Showing papers in "Journal of Loss Prevention in The Process Industries in 2014"

Dynamic safety risk analysis of offshore drilling

Abstract: The exploration and production of oil and gas involve the drilling of wells using either one or a combination of three drilling techniques based on drilling fluid density: conventional overbalanced drilling, managed pressure drilling and underbalanced drilling. The conventional overbalanced drilling involves drilling of wells with mud which exerts higher hydrostatic bottom-hole pressure than the formation pore pressure. Unlike the conventional overbalanced drilling, underbalanced drilling involves designing the hydrostatic pressure of the drilling fluid to be lower than the pore pressure of the formation being drilled. During circulation, the equivalent circulating density is used to determine the bottom-hole pressure conditions. Due to lower hydrostatic pressure, underbalanced drilling portends higher safety risk than its alternatives of conventional overbalanced drilling and managed pressure drilling. The safety risk includes frequent kicks from the well and subsequent blowout with potential threat to human, equipments and the environment. Safety assessment and efficient control of well is critical to ensure a safe drilling operation. Traditionally, safety assessment is done using static failure probabilities of drilling components which failed to represent a specific case. However, in this present study, a dynamic safety assessment approach for is presented. This approach is based on Bow-tie analysis and real time barriers failure probability assessment of offshore drilling operations involving subsurface Blowout Preventer. The Bow-tie model is used to represent the potential accident scenarios, their causes and the associated consequences. Real time predictive models for the failure probabilities of key barriers are developed and used in conducting dynamic risk assessment of the drilling operations. Using real time observed data, potential accident probabilities and associated risks are updated and used for safety assessment. This methodology can be integrated into a real time risk monitoring device for field application during drilling operations.

Integrated leakage detection and localization model for gas pipelines based on the acoustic wave method

Abstract: With the development of natural gas transportation systems, major accidents can result from internal gas leaks in pipelines that transport high-pressure gases. Leaks in pipelines that carry natural gas result in enormous financial loss to the industry and affect public health. Hence, leak detection and localization is a major concern for researchers studying pipeline systems. To ensure the safety and improve the efficiency of pipeline emergency repair, a high-pressure and long-distance circular pipe leakage simulation platform is designed and established by similarity analysis with a field transmission pipeline, and an integrated leakage detection and localization model for gas pipelines is proposed. Given that the spread velocity of acoustic waves in pipelines is related to the properties of the medium, such as pressure, density, specific heat, and so on, this paper proposes a modified acoustic velocity and location formula. An improved wavelet double-threshold de-noising optimization method is also proposed to address the original acoustic wave signal collected by the test platform. Finally, the least squares support vector machine (LS-SVM) method is applied to determine the leakage degree and operation condition. Experimental results show that the integrated model can enhance the accuracy and precision of pipeline leakage detection and localization.

Quantitative assessment of domino and NaTech scenarios in complex industrial areas

Abstract: Since the late 80s the application of quantitative risk assessment to the issue of land-use planning with respect to major accident hazards emerged as a topic to be addressed within the safety assessment of chemical and process plants. However, in the case of industrial clusters or complex industrial areas specific methodologies are needed to deal with high-impact low-probability (HILP) events. In the present study, innovative methodologies developed for the quantitative assessment of risk due to domino and NaTech scenarios are presented. In recent years a set of models for the calculation of equipment damage probability were developed. A specific effort was dedicated to the improvement of models for the calculation of equipment damage probability in these accident scenarios. In the present study, the application of these models to case-studies was analyzed. The results of the improved models obtained for NaTech quantitative assessment were compared to previous results in the literature. A specific innovative approach was developed to multi-level quantitative assessment of domino scenarios, and its potential was analyzed. The results were examined also evidencing the role and the progress with respect to the pioneering work started on these topics by Franco Foraboschi.

