Water extinguishers are among the most commonly used. They are excellent for heat removal on Class A fires. Extreme caution should be exercised when using a water extinguisher to ensure that the water, which is under extreme pressure, does not scatter lightweight materials and spread the fire.
Common characteristics for water fire extinguishers are:
Capacity. Standard size is 2 gallons.
Range. 30-40 feet.
Pressure. 110 pounds per square inch (psi).
Dry Chemical Extinguishers
Dry chemical extinguishers are also commonly used. Regular dry chemical extinguishers have a sodium bicarbonate base and are effective on Class B and C fires. Multipurpose dry chemical extinguishers have a monoammonium phosphate base and are effective for Class A, B, and C fires. Both types of dry chemical extinguishers are nontoxic. Both should be inverted monthly to prevent caking. Common characteristics for dry chemical extinguishers are:
Capacity. Approximately 10-20 seconds discharge time.
Range. 8-12 feet.
Pressure. 175-250 psi.
Other Types Of Extinguishers
Although still in use, carbon dioxide, halon, and foam extinguishers are becoming less common.
Carbon Dioxide Extinguishers are used primarily on Class C fires and are also effective on Class B fires. They have limited use on Class A fires because of reflash potential. They suppress fire by displacing or diluting oxygen levels.
Halon Extinguishers are best used on Class B or C fires. Halon is a clean agent and is nontoxic when used in low concentrations or in non-confined areas. However, halon extinguishers are being phased out because of potential impact on the environment.
Foam Extinguishers are used for special applications and are less common.
Operating A Fire Extinguisher
A portable fire extinguisher includes the following components:
Pressure gauge
Hose
Cylinder
Carrying handle and trigger
These components are shown in the figure below.
Always operate extinguishers in an upright position. As shown in the figure below, the acronym to remember when operating a portable extinguisher is P.A.S.S.:
Pull, Aim, Squeeze, Sweep. Aim at the base of the fire.
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Steam smothering
The use of steam smothering in the hydrocarbon industries is typically limited to fires that might occur as a result of a tube leak in furnace or heater. The steam is most effective in smothering fires when they are located in relatively small confined areas. Steam extinguishes fire by the exclusion of free air and the reduction of available oxygen content to the immediate area, similar to other gaseous suppression agents. Use of snuffing steam requires some knowledge in the principle of fire smothering and readily available supplies of steam generation. Snuffing steam also presents a personal burn hazard from superheated water vapour exposure if directed onto or near unprotected skin. Use of other fire extinguishing agents is generally preferred over the use of snuffing steam.
Foamwater Suppression System
Foamwater systems are provided wherever there are large quantities of liquid hydrocarbons that pose a high fire risk. Foam is an aggregate of water, chemical compounds and air filled bubbles that float on the surface of combustible liquids. They are used primarily to provide a cohesive floating blanket on the liquid surface of the liquid material it is protecting. It extinguishes a fire by smothering and cooling the fuel, i.e., liquid surface, and prevents re-ignition by preventing the information of combustible mixtures of vapour and air over the liquid surface. Foam will also cool the fuel and surrounding equipment involved in the fire. Foams are supplied in concentrates that are appropriately proportioned into water supply systems. They are then aspirated with air to produce the foam bubbles.
Gaseous systems
Carbon Dioxide Systems
Carbon Dioxide (CO2) is a non-combustible gas that can penetrate and spread to all parts of a fire, diluting the available oxygen to a concentration that will not support combustion. CO2 systems will extinguish fires in practically all combustibles except those which have their own oxygen supply and certain metals that cause decomposition of the carbon dioxide, CO2 does not conduct electricity and can be used on energized electrical equipment. It will not freeze or deteriorate with age. Carbon dioxide is a dangerous gas to human life since it displaces oxygen. Concentrations above 9 percent are considered hazardous, while 30 percent or more are needed for fire extinguishing system. Carbon dioxide systems are generally ineffective in outdoor applications since wind effects and dissipate the vapors rapidly. It has a vapor density of 1.529 and therefore will settle to low points of an enclosure.
For fire extinguishment or inserting purposes CO2 is stored in liquid form that provides for its own pressurized discharge.
Disadvantages
CO2 systems have the following disadvantages:
The expelled CO2 gas presents a suffocation hazard to Humans in the exposed area. All such areas would require strict access control.
CO2 gas is considered a 'greenhouse' gas and may in the future be considered an environmental concern.
Fixed CO2 systems require a large storage area and have considerable weight which limits their benefit offshore.
Deep seated fires may not be fully extinguished by a gaseous fire suppressant agent.
