The main messages from the “batting cleanup” presentation on fire suppression systems, by ORR Protection’s Chuck Hatfield, are that NFPA Code requirements include the life (human) safety and reliability of suppression equipment, whether low- or high-pressure type; and that the industry is “moving away from CO2 based suppression to water-mist systems.”
One reason for the shift is that life safety risk is higher with CO2. Another is the psychological effects—there has been a higher level of deaths in confined spaces protected by CO2 in recent years. A third is that water presents an effectively “unlimited” supply of suppressant compared to CO2.
The presenter distinguished among three types of areas with respect to fire: those requiring LOTO for entry; normally occupied areas, those not governed by LOTO; and normally unoccupied areas, those which cannot be occupied by a person. NFPA has new requirements for equipment to enhance life safety in normally occupied areas. Visit www.nfpa.org for details. An odorizer is an option and is very expensive, according to the presenter. Lockout valves must be monitored.
NFPA 750 and FM 5560 apply to water-mist systems. Fundamentally, all convert water mist into steam which acts like an inert gas, and promote three extinguishing mechanisms—inerting, cooling, and fuel wetting. System varieties include self-contained cylinder units, or diesel engine, gas engine, or electric power drives.
Attributes include the following: They incorporate smoke scrubbing devices, consume a relatively small amount of water, one pump/system can serve multiple generating units (for example, three gas-turbine units), and can be equipped with plug-and-play releasing panels.
The presenter responded to questions on the following topics:
- Sources of water—fire water main loop if potable water, cooling water, or demineralizer water (if the tank is large enough).
- Spent water collection—generally not required; some fire-prone skids like lube oil have a containment wall around them.
- Testing spray heads for atomization—test on system commissioning, then blow air to make sure nozzles are free-flowing. NFPA requires blowout with air annually, annual water bottle inspection, and backup-battery tests every six months.