Showing papers by "Faisal Khan published in 2013"

Domino effect analysis using Bayesian networks.

Abstract: A new methodology is introduced based on Bayesian network both to model domino effect propagation patterns and to estimate the domino effect probability at different levels. The flexible structure and the unique modeling techniques offered by Bayesian network make it possible to analyze domino effects through a probabilistic framework, considering synergistic effects, noisy probabilities, and common cause failures. Further, the uncertainties and the complex interactions among the domino effect components are captured using Bayesian network. The probabilities of events are updated in the light of new information, and the most probable path of the domino effect is determined on the basis of the new data gathered. This study shows how probability updating helps to update the domino effect model either qualitatively or quantitatively. The methodology is applied to a hypothetical example and also to an earlier-studied case study. These examples accentuate the effectiveness of Bayesian network in modeling domino effects in processing facility.

Explosibility of micron- and nano-size titanium powders

Abstract: Explosibility of micron- and nano-titanium was determined and compared according to explosion severity and likelihood using standard dust explosion equipment. ASTM methods were followed using a Siwek 20-L explosion chamber, MIKE 3 apparatus and BAM oven. The explosibility parameters investigated for both size ranges of titanium include explosion severity (maximum explosion pressure (Pmax) and size-normalized maximum rate of pressure rise (KSt)) and explosion likelihood (minimum explosible concentration (MEC), minimum ignition energy (MIE) and minimum ignition temperature (MIT)). Titanium particle sizes were −100 mesh (

Analysis of pitting corrosion on steel under insulation in marine environments

Abstract: Corrosion under insulation (CUI) is an important issue in marine environments. Pitting corrosion is a significant contributor to this issue. The ability to understand and model pitting behavior is integral to designing and maintaining assets in marine environments to decreased costs and increase safety and productivity. This paper reviews and analyses six categories of pitting knowledge to assess the current depth and breadth of understanding and to identify knowledge gaps in each category. The categories investigated are: identification of pitting, experimental methods, mechanism of pitting, modeling of pitting corrosion rates, remaining life assessment modeling, and risk-based inspections. This analysis finds that the depth of knowledge on pitting corrosion rate modeling and pitting mechanism is limited and requires further detailed study. The outcome of such study will strengthen pitting corrosion rate modeling, the accuracy of fitness-for-service assessments and risk-based inspection strategies.

Dynamic Risk Assessment and Fault Detection Using Principal Component Analysis

Abstract: A methodology to calculate process risk in combination with a data based fault detection method is proposed in this paper. The proposed approach aims to identify and screen the faults which are not...

Accident modeling and risk assessment framework for safety critical decision-making: application to deepwater drilling operation

Abstract: Rising global energy demand is encouraging oil companies to invest in deepwater drilling. However, there are numerous engineering and safety challenges involved in this activity. The BP Deepwater Horizon accident (Macondo well blowout) has raised serious concerns about the safety of deepwater drilling. The major reasons for such a catastrophic blowout event are the lack of continuous assessment of risk and the lack of risk-based decision making to take timely and adequate preventive actions. The present work proposes an accident modeling and risk assessment framework based on accident precursors (early warnings). This framework uses the system hazard identification, prediction and prevention methodology to model the unwanted situation. The proposed risk assessment framework generates results that can be used to: (1) analyze the dynamic performance of safety barriers, (2) analyze the probability of occurrence of different severity levels, (3) analyze the dynamic risk profile of different severity levels and the aggregated risk profile, and (4) help to make safety-critical decisions based on aggregated risk profile. The present work provides an assessment of offshore deepwater drilling risk assessment and a basis to make timely and precise safety critical decisions. The risk assessment methodology is demonstrated on the Macondo well blowout accident. This case study highlighted the applicability and advantages of using the proposed method in drilling operations. Language: en