Integrating lean principles and fuzzy bow-tie analysis for risk assessment in chemical industry

Abstract: In this research, a framework combining lean manufacturing principles and fuzzy bow-tie analyses is used to assess process risks in chemical industry. Lean manufacturing tools and techniques are widely used for eliminating wastes in manufacturing environments. The five principles of lean (identify value, map the value stream, create flow, establish pull, and seek perfection) are utilized in the risk assessment process. Lean tools such as Fishbone Diagram, and Failure Mode and Effect Analysis (FMEA) are used for risk analysis and mitigation. Lean principles and tools are combined with bow-tie analysis for effective risk assessment process. The uncertainty inherent with the risks is handled using fuzzy logic principles. A case study from a chemical process industry is provided. Main risks and risk factors are identified and analyzed by the risk management team. Fuzzy estimates are obtained for the risk factors and bow-tie analysis is used to calculate the aggregated risk probability and impact. The risks are prioritized using risk priority matrix and mitigation strategies are selected based on FMEA. Results showed that the proposed framework can effectively improve the risk management process in the chemical industry.

The significance of domino effect in chemical accidents

Abstract: A historical survey was performed on 330 accidents involving domino effect, occurred in process/storage plants and in the transportation of hazardous materials; only accidents occurred after 1st-January-1961 have been considered. The main features – geographical location, type of accident, materials involved, origin and causes, consequences, domino sequences – were analyzed, with special consideration to the situation in the developing countries and compared to those from other previous surveys. Among the involved substances, LPG was the most frequent one, followed by liquid hydrocarbons. Process plants (38.5% of cases) and storage areas (33%) were the most common settings; 10.6% of past domino accidents occurred in transfer operations. The ratio between “two-step” and “three-step” domino accidents was found to be 6. A specific analysis of the accidents (84) occurred in the 21st century was performed, comparing them with the total set of accidents. Finally, a set of specific recommendations inferred from the results is provided.

Explosion characteristics of micron- and nano-size magnesium powders

Abstract: Explosion characteristics of micron- and nano-size magnesium powders were determined using CSIR-CBRI 20-L Sphere, Hartmann apparatus and Godbert-Greenwald furnace to study influence of particle size reduction to nano-range on these. The explosion parameters investigated are: maximum explosion pressure (Pmax), maximum rate of pressure-rise (dP/dt)max, dust explosibility index (KSt), minimum explosible concentration (MEC), minimum ignition energy (MIE), minimum ignition temperature (MIT), limiting oxygen concentration (LOC) and effect of reduced oxygen level on explosion severity. Magnesium particle sizes are: 125, 74, 38, 22, 10 and 1 μm; and 400, 200, 150, 100, 50 and 30 nm. Experimental results indicate significant increase in explosion severity (Pmax: 7–14 bar, KSt: 98–510 bar·m/s) as particle size decreases from 125 to 1 μm, it is maximum for 400 nm (Pmax: 14.6 bar, KSt: 528 bar·m/s) and decreases with further decrease of particle size to nano-range 200–30 nm (Pmax: 12.4–9.4 bar, KSt: 460–262 bar·m/s) as it is affected by agglomeration of nano-particles. MEC decreases from 160 to 30 g/m3 on decreasing particle size from 125 to 1 μm, its value is 30 g/m3 for 400 and 200 nm and 20 g/m3 for further decrease in nano-range (150–30 nm). MIE reduces from 120 to 2 mJ on decreasing the particle size from 125 to 1 μm, its value is 1 mJ for 400, 200, 150 nm size and <1 mJ for 50 and 30 nm. Minimum ignition temperature is 600 °C for 125 μm magnesium, it varies between 570 and 450 °C for sizes 38–1 μm and 400–350 °C for size range 400–30 nm. Magnesium powders in nano-range (30–200 nm) explode less violently than micron-range powder. However, likelihood of explosion increases significantly for nano-range magnesium. LOC is 5% for magnesium size range 125–38 μm, 4% for 22–1 μm, 3% for 400 nm, 4% for 200, 150 and 100 nm, and 5% for 50 and 30 nm. Reduction in oxygen levels to 9% results in decrease in Pmax and KSt by a factor of 2–3 and 4–5, respectively, for micron as well as nano-sizes. The experimental data presented will be useful for industries producing or handling similar size range micron- and nano-magnesium in order to evaluate explosibility of their magnesium powders and propose/design adequate safety measures.

