What is an externally pressurized Heptafluoropropane system?

　　The heptafluoropropane fire suppression system is a relatively common type of fire protection system, typically categorized into three main types: piped network, cabinet-type, and suspended systems. Today, we'll introduce the externally pressurized heptafluoropropane system, which falls under the category of piped-network heptafluoropropane systems.

　　The difference between externally pressurized and internally pressurized HFC-227ea: Externally pressurized HFC-227ea features a separate cylinder bank outside the system dedicated to storing nitrogen gas, whereas internally pressurized systems store the propellant internally—meaning there’s only a single steel cylinder used.

　　The externally pressurized HFC-227ea system stores the liquid HFC-227ea fire suppressant in a container without using nitrogen for pressurization. The storage pressure equals only the saturation vapor pressure of the extinguishing agent, while the compressed gas used to propel the agent into the protected area remains at a much higher pressure—so please store it separately in another container.

　　When the system is operating, high-pressure motive gas is reduced in pressure by a pressure-reducing valve and then injected into the fire-suppression agent storage cylinder (while simultaneously opening the container bottle head valve). The motive gas propels the extinguishing agent to rapidly move through the pipeline network system—via siphon tubes and the container valve—and ultimately discharges it at the nozzles within the protected area, effectively enabling fire suppression.

　　Since the extinguishing agent and the propellant gas are stored in separate containers, this approach addresses two key issues: First, the extinguishing agent remains isolated from nitrogen during storage, preventing the gas from dissolving into the agent. Nitrogen is used to maintain system pressure; once the system is activated, the pressure of the extinguishing agent throughout its delivery and discharge process consistently exceeds its storage pressure, ensuring no vaporization of the agent or precipitation of nitrogen occurs. This effectively minimizes the risk of two-phase flow of the extinguishing agent during transportation.

　　Therefore, the extinguishing agent remains stable in a flowing state during transportation, with the propellant gas consistently positioned at the end of the agent. In an externally pressurized HFC-227ea system, the liquid extinguishing agent is rapidly propelled through the pipeline as a single-phase fluid. This method delivers the agent at a speed that is both faster and more stable compared to pressure-storage systems. As a result, the system enhances the efficiency of pipeline-based agent delivery, enabling longer transmission distances, higher discharge pressures, and the ability to use narrower pipes while still conveying larger volumes of extinguishing agent.

　　External-pressure HFC-227ea typically outperforms internal-pressure HFC-227ea in fire suppression performance for certain applications, but this comes at the cost of a higher price and larger footprint. Therefore, when making your selection, it’s important to carefully consider what truly suits your needs—after all, the best option is the one that fits you perfectly.