An uncertainty and sensitivity analysis of dynamic operational risk assessment model: A case study

In Dynamic Operational Risk Assessment (DORA) models, component repair time is an important parameter to characterize component state and the subsequent system-state trajectory. Specific distributions are fit to the industrial component repair time to be used as the input of Monte Carlo simulation of system-state trajectory. The objective of this study is to propose and apply statistical techniques to characterize the uncertainty and sensitivity on the distribution model selection and the associated parameters determination, in order to study how the DORA output that is the probability of operation out-of-control, can be apportioned by the distribution model selection. In this study, eight distribution fittings for each component are performed. Chi-square test, Kolmogorov–Smirnov test, and Anderson-Darling test are proposed to measure the goodness-of-fit to rank the distribution models for characterizing the component repair time distribution. Sensitivity analysis results show that the selection of distribution model among exponential distribution, gamma distribution, lognormal distribution and Weibull distribution to fit the industrial data has no significant impact on DORA results in the case study.     

Effects of ferric oxide on decompositions of methyl ethyl ketone peroxide

Methyl ethyl ketone peroxide (MEKPO) is a widely used initiator for polymerization reaction and hardener in glass-reinforced plastic. However, MEKPO is an unstable reactive chemical and has caused several serious accidents all over the world. This work studied the thermal stability of MEKPO in the presence of ferric oxide as the contaminant through calorimetric and kinetic studies. The calorimetry was performed using Automatic Pressure Tracking Adiabatic Calorimeter (APTAC) to identify the effects of ferric oxide (different concentration) on important reactive hazards such as onset temperature and pressure hazard. Kinetic modeling was then performed to study the kinetics of the runaway reaction and estimate important kinetic parameters. The results indicate that in the low concentration range (<0.3%), ferric oxide has no significant effect on the thermal stability of MEKPO. However, in the high and intermediate concentration range of ferric oxide (i.e., 10%), the negative effect on the thermal stability of MEKPO was observed. This result is in agreement with the kinetic study result that the activation energy and frequency factor decrease dramatically in the high ferric oxide concentration range. The results provide necessary process safety information for the handling of MEKPO and also technical basis for the further study in this area.     

Case study analysis of the financial impact of catastrophic safety events

Several catastrophic events in the process industry have caused extensive damage to life and property and have forever changed the process safety landscape. Despite the commitment from the industry, incidents still occur with similar root causes, impacting major companies in various ways. This work examines the financial impact of such incidents on the stability and future of affected companies in different industries. Several devastating incidents were analyzed to evaluate the direct impact in the short- and long-term and to discuss factors influencing the ability of affected companies to withstand the consequence of catastrophic events.     

Challenges and needs for process safety in the new millennium

Process industries have made quite a bit of progress in process safety since the tragic night of December 2, 1984 in Bhopal. Nonetheless, incidents continue to occur on a regular basis due to insufficient understanding of the urgency to identify best practices and drive for process safety improvements in the organization. This paper addresses some of the critical challenges in implementing effective safety programs: (a) failure to learn from past incidents and to capture those lessons into process design, procedures, training, maintenance, and other programs, (b) insufficient attention to leading indicators, and (c) an increase in complexity of process operations and lack of communication. In the presence of these challenges, there is a great need to develop better solutions by utilizing good science based approaches and best practice studies. Potential research areas include, but are not limited to, incident database analysis, reactive chemicals, inherently safer design, combustible dust explosion, facility siting, and the flammability of fuel mixtures and aerosols. In addition, an example was presented on LNG industry safety to illustrate that science-based research is needed to ensure the safe operation and to avoid or mitigate unintended consequences.     

The legacy of Bhopal: The impact over the last 20 years and future direction

Chemical process safety was not a major public concern prior to 1984. As far as chemical hazards were concerned, public fears focused on disease (cancer) and environmental degradation. Even a series of major process incident tragedies did not translate into widespread public concerns about major incidents in chemical plants that might disastrously affect the public. This situation changed completely after the December 1984 disaster at the Union Carbide plant in Bhopal. Not only was the public's confidence in the chemical industry shaken, the chemical industry itself questioned whether its provisions for protection against major incidents were adequate.

