Faisal Khan - Academia.edu (original) (raw)

Papers by Faisal Khan

Canadian Journal of Chemical Engineering, 2008

In recent years there has been an increased effort to develop inherently safer chemical processes... more In recent years there has been an increased effort to develop inherently safer chemical processes, focusing on changing the process to eliminate hazards, rather than accepting the hazards and developing add-on features to control them. This paper discusses design approaches to inherently safer processing, including examples of inherent safety principles. The paper also presents a state-of-the-art review of the initiatives taken by various groups and agencies worldwide to promote inherent safety, and the tools developed to measure inherent safety for chemical processes. The discussion concludes with thoughts on why inherent safety is not yet a routine practice for accomplishing risk reduction, and suggestions for ways to make it routine (with reference to a brief case study).Ces dernières années, les efforts se sont accrus pour développer des procédés chimiques intrinsèquement plus sûrs, en particulier en modifiant les procédés de façon à supprimer les risques, plutôt qu'en acceptant les risques et en développant de nouvelles caractéristiques pour les contrôler. On examine dans cet article les approches pour concevoir des procédés intrinsèquement plus sûrs, et notamment des exemples de principes de sécurité intrinsèque. On présente également une étude sur les derniers développements et les initiatives prises par divers groupes et organismes dans le monde pour promouvoir la sécurité intrinsèque, ainsi que les outils mis au point pour mesurer la sécurité intrinsèque des procédés chimiques. La discussion se termine par un exposé des raisons pour lesquelles la sécurité intrinsèque n'est pas encore pratiquée de manière routinière pour réduire les risques, et des suggestions sont faites pour la rendre routinière (en faisant référence à une brève étude de cas).

Stochastic Environmental Research and Risk Assessment, 2013

ABSTRACT A new methodology is developed to estimate an aquatic community toxicity threshold conce... more ABSTRACT A new methodology is developed to estimate an aquatic community toxicity threshold concentration based on the limited toxicity data that are available for thiosalts. To analyze the indirect effect of thiosalts on decreasing pH, an exposure model is developed that estimates the residual concentration of thiosalts and pH in the water body. The results from this model are incorporated in thiosalts risk assessment and a case study is used to illustrate the applicability of the proposed model. In this study, the exposure model predicts that, trithionate and tetrathionate degraded to SO42− SO 4 2 − ions, HSO3− HSO 3 − ions, SO32− SO 3 2 − ions and elemental sulfur. The concentration of thiosulfate, trithionate and tetrathionate, initially at 25, 40 and 6 mg/L, respectively are expected to decrease. Over the duration of 77 h, thiosulfate degrades completely, while the estimated residual trithionate and tetrathionate concentrations are 13 and 5.77 mg/L, respectively. pH of the undiluted effluent is estimated to decrease from 9.2 to 5.6 within an hour of the effluent discharge and decreases further to 4 over a period of next 3 days. A framework and methodology developed in this paper can be utilized to estimate the potential direct and indirect risk of thiosalts exposure to ecological entities.

Proceedings of Offshore Technology Conference, 2010

Abstract A consortium of university-industry researchers are developing sustainable and environme... more Abstract A consortium of university-industry researchers are developing sustainable and environmentally friendly enhanced oil recovery (EOR) technology for oil fields off the east coast of Newfoundland, Canada. This paper is foundational work on potential ...

Risk Analysis, 2014

A comprehensive methodology for economic consequence analysis with appropriate models for risk an... more A comprehensive methodology for economic consequence analysis with appropriate models for risk analysis of process systems is proposed. This methodology uses loss functions to relate process deviations in a given scenario to economic losses. It consists of four steps: definition of a scenario, identification of losses, quantification of losses, and integration of losses. In this methodology, the process deviations that contribute to a given accident scenario are identified and mapped to assess potential consequences. Losses are assessed with an appropriate loss function (revised Taguchi, modified inverted normal) for each type of loss. The total loss is quantified by integrating different loss functions. The proposed methodology has been examined on two industrial case studies. Implementation of this new economic consequence methodology in quantitative risk assessment will provide better understanding and quantification of risk. This will improve design, decision making, and risk management strategies.

Reliability Engineering & System Safety, 2012

Accident probability estimation is a common and central step to all quantitative risk assessment ... more Accident probability estimation is a common and central step to all quantitative risk assessment methods. Among many techniques available, bow-tie model (BT) is very popular because it represent the accident scenario altogether including causes and consequences. However, it suffers a static structure limiting its application in real-time monitoring and probability updating which are key factors in dynamic risk analysis. The present work is focused on using BT approach in a dynamic environment in which the occurrence probability of accident consequences changes. In this method, on one hand, failure probability of primary events of BT, leading to the top event, are developed using physical reliability models, and constantly revised as physical parameters (e.g., pressure, velocity, dimension, etc) change. And, on the other hand, the failure probability of safety barriers of the BT are periodically updated using Bayes' theorem as new information becomes available over time. Finally, the resulting, updated BT is used to estimate the posterior probability of the consequences which in turn results in an updated risk profile.

Southern Medical Journal, 2010

Cardiovascular diseases remain the most common cause of both morbidity and mortality in the indus... more Cardiovascular diseases remain the most common cause of both morbidity and mortality in the industrialized world. The frequency of sleep-related breathing disorders (SRBD) is significantly increased in individuals with cardiovascular diseases such as heart failure. Given the co-morbidities associated with SRBD coexisting with HF, prompt recognition and early management of SRBD is critical to improving the overall prognosis and quality of life in heart failure patients with concomitant SRBD.

