Automatic Fire-extinguishing Systems

Halons are used in automatic fire-extinguishing systems, such as those located in flammable solvent storage areas, and in specialty fire extinguishers, such as those on aircraft. It has proven difficult to find substitutes for halons that have the same excellent performance characteristics. 

NFPA 45, 4.1-4.6 4.3.3 All laboratory units shall be provided with fire protection appropriate to the fire hazard, including automatic fire extinguishing systems, standpipe and hose systems, portable fire extinguishers, fire alarm systems, fire prevention programs, and emergency plans. 

OSHA does not mandate automatic fire extinguishing systems, but the General Industry Standards, Subpart L, Sections 1910.155-165, do provide regulations covering the essential requirements which installed systems must meet. 

In areas where fire potential and the risk of injury or damage are high, automatic fire-extinguishing systems are often used. These may be of the water sprinkler, foam, carbon dioxide, halon, or dry chemical type. If an automatic fire-extinguishing system is in place, laboratory workers should be informed of its presence and advised of any safety precautions required in connection with its use (e.g., evacuation before a carbon dioxide total-flood system is activated, to avoid asphyxiation). 

Automatic fire extinguishing systems such as sprinklers, drenchers or gas systems operate when the heat of the fire in the region of a detector head reaches predetermined levels and cause the seal in the detector head to fracture releasing the extinguishant. These systems can incorporate a facility to raise the alarm. 

When emergency alarm, detection or automatic fire-extinguishing systems are required in Section 8003, such systems shall be supervised by an approved central, proprietary or remote station service or shall initiate an audible and visual signal at a constantly attended on-site location. (UFC 8003.1.16). 

Table 6.13 General requirements for fixed fire-extinguishing systems (Activation may be automatic by a detection system, or manual)...

Withdrawn) 1987 AMD 3 Portable fire extinguishers (AMD 8585) dated 15 December 1995. Withdrawn, superseded by BS 7863 1996, BS 7867 1997 and BS EN 3-1 to 6 (Withdrawn) 1977 Components of automatic fire detection systems. Part 1 Introduction. Withdrawn, superseded by BS EN 54-1 1996... 

Where a detection system is part of an automatic, fixed fire extinguishing system, complete compatibility between the systems is essential. 

An automatic carbon dioxide fire-extinguishing system. 

Do you have automatic fire suppression systems available in all building (Y/N) List of fire extinguishing systems types available for fire loads (Y/ISl)... 

Due to these potential secondary effects of fire and fire protection on plant safety in particular plant areas, the fire extinguishing systems are not actuated automatically. 

The fire scenario selected to be analyzed deals with the fire fighting means designated to be applied in a reference NPP once a fire occurs for any reason. One major assumption is the failure of the automatic actuation of the fixed fire extinguishing system in the compartment where the fire is supposed to start. This implies that fire fighting mainly depends on the operability of the fire detection and darm system, the performance of human actions as well as on the operability of active fire barrier elements (e.g. fire dampers and fire doors) and of the fire extinguishing systems which can be manually actuated. 

If equipment and procedures work as intended, fire fighting is a rather short process, because the compartment where the fire is assumed to occur is equipped with a fixed fire extinguishing system which suppresses the fire with a sufficiently large amount of water after actuation by the fire detection and alarm system. However, one major assumption of the andysis presented here was the failure of the automatic actuation of the fixed fire extinguishing system. This implies that the fire has to be extinguished by manual fire fighting means performed by the plant personnel in charge. 

Fire analysis can be performed to a different level of details. The approaches on this vary from study to study. In many fire analysis conservative assumptions are made, e g. when fire occurs in a certain room all components in the room are lost. These assumptions may not necessarily be applicable for shutdown operating mode. During plant outage there are a lot more people in the plant that could either detect or extinguish the fire, though the automatic fire detection system may be out-of-service at that time. The fire analysis for plant outage should also considered that the fire zones during power operation could be different than in shutdown. 

If an ethyl ether fire occurs, carbon dioxide, carbon tetrachloride, and dry chemical fire extinguishers meeting National Eire Prevention Association Code 1 and 2 requirements may be used successhiUy (23). Water may also be effectively appHed (see Plant safety). Hose streams played into open tanks of burning ethyl ether serve only to scatter the Hquid and spread the fire. However, ether fires may be extinguished by a high pressure water spray that cools the burning surface and smothers the fire. Automatic sprinklers and deluge systems are also effective. 

Extinguishing system A system designed to extinguish fires by means of certain chemicals, gases, or water, either manual or automatic. 

A combination of detectors may be appropriate. They may activate an alarm only, or actuate a combined alarm/extinguishment system. With a bank of detectors a voting system may be used to increase reliability and reduce the frequency of spurious alarms. Detection/alarm systems may also be interlinked with, e.g., fire-check doors held back on electromagnetic catches such that the doors close automatically upon activation of the detection system. 

All responsible organizations will have a fire protection program to protect their assets. For some, it may be fire extinguishers in the warehouse while for others it is a department of professionals supplementing numerous automatic fire detection and suppression systems. Due to the nature of the program, it is often necessary to involve several individuals, each having a specific, assigned responsibility. 

Containment systems are also used in conjunction with an automatic foam-water sprinkler/deluge system where rapid fire extinguishment is expected. 

Since control rooms are normally constantly manned, it is considered unlikely that a fire could progress undetected to a hazardous size. Fixed fire protection systems, whether manually or automatically activated, are seldom installed in control rooms of processing facilities, mainly due to the fact that they are normally constantly manned. As such, it is considered unlikely that any fire that does occur would progress undetected to a size that cannot be extinguished by manual intervention (fire extinguishers, hose reel, etc.). 

Where water will create a serious fire or personnel hazard, a suitable nonwater automatic extinguishing system should be considered. Penetrations through fire-rated floor, ceiling, and wall assemblies by pipes, conduits, bus ducts, cables, wires, air ducts, pneumatic tubes and ducts, and similar building service equipment should be protected in accordance with NFPA 101 , Life Safety Code. All floor openings should be sealed or curbed to prevent liquid leakage to lower floors. Door assemblies in 1 -hour rated fire barriers should be y4-hour rated. Door assemblies in 2-hour rated fire barriers should be 1 V2-hour rated. 

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