Fixed water spray systems may be designed to mitigate flammable vapors and they work primarily by entraining air into the spray cone and mixing the air and water droplets with the flammable vapor, thereby diluting the vapor. It should be noted that this project is to determine the design criteria if fixed water spray should be activated upon confirmed gas detection, and not intended for explosion suppression. However, exercise care when selecting this approach because some research have shown that congested areas (example offshore platforms) may cause increase of explosion because of the turbulence generated by water spray. The current industry standards including NFPA 15, Standard for water spray fixed systems for fire protection, while providing information on vapor mitigation using fixed water spray (section 7.5), do not provide the design criteria on how much water and pressure is required to effectively mitigate a specified minor vapor leak. API 2030 does not address the use of fixed water spray for vapor mitigation. In addition, in the event of an ignition, the amount of water, and pressure required to control the fire is not defined. This has resulted in the inconsistent application of NFPA 15 for vapor mitigation by engineers and consultants.
Research goal: The goal of this research project is to evaluate the effectiveness of fixed water sprays to prevent the development of flammable vapor clouds and control the fire in case of ignition. The specific objectives are to provide test data to develop a design criteria on how much water and pressure is required to effectively mitigate: i. Specific leaks of saturated propane, propane vapor and methane vapor. ii. At specific vapor leak rates of 0.1 kg/s and 0.3 kg/s. The results will be useful for NFPA 15, section 7.5 technical committee and API 2030.
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