004 American Institute of Chemical Engineers Process Saf Prog, 2004

Fault tree and layer of protection hybrid risk analysis

Abstract: Layer of protection analysis (LOPA) is a relatively quick and straightforward method for quantifying risk. However, LOPA may be inadequate if used for compound failures when the required failure rate data are not available or when the failures are not independent. Fault tree analysis (FTA) can be used in these situations. FTA is designed to thoroughly and accurately evaluate compound failures and account for any dependencies between failures. FTA can augment LOPA, combining the best qualities of both methods into one powerful hybrid tool for risk analysis. © 2004 American Institute of Chemical Engineers (AIChE) Process Saf Prog 23:185-190, 2004

New vision of emergency response planning

Abstract: In an emergency situation, seconds can mean the difference between relief and tragedy. Important information must be presented clearly and cohesively to enable decision making under crisis conditions. This paper describes a project in which an Emergency Response System (ERS) has been developed for the Uthmaniyah gas plant (UGP). The ERS is essentially made up of two applications: the SAFER Real-Time application made by SAFER Systems of the United States and a customized Geographical Information System (GIS) application developed by the Saudi Aramco Information Technology group. The SAFER system provides the user with immediate plume graphics based on local topography, maps, real-time weather, chemical release specifics, and gas sensors data. This information is fed to a scientific gas dispersion model to predict the movement and concentration of gas or liquid release. The GIS allows the effect of the plume on people and structures to be analyzed in detail. Combined together, the ERS provides a tool for modeling and monitoring an accidental release. It will improve emergency planning, decision making, and response within the UGPD. The above information is shared with emergency responders such as the fire department, security, and medical personnel via the network. As a result, they would dispatch their resources via the safest route. As weather conditions change, the plume dispersion will change and, hence, emergency response efforts will shift accordingly. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 56–61, 2004

Estimation of risk indices of chemicals during transportation

Abstract: The National Fire Protection Association (NFPA) rankings for health, flammability, reactivity, and special hazards have been considered the basis for calculating the risk indices of materials in transportation as they have adopted the United Nations criteria for toxicity and corrosivity, which also addresses hazards in transportation to some extent. Using these NFPA rankings a method has been developed to calculate the risk indices of chemicals during transportation. Other factors such as quantity of material moving, distance between the point of release and population, rate of dispersion and probability of an accident were also considered in this paper for calculating the transportation risk index of a chemical. This index can be used as a guide for assessing the potential hazards of a chemical during its transportation. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 149–154, 2004

Major hazard risk assessment for existing and new facilities

Abstract: This paper outlines a risk assessment methodology that has been developed through work with major hazard facilities, including ammonia plants in Australia, satisfying regulations equivalent to the European Seveso II Directive. The methodology is an approach for ensuring an undertaking of effectively assessing the risks associated with major hazards that will not only satisfy regulations and corporate requirements, but also, more importantly, provide a framework for sustainable business processes, by enabling the methodology to be integrated into normal business management processes. The approach enables existing management systems to be effectively incorporated into the evaluation processes. Common pitfalls encountered during the risk assessment process are also discussed. © 2004 American Institute of Chemical Engineers Process Saf Prog, 2004

Process safety in the future—A view from the chemistry

Abstract: This paper advances the thesis that a complete assessment of the chemical process safety must be founded on specific chemical hazards data. Usually, these data can only be obtained from appropriately designed experiments using the correct testing techniques. The basis of safety and the window of safe operations arise from the relevant process safety data. BakerRisk's experience with the chemical processing industry (CPI) has shown that the PSM elements Safety Information, Process Hazards Analysis, and Operating Procedures are often documented without adequate hazards test data for the covered process. The information is often qualitative; it may be taken from inappropriate laboratory data and may not address the specific process deviation or worst-case situation(s). This lack of hazards test data represents an information void that tabletop or literature process hazard analyses alone cannot fill. Five observations and recommendations are offered: Chemical process safety supported by hazards testing is the right thing to do, whether the process is covered or not and whether the process is at the manufacturing stage or not; Hazards testing to identify and evaluate potential upset conditions should be an integral part of a company's process safety program. It is a major information source for process hazard analyses; The information obtained is specific to the thermodynamics and kinetics of the process chemistry; The information enables clear identification of operational, thermal, and reactivity hazards of processes involving highly hazardous chemicals; The scope of the chemical hazards testing should be matched with the quantities of chemicals involved and the development stage of the product. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 163–169, 2004

Management system failures identified in incidents investigated by the U.S. Chemical Safety and Hazard Investigation Board