Past, present and future of Quantitative Risk Assessment (QRA) and the incentive it obtained from Land-Use Planning (LUP)

Abstract: This paper tells the story about the development of Quantitative Risk Assessment, how it was conceptualized in the early 1970s in the nuclear industry, how it was employed within the chemical industry soon after, and what its status is today. The different purposes of QRA are explained, and we elaborate on one of the purposes, that is, Land-Use Planning. The role of Professor Ben Ale, as a process safety pioneer, is discussed throughout the history. We finally provide some on-going state-of-the-art research and projects to further improve QRA approaches, and we sketch the future of QRA and its relation with LUP.

CFD simulations of dust dispersion in the 20 L vessel: Effect of nominal dust concentration

Abstract: Measurements of flammability and explosion parameters for dust/air mixtures require uniform dispersion of the dust cloud inside the test vessel. In a previous work, we showed that, in the standard 20 L sphere, the dust injection system does not allow generation of a uniform cloud, but rather high gradients of dust concentration are established. In this work, we used a previously validated three-dimensional CFD model to simulate the dust dispersion inside the 20 L sphere at different dust nominal concentrations (and fixed dust diameter). Results of numerical simulations have shown that, as the dust nominal concentration is increased, sedimentation prevails and, thus, when ignition is provided, the dust is mainly concentrated at the vessel walls.

A dynamic alarm management strategy for chemical process transitions

Abstract: Chemical processes frequently operate upon a multitude of steady states and transitions between these states are inevitable. Unfortunately, transitions are exactly where alarm floods often occur. Alarm floods cause critical alarms overwhelmed and thus increase the probability of larger safety issues. Existing techniques for the design of alarm systems mostly focus on one steady state of operation and yet cannot effectively deal with alarm floods during transitions. In this paper, a dynamic alarm management strategy is proposed for controlling alarm floods during transitions of chemical processes. In this strategy, the artificial immune system-based fault diagnosis (AISFD) method and a Bayesian estimation based dynamic alarm management (BEDAM) method are integrated. During transitions, dynamic alarm limits obtained by the BEDAM method can control alarm floods. However, if a process fault occurs during transitions, a flood of alarms could still be yielded. To generate useful alarms in fault situations, an artificial immune system based on dynamic time warping (DTW) is used for fault detection and diagnosis. Finally, in case studies, the dynamic alarm management strategy is applied to the startup stage and a throughput change transition in a pilot-scale distillation column.

Effects of N2/CO2 on explosion characteristics of methane and air mixture

Abstract: An experimental apparatus for the methane and air mixture explosion with N2/CO2 in a closed vessel was set up. A series of experiments have been performed to analyze the effects of N2/CO2 on explosion strength, limiting oxygen concentration, flammability limits and explosion suppression. Results show that explosion strength decreases with the volume fraction of N2/CO2 in the mixture. Limiting oxygen concentration decreases linearly with the volume fraction of N2 in N2/CO2 mixture. The flammability limits change linearly with the volume fraction of N2/CO2 in the mixture. The higher the volume fraction of CO2 in N2/CO2 mixture, the better the explosion suppression effect is. Based on experimental data, fitted equations and diagrams are made to predict methane flammability limits with N2/CO2 under different volume fraction ratio of N2 and CO2. The research results can be used as a reference for the inerting treatment design of methane explosion protection in process industries.

Seismic vulnerability of gas and liquid buried pipelines

Abstract: Lifelines play a crucial and essential role in human life and in economic development. The resilience of those systems under extreme events as earthquakes is a primary requirement, especially when large amount of toxic and flammable material are transported. In this work, the seismic vulnerability of buried gas and liquid pipelines has been analyzed, starting from a large number of damage data to pipelines collected from post-earthquake reconnaissance reports. Seismic fragility formulations and threshold values for the earthquake intensity with respect to the release of content from different types of pipelines have been derived. The main outcome of the work is therefore a novel seismic assessment tool which is able to cover the needs of industrial risk assessment procedures and land use planning requirements.