Risk Analysis, 2006

Process plants deal with hazardous (highly flammable and toxic) chemicals at extreme conditions o... more Process plants deal with hazardous (highly flammable and toxic) chemicals at extreme conditions of temperature and pressure. Proper inspection and maintenance of these facilities is paramount for the maintenance of safe and continuous operation. This article proposes a risk-based methodology for integrity and inspection modeling (RBIIM) to ensure safe and fault-free operation of the facility. This methodology uses a gamma distribution to model the material degradation and a Bayesian updating method to improve the distribution based on actual inspection results. The method deals with the two cases of perfect and imperfect inspections. The measurement error resulting from imperfect inspections is modeled as a zero-mean, normally distributed random process. The risk is calculated using the probability of failure and the consequence is assessed in terms of cost as a function of time. The risk function is used to determine an optimal inspection and replacement interval. The calculated inspection and replacement interval is subsequently used in the design of an integrity inspection plan. Two case studies are presented: the maintenance of an autoclave and the maintenance of a pipeline segment. For the autoclave, the interval between two successive inspections is found to be 19 years. For the pipeline, the next inspection is due after 5 years from now. Measurements taken at inspections are used in estimating a new degradation rate that can then be used to update the failure distribution function.

Risk Analysis, 2008

This study illustrates a newly developed methodology, as a part of the U.S. EPA ecological risk a... more This study illustrates a newly developed methodology, as a part of the U.S. EPA ecological risk assessment (ERA) framework, to predict exposure concentrations in a marine environment due to underwater release of oil and gas. It combines the hydrodynamics of underwater blowout, weathering algorithms, and multimedia fate and transport to measure the exposure concentration. Naphthalene and methane are used as surrogate compounds for oil and gas, respectively. Uncertainties are accounted for in multimedia input parameters in the analysis. The 95th percentile of the exposure concentration (EC 95% ) is taken as the representative exposure concentration for the risk estimation. A bootstrapping method is utilized to characterize EC 95% and associated uncertainty. The toxicity data of 19 species available in the literature are used to calculate the 5th percentile of the predicted no observed effect concentration (PNEC 5% ) by employing the bootstrapping method. The risk is characterized by transforming the risk quotient (RQ), which is the ratio of EC 95% to PNEC 5% , into a cumulative risk distribution. This article describes a probabilistic basis for the ERA, which is essential from risk management and decision-making viewpoints. Two case studies of underwater oil and gas mixture release, and oil release with no gaseous mixture are used to show the systematic implementation of the methodology, elements of ERA, and the probabilistic method in assessing and characterizing the risk.

Risk Analysis, 2013

A new methodology is introduced based on Bayesian network both to model domino effect propagation... more A new methodology is introduced based on Bayesian network both to model domino effect propagation pattern 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.

Renewable Energy, 2005

... Fig. 2. Definition of various life cycle boundaries (revised after Khan et al. [23]). View Wi... more ... Fig. 2. Definition of various life cycle boundaries (revised after Khan et al. [23]). View Within Article. ... The characterization formula for GWP is depicted below, for details refer to Overcash [33], Rossiter [36], and Khan et al. [23] and [24]. ...

Process Safety Progress, 2003

Abstract Inherent safety is a proactive approach for loss prevention during process plant design.... more Abstract Inherent safety is a proactive approach for loss prevention during process plant design. It has been proven that, considering the lifetime costs of a process and its operation, an inherent safety approach can lead to a cost-optimal option. Application of inherent safety at the early stages of process design yields the best results with respect to process selection, conceptual design, and engineering design. However, in spite of being an attractive and cost-effective approach to loss prevention, it is not widely used. Reasons have been ...

Process Safety Progress, 2004

A methodology has been developed to enable the explicit use of the principles of inherent safety ... more 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.

Process Safety Progress, 2009

Neuro-Ophthalmology, 2008

Journal of Loss Prevention in the Process Industries, 2008

Journal of Loss Prevention in the Process Industries, 2006

... The literature (Brown, Willis, &amp; Prussia, 2000; Cheyne, Tomas, Cox, &amp;... more ... The literature (Brown, Willis, &amp; Prussia, 2000; Cheyne, Tomas, Cox, &amp; Oliver, 1999; Guastello, 1989; Thompson, Hilton, &amp; Witt, 1998; Tomas, Melia ... the discussion of results to follow in this paper, a basic description of the model structure and philosophy (Attwood, Khan, &amp; Veitch ...

Journal of Hazardous Materials, 2001

Trees, shrubs, and other vegetation can absorb and assimilate certain air pollutants if the pollu... more Trees, shrubs, and other vegetation can absorb and assimilate certain air pollutants if the pollutants are present within tolerable levels. This concept is being increasingly used in developing strips of vegetation, often called 'greenbelts' around sources of pollution. But several intricacies are associated with the exercise of effective and optimal designing of greenbelts. The pattern of dispersion of air pollutants, as effected by the density of the gaseous plume and the meteorology of the area, must be studied with great precision because these aspects would determine the location and the geometry of the greenbelt. The species composition in the greenbelt should confirm to the pollutants to be attenuated as to the geoclimatic conditions of the region. Decisions on the tree heights, and the sequence of plantation of trees and other vegetation also similarly require complex inputs. In this paper, the authors have addressed these issues and have presented a set of mathematical models, which may help in the rational and optimal design of greenbelts.

Fire Safety Journal, 2012

Fire Safety Journal, 2013

Fire and explosion are accidents which potentially can occur in oil and gas processing facilities... more Fire and explosion are accidents which potentially can occur in oil and gas processing facilities. While fire and explosion could occur as a consequence of each other, most published work has assessed fire and explosion separately, ignoring interactions between the two phenomena.