Investigation of Fire Extinguishment in Large Facilities based on Physical Scaling, Modeling and Testing

Abstract

An investigation was conducted to determine the feasibility of extending the total flooding water mist protection previously developed for a 7.47 × 7.47 × 7.47-m³ ignitable liquid dispensing facility to a larger building, for a longer but acceptable fire extinguishing time. The targeted building height and door opening were 7.62 m and 3.81 × 3.81 m², respectively. Same as for the 7.47-m cubic facility, the fire challenge was the combination of a cascading heptane fire spilling from the top of a fuel tank and the resulting shielded pool fire on the floor. The Froude-based scaling methodology and a well-stirred reactor model were used to assess the maximum building size and associated water mist requirement for a 0.48-scale mockup of the 7.62-m high facility, under the constraint of meeting the designated fire extinguishment time. A series of fire tests was then conducted in the 0.48-scale mockup to verify that the fire could indeed be extinguished within the designated duration for the determined building size and protection requirement. In general, it took less time to extinguish the fire as the water mist discharge rate was increased. The water mist sprays deployed in the door opening tended to reduce the fire extinguishment time by reducing air flow through the door opening, but not significantly in this investigation. However, the deployment of water mist sprays in the door opening is highly recommended to confine the spill fire within the protected building. The tests also showed that it took longer time to extinguish the fire as the fire was closer to the door opening. Based on the 0.48-scale test results and scaling relationships, the water mist protection requirement and corresponding fire extinguishment time for the 7.62-m high facility were projected for a building floor area of 580 m².