Dynamic risk assessment and fault detection using a multivariate technique

Abstract: In the context of process safety, significant improvements are needed in fault detection methods, especially, in the areas of early detection and warning. In this article, a multivariate risk-based fault detection and diagnosis technique is proposed. The key elements of this technique are to eliminate faults that are not serious and to provide a dynamic process risk indication at each sampling instant. A multivariable residual generation process based on the Kalman filter has been combined with a risk assessment procedure. The use of the Kalman filter makes the method more robust to false alarms, which is an important aspect of any fault detection algorithm that targets the safety of a process. In addition, we consider significant differences in the severity of the faults associated with different process variables. We also take into account the varying intensity of damage caused by the increasing and decreasing rates of fault and the need to treat those cases differently. © 2013 American Institute of Chemical Engineers Process Saf Prog 32: 365–375, 2013

A quantitative risk management framework for dust and hybrid mixture explosions

Abstract: The research main objective is: to manage the risks of any expected dust or hybrid mixture explosion in industrial complexes (large-scale).

Risk-based design of safety measures to prevent and mitigate dust explosion hazards

Abstract: Dust explosion is one of the main threats to equipment safety and human health in industries. Complex factors leading to accidents, serious consequences, and relevant safety measures are the main interests of governmental agencies, researchers, and industrial companies. However, a generic risk analysis model for dust explosions is absent. The bow-tie model can be used to investigate the relationships among basic causes, safety barriers, and possible consequences of an accident scenario. In this paper, a framework is established for quantitative risk assessment of dust explosions based on bow-tie analysis via review and analysis of previous major dust explosions. A large inventory of relevant safety measures is presented, and the implementation and efficacy of such safety measures to reduce the risk of dust explosions is thoroughly discussed. Finally, the methodology is applied to a case study. The results show that the generic bow-tie developed in this study can be tailored to a wide variety of dust explo...

An optimal level of dust explosion risk management: Framework and application

Abstract: The current research provides guidance on the prevention and mitigation of dust explosion using a Quantitative Risk Management Framework (QRMF). Using concepts drawn from previous studies, the framework consists of three main steps: (i) a new combined safety management protocol, (ii) the use of DESC (Dust Explosion Simulation Code) and FTA (Fault Tree Analysis) to assess explosion consequences and likelihood, respectively, and (iii) application of the hierarchy of controls (inherent, engineered and procedural safety). QRMF assessment of an industrial case study showed that the original process was at high risk. DESC simulations and Probit equations determined the destructive percentages. FTAs revealed high probabilities of explosion occurrence; in addition, detailed individual and societal risks calculations were made, before and after the framework was applied. Based on the hierarchy of controls technique, the framework showed significant risk reduction to the point where the residual risk was acceptable for the process.

Risk based integrity modeling of offshore process components suffering stochastic degradation

Abstract: Purpose – The purpose of this paper is to develop a risk‐based integrity model for the optimal replacement of offshore process components, based on the likelihood and consequence of failure arising from time‐dependent degradation mechanisms.Design/methodology/approach – Risk is a combination of the probability of failure and its likely consequences. Offshore process component degradation mechanisms are modeled using Bayesian prior‐posterior analysis. The failure consequences are developed in terms of the cost incurred as a result of failure, inspection and maintenance. By combining the cumulative posterior probability of failure and the equivalent cost of degradations, the operational life‐risk curve is produced. The optimal replacement strategy is obtained as the global minimum of the operational risk curve.Findings – The offshore process component degradation mechanisms are random processes. The proposed risk‐based integrity model can be used to model these processes effectively to obtain an optimal rep...