The recognition of the need for technical advances and implementation of management systems led to a number of initiatives by various stakeholders throughout the world. Governments and local authorities throughout the world initiated regulatory regimes. Has all that has resulted from the legacy of Bhopal reduced the frequency and severity of incidents? How can we answer this question? As we move into more and more globalization and other complexities what are the challenges we must address? According to the authors, some of these challenges are widespread dissemination and sharing of lessons learned, risk migration because of globalization, changing workforce, and breakthroughs in emerging areas in process safety.     

Lessons learned from recent incidents: Facility siting, atmospheric venting, and operator information systems

Recent incidents have focused attention on a number of technical and management systems that need to be addressed by industry. A multiple layer of protection approach is essential for the prevention of incidents and/or reduction of consequences. Safety culture and operational discipline are the overall embracing factors that influence the safety performance of a facility. However, as recent events have indicated, there are a number of technical and engineering issues that must also be developed and implemented appropriately. Some of these issues that could lead to incidents with catastrophic consequences include facility siting and atmospheric relief venting. Impact of operator information systems on the prevention of releases of hazardous materials from their containment is also another significant factor that should be given appropriate attention.

This paper describes these three topics based on the findings from recent incidents and historical data. Engineering standards, regulatory requirements, and industry practices are discussed for facility siting, atmospheric relief venting, and operator information systems. Finally, a summary of gaps and needs in technology, standards, and practices is presented.     

Fire and explosion assessment on oil and gas floating production storage offloading (FPSO): An effective screening and comparison tool

Fires and explosions have been identified as major potential hazards for Oil and Gas Floating Production Storage Offloading (FPSO) installations and pose risk to personnel, assets, and the environment. Current fire and explosion assessment (FEA) tools require physical effect modeling software and follows standards from API, ISO, and engineering practices. However, the tools are not specific to any particular system such as an FPSO, and do not provide comprehensive guidance for safety engineers to perform FEA.This paper discusses the development of a screening and comparison tool for FEA on FPSOs and the incorporation of an expert system into the tool. The results are computerized using MS Excel/VBA to provide a structured and comprehensive assessment on each equipment and module handling natural gas, crude oil, methanol and diesel on FPSO topsides.This tool features built-in calculations for jet and pool fire size estimation for gas/liquid releases, and the ability to perform Quantitative Risk Analysis (QRA) to specify the personnel and equipment risk for varying leak sizes and process conditions. Control and recovery measures are incorporated as an expert system based on report findings, engineering practices, and relevant standards. Bowtie analysis is applied in the tool to define detailed control and recovery measures for the FPSO based on the incident scenarios. An explosion assessment is performed by incorporating physical effect modeling software results.Unique features provided in the tool include fire and radiation contour mapping on an FPSO layout to help determine personnel and equipment risk more accurately and fire pump sizing that can be used to verify the amount of water deluge system required to mitigate fires and explosions. In addition, flexibility of data input (process data, failure rate data, etc.) and user interfaces assist safety engineers to screen and compare process alternatives, check design quality, and evaluate design options at any design stage.     

Trends In Regulatory Acceptance Of Risk-Based Cleanup Goals And Natural Attenuation For Site Closure

Since 1994, there has been a significant regulatory shift toward risk-based cleanup standards based on the site-specific risk of the more toxic and mobile compounds; namely, benzene, ethyl benzene, toluene, and xylene (BTEX). This regulatory shift has been accompanied by a growing acceptance of natural attenuation as an important component of petroleum site remediation. This article briefly reviews regulatory progress toward risk-based remediation and describes the successful application of risk-based corrective actions (RBCAs) at two fuel contaminated sites on Air Force installations. By developing site-specific cleanup goals, and combining natural attenuation, source reduction, and land use controls, innovative risk-based closure plans have been implemented on these sites.