“Vapor Mitigation Testing Using Fixed Water Spray System” – BakerRisk & NFPA research paper
The National Fire Protection Association (NFPA) prides themselves as being a prime source for “knowledge resources on fire, electrical and related hazards”. BakerRisk recently teamed with the NFPA’s Fire Protection Research Foundation (FPRF) to conduct a test program to determine the adequacy of deluge as a means of vapor mitigation.
This program was designed around an extensive controlled dispersion test program including over 70 tests conducted with saturated propane, propane vapor, and methane vapor at 0.1 kg/s and 0.3 kg/s. For the testing program, gas concentrations were measured by 28 detectors scattered throughout an 80 ft x 80 ft test pad. In addition to the live testing, this project included a thorough literature review of the topic, comparison consequence modeling of the tests using BakerRisk’s SafeSite3G© software, and a CFD analysis of the saturated propane tests.
BakerRisk is thankful to the FPRF as well as all the test sponsors who have contributed time, equipment, funding, and technical advice throughout this project.
An excerpt from the Executive Summary is below:
“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. 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 also not defined. This has resulted in the inconsistent application of NFPA 15 for vapor mitigation by engineers and consultants. The goal of this research project was to evaluate the effectiveness of fixed water sprays to suppress the development of flammable vapor clouds and control the fire in case of ignition. The specific objectives were to provide test data to aid in the development of design criteria on how much water and pressure is required to effectively mitigate specific leaks of saturated propane, propane vapor, and methane vapor; and specific vapor leak rates of 0.1 kg/s and 0.3 kg/s.”
Visit the official NFPA site here to download the report.