Explosibility of Polyamide and Polyester Fibers

Abstract: The current research is aimed at investigating the explosion behavior of hazardous materials in relation to aspects of particulate size. The materials of study are flocculent (fibrous) polyamide 6.6 (nylon) and polyester (polyethylene terephthalate). These materials may be termed nontraditional dusts due to their cylindrical shape which necessitates consideration of both particle diameter and length. The experimental work undertaken is divided into two main parts. The first deals with the determination of deflagration parameters for polyamide 6.6 (dtex 3.3) for different lengths: 0.3 mm, 0.5 mm, 0.75 mm, 0.9 mm and 1 mm; the second involves a study of the deflagration behavior of polyester and polyamide 6.6 samples, each having a length of 0.5 mm and two different values of dtex, namely 1.7 and 3.3. (Dtex or decitex is a unit of measure for the linear density of fibers. It is equivalent to the mass in grams per 10,000 m of a single filament, and can be converted to a particle diameter.) The explosibility parameters investigated for both flocculent materials include maximum explosion pressure (Pmax), size-normalized maximum rate of pressure rise (KSt), minimum explosible concentration (MEC), minimum ignition energy (MIE) and minimum ignition temperature (MIT). ASTM protocols were followed using standard dust explosibility test equipment (Siwek 20-L explosion chamber, MIKE 3 apparatus and BAM oven). Both qualitative and quantitative analyses were undertaken as indicated by the following examples. Qualitative observation of the post-explosion residue for polyamide 6.6 indicated a complex interwoven structure, whereas the polyester residue showed a shiny, melt-type appearance. Quantitatively, the highest values of Pmax and KSt were obtained at the shortest length and finest dtex for a given material. For a given length, polyester displayed a greater difference in Pmax and KSt at different values of dtex than polyamide 6.6. Long ignition delay times were observed in the BAM oven (MIT measurements) for polyester, and video framing of explosions in the MIKE 3 apparatus (MIE measurements) enabled observation of secondary ignitions caused by flame propagation after the initial ignition occurring at the spark electrodes.

Safety challenges in harsh environments: Lessons learned

Abstract: Development of natural resources in harsh environments presents significant technical and logistical challenges. An industrial workshop on “safety and integrity management of operations in harsh environments” was organized by the safety and risk engineering group at Memorial University of Newfoundland to bring together industrial practitioners, regulatory authorities, and research and development institutions to identify the safety and integrity challenges in harsh environments, share experience, and develop a roadmap for desired solutions. This article summarizes the lessons learned from the workshop on safety issues in harsh environments. The workshop identified that there are safety challenges regarding construction and operation including a lack of detailed standards, optimization with respect to winterization, and data scarcity. The remoteness of operations in harsh environments is an additional challenge. Finally, human factors add another set of challenges that arise from the physical and psychological behavior of personnel in harsh and remote environments. © 2014 American Institute of Chemical Engineers Process Saf Prog 34: 191–195, 2015

Modelling of the effect of size on flocculent dust explosions

Abstract: The effect of size on the severity of explosions involving flocculent materials has been simulated by means of a model previously developed for spherical particles and here extended to the cylindrical geometry of flock. The model consists of the identification of the regime (internal and external heating, pyrolysis/devolatilization reaction, and volatiles combustion) controlling the explosion by the evaluation of dimensionless numbers (Bi, Da, Th and Pc) and then of the estimation of the deflagration index as a function of flocculent size. The model has been validated by means of explosion data of polyamide 6.6 (nylon) at varying diameter and length. The comparison between model and experimental data show a fairly good agreement.

Quantifying the effect of strong ignition sources on particle preconditioning and distribution in the 20-L chamber

Abstract: Computational fluid dynamics is used to investigate the preconditioning aspect of overdriving in dust explosion testing. The results show that preconditioning alters both the particle temperature and distribution prior to flame propagation in the 20-L chamber. A parametric study gives the fluid pressure and temperature, and particle temperature and concentration at an assumed flame kernel development time (10 ms) for varying ignitor size and particle diameter. For the 10 kJ ignitor with 50% efficiency, polyethylene particles under 50 μm reach 400 K and may melt prior to flame propagation. Gases from the ignitor detonation displace the dust from the center of the chamber and may increase local particle concentration up to two times the nominal value being tested. These effects have important implications for explosive testing of dusts in the 20-L chamber and comparing to larger 1-m 3 testing, where these effects may be negligible.

