Inherent Safety Concept Research Articles

Tank pool fire domino effect prevention by inherently safer layout planning: A techno-economic analytical index

Tank pool fire domino effects, represented by their capacities of accident consequence escalation and extensive damages, present substantial safety challenges within chemical storage systems. In this work, the inherent safety concept is introduced to proactively address these challenges while ensuring cost-effectiveness. Accordingly, a dedicated novel metric called Inherent Safety & Economic Risk Index (IS&ERI) is proposed to make safety and cost trade-offs for indicating the risk levels of various tank farm layout options. To develop the IS&ERI, the Dow's loss estimate procedure is adapted for representing the economic implications, and the Bayesian Networks are employed for indicating the failure probabilities of target units considering the synergistic effects of multiple pool fires. Two improved graph theory metrics are presented to determine the root nodes of the Bayesian Networks. For demonstrating the proposed IS&ERI, a case study is conducted and the results show that the IS&ERI of 4 tank farm layout options are 0.2991, 0.3120, 0.3525, and 0.2285, implying that Option 4 is the best layout with the lowest potential loss in case of the pool fire domino effects. As the key research contribution, the IS&ERI is presented and it can be used as a useful tool to compare and select the best tank farm layout option to eliminate or significantly reduce the knock-on effects of tank pool fires at their sources.

A mechanistic framework for the leakage risk reduction of mobile hydrogen refueling stations based on inherent safety concepts

This study presents a mechanistic framework for assessing and mitigating hydrogen leakage risks in Mobile Hydrogen Refueling Stations (MHRS) based on inherent safety concepts. A bow-tie model is proposed to identify potential hazards, event pathways, and consequences. Subsequently, this model is mapped into Bayesian Networks (BN) to enable quantitative risk assessment. Fuzzy set theory is adopted to address the uncertainty of prior probabilities, using a Noisy-MAX model to optimize the BN conditional probabilities. To mitigate leakage risks, a dedicated inherently safer design checklist is developed to identify opportunities for incorporating inherent safety. A case study demonstrates that the leakage potentials decrease from 0.2600 to 0.1997, and the leakage consequences decrease by approximately 22%. This work presents a novel mechanism using inherent safety to reduce the hydrogen leakage risk of MHRS, which is useful for creating an inherently safer MHRS with fundamental and natural robustness against hydrogen leakage.

A mechanistic model for industrial workplace design based on inherent safety and health concepts

AbstractThis study aims to establish a mechanistic model of using inherent safety and health concepts to conduct industrial workplace risk reduction strategies during the project planning stage. Accordingly, a dedicated implementation tool termed inherently safer and healthier design model for industrial workplaces (ISHDM‐IW) is developed. First, the safety and health by design checklist is adapted to derive industrial workplace safety and health risk indicators. Then, the risk indicators are rated and weighted using the methods of risk matrix and precedence chart. Subsequently, the risk indicators are aggregated via fuzzy risk representation with the indicators' risk values and weights. Last, the inherent safety and health principles are used to do risk‐based baseline design optimization. The case study demonstrates the capabilities of the proposed ISHDM‐IW to upgrade the workplace design scheme from risk level II to risk level I, thus generating a more satisfactory workplace design alternative. The proposed ISHDM‐IW offers a novel design mechanism of inherent safety and health for industrial workplaces, which can be expected to ensure employees' safety, health, and well‐being with fundamentally better ergonomics of industrial work environments.

Development of comprehensive healthier process plants based on inherent safety concept

Emerging from inherent safety, Inherent Occupational Health (IOH) is gaining increasing attention for its role in fundamentally mitigating potential hazards that may adversely affect worker health. Conventional IOH approaches mainly focus on hazards associated with chemical processes, with limited attention given to addressing comprehensive health hazards (e.g., noise, vibration, and ergonomic issues) that may result in occupational issues like hearing loss, musculoskeletal problems, and respiratory conditions. An implementation tool for assessing the overall healthiness of process plant alternatives is yet to be established. To address these gaps, this work developed a Process Plant Healthiness Metric (PPHM) for generating holistic inherently healthier alternatives via the proposed Health Risk Management Framework (HRMF). Firstly, a generic health index framework was established. On this basis, multidimensional health risks were identified and measured by the Residual Hazard Index and Failure Modes and Effects Analysis. Fuzzy Logic was adopted to address data sensitivity and inconsistency. Subsequently, Fuzzy Logic and Analytic Hierarchy Process were integrated into Bayesian Networks to develop the PPHM. To cope with key risk factors, the HRMF based on inherent safety concept is proposed and employed as a mind-trigger. The PPHM was validated by a case study of a methyl allyl chloride plant. The results revealed that following the implementation of HRMF-based interventions, the value of PPHM increased from 2.17 to 3.87, and the unhealthiness rate decreased from 0.0257 to 0.000558, thereby establishing a relatively healthier alternative. This work enables a holistic identification, assessment, and mitigation of comprehensive health risks within process plants during the design phase. It facilitates a shift in the inherently safer design ideology from process health to plant health.

