Automatic fire suppression


Automatic fire suppression

While fire fighting may be defined as the act of extinguishing destructive fires, automatic fire suppression is more of means to control and extinguish fires before they become destructive and without human intervention.

According to the National Fire Protection Association, there were 1,602,000 fires reported in the United States in 2005. There were 3,675 civilian deaths, 17,925 civilian injuries, and $9.2 billion in property damage. A fire department responded to a fire every 20 seconds and a structure fire was reported every 62 seconds. [ National Fire Protection Association, “The U.S. Fire Problem,” www. nfpa.org.]

Although man has fought fire for centuries, it was not until Feb. 10, 1863 that the first fire extinguisher patent was issued to Alanson Crane of Virginia. The first fire sprinkler system was patented by H.W. Pratt in 1872. But the first practical automatic sprinkler system was invented in 1874 by Henry S. Parmalee of New Haven, CT. He installed the system in a piano factory he owned.

The Society of Fire Protection Engineers was founded in Boston on Oct. 31, 1950,

Types of automatic systems

Today there are numerous types of Automatic Fire Suppression Systems. Systems are as diverse as the many applications. In general, however, Automatic Fire Suppression Systems fall into two categories. These are engineered and pre-engineered systems.

Engineered Fire Suppression Systems are design specific. Engineered systems are usually for larger installations where the system is designed for the particular application. Examples include marine and land vehicle applications, computer clean rooms, public and private buildings, industrial paint lines, dip tanks and electrical switch rooms. Pre-Engineered Fire Suppression Systems do not require the involvement of a design engineer beyond the original product design. Pre-engineered systems are comprised of pre-designed components. Examples of pre-engineered systems include commercial kitchen systems and industrial paint rooms and paint booths and industrial storage areas.

Pre-engineered systems most commonly use a simple wet or dry chemical agent, such as potassium carbonate or monoammonium phosphate (MAP). Engineered systems use a number of gaseous or solid agents. Many are specifically formulated. Some, such as 3M™ Novec™ 1230 Fire Protection Fluid, are stored as a liquid and discharged as a gas.

Components

By definition, an automatic fire suppression system can operate without human intervention. To do so it must possess a means of detection, actuation and delivery.

In many systems, detection is accomplished by mechanical or electrical means. Mechanical detection uses fusible-link or thermo-bulb detectors. These detectors are designed to separate at a specific temperature and release tension on a release mechanism. Electrical detection uses heat detectors equipped with self-restoring, normally-open contacts which close when a predetermined temperature is reached.

Remote and local manual operation is also possible.

Delivery is accomplished by means of piping and nozzles. Nozzle design is specific to the agent used and coverage desired.

Extinguishing agents

In the early days, water was the exclusive fire suppression agent. Although still used today, water has limitations. Most notably, its liquid and conductive properties can cause as much property damage as fire itself.

Health and environmental concerns

Despite their effectiveness, chemical fire extinguishing agents are not without disadvantages. In the early 20th century, carbon tetrachloride was extensively used as a dry cleaning solvent, a refrigerant and as a fire extinguishing agent. In time, it was found carbon tetrachloride could lead to severe health affects.

From the mid 1960s Halon 1301 was the industry standard for protecting high value assets from the threat of fire. Halon 1301 had many benefits as a fire suppression agent; it is fast acting, safe for assets and required minimal storage space. Halon 1301s major drawbacks are that it depletes atmospheric ozone and is potentially harmful to humans.

Since 1987, some 191 nations have signed The Montreal Protocol on Substances That Deplete the Ozone Layer. The Protocol is an international treaty designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion. Among these were halogenated hydrocarbons often used in fire suppression. As a result manufacturers have focused on alternatives to halogenated hydrocarbons, such as Halon 1301 and Halon 1211.

A number of countries have also taken steps to mandate the removal of installed Halon systems. Most notably these include Germany and Australia, the first two countries in the world to require this action. In both of these countries complete removal of installed Halon systems has been completed except for a very few essential use applications. The European Union is currently undergoing a similar mandated removal of installed Halon systems.

Modern systems

Since the early 1990s manufacturers have successfully developed safe and effective Halon alternatives. These include DuPont FM-200®, American Pacific’s Halotron and 3M™ Novec™ 1230 Fire Protection Fluid. Generally, the Halon replacement agents available today fall into two broad categories, in-kind (gaseous extinguishing agents) or not in-kind (alternative technologies). In-kind gaseous agents generally fall into two further categories, Halocarbons and Inert Gases. Not in-kind alternatives include such options as water mist or the use of early warning smoke detection systems.

ee also

* Gaseous fire suppression

References

External links

* [http://www.nfpa.org/ National Fire ProtectionAssociation]


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