Frank Markert

Airborne releases from fires involving chemical waste : a multidisciplinary case study

A multidisciplinary study of fires in chemical waste at a Danish chemical company has been carried out in order to estimate the concentrations of combustion products in the surroundings. The first part of the study addressed the characterisation of the waste and the assessment of fire cases which formed the basis for the experimental work and determination of fire effluents. The combustion experiments were carried out using a tubular furnace, following DIN 53436. Secondly, the source term concentrations were estimated, and calculations of plume rise and dispersion of combustion products in the surroundings were performed. Finally, an uncertainty assessment has been carried out for each part of the study. For some of the issues the uncertainties are described qualitatively and for others the uncertainties are expressed quantitatively.

Modelling of Safety Barriers Including Human and Organisational Factors to Improve Process Safety

It is believed that traditional safety management needs to be improved on the aspect of preparedness for coping with expected and unexpected deviations, avoiding an overly optimistic reliance on safety systems. Remembering recent major accidents, such as the Deep Water Horizon, the Texas City explosion, and the Mont Blanc Tunnel Fire, such an approach may have helped to maintain the integrity of the designed provisions against major deviations resulting in these disasters. In order to make this paradigm operational, safety management and in particular risk assessment tools need to be refined. A valuable approach is the inclusion of human and organisational factors into the simulation of the reliability of the technical system using event trees and fault trees and the concept of safety barriers. This has been demonstrated e.g. in the former European research project ARAMIS (Accidental Risk Assessment Methodology for IndustrieS, see Salvi et al 2006). ARAMIS employs the bow-tie approach to modelling hazardous scenarios, and it suggests the outcome of auditing safety management to be connected to a semi-quantitative assessment of the quality of safety barriers. ARAMIS discriminates a number of different management issues such as competence management, dealing with conflicts, management of maintenance and inspection, and management of procedures. Shortcomings in these management processes effectuate increased probabilities of failure-on-demand (PFD) of the safety barriers, depending on the type of safety barrier (passive, automated, or involving human action). Such models are valuable for many purposes, but are difficult to apply to more complex situations, as the influences are to be set individually for each barrier. The approach described in this paper is trying to improve the state-of-the–art, and it is based on the understanding that certain human and organisational factors may be seen as a kind of common cause failures that influence the performance of several barriers. Therefore, the model links the performance of a barrier with the necessary set of specific activities to maintain and/or to control that barrier. These specific activities are executed within one of the aforementioned management processes, and the efficiency of the activity will depend on the quality of this management process.

Risk Analysis of Complex Hydrogen Supply Chains

Abstract This chapter focuses on methods to assess safety risks in the future hydrogen-based infrastructure. Risks can appear in any single part of the supply chain, for example, the production unit, or in a combination of several supply chain elements. Static and dynamic risk assessment methods are detailed and a case study using a simulation approach is shown. The chapter concludes that hydrogen supply chains are complex systems that need thorough risk assessment to resolve safety issues caused by system interdependencies.

Process Risk Assessment using Dynamic Simulation of Scenarios

Process plants may be very complex and may combine various processes in close proximity. Hence, the response to accidents may easily grow complex. Traditionally, after gathering and getting acquainted with the plants technical information, risk is analysed in prescribed steps starting with hazard identification, description of accident scenarios and using the conventional approach to develop static event trees for events following a loss of containment. Modelling the impacts and consequences needs models to describe the release, dispersion and effect of the hazardous material, as well as models for predicting the egress time of people, response times of detectors and other safety equipment. A common assumption is the independence of these models and their sequential treatment, but often the consequences and effects are mutually dependent. The prediction of the consequences and effects are deterministic assignments applying simplified engineering models with averaged/expected values as input to account for the characteristics of the system, e.g. describing the physical and environmental phenomena and workers responses. The size of the release and dispersion depends on technical and environmental parameters. Ignition sources may be permanent or temporarily present at various locations near the release. The response times of detectors may be dependent on the velocity of cloud spread. The available save egression time depends on these parameters. Such dynamics are easily modelled using Discrete Event Simulation (DES) of the scenarios, which is a Monte Carlo type method. The paper describes the application of DES to conduct the analysis part of a risk assessment that enables better time resolution in the modelling of the specific scenarios, simulate the interactions between concurrent chains of events under the hazardous scenarios, and produce probabilistic risk measures. The outcome provides possibilities to structure the results in a comprehensive way. Scenarios with severe consequences can be ‘played back’ to learn from them and can be animated, which apart from the learning effect provides a new way of validation.

SAFETYNET : a European network for process safety

SAFETYNET is a European Thematic Network on Process Safety funded under the Brite-Euram Programme. The aim of this network is to reduce the time delay between research results and their practical use in industry in order to stimulate further development and adoption of technologies in the field of process safety. This is mainly done in areas related both to the safe operation of process plants and production facilities and to the prevention of accidents.