GexCon AS

Bergen, Norway

GexCon AS

Bergen, Norway

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Hansen O.R.,GexCon AS | Gavelli F.,GexCon AS | Ichard M.,GexCon AS | Davis S.G.,GexCon AS
Journal of Loss Prevention in the Process Industries | Year: 2010

The siting of facilities handling liquefied natural gas (LNG), whether for liquefaction, storage or regasification purposes, requires the hazards from potential releases to be evaluated. One of the consequences of an LNG release is the creation of a flammable vapor cloud, that may be pushed beyond the facility boundaries by the wind and thus present a hazard to the public. Therefore, numerical models are required to determine the footprint that may be covered by a flammable vapor cloud as a result of an LNG release. Several new models have been used in recent years for this type of simulations. This prompted the development of the "Model evaluation protocol for LNG vapor dispersion models" (MEP): a procedure aimed at evaluating quantitatively the ability of a model to accurately predict the dispersion of an LNG vapor cloud.This paper summarizes the MEP requirements and presents the results obtained from the application of the MEP to a computational fluid dynamics (CFD) model - FLACS. The entire set of 33 experiments included in the model validation database were simulated using FLACS. The simulation results are reported and compared with the experimental data. A set of statistical performance measures are calculated based on the FLACS simulation results and compared with the acceptability criteria established in the MEP. The results of the evaluation demonstrate that FLACS can be considered a suitable model to accurately simulate the dispersion of vapor from an LNG release. © 2010 Elsevier Ltd.


Van Den Schoor F.,Catholic University of Leuven | Middha P.,GexCon AS | Van Den Bulck E.,Catholic University of Leuven
Fire Safety Journal | Year: 2013

A risk analysis is presented for an enclosed 30×30 m car park in which LPG (liquefied petroleum gas) vehicles are allowed to park. An event tree analysis is used to define 26 different incident scenarios and their probabilities. FLACS, a specialised CFD program, is used to calculate the formation of a flammable vapour cloud and its dilution by means of the ventilation system as well as the overpressures generated in a vapour cloud explosion. Existing empirical methods are used to calculate the overpressures generated by a BLEVE and the heat radiated by a fire ball and a jet fire. The simulations have shown that a release from a 70 l LPG fuel tank can lead to vapour clouds of up to 200 m3 that fill the entire height of the car park, while the explosion simulations have shown that such vapour clouds can lead to overpressures above 30 kPa in the entire car park. The ventilation simulations have shown that high flow rates of approximately 0.060 m 3/s per m2 of car park floor area are necessary to rapidly dilute these large vapour clouds. © 2012 Elsevier Ltd.


Middha P.,GexCon AS | Engel D.,GexCon AS | Hansen O.R.,GexCon AS
International Journal of Hydrogen Energy | Year: 2011

One of the main benefits sought by including hydrogen in the alternative fuels mix is emissions reduction - eventually by 100%. However, in the near term, there is a very significant cost differential between fossil fuels and hydrogen. Hythane (a blend of hydrogen and natural gas) can act as a viable next step on the path to an ultimate hydrogen economy as a fuel blend consisting of 8-30% hydrogen in methane can reduce emissions while not requiring significant changes in existing infrastructure. This work seeks to evaluate whether hythane may be safer than both hydrogen and methane under certain conditions. This is due to the fact hythane combines the positive safety properties of hydrogen (strong buoyancy, high diffusivity) and methane (much lower flame speeds and narrower flammability limits as compared to hydrogen). For this purpose, several different mixture compositions (e.g. 8%, 20% and 30% hydrogen) are considered. The evaluation of (a) dispersion characteristics (which are more positive than for methane), (b) combustion characteristics (which are closer to methane than hydrogen), and (c) Combined dispersion + explosion risk is performed. This risk is expected to be comparable to that of pure methane, possibly lower in some situations, and definitely lower than for pure hydrogen. The work is performed using the CFD software FLACS that has been well-validated for safety studies of both natural gas/methane and hydrogen systems. The first part of the work will involve validating the flame speeds and flammability limits predicted by FLACS against values available in literature. The next part of the work involves validating the overpressures predicted by the CFD tool for combustion of premixed mixtures of methane and hydrogen with air against available experimental data. In the end, practical systems such as vehicular tunnels, garages, etc. is used to demonstrate positive safety benefits of hythane with comparisons to similar simulations for both hydrogen and methane. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.


