Dry chemical extinguishing systems

NFPA 17 Standard for Dry Chemical Extinguishing Systems, 1998 edition. National Fire Protection Association, Quincy, MA. 

Dry chemical extinguishing systems-This is used primarily for flammable liquid fires since they provide a rapid flame knockdown and e.xtinguishment. 

In addition to the sprinkler system adequacy, is additional fire protection, such as an automatic dry chemical extinguishing system or a other system, warranted Is an explosion suppression system warranted ... 

The fryers and cooking apparatus found in cafeterias will most likely be protected by kitchen hood systems. NFPA 17 Standard for Dry Chemical Extinguishing Systems and NFPA 17A Standard for Wet Chemical Extinguishing Systems will apply depending on the type of agent deployed by the system. Jones (2009) explains these systems and their requirements by comparing th with sprinkler systems, in that... 

Dry-chemical extinguishing systems are used to protect flammable-liquid storage rooms, dip tanks, kitchen range hoods, deep-fat fryers, and similar hazardous areas and appliances. Because dry chemical is nonconductive, these systems are useful in the protection of oil-filled transformers and circuit breakers. Dry-chemical systems are not recommended for tele-phone-switchboard or computer protection. Dry chemicals are also widely used in portable fire extinguishers. 

National Fire Protection Association (NFPA). NFPA 17, standard for dry chemical extinguishing systems. Quincy, MA NFPA 2013. 

The process area has combustible gas detectors, fireproofing, and a water deluge system. Cable trays are protected with deluge, and portable dry chemical extinguishers are in the process area. Diesel-powered fire water pumps can provide a maximum fire water demand for 4 hr. 

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. 

Fire extinguishing systems can include foam, carbon dioxide and dry chemical. Wetting agents and high e.xpansion foam have been used in some plant protection systems. All fire extinguishing systems should be evaluated for the potential health risks as well as overall effectiveness before incorporation into a plant. 

Combination extinguishing systems-Combining dry chemicals and foam agents unites the fast flame control of the dry chemical with the cooling and sealing ability of foam to provide an efficient portable extinguishing system. 

Self contained dual agent systems, (foam/water and dry chemical), are provided for manual fire fighting efforts against three dimensional pressure leaks and large diameter pool fires. The design affords fast fire knockdown, extinguishment and sealant against re-flash. A skid... 

Exposure protection systems provide protection by the application of water to structures and equipment for the anticipated duration of the exposure fire. Water spray curtains are generally less effective than direct application due to unfavorable conditions such as wind, thermal updrafts, and inadequate drainage. Extinguishing agents such as CO2 or dry chemical agents are not able to provide this type of cooling. 

Sodium bicarbonate- and borax bicarbonate-based dry chemicals were among the first dry agents used in portable fire extinguishers. About 1960, the sodium bicarbonate dry chemical was modified to make it compatible with protein-based, low-expansion foam to create a dual agent extinguishing system. Shortly thereafter, the more effective Purple K based extinguishers replaced sodium bicarbonate extinguishers. 

These agents are effective on small spill fires. If there is risk of re-ignition from embers or hot surfaces, these ignition sources should be quenched or cooled with water and secured with foam, or the source of fuel should be shut off before attempting extinguishment. An example of a dry chemical system is shown in Figure 7-36. 

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