Sustainable process design for heat exchanger network considering inherent safety and process economics

AbstractProcess lifecycle has several stages, including process design covered in multiple stages. Process economics is a vital factor in finalizing the process design. Besides economics, inherent safety is an important concept contributing to sustainable process design generation. The inherent safety concept has been applied via equipment characteristics for individual equipment. Since a method considering inherent safety with equipment aspects and process economics has not been available, therefore, a new method has been proposed, namely sustainable process design for heat exchanger network (SPDHEN), to integrate inherent safety, equipment aspects, and process economics. SPDHEN uses indexing to identify the critical heat exchanger, which is then examined via hazard analysis for an explosion. For unacceptable hazards, inherent safety principles are engaged to generate design alternatives for which process economics is examined too. The final design would be inherently safer with the best profit margin. The proposed method has been studied for the ammonia synthesis loop. It is concluded that the explosion hazard has been reduced to a tolerable level by using inherent guide words with a marginal compromise on quantity of ammonia produced, that is, 0.32%. This method is straightforward and can be useful for process engineers to generate sustainable process designs for heat exchanger networks considering safety and process economics simultaneously.

Inherent safety concept based proactive risk reduction strategies: A review

The growing scale and complexity of process industries have brought safety, health, and environmental issues to the forefront. As a result, proactive risk reduction strategies (RRSs) are commonly employed to address these issues by reducing the frequency or mitigating the consequences of potential incidents. Among these strategies, inherent safety, which is a proactive measure of loss prevention and risk management, is considered to be the most effective method. This review aims to provide a comprehensive analysis of RRSs for achieving inherency, as well as techniques for evaluating the performance of inherent safety, health, and environmental aspects. Background information is presented, including the development and implementation of the inherently safer process design, as well as the approaches for achieving inherently healthier and environmentally friendlier processes. Subsequently, the execution approaches and practical applications of other RRSs are discussed to highlight the distinctiveness and benefits of inherent safety. Next, this study examined the characteristics of inherency assessment tools (IATs) based on available information at different process stages. Furthermore, the evaluation methods and historical development of IATs are investigated from the perspectives of safety, occupational health, and environmental considerations, followed by a statistical analysis of IATs. It is concluded that the no-chemical hazards-based IATs have not been extensively studied yet, which may improve the safety level of process plants from the perspective of comprehensive inherency risk reduction. As a way forward, future research opportunities are proposed to promote the implementation of greater optimized risk management.

Bayesian networks based laboratory retrofitting towards inherent safety: A risk-based implementation framework

Over the years, a number of high-profile laboratory accidents involving severe injuries, fatalities, and economic losses have been reported, prompting a significant increase in efforts towards laboratory safety. However, the dominant safety measures rely excessively on add-on safeguards such as sprinklers and respirators and pay little attention to reducing the hazardous factors at their sources. This study introduced the inherent safety concept to minimize laboratory hazards and developed a dedicated implementation tool called Generic Laboratory Safety Metric (GLSM). The Traditional Laboratory Safety Checklist (TLSC) was first used to represent the safety indicators, and then the Precedence Chart (PC) and Bayesian Networks (BN) methods were used to reconcile the safety indicators to develop the GLSM. The developed GLSM was subsequently demonstrated through a case study of a university laboratory. The results revealed that the safety level increased from 2.44 to 3.52 after the risk-based inherently safer retrofitting, thus creating laboratory conditions with a relatively satisfactory safety level. This work presented a set of generic solutions to laboratory retrofitting towards inherent safety with a novel GLSM as the implementation tool. The proposed GLSM would contribute to risk quantification and identification of key risk factors for assigning targeted and fundamental safety measures to achieve inherently safer laboratories.

