Clean agent fire protection for power generation facilities

Power generation facilities produce electricity, and include hydroelectric, nuclear, and fossil fuel based power plants. All of these plants provide a wide variety of challenging fire hazards, due to the presence of flammable fuels, various types of electronic equipment and rotating machinery. The occurrence of a fire in these facilities poses a significant business risk due to the high cost of downtime and its effect on users who depend on an uninterrupted supply of electricity for the operation of their mission critical businesses and equipment.

Clean agent protection in electric generating plants: NFPA 850

Clean agents are widely employed for the fire protection of various areas within a power plant, including the protection of control rooms, computer and control system equipment, turbine enclosures, UPS rooms, battery rooms, substations, cable voids, electrical switch rooms and switchgear. Recommended guidelines for the protection of power plants can be found in NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations, NFPA 851, Recommended Practice for Fire Protection for Hydroelectric Generating Plants and NFPA 805: Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants.

NFPA 850 provides recommendations for fire prevention and fire protection for electric generating plants and high voltage direct current converter stations, and in Section 6.6.2 indicates that the selection of an extinguishing agent or a combination of extinguishing agents should be based on (1) the type of hazard, (2) the effect of agent discharge on equipment, and (3) the health hazards.

Table 1: Clean Agent Requirements: Class C Hazards. aNFPA 2001 (2018); bFM Data Sheet 4-9 (2019). — Table 1: Clean Agent Requirements: Class C Hazards.
aNFPA 2001 (2018); bFM Data Sheet 4-9 (2019).

Type of hazard

All of the clean agent types, whether halocarbon (e.g., FM-200), perfluoroketone (Novec 1230) or inert gas (e.g., Inergen) are suitable for the protection of Class A, B and C fire hazards.

The major use of clean agents in power plants is the protection of electronic equipment, a Class C fire hazard. Table 1 compares the clean agent requirements for Class C fire hazards, and it can be seen that the most effective agent on a mass basis is FM-200. Novec 1230 systems require 20% more mass of agent, and Inergen systems require 25% more mass of agent compared to FM-200 systems for Class C hazards of less than 480 volts. For Class C hazards involving voltages equal to or exceeding 480 volts, Novec 1230 systems require 57% more mass of agent, and Inergen systems require 20% more mass of agent compared to FM-200 systems. As a result, the weight and space requirements for Novec 1230 and Inergen systems exceed those for FM-200 systems, regardless of the voltage level.

Table 2. Comparison of FM-200 and Novec 1230 Toxicology (Yellow indicates lower toxicity by the indicated toxicological measure) a NFPA 2001 (2018); b DuPont FM-200 SDS; c NICNAS Report STD 1019, p. 10; d Chemours FM-200 PUSH Bulletin; e 3M Novec 1230 SDS; f Armstrong Laboratory Report AL/OE-TR-1995-0022 (1995); g Novec 1230 Fire Protection Fluid Safety Assessment [3M].

Effect of agent discharge on equipment

All of the clean agent types, whether halocarbon (e.g., FM-200), perfluoroketone (Novec 1230) or inert gas (e.g., Inergen) provide “clean” extinguishment, with no generation of residues or corrosive or abrasive products following extinguishant system activation. This eliminates or greatly reduces any downtime and/or business interruption associated with the fire event.

Table 3. Clean Agent Nozzle Coverage Areas.

Health hazards

All of the clean agent types, whether halocarbon (e.g., FM-200), perfluoroketone (Novec 1230) or inert gas (e.g., Inergen) are approved for use in normally occupied areas.

The clean agents are characterized by differences in their toxicological profiles, as seen in Table 2. Inert gas agents such as Inergen do not undergo any chemical reactions within the body, and as a result are of very low toxicity. The No Effect Level (NEL) and Lowest Effect Level (LEL) for Inergen are 43% and 52%, respectively [NFPA 2001, 2018 edition].

Like Inergen, FM-200 does not react in the human body and hence is of very low toxicity. Novec 1230 is chemically reactive, and when inhaled reacts with water in the lungs. As seen in Table 2, FM-200 offers a higher safety margin/safety in use compared to Novec 1230, as it has lower toxicity compared to Novec 1230, as measured by a number of toxicological effects.

Table 4. System Design Example: 38 m x 38 m x 3 m IT Facility Class C Hazard, less than 480 Volts.

Additional considerations in clean agent selection

Mass efficiency and nozzle area coverage

As discussed above, FM-200 is the most effective of the clean agents based on mass requirements for the protection of Class C hazards. Table 3 compares the nozzle area coverages achievable with the various clean agent types. Due to its high boiling point, achieving uniform distribution of Novec 1230 throughout an enclosure is more difficult compared to the case of low boiling agents such as FM-200 or Inergen. This difficulty in achieving uniform distribution is reflected in the relatively low nozzle area coverages provided by Novec 1230 systems seen in Table 3. Inert gas systems also tend to have lower maximum nozzle area coverages: for example, FM-200 systems can achieve maximum nozzle area coverages of almost four times that of Inergen systems.

Decreased nozzle area coverage leads to an increase in system cost due to the requirement of additional nozzles and piping. Table 4 compares the case of a 38 m x 38 m x 3 m (4332 m3) facility. In addition to requiring 20% more Novec 1230 by mass, four times the number of nozzles are required for protection with Novec 1230 compared to protection with FM-200. Table 4 also demonstrates the large weight and volume penalties associated with inert gases.

Table 5. Sample of Powerplants and Substations Protected by FM-200: Kingdom of Saudi Arabia.

Sustainability

From an environmental impact viewpoint, all of the current clean agents are acceptable: none of the agents contribute to ozone depletion, the inert gases do not contribute to global warming, and the use of HFC and perfluoroketone clean agents results in a negligible contribution to global warming. Based on US EPA data, the impact on global warming of all HFCs in fire protection applications represents less than 0.02% of the impact on global warming of all greenhouse gases [US EPA, Inventory of US GHG Emissions & Sinks, 2018].

The manufacturers of both FM-200 and Novec 1230 offer 20-year environmental warranties as an assurance of the sustainability of the products. Chemours offers their 20-year Falcon and 20-year Eagle Programs for FM-200, and 3M offers their 20-year Blue Sky Warranty for Novec 1230. These warranties provide a guarantee that the agents are long-term solutions.

Conclusion

Due to their efficiency, safety, speed of extinguishment, sustainability, and elimination or minimization of the downtime and business interruption associated with a fire extinguishment event, the clean agents are ideally suited for the protection of various components of the modern-day power plant, including the protection of control rooms, computer and control system equipment, turbine enclosures, UPS rooms, battery rooms, substations, cable voids, electrical switch rooms and switchgear. Clean agents are widely employed in the fire protection of power plants throughout the world, as evidenced in Table 5, which lists just a small selection of power plants and substations within the Kingdom of Saudi Arabia which are protected by the clean agent FM-200.

For more information, go to FM200.com