Accident modelling and analysis in process industries

Abstract: Accident modelling is a methodology used to relate the causes and effects of events that lead to accidents. This modelling effectively seeks to answer two main questions: (i) Why does an accident occur, and (ii) How does it occur. This paper presents a review of accident models that have been developed for the chemical process industry with in-depth analyses of a class of models known as dynamic sequential accident models (DSAMs). DSAMs are sequential models with a systematic procedure to utilise precursor data to estimate the posterior risk profile quantitatively. DSAM also offers updates on the failure probabilities of accident barriers and the prediction of future end states. Following a close scrutiny of these methodologies, several limitations are noted and discussed, and based on these insights, future work is suggested to enhance and improve this category of models further.

Comprehensive evaluation on self-ignition risks of coal stockpiles using fuzzy AHP approaches

Abstract: Self-ignition in coal stockpiles is a serious economic, environmental and safety problem. Evaluation is an effective way to identify the self-ignition hazards in implicit environment of coal piles and provides a guide for countermeasures against spontaneous combustion in coal piles. In this paper, a comprehensive evaluation system is proposed. The trapezoidal and the triangular extent fuzzy AHP methods are employed to handle the imprecision and uncertainty of the effects of factors. A coal stockpile stored at the Bulk Cargo Logistics of Tianjin Port of China and three coal piles in the Teruel basins of Spain are studied to demonstrate the validity of the index system and the effectiveness of fuzzy AHP approaches. The evaluated results indicate that the proposed evaluation system and approaches are valid and objective for evaluating self-ignition risks of coal stockpiles; compared with the trapezoidal fuzzy AHP method, the triangular extent fuzzy AHP approach is more effective to evaluate self-ignition risks of coal piles for the priorities of factors impacting self-ignition risks are highlighted by their weight comparisons' calculation using the triangular extent analysis. The comprehensive evaluation system is beneficial to manage self-ignition risks of coal piles from a holistic point of view and to establish an early warming system of self-ignition risks of coal piles.

Experimental study on the suppression of gas explosion using the gas–solid suppressant of CO2/ABC powder

Abstract: Gas explosion is the leading accident in underground coal mining in China. Using the self-improved 20 L spherical experimental system, the impacts of 8% CO2, ABC powder at various concentrations and mixture of them on the suppression of mine gas explosion were investigated. The results indicate that cooperative synergism exists between ABC powder and CO2. Their combination has a better effect than each of the two components acting alone, especially for the gas of larger concentration. When 0.25 g/L ABC powder was mixed with 8% CO2, the explosion limits were reduced by about 55%, the time to reach the peak explosion pressure was prolonged 3.56 times on average. Meanwhile, the maximum explosion pressure declined on an average of 59.4% and the maximum explosion overpressure rising rate decreased on an average of 91.1%. A combination of 0.20 g/L ABC powder and 8% CO2 completely suppressed 11% gas explosion. The explosion suppression mechanism of CO2 and ABC powder were probed theoretically. CO2 plays a key part in the whole explosion processes, and it can effectively suppress the forward reaction between gas and oxygen. While it is during the middle-later period of explosion processes that ABC powder plays a critical role. The particles decomposed from heated ABC powder such as nitrogen and phosphor will react with free radicals rapidly. Besides, atoms as N, P are capable of participating in chain reaction and reacting with active groups, significantly suppressing the gas explosion.

Multiple pool fires: Occurrence, simulation, modeling and management

Abstract: When two or more pool fires burn in such close proximity of one another that they can influence each other, they are termed ‘multiple pool fires’ (MPF). The characteristics and the structure of MPFs are significantly different from that of stand-alone pool fires. Even though MPFs have known to occur fairly often in chemical process industries, much lesser work has been done towards simulation, modeling and control of MPFs as compared to stand-alone pool fires. This paper is perhaps the first-ever attempt at surveying the MPF state-of-the-art. It recounts MPF accidents and catalogs the controlled experiments that have been done to understand the mechanism and impact of MPFs. Attempts to model MPFs have been assessed and possible ways to manage MPFs have been touched upon.