Qualitative risk analysis of the overhead hydrogen piping at the conceptual process design stage

Namie, which is a town in Fukushima prefecture in Japan, has started a green innovation project using hydrogen to eliminate CO 2 release by 2050 and establish a zero-carbon city. One idea is to develop an overhead hydrogen piping, which is a low-pressure hydrogen supply system, in public spaces. To develop and implement the piping in Namie and other areas, it is important to both develop the process and perform the risk analysis during a preliminary process design stage. The purpose of this study was to qualitatively analyze and identify the critical risks and effective safety measures for the piping. A total of 183 accidental scenarios were identified by using a hazard identification study, and the preventive and mitigation safety measures were summarized. Hydrogen dispersion simulations revealed that low-pressure hydrogen dispersion leaking from small holes and fractured piping in public spaces could result in concerning risks depending on the leak size, direction, position, obstacles, and ignition source. In addition, a shutdown system of the piping was evaluated with a multiphysics modeling simulation, and its importance was discussed to proceed with detailed investigations. Finally, we suggested risk reduction measures based on the concept of inherent safety for the development of low-pressure hydrogen systems, and the findings can be applied to cases such as Namie. • The overhead hydrogen piping was developed. • Qualitative risk assessment using hazard identification study was carried out. • 183 accidental scenarios were identified, and safety measures were summarized. • The flammable concentration of hydrogen was predicted by dispersion simulations. • A piping shutdown valve was evaluated as a critical safety measure.

Inherent health oriented design for preventing sick building syndrome during planning stage

Derived from inherent safety concept, inherent health is a new approach that aims to unearth proactive, fundamental, and permanent solutions that could eliminate or significantly reduce health risks at source, thus avoiding adding extensive end-of-pipe protections. To date, however, limited attention has been given to using this new approach to prevent Sick Building Syndrome (SBS), and an assessment tool for quantifying the "sickness" at planning stage is yet to be established. To this end, this work investigated the feasibility of addressing SBS via Inherent Health Oriented Design (IHOD) and developed SBS Contributory Indices (SBSCI) for quantifying the sickness severity. Firstly, the contributory indices were extracted from a well-practiced checklist of SBS determinants. Then, the indices were reconciled using Analytic Hierarchy Process (AHP) and equation-based Bayesian Networks (BN), and finally, the newly developed metric (i.e., SBSCI) was exemplified by a case study. The results show that the sickness level decreased by approximately 82% after IHOD modifications, implying that the modified architectural design can be less sick (inherently healthier) than the baseline design. This work presents a nexus study between the implications of "inherent" solutions and healthy buildings. This cross-cutting study would offer a new perspective on the early inspection and prevention for sick building induced health problems.

The concept of inherent safety of generation V nuclear power plants

Elimination of significant risks in nuclear power production is at the present stage a necessity and goal-setting that determines its development in the near future. Of particular importance is the problem of maximum credibility and convincingly substantiated stability of nuclear power plants against severe accidents. The lack of clear logic, transparency and guarantees in the reliability of the announced nuclear safety significantly hinders its development, unnecessarily overcomplicating expensive technical solutions, thereby weakening the competitiveness of nuclear power. The originally proposed Concept of Inherent Safety set the task of solving the above problems; however, its specific content has not been explicitly presented so far, which allows many competitors to use its terminology to promote projects that are not directly related to the ‘spirit and letter’ of Inherent Safety. This paper is intended to fill this gap. The authors also discuss the conditions for the generation and development of new self-protection means for innovative nuclear reactors as well as the phenomenological and technical aspects for their implementation based on the deterministic formalism.

Developing friendlier biodiesel production process via systematic inherent safety interventions

The efficacy of inherent safety interventions for shaping Friendlier Chemical Processes (FCP) has been demonstrated in simultaneously augmenting safety (S), health (H), and environmental (E) performance while operating economically. However, there is limited attention to linking inherent safety concept with HE and cost issues when modifying process design, and a hierarchical metric used for measuring the inherent friendliness is yet to be presented. To this end, this study developed a Reconciled Friendly Process Metric (RFPM) for generating FCP via Systematic Inherent Safety (SIS) modifications. Firstly, the prestigious inherent SHE and cost metrics were selected and adapted to measure friendliness features. Then, the metrics were reconciled by Analytic Hierarchy Process (AHP) and Fuzzy Comprehensive Evaluation (FCE), and finally, the RFPM was validated through biodiesel production process. The results show that the base design is estimated as under Moderate (M) condition, while the modified design is estimated as under Relatively Friendly (RF) condition, which implies that the modified design is inherently friendlier than the base design. This newly developed RFPM can be used as a tool for hierarchically indicating the friendliness of processing scenarios and making trade-offs among safety, health, environmental, and cost concerns during design stage.

A brief review of the development of high temperature gas cooled reactor

With the continuous development of nuclear energy, the high temperature gas cooled reactor (HTGR) is considered as one of the advanced reactor types of the fourth generation nuclear power system because of its new inherent safety concept, modular concept, high economic competitiveness and increasing construction flexibility. In this paper, the development history of high temperature HTGR is briefly summarized and the latest research is summarized.