Middha P.,GexCon AS | Ichard M.,GexCon AS | Arntzen B.J.,GexCon AS
International Journal of Hydrogen Energy | Year: 2011

Hydrogen is widely recognized as an attractive energy carrier due to its low-level air pollution and its high mass-related energy density. However, the safety characteristics of hydrogen are a concern, primarily due to its wide flammability range and high burning velocity. A significant fraction of hydrogen is stored and transported as a cryogenic liquid. Therefore, loss of hydrogen containments may lead to the formation of a pool on the ground. In general, very large spills will give a pool, whereas moderate sized spills may evaporate immediately. Accurate hazard assessments of storage systems require a proper prediction of the liquid hydrogen pool evaporation and spreading when conditions are conducive to the formation of a pool. A pool model handling the spread and the evaporation of liquid spills on different surfaces has recently been implemented in the 3D-Computational Fluid Dynamics (CFD) tool FLACS [1-4]. As the influence of geometry on the liquid spread is taken into account in the pool model, realistic industrial scenarios can be investigated. The model has been extensively validated for Liquefied Natural Gas (LNG) spills [5,6]. The model has previously been tested for LH2 release in the framework of the EU-sponsored Network of Excellence HySafe where experiments carried out by BAM were modelled. In the large-scale BAM experiments [7], 280 kg of liquid hydrogen was spilled in 6 tests adjacent to buildings. In these tests, the pool spreading, the evaporation, and the cloud formation were investigated. Simulations of these tests are found to compare reasonably well with the experimental results. In the present work, the liquid hydrogen spill experiments carried out by NASA are simulated with the pool model. The large-scale NASA experiments [8,9] consisted of 7 releases of liquefied hydrogen at White Sand, New Mexico. The release test 6 is used. During these experiments, cloud concentrations were measured at several distances downwind of the spill point. With the new pool model feature, the FLACS tool is shown to be an efficient and accurate tool for the investigation of complex and realistic accidental release scenarios of cryogenic liquids. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.


Middha P.,GexCon AS | Hansen O.R.,GexCon AS | Grune J.,ProScience | Kotchourko A.,Karlsruhe Institute of Technology
Journal of Hazardous Materials | Year: 2010

Computational fluid dynamics (CFD) tools are increasingly employed for quantifying incident consequences in quantitative risk analysis (QRA) calculations in the process industry. However, these tools must be validated against representative experimental data, involving combined release and ignition scenarios, in order to have a real predictive capability. Forschungszentrum Karlsruhe (FZK) has recently carried out experiments involving vertically upwards hydrogen releases with different release rates and velocities impinging on a plate in two different geometrical configurations. The dispersed cloud was subsequently ignited and resulting explosion overpressures recorded. Blind CFD simulations were carried out prior to the experiments to predict the results. The simulated gas concentrations are found to correlate reasonably well with observations. The overpressures subsequent to ignition obtained in the blind predictions could not be compared directly as the ignition points chosen in the experiments were somewhat different from those used in the blind simulations, but the pressure levels were similar. Simulations carried out subsequently with the same ignition position as those in the experiments compared reasonably well with the observations. This agreement points to the ability of the CFD tool FLACS to model such complex scenarios even with hydrogen as a fuel. Nevertheless, the experimental set-up can be considered to be small-scale. Future large-scale data of this type will be valuable to confirm ability to predict large-scale accident scenarios. © 2010 Elsevier B.V.


Price D.,GexCon AS
ZKG International | Year: 2014

Many European cement kilns are now co-processing alternative fuels for coal substitution to reduce their carbon emissions and to reduce operational fuel costs. Typically, the risks from gas explosions gets much more interest than dust explosions. Both DSEAR (UK) and ATEX (EU) requires the employer to identify areas which are hazardous due to the presence of an explosive atmosphere and to take measures to entirely remove or reduce the extent of these areas. Reducing an explosive atmosphere is given top priority over other risk reduction measures such as reducing potential ignition sources or reducing the consequences of an event. The Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) relates to explosive gas and dust atmospheres and compliance with DSEAR is a legal requirement in the UK.


Davis S.G.,GexCon AS | Hansen O.R.,GexCon AS
Journal of Loss Prevention in the Process Industries | Year: 2010

On November 22, 2006 the largest explosion in the history of Massachusetts occurred in Danvers, MA at approximately 2:46 am. This paper presents a detailed analysis into the potential causes and lessons learned from the Danvers explosion. Other investigative groups concluded that the cause of the explosion was an overheated production tank. However, the analyses presented here demonstrate that their proposed scenario could not have occurred and that other potential causes are more likely. Using the computational fluid dynamics tool FLACS, it was possible to investigate the chain of events leading to the explosion, including: (1) evaluating various leak scenarios by modeling the dispersion and mixing of gases and vapors within the facility, (2) evaluating potential ignition sources within the facility of the flammable fuel-air mixture, and (3) evaluating the explosion itself by comparing the resulting overpressures of the exploding fuel-air cloud with the structural response of the facility and the observed near-field and far-field blast damage. These results, along with key witness statements and other analyses, provide valuable insight into the likely cause of this incident. Based on the results of our detailed analysis, lessons learned regarding the investigative procedure and methods for mitigating this and future explosions are discussed. © 2009 Elsevier Ltd. All rights reserved.