Dynamic behavior of direct spring loaded pressure relief valves in gas service: Model development, measurements and instability mechanisms

Abstract: A synthesis of previous literature is used to derive a model of an in-service direct-spring pressure relief valve. The model couples low-order rigid body mechanics for the valve to one-dimensional gas dynamics within the pipe. Detailed laboratory experiments are also presented for three different commercially available values, for varying mass flow rates and length of inlet pipe. In each case, violent oscillation is found to occur beyond a critical pipe length, which may be triggered either on valve opening or closing. The test results compare favorably to the simulations using the model. In particular, the model reveals that the mechanism of instability is a Hopf bifurcation (flutter instability) involving the fundamental, quarter-wave pipe mode. Furthermore, the concept of the effective area of the valve as a function of valve lift is shown to be useful in explaining sudden jumps observed in the test data. It is argued that these instabilities are not alleviated by the 3% inlet line loss criterion that has recently been proposed as an industry standard.

Development of inherently safer distillation systems

Abstract: The design of distillation systems has typically been carried out based on economic objectives, driven by operating costs and energy requirements. Other aspects, such as safety considerations, are carried out after the design has been developed. In this work, the application of risk measurements as part of the design of distillation systems is presented. Principles of quantitative risk analysis together with economic objectives are used for the design of two types of distillation arrangements, namely conventional distillation and multi-effect distillation. Two types of mixtures that address different safety implications are taken as case studies. Their operating costs and safety implications as part of their separation characteristics are quantified. It is shown how the application of the methodology here presented allows the detection of critical design variables not only from economic terms but also as far as their safety implications. The analysis provides the basis for the design of inherently safer distillation systems.

Participation of large particles in coal dust explosions

Abstract: Float coal dust is produced during the coal mining process in underground mines. If it is entrained, the float coal dust presents a dangerous explosion hazard to miners when it reaches the minimum explosible concentration and is ignited. However, coal dust can be inerted if properly mixed with generous amounts of pulverized rock dust such as limestone to result in a homogeneous dust mixture with a total incombustible content (TIC) ≥80%. In the United States, it is mandatory for the rock dust to be 100% passing through a 20 mesh (841 μm) sieve and 70% or more passing through a 200 mesh (75 μm) sieve. Laboratory experiments have been conducted using the National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) 20-L and the Fike Corporation 1-m 3 explosion chambers. Coal and rock dust samples were prepared by sieving and were used to investigate the effect of particle size on explosibility and inerting effectiveness. The results from both chambers show that large coal particles >60 mesh (>250 μm) do not explode/ignite at dust concentrations up to 600 g/m 3 , and limestone rock dust particles >200 mesh (>75 μm) require a significantly higher TIC of 90% to inert Pittsburgh pulverized coal (PPC). This data illustrates the significance of particle size for preventing coal dust explosions and the importance of measuring particle size as well as TIC (which includes moisture as well as incombustibles) to determine the true explosibility of a dust sample.

STAMP – Holistic system safety approach or just another risk model?

Abstract: Risk management has a number of accident causation models that have been used for a number of years. Dr. Nancy Leveson (2002) has developed a new model of accidents using a systems approach. The new model is called Systems Theoretic Accident Modeling and Processes (STAMP). It incorporates three basic components: constraints, hierarchical levels of control, and process loops. In this model, accidents are examined in terms of why the controls that were in place did not prevent or detect the hazard(s) and why these controls were not adequate to enforcing the system safety constraints. A STAMP accident analysis is presented and its usefulness in evaluating system safety is compared to more traditional risk models. STAMP is applied to a case study in the oil and gas industry to demonstrate both practicality and validity of the model. The model successfully identified both direct and indirect violations against existing safety constraints that resulted in the accident at each level of the organization.

Computational fluid dynamics simulation of LNG pool fire radiation for hazard analysis

Abstract: In this paper, a three-dimensional computational fluid dynamics (CFD) model has been conducted on liquefied natural gas (LNG) pool fire radiation. Besides the general governing equations (continuity, energy and momentum), three key components as viscous model of large eddy simulation (LES), non-premixed combustion model, and radiation model for pool fire radiation have been considered to take account of the unsteady and pulsed burning flames, which are especially important in capturing characteristics of large LNG pool fire. The experimental data from Montoir series field tests of LNG pool fire, which could demonstrate a relatively complete performance of large LNG pool fire, have been applied to validate the CFD model of fire radiation. The relative error is less than 10% and the results are in good agreement with the test data. CFD model performs better than the commonly used engineering model as Solid Flame Model. The verified CFD model is then applied to perform a hazard analysis for a LNG satellite station. The spacing distances between facilities (e.g. LNG tanks and vaporizers) and ignition source have been evaluated numerically to avoid thermal radiation damage. It is concluded that the spacing distance between AAV banks and impoundment walls should be enlarged.

