Hydrocarbon Explosions Research Articles

A new method for accidental limit states design of thin-walled structures subjected to hydrocarbon explosion loads

Design requirements for offshore platform topsides include the assessment of their structural resistance to gas explosions. The design is normally based on loads derived from complex computer fluid dynamics (CFD) simulations. Dimensioning and design explosion loads for topsides are defined based on probabilistic models of loads, which take into account installation and environmental uncertainties. Design standards and functional specifications from platform operators require that structural safety be implemented and inherent structural robustness documented during the design phase of topsides. This paper presents a reliability-based robustness assessment method for structures designed using accidental limit states to resist hydrocarbon explosion loads. The applicability of the new method is demonstrated by calculation of probability of damage and structural robustness of explosion-resisting walls designed for topsides of offshore platforms.

Strength assessment of stiffened blast walls in offshore installations under explosions

Offshore installations are exposed to hydrocarbon explosions and/or fire accidents. Especially, explosions lead to serious damages to human, safety, and environment. To minimise and prevent the damage from explosions, blast walls are generally installed in oil and gas production structures. Typical blast walls are classified into flat, corrugated, and stiffened types. Among them, corrugated blast walls are frequently used for reasons such as construction, cost, and energy absorption.However, it has been known that a corrugated type of blast wall buckles between the web and flange under the explosion loads, and loses its stiffness. It means that the buckling phenomenon of a blast wall is closely related to the structural strength. This study investigates on the structural characteristics of a blast wall under quasi-static and dynamic (explosion) loads with or without a flat-plated stiffener. Finally, it can be concluded that the flat type of stiffeners are located at the buckling region to delay the buckling and improve the strength of blast walls.

Synthesis of porous In2O3 microspheres as a sensitive material for early warning of hydrocarbon explosions

We report the template-free synthesis of porous nanoparticle-assembled In2O3 microspheres that can serve as a highly sensitive material for the detection of C1–C3 hydrocarbons.

Structural impact response characteristics of an explosion-resistant profiled blast walls in arctic conditions

Environmental changes, especially global climate change, are creating new challenges to the development of the Arctic regions, which have substantial energy resources. And attention to offshore structures has increased with oil and gas development. The structural impact response of an explosion-resistant profiled blast walls normally changes when it operates in low temperatures. The main objectives of this study are to investigate the structural response of blast walls in low temperature and suggest useful guidelines for understanding the characteristics of the structural impact response of blast walls subjected to hydrocarbon explosions in Arctic conditions. The target temperatures were based on the average summer temperature (<TEX>$-20^{\circ}C$</TEX>), the average winter temperature (<TEX>$-40^{\circ}C$</TEX>) and the coldest temperature recorded (approximately <TEX>$-68^{\circ}C$</TEX>) in the Arctic. The nonlinear finite element analysis was performed to design an explosion-resistant profiled blast wall for use in Arctic conditions based on the behaviour of material properties at low temperatures established by performing a tensile test. The conclusions and implications of the findings are discussed.

A methodology for determining efficient gas detector locations on offshore installations

More than 70% of accidents that occur on offshore installations are result of hydrocarbon explosions and fires, which, because they involve blast effects and heat, are extremely hazardous and have serious consequences in terms of human health, structural safety and the surrounding environment. Most such accidents are caused by gas leaks, which, if undetected, can lead to the formation of a concentrated gas cloud that can ignite or explode. An effective gas detection system is important for preventing gas-related catastrophic accidents and can mitigate risk on offshore installations. The aim of this study is to develop a risk-based methodology to aid the initial placement of gas detectors for an efficient gas detection system that will function optimally in all possible scenarios on offshore installations.

