My question:
How much water flow in GPM is necessary to cool a 1,000 gallon LPG tank that is involved in a pool fire to prevent it from experiencing a BLEVE?
Their answer…
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Given your work with SAFTENG.net, you likely know that while 55 GPM is the "engineering" minimum for fixed systems, the NFPA 58 and API 2510 standards emphasize that if you cannot apply water effectively to the vapor space almost immediately, the risk of shell failure remains high regardless of the flow rate.
To prevent a Boiling Liquid Expanding Vapor Explosion (BLEVE) in a 1,000-gallon LPG tank involved in a pool fire, the required water flow is determined by the tank’s surface area and the application density specified by safety standards.
- Calculation Parameters
According to NFPA 15 (Standard for Water Spray Fixed Systems for Fire Protection) and API 2510 (Design and Construction of LPG Installations), the standard cooling rate for vessels exposed to fire is 0.25 GPM/sq. ft. of the total vessel surface area.
Tank Dimensions: A standard 1,000-gallon horizontal LPG tank typically measures approximately 41 inches in diameter and 192 inches (16 feet) in length.
Total Surface Area: Using the formula for a cylinder (A=2πrh+2πr2), the surface area of a 1,000-gallon tank is approximately 200 to 215 square feet.- Required Flow Rate
Based on the 0.25 GPM/sq. ft. density:
Calculation: 215 sq. ft.×0.25 GPM/sq. ft.=53.75 GPM
Minimum Requirement: You need approximately 55 to 60 GPM of water delivered directly to the tank surface to maintain effective cooling.- Critical Considerations for BLEVE Prevention Focus on the Vapor Space: In a pool fire, the liquid inside the tank acts as a heat sink for the “wetted” portion of the shell. The most critical area to cool is the vapor space (the top of the tank), where the steel can weaken rapidly because there is no liquid to absorb the heat. Application Method: To be effective, the water must create a continuous film over the entire surface. If using a fire hose (manual application) rather than a fixed spray system, the flow requirement is often much higher (typically 250–500 GPM) to account for wind, evaporation, and the difficulty of maintaining a steady film from a distance. Time Sensitivity: If a 1,000-gallon tank is directly impinged by a high-intensity fire, a BLEVE can occur in as little as 10 to 20 minutes. If cooling cannot be established immediately, evacuation is the only safe option.
Summary Table
Factor Specification
Standard Application Rate 0.25 GPM / sq. ft.
Estimated Surface Area ~215 sq. ft.
Calculated Cooling Flow ~55 GPM
Recommended Hose Stream 250+ GPM (for reach and coverage)
Given your work with SAFTENG.net, you likely know that while 55 GPM is the “engineering” minimum for fixed systems, the NFPA 58 and API 2510 standards emphasize that if you cannot apply water effectively to the vapor space almost immediately, the risk of shell failure remains high regardless of the flow rate.