Effects of hydrogen addition on the confined and vented explosion behavior of methane in air

Abstract: Multi-component gas mixture explosion accidents occur and recur frequently, while the safety issues of multi-component gas mixture explosion for hydrogen–methane mixtures have rarely been addressed. Numerical simulation study on the confined and vented explosion characteristics of methane-hydrogen mixture in stoichiometric air was conducted both in the 5 L vessel and the 64 m 3 chamber, involving different mixture compositions and initial pressures. Based on the results and analysis, it is shown that the addition of hydrogen has a negative effect on the explosion pressure of methane-hydrogen mixture at adiabatic condition. While in the vented explosion, the addition of the hydrogen has a significant positive effect on the explosion hazard degree. Additionally, the addition of hydrogen can induce a faster reactivity and enhance the sensitivity of the mixture by reducing the explosion time and increasing the rate of pressure rise both in confined and vented explosion. Both the maximum pressure and the maximum rate of pressure rise increase with initial pressure as a linear function, and also rise with the increase of hydrogen content in fuel. The increase in the maximum rate of pressure rise is slight when hydrogen ratio is lower than 0.5, however, it become significant when hydrogen ratio is higher than 0.5. The maximum rate of pressure rise for stoichiometric hydrogen-air is about 10 times the one of stoichiometric methane-air. Furthermore, the vent plays an important role to relief pressure, causing the decrease in explosion pressure and rate of pressure rise, while it can greatly enhance the flame speed, which will extend the hazard range and induce secondary fire damages. Additionally it appears that the addition of hydrogen has a significant increasing effect on the flame speed. The propagation of flame speed in confined explosion can be divided into two stages, increase stage and decrease stage, higher hydrogen content, higher slope. But in the vented explosion, the flame speed keeps increasing with the distance from the ignition point.

Boiling liquid expanding vapour explosions (BLEVEs): A brief review

Abstract: BLEVEs remain a complex multi-faced phenomenon. The point of departure of the paper is the extensive review by Abbasi and Abbasi (2007) , and the paper starts with presenting some deviating definitions and suggested characteristics of BLEVEs. Then a step-by-step description of the chain of events in typical BLEVEs follows. In most cases the first step will be that a vessel containing a gas that has been liquefied by pressurization (PLG) gets accidentally exposed to heat (most often a fire). The next step is that the vessel suddenly fails due to the increased internal vapour pressure and the weakening of the vessel material. The resulting very sudden depressurization of the hot liquid gives rise to intense, often volumetric, evaporation. The central role of the superheat limit temperature (SLT) of the liquid in the evaporation process is discussed. The very rapid evaporation in turn gives rise to powerful blast wave emission. If the evaporated liquid is combustible and gets ignited, a huge fireball will most often be generated. Properties and effects of fireballs from BLEVEs are discussed. The shattering of the initial vessel may cause propelling of high-speed missiles, which when hitting other PLG vessels may give rise to secondary BLEVEs. The remaining part of the combustible liquid from a BLEVEed vessel that has not evaporated will, when ignited, give rise to pool fires. Emission of toxic gases/vapours requires special actions. However, BLEVEs can also occur with non-toxic gases, and even in the absence of an initial fire. The induction time preceding a BLEVE is an important parameter, e.g. for the time available for rescue operations. Long-duration BLEVEs require special concerns. A part of the paper is devoted to various categories of BLEVE case histories. Available means for preventing process situations that can lead to BLEVEs are then discussed. If PLG-vessels get engulfed in fire measures for preventing catastrophic vessel failure may be activated. Finally measures for mitigating the consequences if BLEVEs do occur in spite of taking preventive measures are discussed.

