Friday, February 26, 2016

Automatic fire suppression

Automatic fire suppression systems control and extinguish fires without human intervention. fire sprinkler system, gaseous fire suppression, and condensed aerosol fire suppression.

Examples of automatic systems include
The first fire extinguisher patent was issued to Alanson Crane of Virginia on Feb. 10, 1863. 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.

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: 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. 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.

Pre-Engineered Fire Suppression Systems use pre-designed elements to eliminate the need for
potassium carbonate or monoammonium phosphate (MAP), to protect spaces such as paint rooms and surfactant additive, and target retrofit applications where the risk of fire or fire injury is high but where a conventional fire sprinkler system would be unacceptably expensive. In addition, residential range hood fire suppression systems are becoming more common in shared-use cooking spaces, such as those found in assisted living facilities, hospice homes, and group homes.
booths, storage areas and commercial kitchens. A small number of residential designs have also emerged that typically employ water mist with or without a engineering work beyond the original product design. Typical industrial solutions use a simple wet or dry chemical agent, such as those found in assisted living facilities, hospice homes, and group homes.

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.
Actuation usually involves either a pressurised fluid and a release valve, or in some cases an electric pump.
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.

AgentPrimary IngredientApplications
HFC 227ea (e.g.FM-200)HeptafluoropropaneElectronics, medical equipment, production equipment, libraries, data centers, medical record rooms, server rooms, oil pumping stations, engine compartments, telecommunications rooms, switch rooms, engine and machinery spaces, pump rooms, control rooms
 
FK-5-1-12 (3M Novec 1230 Fire Protection Fluid)Fluorinated KetoneElectronics, medical equipment, production equipment, libraries, data centers, medical record rooms, server rooms,
oil pumping stations, engine compartments, telecommunications rooms, switch rooms, engine and machinery spaces, pump rooms, control rooms

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 effects.
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 1301's 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 Halon 1301 and Halon 1211 (halogenated hydrocarbons).
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.
 


 
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