Oxygen Deficient Gas Inerting Systems
To reduce the risk of explosion and fires from enclosed spaces of volatile hydrocarbon storage tanks, a gas with that would be considered deficient in oxygen is provided to exclude oxygen from entering the enclosure. Large ocean going tanker vessels are equipped with a continuous inert gas system that blankets storage holds or tanks with an oxygen deficient gas (combustion exhaust gases from the prime mover). Similarly some crude oil storage tanks are provided with a processed gas as a method of excluding oxygen from entering the vapour space of some roof storage tanks.
Halon
Halon is a halogenated compound that contains elements from the halogen series - fluorine, chlorine, bromine and iodine. Halogen atoms from non-combustible gases when they replace the hydrogen atoms in hydrocarbon compounds such a methane or ethane. Except for Halon 1310, bromotrifluoromethane, most halogenated hydrocarbon compounds are corrosive when moisture is present. Halon will also break into corrosive and toxic by products in the presence of a sustained electrical arc.
Halon systems were the ideal fire suppression agent before their implications of environmental impact due to ozone depletion. The industry is gradually phasing out usage of halon systems for this reason. A flowchart to analyze mechanism to supplement or eliminate Halon systems for electrical or computer processing areas. Some of the prime reasons to eliminate the use of Halon system is that the facility may be constantly manned with a relatively low fire risk. Other facilities may have a very low combustible load and can be supplemented by highly sensitive fire detection means, such as a VESDA fire detection system.
Fixed fire protection system
Some of the fixed fire protection systems can suppress the fire and to resisting the fire spread.
Dry Risers
Dry risers, so called because they contain no water in the pipes, are installed within a building and provided with a landing valve in the staircase lobby. The riser terminates at the street level in the form of a fire brigade connection.
The connection enables the fire-brigade to connect the fire-brigade connection either to a street fire-hydrant directly or to a fire-brigade pumper and charge the dry riser with water. The water can then be drawn off at any floor above from the landing valve. Dry risers help to eliminate the long run of hose lines through the building stairways. It also eliminates the danger operation of freezing the standing water in the dry riser.
Wet Risers
Wet risers are fixed pipe-installations, installed within a building and permanently charged with water under pressure from a reliable water supply source.
Hydrant stations are provided to serve an area of 926 sqm. It is advisable to place it in fire protected areas near each fire escape staircase or lobby so that it can be located easily.
Each hydrant station comprises:
A first-aid hose reel with 20mm diameter rubber-hose about 30-36 m long with a 6 mm diameter nozzle.
Single or double headed 63 mm diameter landing valve
Using non-flammable materials or fire-stopping materials as the building's element to control the fire spread, it can provide enough time to let the residents run away when fire occur. Besides that, it also provides enough time for fire department reach the place of fire within the period. Install fire door is an example usually we find inside the building. Extra, windows can also be chosen to be protected by fire-rated shutters that close automatically at high temperatures.
Fire doors
Doors which are fire-resisting and self-closing are usually referred to as 'fire doors'. Fire doors are a vital part of a fire defence system as their purpose is to hold back fire and smoke.
They are normally provided to carry out one of two functions:
to protect the integrity of a structural fire compartment by holding back fire and smoke
to protect the means of escape for the occupiers of the building for a sufficient period of time for them to escape from the building.
Fire doors can give fire protection for periods ranging from 30 minutes to 4 hours.
At last, we need use non-combustible materials in concealed spaces inside a building, such as the spaces over suspended ceilings, under raised floors, within pipe service ducts, etc. Besides that, can also install automatic fire detection and suppression systems in these uninhabited spaces to deprived oxygen, replace it using another gas (carbon dioxide, halon) or cover by the fuel (foam, dry chemicals). Compartmentation also is a method to break up the continous of a fire spread.
Fire Suppression System
Typical Application
Portable Extinguishers
Offices
Warehouses
Switchgear
All plant areas
Hydrants (if fire brigade available)
All process and utility areas
Hydrocarbon storage areas
Warehouses
Offices
Hose Reels
Process areas
Warehouses
Offices
Accommodations
Firewater monitor
Process areas
Hydrocarbon storage areas
Hydrocarbon loading areas
Wet pipe sprinklers
Offices
Accommodations
Warehouses
Dry chemical systems
Kitchens
Loading or unloading racks (mostly when water system is uneconomical or unavailable)
Dual agent systems
Aircraft operations
(fixed wing and rotary)
Dry pipe sprinklers
Warehouses
Critical cable vaults
Cooling towers
Water spray or deluge
Process vessel cooling
General area coverage
Pumps
Critical or high value transformers
Foamwater deluge and monitors
Hydrocarbon spill potentials
Truck and rail racks (loading and unloading)
Ship docks
Pump stations
CO2 systems
Electrical switchgear facilities
Gas turbine enclosure
Communication panels or racks
Halon Substitutes
Critical computer assets or operations