System Safety Principles: A Multidisciplinary Engineering Perspective

Abstract: System safety is of particular importance for many industries. Broadly speaking, it refers to the state or objective of striving to sustainably ensure accident prevention through actions on multiple safety levers (technical, organizational, and regulatory). While complementary to risk analysis, it is distinct in one important way: risk analysis is anticipatory rationality examining the possibility of adverse events (or accident scenarios), and the tools of risk analysis support and in some cases quantify various aspects of this analysis effort. The end-objective of risk analysis is to help identify and prioritize risks, inform risk management, and support risk communication. These tools however do not provide design or operational guidelines and principles for eliminating or mitigating risks. Such considerations fall within the purview of system safety. In this work, we propose a set of five safety principles, which are domain-independent, technologically agnostic, and broadly applicable across industries. While there is a proliferation of detailed safety measures (tactics) in specific areas and industries, a synthesis of high-level safety principles or strategies that are independent of any particular instantiation, and from which specific safety measures can be derived or related to, has pedagogical value and fulfills an important role in safety training and education. Such synthesis effort also supports creativity and technical ingenuity in the workforce for deriving specific safety measures, and for implementing these principles and handling specific local or new risks. Our set of safety principles includes: (1) the fail-safe principle; (2) the safety margins principle; (3) the un-graduated response principle (under which we subsume the traditional “inherently safe design” principle); (4) the defense-in-depth principle; and (5) the observability-in-depth principle. We carefully examine each principle and provide examples that illustrate their use and implementation. We relate these principles to the notions of hazard level, accident sequence, and conditional probabilities of further hazard escalation or advancement of an accident sequence. These principles are a useful addition to the intellectual toolkit of engineers, decision-makers, and anyone interested in safety issues, and they provide helpful guidelines during system design and risk management efforts.

Flame-propagation behavior and a dynamic model for the thermal-radiation effects in coal-dust explosions

Abstract: To reveal the flame-propagation behavior and the thermal-radiation effects during coal-dust explosions, two coal-dust clouds were tested in a semi-enclosed vertical combustion tube. A high-speed video camera and a thermal infrared imaging device were used to record the flame-propagation process and the thermal-radiation effects of the fireball at the combustion-tube outlet. The flame propagated more quickly and with a higher temperature in the more volatile coal-dust cloud. The coal-dust concentration also significantly affected the propagation behavior of the combustion zone. When the coal-dust concentration was increased, the flame-propagation velocity and the fireball temperature increased before decreasing overall. Based on the experimental results, a dynamic model of the thermal radiation was employed to describe the changes in the fireballs quantitatively and to estimate the thermal-radiation effects during coal-dust explosions.

Quantitative risk assessment of the Italian gas distribution network

Abstract: European Critical Infrastructures include physical resources, services, information technology facilities, networks and infrastructure assets, which, if disrupted or destroyed would have a serious impact on the health, safety, security, economic or social well-being of the Member States. The gas distribution network is a critical infrastructure and its failure can cause damage to structures and injury to people. The aim of this paper is to analyze and then assess the risk of the Italian high pressure natural gas distribution network. The paper describes an application of a methodology for quantitative risk assessment. Failure frequencies considered in risk calculation were found in the European Gas pipeline Incident data Group (EGIG) database, whereas consequences were computed as a function of pipe diameter and operating pressure for each section of the network. The results of this quantitative risk assessment is the determination of local and social risks for the Italian North East Area.

Integrated risk assessment for LNG terminals

Abstract: This paper presents an integrated risk assessment framework for Liquefied Natural Gas (LNG) terminals. The basic steps for risk assessment are the following: a) hazard identification, b) accident sequence modeling, where logic models such as Event Trees and Fault Trees are developed c) data acquisition and parameter estimation, used to estimate frequencies of the initiating events, component unavailability and probabilities of human actions, d) accident sequence quantification, where all accident sequences are assessed, e) consequence assessment, where release, evaporation rate, radiation levels and overpressure owing to immediate or delayed ignition of LNG is performed and f) integration of results where risk indices are assessed. Risk assessment of an onshore and an offshore LNG terminal is performed, according to the basic methodological steps, and the distances where individual risk levels equal to 10 −5 –10 −7 /yr are assessed and presented in the form of individual contours. A section dedicated to I.A. Papazoglou, pioneer in Quantitative Risk Assessment both in the nuclear and chemical industry is also provided.

