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.

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.

Tuesday, February 16, 2016

El Niño

El Niño /ɛl ˈnnj/ (Spanish pronunciation: [el ˈniɲo]) is the warm phase of the El Niño Southern Oscillation (commonly called ENSO) and is associated with a band of warm ocean water that Pacific International Date Line and 120°W), including off the Pacific coast of South America. El Niño Southern Oscillation refers to the cycle of warm and cold temperatures, as measured by sea surface temperature, SST, of the tropical central and eastern Pacific Ocean. El Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific. The cool phase of ENSO is called "La Niña" with SST in the eastern Pacific below average and air pressures high in the eastern and low in western Pacific. The ENSO cycle, both El Niño and La Niña, causes global changes of both temperatures and rainfall. Mechanisms that cause the oscillation remain under study.
(between approximately the
develops in the central and east-central equatorial

El Niño is defined by prolonged warming in the Pacific Ocean sea surface temperatures when compared with the average value.
The U.S NOAA definition is a 3-month average warming of at least 0.5 °C (0.9 °F) in a specific area of the east-central tropical Pacific Ocean; other organizations define the term slightly differently. Typically, this anomaly happens at irregular intervals of two to seven years, and lasts nine months to two years. The average period length is five years. When this warming occurs for seven to nine months, it is classified as El Niño "conditions"; when its duration is longer, it is classified as an El Niño "episode".
The first signs of an El Niño are a weakening of the Walker circulation or trade winds and strengthening of the Hadley circulation and may include:

  1. Rise in surface pressure over the Indian Ocean, Indonesia, and Australia
  2. Fall in air pressure over Tahiti and the rest of the central and eastern Pacific Ocean
  3. Trade winds in the south Pacific weaken or head east
  4. Warm air rises near Peru, causing rain in the northern Peruvian deserts
El Niño's warm rush of nutrient-poor water heated by its eastward passage in the Equatorial Current, replaces the cold, nutrient-rich surface water of the Humboldt Current.
A recent study has appeared applying network theory to the analysis of El Niño events; the study presented evidence that the dynamics of a described "climate network" were very sensitive to such events, with many links in the network failing during the events.

Effects of ENSO warm phase (El Niño)

Economic impact
When El Niño conditions last for many months, extensive ocean warming and the reduction in easterly trade winds limits upwelling of cold nutrient-rich deep water, and its economic impact to local fishing for an international market can be serious.

More generally, El Niño can affect commodity prices and the macroeconomy of different countries. It can constrain the supply of rain-driven agricultural commodities; reduce agricultural output, construction, and services activities; create food-price and generalised inflation; and may trigger social unrest in commodity-dependent poor countries that primarily rely on imported food. A University of Cambridge Working Paper shows that while Australia, Chile, Indonesia, India, Japan, New Zealand and South Africa face a short-lived fall in economic activity in response to an El Niño shock, other countries may actually benefit from an El Niño weather shock (either directly or indirectly through positive spillovers from major trading partners), for instance, Argentina, Canada, Mexico and the United States. Furthermore, most countries experience short-run inflationary pressures following an El Niño shock, while global energy and non-fuel commodity prices increase The IMF estimates a significant El Niño can boost the GDP of the United States by about about 0.5% (due largely to lower heating bills) and reduce the GDP of Indonesia by about 1.0%.

Health and social impacts
Extreme weather conditions related to the El Niño cycle correlate with changes in the incidence of epidemic diseases.
For example, the El Niño cycle is associated with increased risks of some of the diseases transmitted by mosquitoes, such as malaria, dengue, and Rift Valley fever. Cycles of malaria in India, Venezuela, Brazil, and Colombia have now been linked to El Niño. Outbreaks of another mosquito-transmitted disease, Australian encephalitis (Murray Valley encephalitis—MVE), occur in temperate south-east Australia after heavy rainfall and flooding, which are associated with La Niña events. A severe outbreak of Rift Valley fever occurred after extreme rainfall in north-eastern Kenya and southern Somalia during the 1997–98 El Niño.
ENSO conditions have also been related to Kawasaki disease incidence in Japan and the west coast of the United States, via the linkage to tropospheric winds across the north Pacific Ocean.
ENSO may be linked to civil conflicts. Scientists at The Earth Institute of Columbia University, having analyzed data from 1950 to 2004, suggest ENSO may have had a role in 21% of all civil conflicts since 1950, with the risk of annual civil conflict doubling from 3% to 6% in countries affected by ENSO during El Niño years relative to La Niña years.

Recent occurrences
Since 2000, El Niño events have been observed in 2002–03, 2004–05, 2006–07, 2009–10 and 2015–16.
In December 2014, the Japan Meteorological Agency declared the onset of El Niño conditions, as warmer than normal sea surface temperatures were measured over the Pacific, albeit citing the lack of atmospheric conditions related to the event. In March and May 2015 both NOAA's Climate Prediction Center (CPC) and the Australian Bureau of Meteorology respectively confirmed the arrival of weak El Niño conditions. El Niño conditions were forecast in July to intensify into strong conditions by fall and winter of 2015. In July the NOAA CPC expected a greater than 90% chance that El Niño would continue through the 2015-2016 winter and more than 80% chance to last into the 2016 spring. In addition to the warmer than normal waters generated by the El Niño conditions, the Pacific Decadal Oscillation was also creating persistently higher than normal sea surface temperatures in the northeastern Pacific. In August, the NOAA CPC predicted that the 2015 El Niño "could be among the strongest in the historical record dating back to 1950.” In mid November, NOAA reported that the temperature anomaly in the Niño 3.4 region for the 3 month average from August to October 2015 was the 2nd warmest on record with only 1997 warmer.

Relation to climate change
During the last several decades the number of El Niño events increased, although a much longer period of observation is needed to detect robust changes.
The question is, or was, whether this is a random fluctuation or a normal instance of variation for that phenomenon or the result of global climate changes as a result of global warming. A 2014 study reported a robust tendency to more frequent extreme El Niños, occurring in agreement with a separate recent model prediction for the future.
Several studies of historical data suggest the recent El Niño variation is linked to anthropogenic climate change; in accordance with the larger consensus on climate change. For example, even after subtracting the positive influence of decade-to-decade variation (which is shown to be present in the ENSO trend), the amplitude of the ENSO variability in the observed data still increases, by as much as 60% in the last 50 years.
It may be that the observed phenomenon of more frequent and stronger El Niño events occurs only in the initial phase of the climate change, and then (e.g., after the lower layers of the ocean get warmer, as well), El Niño will become weaker than it was. It may also be that the stabilizing and destabilizing forces influencing the phenomenon will eventually compensate for each other. More research is needed to provide a better answer to that question. However, a new 2014 model appearing in a research report indicated unmitigated climate change would particularly affect the surface waters of the eastern equatorial Pacific and possibly double extreme El Niño occurrences.
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