해양플랜트 설비 Corrugated Blast Wall의 폭발 충격응답 인자 특성에 관한 파라메트릭 연구

*The Ship and Offshore Research Institute Pusan National Univer sity, Busan, KoreaKEY WORDS: Explosion 폭발, Corrugated blast wall 파형 방폭벽, Impact response characteristics 충격응답특성.ABSTRACT: More than 70% of the accidents that occur on offshore installat ions stem from hydrocarbon explosions and fires, which, because they involve blast effects and heat, are extremely hazardous and hav e serious consequences in terms of human health, structural saf ety,and the surrounding environment. Blast barriers are integral structures in a typical offshore topside module to protect personnel and safety critical equipment by preventing the escalation of events caused by hydr ocarbon explosions. Many researchers have shown the adequacy of the simple design tool commonly used by the offshore industry for the analysis an d design of blast walls. However, limited information is availa ble for corrugated blast wall design with explosion impact response characteristic s. Therefore, this paper presents a parametric study on the exp losion impact response characteristics of an offshore installation’s stainless steel c orrugated blast wall. This paperalso investigates and recommend s design parameters for the structural design of a corrugated blast wall based on a nonlinear structural analysis of experiential results.교신저자 서정관: 부산광역시 금정구 부산대학로 63번길, 051-510-2415, seojk@pusan.ac.kr본 연구는 2011년 부산에서 개최된 한국해양과학기술협의회 공동학술대회에 발표된 논문을 근간으로 하고 있음을 밝힙니다 .

FE analysis of unstiffened and stiffened corrugated panels subjected to blast loading

This paper presents the results of a dynamic analysis on unstiffened and stiffened corrugated panels subjected to hydrocarbon explosion. A parametric study is also conducted on simplified models of the stiffened corrugated panels considering the effect of stiffeners on the compressive flange under different loading levels. The 1/2 symmetry of corrugated panels is modeled. This numerical study is performed using NX Nastran version 7.5. The unstiffened panel produces localized buckling at the center of corrugation and large permanent deformation by increasing the peak pressure. The stiffened panels suppress the structural response, and the vee stiffeners are structurally more effective than the round ones.

Assessment of hydrocarbon explosion and fire risks in offshore installations: recent advances and future trends

This article presents a review of the state-of-the-art technologies used in assessing the risk of hydrocarbon explosions and fires in offshore installations. Both qualitative and quantitative risk assessment approaches are described, and the modelling techniques employed in the quantitative assessment of explosions and fires are presented. Procedures developed through a joint industry project on the explosion and fire engineering of floating, production, storage and off-loading units (abbreviated as EFEF JIP) led by the authors are introduced. This article does not attempt to survey the literature, but rather to summarise recent advances and future trends in terms of the technological aspects of the risk assessment of offshore installations subject to explosions and fire.

Quantitative assessment of hydrocarbon explosion and fire risks in offshore installations

A risk-based design framework should involve both risk assessment and risk management. This article introduces and describes a number of procedures for the quantitative assessment and management of fire and gas explosion risks in offshore installations. These procedures were developed in a joint industry project on the explosion and fire engineering of floating, production, storage and off-loading units (the EFEF JIP), which was led by the authors. The present article reports partial results, focussing on defining the frequency of fires and explosions in offshore installations. Examples of the aforementioned procedures’ application to a hypothetical floating, production, storage, and off-loading unit (FPSO) are presented. A framework for the quantitative risk assessment of fires and explosions requires the definition of both the frequency and consequences of such events. These procedures can be efficiently applied in offshore development projects, and the application includes the assessment of design explosion and fire loads as well as the quantification of effects of risk control options (RCO) such as platform layout, location and number of gas detectors, isolation of ignition sources etc.

CFD simulations of gas explosion and fire actions

Hydrocarbon (gas) explosions and fire are the hazardous events that present the greatest potential risk for offshore installations. More refined computations of the consequences of explosions and fire within the framework of quantified risk assessment and management for offshore installations are therefore required. Although the action characteristics of such hazardous events must be identified prior to an analysis of their consequences, the objective of the present paper is to develop a modeling technique for computational fluid dynamics (CFD) simulations of hydrocarbon explosions and fire. The results of this study form part of phase I of the three-phase Joint Industry Project on Explosion and Fire Engineering in floating production, storage and offloading systems (FPSO) (abbreviated by EFEF JIP).