Comparison of safety indexes for chemical processes under uncertainty

The fatal consequences of industrial incidents have made evident the need for suitable tools to develop inherently safer process design options. Traditionally, in a process design project, the evaluation of safety aspects is left for analysis after the detailed design has been completed. This approach leads to the use of control loops, barriers and protection layers as the only ways to prevent incidents and to reduce the possible outcomes. An alternative to this approach is the application of the concept of inherent safety, which was introduced to set up several principles that aim to enhance process safety by eliminating, avoiding or minimizing sources of risk.In this work, we present a comparison of different safety metrics in their role to evaluate the risk associated with a given process design. The indices selected for consideration are the Dow’s fire and explosion index (F&EI), the fire and explosion damage index (FEDI), the process route index (PRI) and the process stream index (PSI). All these indices use different input information and their outcomes have different rankings. The metrics were applied to an ethylene production process from shale gas to identify hazard levels, and the location of streams and pieces of equipment that pose the highest hazard within the process. An evaluation of the indices in their capability to track design changes in operating conditions aiming to improve the safety level of the process was developed. To perform the assessment of the safety metrics in a more extensive manner, an uncertainty analysis based on a Monte Carlo simulation framework was implemented and compared to the traditional use of single-value design variables. Within this context, an insightful assessment of uncertainty’s effect on process safety characteristics was achieved because of the identification of ranges of safety-relevant performance outcomes (zones of risks and opportunities) that can be probabilistically characterized. The application of the approach to the ethylene process showed how some indexes are better suited to capture the hazard characteristics associated with the process when changes in the operating conditions of most hazardous section were implemented. The methodology can be extended to other processes of interest, and may serve as a basis for the safety and process design community to propose adjustments in the structure of safety indices based on a better understanding of their performance and reliability as part of broader efforts towards their continuous improvement and refinement.

Solvent design and inherent safety assessment of solvent alternatives for palm oil recovery

The concept of inherent safety is important in developing an inherently safer and user-friendly process. This paper discusses a new integrated approach of computer-aided product design and inherent safety assessment. Computer-aided Molecular Design (CAMD) approach was utilized in this work to identify potential alternative to n-hexane, the widely used industrial solvent in extracting residual palm oil from pressed palm fibre. The formulation of solvent mixtures was optimized to meet the targeted physical properties before being tested using the Soxhlet Extraction method. Inherent safety assessment to assess the solvent's flammability, toxicity, reactivity, and explosiveness was conducted on the new solvent mix, Mixture 1 (n-hexane + ethanol), Mixture 2 (n-hexane + acetone) and Mixture 3 (n-hexane + n-butanol). It was found that Mixture 1 and 3 are safer than n-hexane and able to extract more oil than n-hexane and Mixture 2. However, the utilization of the solvent is dependent on the end product from the residual palm oil.

A graphical inherent safety assessment technique for preliminary design stage

User-friendly plants are needed for equipment failure to not seriously affect its safety, productivity, or efficiency. Safer and user-friendly plants can be designed through the implementation of hazard prevention strategies during the design phase, which is known as the concept of inherent safety. The Graphical Inherent Safety Assessment Technique (GISAT) for preliminary engineering design stage is presented in this paper. GISAT incorporates information obtainable from the process flow diagram (PFD) in the assessment of inherent safety features of a process. This technique evaluates three inherent safety parameters, namely flammability, explosiveness, and toxicity. GISAT also utilises accident statistics in the construction of its graphical rating as the hazard level indicator for chemical process equipment assigned under five groups—reactor, heat transfer equipment, separation equipment, storage tank, and other equipment. In this technique, quantity of the chemicals involved in an equipment represents the weightage of the assessment that is used to identify the root-cause of hazards in each equipment. Hydrodealkylation process of toluene (HDA) to produce benzene is used as a case study to demonstrate the application of GISAT. The results indicate that heat transfer equipment E102 as safer in terms of flammability compared to other equipment while all equipment were found to be safer in term of explosiveness. Separation equipment V102, heat transfer equipment E102, and recycle gas compressor C101 were found to be safer in terms of toxicity. Meanwhile, heat transfer equipment E101, E102, and E103 as well as gas compressor C101 are regarded as safer in terms of fire, explosion, and toxic release combination type of accident as represented by the GISAT Total Score. After the level of hazard in each equipment have been identified, hazard prevention strategies can be applied to equipment with higher level of hazard for hazard reduction.