Risk-based Winterization for Vessels Operations in Arctic Environments

Abstract: Because the oil and gas industry has an increasing interest in the hydrocarbon exploration and development in the Arctic regions, it becomes important to design exploration and production facilities that suit the cold and harsh operating conditions. In addition to well-established minimum class requirements for hull strengthening, winterization should be considered as a priority measure early in the design spiral for vessels operating in the Arctic environments. The development of winterization strategies is a challenging task, which requires a robust decision support approach. This article proposes a risk-based approach for the selection of winterization technologies and determination of winterization levels or requirements on a case-by-case basis. Temperature data are collected from climatology stations located in the Arctic regions. Loading scenarios are defined by statistical analysis of the temperature data to obtain probabilistic distributions for the loadings. Risk values are calculated under different loading scenarios. Based on the risk values, appropriate winterization strategies can be determined. A case study is used to demonstrate how the proposed approach can be applied to the identification of heating requirements for gangways.

Human Factor Risk Assessment During Emergency Condition in Harsh Environment

Abstract: This paper presents a quantitative approach to human factors risk analysis during emergency conditions on an offshore petroleum facility located in a harsh environment. Due to the lack of human factors data for emergency conditions, most of the available human factors risk assessment methodologies are based on expert judgment techniques. Expert judgment is a valuable technique, however, it suffers from vagueness, subjectivity and incompleteness due to a lack of supporting empirical evidence. These weaknesses are often not accounted for in conventional human factors risk assessment. The available approaches also suffer from the unrealistic assumption of independence of the human performance shaping (HPS) factors and actions. The focus of this paper is to address the issue of handling uncertainty associated with expert judgments and to account for the dependency among the HPS factors and actions. These outcomes are achieved by integrating Bayesian Networks with Fuzzy and Evidence theories to estimate human error probabilities during different phases of an emergency. To test the applicability of the approach, results are compared with an analytical approach. The study demonstrates that the proposed approach is effective in assessing human error probability, which in turn improves reliability and auditability of human factors risk assessment.

Influence of liquid and vapourized solvents on explosibility of pharmaceutical excipient dusts

Abstract: Hybrid mixtures of a combustible dust and flammable gas are found in many industrial processes. Such fuel systems are often encountered in the pharmaceutical industry when excipient (non-active ingredient) powders undergo transfer in either a dry or solvent prewetted state into an environment possibly containing a flammable gas. The research described in this paper simulated the conditions of the above scenarios with microcrystalline cellulose (MCC) and lactose as excipients, and methanol, ethanol and isopropanol as solvents. Standardized dust explosibility test equipment (Siwek 20-L explosion chamber, MIKE 3 apparatus and BAM oven) and ASTM test protocols were used to determine the following explosibility parameters: maximum explosion pressure (Pmax), size-normalized maximum rate of pressure rise (KSt), minimum explosible concentration (MEC), minimum ignition energy (MIE), and minimum ignition temperature (MIT). Because the MIKE 3 apparatus and BAM oven are not closed systems, only baseline excipient-alone testing and excipient pre-wetted with solvent testing were possible for MIE and MIT determination. With the Siwek 20-L chamber (a closed system), it was feasible to conduct Pmax, KSt and MEC testing for all three cases of the dust alone, prewetted with solvent, and with solvent admixed to the combustion atmosphere at 80 % of the lower flammability limit for each solvent prior to dust dispersal. The experimental results demonstrate the significant enhancements in explosion likelihood and explosion severity brought about by solvent admixture in either mode. The extent of solvent influence was found to be specific to the given excipient and method of solvent addition. Solvent burning velocity considerations help to account for some of the experimental observations but for others, a more rigorous evaluation of solvent and excipient physical property data is needed.