Performance-based design of blast resistant offshore topsides, Part II: Modelling and design

A simplified analytical model for deck plates of offshore topsides structures is proposed. Based on the theory of virtual work and an assumed deformed shape function in Cartesian coordinates, a set of equilibrium equations in terms of energy are developed. The equations are formed as a static case and a dynamic case with unsolved variables defined as generalized coordinates. When these equations are re-arranged, they are equivalent to a modal analysis, which can be solved using Lagrange’s equation method. The generalized coordinates in the static case can be solved manually while in the dynamic case, the ordinary differential equations are solved numerically by developing a computer program using a symbolic software package, MAPLE. The proposed method is comparable with finite element analysis results up to a certain threshold at which development of membrane strain and plasticity modes become dominant. When comparing the results to the reported experimental data, the proposed shape functions for deformations in the lateral directions are modified in order to accommodate the observed behaviour. The results compare favourably with test data and finite element analysis as a control case. Despite inconsistent ductility ratios between the proposed method and the finite element analysis at very high overpressures, the method shows good correlation of results at practical design values. Hence, the proposed method would be a useful tool for preliminary appraisal methods especially for design engineers involved in evaluating the performance of deck plating subjected to a range of hydrocarbon explosion scenarios.

Improving the ductile behaviour of offshore topside structures under extreme loads

This study investigates the behaviour of a typical offshore topside structure subjected to blast loading caused by hydrocarbon explosions. The pressure load caused by the explosion is idealised as a linearised triangular impulse which is simultaneously applied on two deck levels modelled using the finite element program, ABAQUS Explicit. Two cases were developed: the original case representing a typical offshore fabricated deck flooring with sniped bottom flanges at connections for stringer beams and the strengthened case which was a modified form of the original case but with rolled steel angles welded at sniped bottom flanges of stringer beams and plate girders. Results from the analysis show that load directions and structural configuration play a prominent role in the response of the topside. The strengthening indicates the beneficial redistribution of local yielding at the sniped connections of the beams to mid-spans which consequently improve the performance level of the structural system. Haunch details are found to cause local failures on plate girders but the failure mechanism is useful for developing a technique to avert further damage. Finally, generalised ductility ratios derived from normalisation of responses at end-spans and mid-spans of the structural components are compared with commonly used design values to justify the damage levels and performance under this extreme loading condition.

Response of profiled barriers subject to hydrocarbon explosions

This paper presents a numerical methodology to investigate the response of stainless steel profiled barriers when subjected to blast loading generated from a hydrocarbon explosion. Results from three large-scale explosion tests are used to validate the Abaqus/Explicit finite-element code adopted in the analyses. A simple failure algorithm based on equivalent plastic strain has been implemented in the numerical code to model the ductile weld tearing behaviour. The effects of strain rates, sensitivity of mesh densities and load idealisation will be discussed. A brief review of deep trough corrugated blastwalls that exhibit very different response behaviour will also be presented. The paper concludes with some parametric studies on load characteristics to determine the capacity of the deep trough corrugated blastwall.

Response of profiled barriers subject to hydrocarbon explosions

Response of profiled barriers subject to hydrocarbon explosions

Scaling of pulse loaded mild steel plates with different edge restraint

This paper reports the results of scaled tests on mild steel square plates with different edge restraint subjected to uniformly distributed triangular pulse pressure loading producing large inelastic deformations without tearing or rupture. The loading is representative of overpressure loading arising from a confined hydrocarbon explosion. A scale factor of 0.5 was examined in this series of tests on 16 plates, eight 1 m by 1 m × 2 mm thick and eight 0.5 m × 0.5 m × 1 mm thick. Both static and dynamic test results are presented. A quasi-static rigid–plastic and elastic–plastic analysis of a fully restrained square plate is also presented and compared with the test results. The transient response of the plates under dynamic loading show some divergence from the laws of geometrically similar scaling while the permanent deformations in both the static and dynamic tests show good compliance with the laws of similitude, within the accuracy expected in such tests.