Abstract: A key mission of the US Chemical Safety and Hazard Investigation Board (CSB) is to determine the root causes of incidents, report the findings, and issue recommendations to prevent similar incidents from occurring. CSB investigators respond to a variety of events occurring in a wide range of workplaces, from chemical plants and refineries to food-flavoring factories and steel mills. The details of each investigation are unique and the root causes are pertinent to each specific case. However, a common thread that emerges in CSB investigations is the inadequacy of management systems that might have prevented the incident from occurring. Examples of the systemic issues identified in CSB reports are: Lack of hazard review to predict and prevent incidents Insufficient investigation and follow-up after previous incidents Inadequate training of staff Failure to implement effective mechanical integrity programs These issues are well recognized as elements of a process safety management (PSM) program, although many incidents investigated by the CSB occurred at facilities that are not regulated by OSHA's process safety management rule.1 Indeed, a number of these incidents occurred at facilities that are well outside society's definition of “chemical plants.” Please note that the opinions and conclusions expressed in this paper are those of the author, and do not necessarily represent the opinions of the Chemical Safety and Hazard Investigation Board. © 2004 American Institute of Chemical Engineers Process Saf Prog, 2004

System safety analysis of hydrogen and methanol vehicle fuels

Abstract: Over the next 10 to 25 years, primary fuels used in automobiles may be changing from gasoline and diesel fuels to new "alternative" fuels. Two fuels that have generated much interest are hydrogen and methanol, and will propel vehicles through new power-plant concepts. However, these new breeds of vehicle systems introduce a new class of safety hazards. This paper will introduce the basic concepts of these new vehicles and briefly describe some of the systems these vehicles have that are not present in conventional gasoline- or diesel-fuels internal combustion vehicles. This paper will then explore the new safety concerns, risks, and hazards associated with these new vehicle systems as well as to predict what elements future safety standards may contain.

Reactivity screening made easy

Abstract: INTRODUCTION During the past decade, large efforts were made by the U.S. chemical and petrochemical industries to implement and maintain effective process safety management (PSM) and responsible care programs. Despite these large investments, incidents continue to occur at an alarming frequency. Many executives of leading companies are trying to understand why. A recent survey conducted by the U.S. Chemical and Safety Hazard Investigation Board (CSB) concluded that reactive chemicals present a significant safety problem for the chemical process industries (see Figure 1). Key root causes identified by the CSB survey included technical and management systems failures. This underscores the importance of the need to understand and manage chemical reaction hazards more effectively. We also believe that the “quality” of implementation, change management, and auditing of corporate PSM programs is the culprit. We focus in this short paper on incidents caused by runaway reactions and provide guidance on how to improve the quality of managing chemical reactions hazards through a combination of screening and experimental tools. The screening tool we offer is the culmination of more than a decade of active work in the area of reaction hazards focused on finding a simple method of determining potential reaction hazards with limited data. One can easily apply this simple hazard index to a wide variety of liquid-phase, gas-phase, and solidphase reactions.

Chemical reaction hazard identification and evaluation: Taking the first steps

Abstract: The circumstances leading to reactive chemicals accidents are often complex, but most of them could have been foreseen by the use of laboratory tests, hazard analysis and chemical reaction engineering techniques. A hazard evaluation and testing strategy that accomplishes these goals will be comprehensive and probably require significant investment of resources. It typically has the following key steps: • Initial hazards review of the process chemistry and unit operations • Identification of potential hazard scenarios • Assessment of the nature and extent of hazard scenarios • Development of prevention strategies • Development of protection strategies • Implementation of prevention and protection measures. Once a hazard has been identified and assessed as a credible threat to safe operation, most companies will take measures to mitigate the hazard. However, for small and mid-sized companies, the initial hazard identification and reactive chemicals assessment continues to be troublesome. This paper presents some specific tools to aid in completing these important first steps. They are straightforward to use and provide the information needed to enable a company to reliably determine and justify the need for further reactive chemical hazard testing. Introduction This paper advances the proposition that an initial chemical reactivity hazards assessment exists that can be performed by small/medium sized chemical manufacturing companies. Given the limited resources of most small and medium sized companies the scope of a chemical reactivity hazards assessment will be limited. The following limitations are proposed as reasonable for an initial review of the new or changed process: • First round assessment takes ≤1 day to complete • Initially no process hazards testing is done • Assessment can be done by trained chemical engineer • Most hazards, but not all, will be identified by the assessment • Conduct hazards testing if need demonstrated by initial assessment No hazard assessment procedure will catch 100% of all hazards present in a process. The intention of this approach is to identify the maximum number of serious potential hazards

Distant replay: What can reinvestigation of a 40-year-old incident tell you? A look at eastman chemical's 1960 aniline plant explosion