Grant
Agency: European Commission | Branch: H2020 | Program: IA | Phase: FoF-09-2015 | Award Amount: 11.42M | Year: 2015

Fortissimo 2 will drive the uptake of advanced modelling, simulation and data analytics by European engineering and manufacturing SMEs and mid-caps. Such an uptake will deliver improved design processes, better products and services, and improved competitiveness. For the European Union as a whole this means improved employment opportunities and economic growth. The importance of advanced ICT to the competitiveness of both large and small companies in the engineering and manufacturing domain is well established. Despite early successes in this area, there are still many barriers to the uptake of such solutions, not least of which are the initial cost and complexity of adoption, particularly in the context of challenging trading conditions. This proposal targets the ICT Innovation for Manufacturing SMEs (I4MS) action line (Phase 2) and builds on Phase 1 of that initiative. Phase 2 addresses the adoption of next generation ICT advances in the manufacturing domain. At the core of Fortissimo 2 are three tranches of Application Experiments (~35 in total). An initial set is included in this proposal and two further sets will be obtained through Open Calls for proposals. These experiments will be driven by the requirements of first-time users (predominately SMEs) and will bring together actors from across the value chain, from cycle providers to domain experts via the Fortissimo Marketplace. This will enable innovative solutions to manufacturing challenges, leading to new and improved design processes, products and services. A key feature of Fortissimo 2 will be the adaption of the Marketplace to meet the needs of end-users. It will offer a responsive and reliable service to companies which want to access HPC and Big resources and expertise. Fortissimo 2 initially involves 732 months of effort, a total cost of 11.1m and EC funding of 10m over a duration of three years, commensurate with achieving its ambitious goals.


Grant
Agency: European Commission | Branch: H2020 | Program: FCH2-RIA | Phase: FCH-04.3-2014 | Award Amount: 1.51M | Year: 2015

The aim of the HySEA project is to conduct pre-normative research on vented deflagrations in enclosures and containers for hydrogen energy applications. The ambition is to facilitate the safe and successful introduction of hydrogen energy systems by introducing harmonized standard vent sizing requirements. The partners in the HySEA consortium have extensive experience from experimental and numerical investigations of hydrogen explosions. The experimental program features full-scale vented deflagration experiments in standard ISO containers, and includes the effect of obstacles simulating levels of congestion representative of industrial systems. The project also entails the development of a hierarchy of predictive models, ranging from empirical engineering models to sophisticated computational fluid dynamics (CFD) and finite element (FE) tools. The specific objectives of HySEA are: - To generate experimental data of high quality for vented deflagrations in real-life enclosures and containers with congestion levels representative of industrial practice; - To characterize different strategies for explosion venting, including hinged doors, natural vent openings, and commercial vent panels; - To invite the larger scientific and industrial safety community to submit blind-predictions for the reduced explosion pressure in selected well-defined explosion scenarios; - To develop, verify and validate engineering models and CFD-based tools for reliable predictions of pressure loads in vented explosions; - To develop and validate predictive tools for overpressure (P) and impulse (I), and produce P-I diagrams for typical structures with relevance for hydrogen energy applications; - To use validated CFD codes to explore explosion hazards and mitigating measures in larger enclosures, such as warehouses; and - To formulate recommendations for improvements to European (EN-14994), American (NFPA 68), and other relevant standards for vented explosions.


Grant
Agency: European Commission | Branch: FP7 | Program: CP | Phase: ENERGY.2009.5.2.2 | Award Amount: 2.73M | Year: 2009

This project addresses the fundamentally important and urgent issue regarding the accurate predictions of fluid phase, discharge rate, emergency isolation and subsequent atmospheric dispersion during accidental releases from pressurised CO2 pipelines to be employed as an integral part of large scale Carbon Capture and Storage (CCS) chain. This information is pivotal to quantifying all the hazard consequences associated with CO2 pipeline failure forming the basis for emergency response planning and determining minimum safe distances to populated areas. The development of state of the art multiphase heterogeneous discharge and dispersion models for predicting the correct fluid phase during the discharge process will be of particular importance given the very different hazard profiles of CO2 in the gas and solid states. Model validations will be based on both small scale controlled laboratory conditions as well as large scale field trials using a unique CCS facility in China. A cost/benefit analysis will be performed to determine the optimum level of impurities in the captured CO2 stream based on safety and economic considerations. The work proposed, carried out over a period of 36 months will embody the understanding gained within safety and risk assessment tools that can be used for evaluating the adequacy of controls in CO2 pipelines, with best practice guidelines also being developed. The proposal addresses the main themes of the Collaborative Call in that it has a predominant research component and its successful outcome would allow the safe and commercial deployment of large scale near zero emission power generation technology based on CCS. The project also enjoys strategic leadership from members the Carbon Sequestration Leadership Forum and highly relevant collaboration with the worlds second largest and fastest producer of CO2, China.

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