Assessing the extent of pipeline gas releases during emergency situations are challenging since traditional methodologies for risk analyses (QRA, CFD) requires significant computer capabilities and time. This means that emergency response teams traditionally have not been able to use gas dispersion modelling for responding to actual accidents. DNV GL, Gassco, and Statoil have developed CATES (Consequence Assessment Tool for Emergency Situations), a dynamic tool to optimize the emergency response to a gas release in order to give a correct view and understanding of the situation. This tool also contributes to reducing the uncertainty with respect to how the public rescue services react in alert and combat phases. The final version of the tool has recently been handed over to Gassco for implementation into their safety management system.
In a given leak situation, the operators of CATES uses the tool to calculate safety distances for public rescue service personnel and their vehicles expressed as number of metres to 50% and 20% LFL (Lower Flammable Limit) respectively, based on pre-calculated cases and simple input (leak size and wind speed). These distances are then plotted as circles on a map through an interface in Gassco/Statoil GIS tool. A PDF of the map, safety distances, and scenario information is produced and communicated to the fire brigades and the police on scene. As the situation develops, results are updated continuously. This information shows how close to the leak site fire fighters with proper PPE and gas meters may go without exposing themselves to unnecessary risk. As opposed to the default 2.2 km radius around the leak site used today by the police, CATES provides distances that are specific for the given pipeline, leak scenario, and location and proving to be much shorter in most instances.
Successive versions of CATES were successfully tested during full scale emergency drills and table top exercises. Both the companies and the public rescue services believe that the tool represents an important support in a possible emergency situation contributing to optimization of emergency preparedness (time and quality) in an accidental situation.