Abstract: On October 4, 1960, Eastman Chemical Company suffered the worst accident in its 83-year history, when an aniline manufacturing facility exploded. Sixteen people were killed, and more than 300 injured, as a result of the blast. This paper analyzes the incident and its aftermath using both historical records and modern analytical techniques. The results provide useful insight into both the technical and cultural safety issues raised, as well as valuable information that can be applied to current processes. Careful analysis, even years after the fact, can reveal new information, as well as reinforce that which is already known. For example, the used of residue curve mapping techniques, combined with the ternary liquid–liquid phase diagram revealed a combination of circumstances that was not anticipated in 1960. As a result of this accident, Eastman instituted a Process Safety Review Committee structure that has continued to this day. One of the results of this structured approach has been an order-of-magnitude reduction in serious incidents, sustained over a four-decade period. © 2004 American Institute of Chemical Engineers Process Saf Prog 23:221–228, 2004

Evaluating relief valve reliability when extending the test and maintenance interval

Abstract: Presently, more and more programs appear that provide processes for evaluating and extending the time between major process shutdowns and maintenance. RBI (risk-based inspections) and Six Sigma processes are two examples of methods currently in use to help drive shutdown extension programs. The relief valves on these processes often go along with the shutdown extension programs without a thorough understanding of the impact on relief valve reliability. Using an analysis for a “stand-by system,” the change in PFD (probability of failure on demand) of the relief system as a function of change in test interval is shown. Human error is another factor that compromises relief valve reliability. Some arguments are offered that suggest reduced inspections increase reliability because there are fewer opportunities for human error. This study addresses the human error question and shows that the human error contribution is constant while the relief valve is in service. Finally, the increase in PFD when increasing the test interval is discussed in terms of the potential increase in risk. The increased risk as a percentage change should be communicated and understood by those deciding to extend shutdown intervals. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 191–196, 2004

Security vulnerability assessment in the chemical industry

Abstract: After the events of September 11, 2001, Air Products and Chemicals Inc. (APCI) developed a Security Vulnerability Assessment (SVA) methodology, consistent with the Center for Chemical Process Safety (CCPS) guidelines. This methodology is designed for efficient and thorough evaluation of a large number of facilities, ranging from small industrial gas sites to large chemical plants. This methodology evaluates the potential consequences and attack scenarios at a facility and the attractiveness of the facility as a terrorist target. The team then provides recommendations for engineering and security improvements. Participation in early SVA development exercises with industry and governmental agencies made it clear that it is critical to have a team approach that includes process safety, security, and site operations functional expertise. This paper presents an overview of the APCI SVA methodology and summarizes major findings and lessons learned. Findings from an SVA provide multiple levels of protection for our assets and the public. The engineering and security solutions from the evaluation are intended to deter, detect, delay, and respond to an attacker. They include: 1Inherently safer alternatives such as reducing inventory, designing fail-safe systems, and improving plant layout. 2Enhanced physical security systems such as fences, access control, and monitored intrusion detection. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 214–220, 2004

Cyber security risk analysis for process control systems using rings of protection analysis (ROPA)

Abstract: Process plants may be subject to terrorist and criminal acts that can cause harm such as the release or diversion of hazardous materials and process or product damage. Such risks are evaluated using threat and vulnerability analysis and possible improvements in security measures and safeguards are identified. However, recommendations for improvements are usually based on engineering judgment. Such subjective assessments can lead to disagreements, and possibly inappropriate measures to reduce risk. Rings of Protection Analysis (ROPA), a simplified risk assessment method, can be used to provide more rational, objective, and reproducible decisions. ROPA parallels Layers of Protection Analysis (LOPA) that is used to evaluate accident risks. ROPA assists in identifying and determining the adequacy of existing protection systems. It is used to help determine whether there are sufficient rings/layers of protection against a threat scenario and whether the risk can be tolerated. A scenario may require multiple protection rings/layers depending on the process and the potential severity of the consequences. ROPA helps provide the basis for clear, functional specifications of required protection layers. This paper describes and demonstrates how ROPA can be applied to cyber security, although it can also be applied to physical security. It considers the selection of security measures and integrates their consideration with other types of protective measures. © 2004 American Institute of Chemical Engineers Process Saf Prog, 2004

Fault tree analysis for risk assessment in the Borexino experiment

Abstract: This paper outlines a methodological approach utilizing quantitative risk analyses and cost–benefits evaluation in order to select the most cost-effective options for risk reduction in industrial plants including structural changes and preventive maintenance. The methodology is based on quantification of top events resorting to fault trees, a sensitivity analysis of the probability of occurrence of top events, and a comparison of corrective measures based on cost and effectiveness criteria. The method is applied to a case study represented by the pseudocumene purification plant of the Borexino experiment in order to show its capability. The experiment is located in the Gran Sasso National Laboratory operated by the Italian National Institute for Nuclear Physics. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 121–131, 2004

