Safety and environmental impact reduction. a case-study applied to coal dry distillation industry

As reported by Trevor Kletz, changes made to improve the environment have sometimes produced unforeseen and hazardous side-effects. Before changing designs, or methods of operation we should try to foresee their effects and we should balance the risks to people against the risks to environment. Notwithstanding technological development, enforcement of ATEX Directives and safety management system application, explosions in the process sector still claim lives and severe economic losses. Experience shows that in the process industry high severity events frequently occur in auxiliary areas, such as transport and storage of raw materials and products. Even a consolidated process like coke dry distillation allows the opportunity of preventing environmental impact, reducing as well explosion risk connected to fugitive emissions. In this activity, two intervention lines were identified: the former deals with accident risk, i.e. the occurrence of hazardous factors that may cause the ignition of coke oven gas during work activities on pressurized gas pipelines. The latter concerns environmental risk reduction referred to the transport of raw material from the harbour temporary storage site to the final plant. Considering explosion risk in confined environment and possible evolving scenarios, a short-cut mathematical approach to the maximum allowed hazardous substance build-up is developed based on the intrinsic hazards of the released material. This framework from one side will help identifying and assessing small hazardous releases consequences in closed areas and set-up appropriate control measures. From the other side, it is adopted in connection with the design of an underground conveyor belt for coal, so as to limit fugitive emissions. In this context, the study involves an in-depth quantitative risk assessment and the planning of severe control and prevention measures suitable to mitigate explosion/fire risk, both reducing the probability and the severity of adverse consequences. The methodology successfully tested at the real-scale can be applied to more complex situations, allowing, as well, the attainment of a more generalized approach for the design, once given the release parameters, the building and plant layout

A propane fire connected to dumping procedure in a process plant

A propane gas cloud was released into the atmosphere during the loop rector dumping procedure in a process plant. After reactor inertization, the bottom valve of the dump tank was opened to collect spent powder and remove it. Unexpectedly, the powder on the floor started evaporating hydrocarbons. A propane cloud drifted very fast through the plant and ignited at the pump station area: even if the flash fire was extinguished immediately, there were several people injured and one fatality. The fire of the powdered material was extinguished later, by sprinkler system and fire brigade intervention. A detailed investigation was carried out and a multi-step methodology was applied to define the sequences and identify the most likely causes of the accident. It was adopted a complete fault tree, trying to find out without a structured scheme any critical causal factor in each relevant branch. Then, starting from the immediate cause, different sub-steps were identified as possible underlying cause, allowing to evidence in a sort of causal chain possible deficiencies in the safety management system, or in the safety culture of the company. Conclusions are drawn about practical recommendations to improve safety in dumping activities within a polymerization plant, adopting as well possible leading indicators for potential major incidents. The presented case study clearly shows how an effective HSE management system and a corresponding organization could have prevented or minimized the occurrence of such an unwanted event

Hazardous materials transportation by road: trends and problems in risk assessment and emergency planning

Hazardous material transportation poses obvious hazards to environment, general public and response personnel. In this context, risk reduction can be achieved by analyzing and designing correctly the routing of shipments, by proper risk assessment procedure. HazMat transportation risk management must include appropriate emergency response services, limiting accident consequences. This paper presents a quantitative risk assessment approach to HazMat transportation, starting from an historical statistical analysis on road accidents. A methodological approach for the assessment of standard vehicle and dangerous good truck flows was applied to a pilot area in the North of Italy, allowing a statistical reinforced evaluation of route intrinsic enhancing/mitigating parameters. The results evidence the distribution of the risk along the different routes and the localization of high spots, with good accuracy and precision. Preventive and mitigating risk measures are discussed in depth, with particular reference to the optimization of emergency equipment (number of prompt action vehicles) by means of an unambiguous and consistent selection criterion that allows reduction of intervention time. Different risk mitigation options, based on changing route or designing alternative slip roads, in transport corridors or tunnels, are investigated as well. The presented approach can represent a useful tool not only to estimate transport risk, but also to define strategies for the reduction of risk (i.e. distribution and limitation of ADR road traffic, improvement of highway section, design of alternative routes) and emergency management