Likelihood, causes, and consequences of focused leakage and rupture of U.S. natural gas transmission pipelines

Abstract: The safety of pipelines that transport energy (particularly natural gas transmission pipelines) has become an important and controversial issue with the general public. This study provides strong evidence that the US transmission pipeline network is safer than many believe. Published estimates of risk of pipeline failure are typically in the range 1.210-4 to 6.110-4 per kmyr. Risk of pipeline failure differs significantly with diameter, with fatality rates of 4.610-6 per kmyr for larger pipelines and 2.410-6 per kmyr for smaller transmission pipelines. The average injury rate was 1.910-5 per kmyr for smaller pipelines, compared to 5.910-6 per kmyr for larger transmission pipelines. The failure rate for large diameter transmission pipelines is larger, the older the pipeline segment. The joint impact of pipeline diameter and wall thickness on failure rate reveals that increased wall thickness is effective in mitigating risks. Overall, natural gas transmission pipelines have significantly lower fatality rates than do truck or railway transport of hazardous materials. For larger transmission pipelines, the estimated rates for serious injuries (3.010-6 per kmyr) and fatalities (6.310-7 per kmyr) for the public, are at a level generally considered acceptable by most countries. 2014 Elsevier Ltd.

Integrated-signal-based leak location method for liquid pipelines

Abstract: Leaks in pipelines can cause major incidents resulting in both human injuries and financial losses. Among the considerable leak detection and location methods, the Negative Pressure Wave (NPW) based method has been widely used in locating leaks in liquid pipelines. The NPW based method only monitors the pressure changes at two ends of a pipeline. But the pressure is apt to be fixed by the end equipment and the change of it induced by a small or slow leakage is too small to be detected, which limit the application of the NPW based method in these situations. This paper presents a novel leak location method based on integrated signal, which is a combination of the pressure and flow rate signals. The representation of the integrated signal is derived from the transient analysis of the leakage. For the change of the integrated signal induced by a leakage is larger than the pressure change and it is also unaffected by the end equipment, the proposed method can be used to detect and locate small or slow leakage in a pipeline and can also be used in pipelines which end pressures are fixed by some kinds of equipment. The validation of the proposed method also confirms its advantages.

Lessons learned for process safety management in China

Abstract: A number of chemical accidents have occurred in China over the past two decades with significant impact on humans and the environment. It is expected that lessons will have been learned from these accidents that will help industries to reduce the risk that catastrophic chemical accidents occur in future. In fact, to some extent there is evidence that lessons have been learned, to the extent that the Chinese government has substantially strengthened legislation and regulatory standards. Nonetheless, there remains a concern that much more still needs to be done to reduce chemical accidents risks in China. Important progress in this area requires not only government support but a commitment across all hazardous industries to learn from past accidents that may in many cases require establishment or considerable improvement of their safety management systems. To assist small and medium-sized enterprises (SMEs), in this effort, results of an analysis of common causes of the chemical accidents reported in the Major Accident Information (MAI) website of Chinese State Administration of Work Safety (SAWS) are presented in this paper In particular, inadequate process hazard analysis (PHA), training and emergency response planning (ERP) were identified as the top three process safety management (PSM) elements that contribute to most of the SMEs accidents in China. Seven recommendations are proposed in order to improve the effectiveness of lesson learning for government agencies and SMEs.

Experimental study of leakage detection of natural gas pipeline using FBG based strain sensor and least square support vector machine

Abstract: Leakage is the most common cause of natural gas pipeline accidents. This work was devoted to natural gas pipeline leakage detection, which is based on detecting negative pressure wave signals caused by leakage. The FBG strain sensor, which is based on monitoring the hoop strain of a pipeline to detect negative pressure wave signals, is fabricated and experimentally tested. Compared to conventional pressure sensors, FBG strain sensors were shown to be less influenced by noise, and they have the advantage of being a nondestructive sensing method. This makes them ideal for sensing pressure transients, which could be analyzed to detect natural gas pipeline leakage. Toward this objective, a least square support vector machine (LS-SVM) classifier was developed as an automatic leakage detection technique. This technique proved to be effective at detecting leakage.