Process equipment common attributes for inherently safer process design at preliminary design stage

Hazards associated with chemical processes can lead to accidents and require therefore proper management. An inherent safety strategy is a proactive approach to serve this purpose, one capable of minimizing hazards whilst offering sustainable process design. Current inherent safety techniques are limited to comparing process routes and selecting safer one using the process parameters, whereas process equipment characteristics are rarely scrutinized. Therefore, this paper consolidates a new technique that integrates the mutually shared attributes of process equipment, in order to offer inherently safer process design at the preliminary design stage. Inherent safety assessment for process equipment (ISAPE) consists of an indexing procedure, followed by risk assessment. The indexing procedure can highlight the critical process equipment, which can be further studied through risk assessment. When the risk is beyond acceptable threshold and must be minimized, inherent safety concepts are implemented, leading towards inherently safer process design. The complete ISAPE technique is exhibited through the case study of the acetone production process. In this case study, various ISD options have been applied to the critical process equipment, identified through the proposed indexing; the options have then been compared to select the best one. The method is easy to use, and as such, it is suitable to be put into practice by design engineers at the preliminary design stage.

Distillation column inherent safety index at preliminary design stage

Distillation columns are widely used in many chemical process industries, especially in oil and gas processing. Accidents in the distillation columns have resulted in enormous loss of human lives and assets. Inadequate design of distillation columns is one of the vital reason for the failure, which can be enhanced through inherent safety concept. Therefore, this paper introduces a new indexing method for designing inherently safer distillation columns right from the preliminary design stage. Distillation Column Inherent Safety Index (DCISI) is based on three sub-indices; chemical index, process index and distillation index. These sub-indices are estimated through individual scores by considering various parameters in each category. For the unacceptable score, modification of process conditions is used to enhance safety level of the design. DCISI is estimated for all combination of conditions and lowest DCISI value indicates the inherently safer design of the distillation column.

Inherently Safer Design and Optimization of Intensified Separation Processes for Furfural Production

Currently furfural production has been the subject of increased interest because it is a biobased chemical able to compete with fossil-based chemicals. Furfural is characterized by flammability, explosion, and toxicity properties. Improper handling and process design can lead to catastrophic accidents. Hence it is of most importance to use inherent safety concepts during the design stage. This work is the first to present several new downstream separation processes for furfural purification, which are designed using an optimization approach that simultaneously considers safety criteria in addition to the total annual cost and the eco-indicator 99. The proposed schemes include thermally coupled configuration, thermodynamic equivalent configuration, dividing-wall column, and a heat integrated configuration. These are compared with the traditional separation process of furfural known as the Quaker Oats Process. The results show that because of a large amount of water present in the feed, similar values are o...

Inherent safety for sustainable process design of process piping at the preliminary design stage

Risk assessment is an accepted approach used worldwide to improve the sustainability of either the existing process plant or the design of a new installation. In the current practices, risk assessment is normally performed once the design has been completed. A better approach is to perform risk assessment at the initial design stages with the application of inherent safety concept to achieve the sustainable cleaner chemical process. This paper consolidates a new technique to improve the safety level of process piping from potential fire risk using the inherent safety concept. Inherently safer process piping (ISPP) technique utilizes fundamental of fluid flow to predict the potential damage from a major fire accident. A relative ranking of process streams is used to identify the critical process streams that have higher chances of damage. Risk assessment is performed to check if the potential fire exceeds the acceptance criteria or not. If the risk is not in the acceptable range, inherent safety principle is used to reduce the risk to the acceptable limit. The ISPP technique is validated using a case study of methanol process plant. This technique could be used to facilitate design practitioners to incorporate inherent safety at the early design stage.

Development of hazard prevention strategies for inherent safety assessment during early stage of process design

Abstract A safety program that prevents hazards from occurring is preferable than the typical approaches of eliminating hazards upon being detected. Chemical plants should be designed so that they are user-friendly and exhibit good safety features to prevent accidents. This can be done by preventing the presence of hazards in the process fundamentally, which is formally known as the inherent safety concept. This paper discusses the development of process hazard prevention strategies (HPS) during the early design stage. The strategies were formulated into a detailed framework which was constructed using thematic analysis. The thematic analysis was used to extract hazard prevention strategies from the accident databases – producing results in the form of keywords, referred here as themes and generated codes. Common keywords that appeared in the accident databases on how to prevent the accidents were gathered and referred to as generated codes in this research. The generated codes were then grouped into five themes namely; materials, design, operating, chemicals and control. This study was applied to the case study of benzene production from toluene involving separation and heat transfer equipment. The HPS themes identified for separation equipment were design, operating and chemicals, while for heat transfer equipment the themes identified were materials, design, operating, chemicals and control. This technique produced similar results as two other techniques on the Bhopal case study and the toluene nitration case study, with justified differences. This not only proves the effectiveness of the framework but also supports the validity of the framework.