Emergency venting requirements for tempered systems considering partial vapor–liquid separation with disengagement parameters greater than unity: Part II: Application

Abstract: Part 1 of this two-paper series presented closed-form analytical expressions for the two-phase emergency relief requirements of top-vented vertical cylindrical containers when the fluids involved exhibit partial disengagement. Both churn-turbulent flow and bubbly flow fluid behaviors, with disengagement parameters greater than unity, were considered. Energy input from either runaway reactions or uncontrolled external heat was included. The methods are limited to systems that are tempered and do not contain noncondensable components. In Part 2, the models developed in Part 1 are applied to specific points along the venting transient, yielding expressions for the required flow rate under emergency conditions. Part 2 elaborates on the limitations of the models, illustrates the use of the models with numerical examples, and compares the results against previous work. The effect of disengagement parameters greater than unity is illustrated in terms of both the required relieving rate and the mass remaining inside the container when disengagement occurs. © 2004 American Institute of Chemical Engineers Process Sag Prog 23: 86–98, 2004

Steel composite structural pressure vessel technology: Future development analysis of worldwide important pressure vessel technology

Abstract: The Steel Composite Structural Pressure Vessel technology invented by the authors is summarized briefly in this paper. This is a unique advanced pressure vessel technology with wide applications in industrial fields. It has been awarded several National Invention Prizes in China and 20 Chinese and U.S. patents. Some outstanding characteristics of this technology are burst resistance, dispersed defects, safety in service, simplified manufacturing, and safe, reliable, economic online safety monitoring. These characteristics result from the multiple functional shell natures of this unique technology. There are four patented technological systems, namely, cross-helically wound flat steel ribbon on a thin inner shell high-pressure vessels, single U-groove steel ribbon interlocked and cross-helically wound on a thin inner shell large high-pressure vessels, total double-layer normal-pressure vessels and storage tanks, and single U-groove steel ribbons interlocked and cross-helically wound onto a thin inner shell low-pressure large storage tanks. These technologies can reduce fabrication cost by 20 to 50%. The first of these technologies was approved by the American Society of Mechanical Engineers (ASME) as Code Case 2269 in 1997 for high-pressure vessels with internal diameter ranging from 12 inch to 12 ft for use in the manufacture of ammonia, urea, and methanol as well as large petroleum hydrogenation hot wall high-pressure reactors and other industrial equipment. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 65–71, 2004

Electronic management of change process

Abstract: Protection safeguards must reliably and effectively detect, diagnose, and control process deviations before the deviations can result in loss events such as fires and explosions. Any process change can potentially affect protection safeguards. Therefore, it is critical to identify process changes and assess their impact on layers of protection, safety instrumented systems (SIS), operating procedures, and alarms. Process change designs should he reviewed, and any needed modifications to safeguards should be implemented as part of the change. Existing management of change processes rely primarily on human knowledge and interaction among various functional groups, making them highly susceptible to human error. In an effort to reduce the risk involved with process changes, we developed a standardized, electronic management of change (eMOC) system and process, which facilitates reviews of process changes, update of company process safety information (PSI), and notification of affected personnel. It also enhances the ability to track and audit changes. Implementation included all necessary software and development/selection of training. The system is web based and includes a standardized electronic form with checklists (including some flexibility for site or division variation) and an automatic workflow routing. All system functions were automated including routing of documents and drawings, record keeping, approvals, notification, tracking, reporting, printing, searching, and audit trails. The process has now been in use for more than 1.5 years and has been used for over 3500 process changes with good results. The major advantages of the system identified by users are tracking, documentation and compliance, automatic routing, and automatic reminder.

Explosion of a railcar containing toluene diisocyanate waste

Abstract: A railcar containing toluene diisocyanate (TDI) waste exploded during the unloading process at a hazardous waste-treatment and disposal facility The TDI waste material was to be used as a fuel at the RCRA-permitted facility Because of the viscous, almost solidlike consistency of the waste, the railcar was steam-heated to facilitate unloading The attempted unloading took place over a 5-day period The railcar was heated on two separate occasions and unloading was unsuccessfully attempted three times The decision was made to reject the railcar shipment, but it remained at the unloading station Approximately 2 days after the last heating cycle, the railcar exploded This paper summarizes the accident investigation, with particular emphasis on the assessment of the reactivity hazards and self-heating potential of the railcar contents Under the circumstances of this accident, TDI should not undergo significant thermal decomposition The evidence suggested the explosion was caused by the thermal decomposition of a contaminant that was not normally present in the TDI waste © 2004 American Institute of Chemical Engineers Process Saf Prog, 2004