Energy absorbing passive impact barrier for profiled blastwalls

After the Piper Alpha accident, the Health and Safety Executive (UK) now require safety cases to be submitted for all new and existing installations on offshore topsides. The findings from a recent Joint Industry Project have revealed that peak overpressures developed from typical hydrocarbon explosions can be much higher than previously used in the design of offshore topsides and thus has necessitated strengthening of many existing installations, including blastwalls. This paper presents one such technique where the response of the blastwalls is modified by the inclusion of a passive impact barrier system placed at a certain offset behind the walls. An explicit non-linear finite element model has been validated against two large scale blast tests of shallow profiled blastwalls. This has included modelling the effect of contact, weld tearing, large displacement and plasticity in order to provide a realistic model. The study has been extended to investigate the response of deep profiled blastwalls with various arrangements of the passive impact barrier systems. The increase in the containment pressure and the influence of strain rate, load duration, offset of the impact barriers and its stiffness are discussed.

Design and analysis of stainless steel profiled blast barriers

Profiled panels have been increasingly used as blastwalls in typical offshore topsides modules to provide a safety barrier for working personnel and critical equipment. Most of the blastwalls are designed using the single degree of freedom method (SDOF) as recommended in the design guidance Technical Note 5 (TN5) issued by the Fire and Blast Information Group (FABIG) and the Steel Construction Institute (SCI). By using nonlinear finite element analysis (NLFEA) to assess the response of blast barriers subjected to hydrocarbon explosions, the adequacy of the design guide has been reviewed and recommendations given. Three profiled sections with different compactness are investigated. Effects of cross-section flattening, local transverse effects, support rotation and the effects of cross-section compactness on the overall behaviour of the blast barriers are discussed. Most importantly, the work presented here will pave the way towards a more rational performance based blast resistant design since the present criteria as set out in the design guide have shown to be limited only to elastic design.

Numerical assessment of explosion resistant profiled barriers

Profiled blast barriers are an integral part of offshore topsides where they are required to protect personnel and safety critical equipment against the effects of a possible hydrocarbon explosion. Limited studies on their response have been presented, particularly at high overpressures. This paper presents a numerical study using finite element analysis to investigate the response of stainless steel profiled barriers subjected to hydrocarbon explosions. By examining three profiles of varying depth (deep, intermediate and shallow) commonly used in offshore topside structures, the criteria governing their behaviour are highlighted. The static capacity and the dynamic response of the barriers are established up to the maximum capacity level and into the post peak or buckling response regime. The parameters that were found to have profound effects on the analyses include imperfections, boundary conditions and modelling assumptions. Through this study, recommendations and guidelines of using finite element analysis for the design or analysis of such explosion resistant barriers are given.

Strain rate effects on the response of stainless steel corrugated firewalls subjected to hydrocarbon explosions

The yield stress of a steel coupon can be enhanced beyond its quasi-static test values when subjected to dynamic load. A number of techniques, such as the overstress constitutive model, have evolved in the past to take account of the enhancement effects. This paper investigates the influence of strain rate modelling on the response of stainless steel corrugated firewalls subjected to blast loading generated from typical hydrocarbon explosions, paying particular attention in the event when the connecting weld between the firewalls and supporting angles has failed. Two failure models, namely the spot-weld model and the shear failure model, have been incorporated into the constitutive material model to account for the weld failure. The investigation involves the use of the commonly adopted overstress strain rate model and dynamic factors proposed in a recent report by the Health and Safety Executive to study the effects of high strain rates on offshore steels. Both approaches are compared and the limitations of the overstress model are highlighted.

Simplified non-linear analysis of plates subjected to hydrocarbon explosions

An elastic Lagrangian formulation for an unstiffened plate subject to blast loading is presented. Building on a previous formulation, which accounted for membrane strains from purely out-of-plane displacement, the addition of in-plane stretching highlights the importance of membrane action. Numerical results of the resulting system of non-linear differential equations from the new model are compared with a non-linear finite element analysis package in terms of the various displacements and membrane strains, with good correlation.