Fire Protection Engineering.
Fire engineers assist architects, building owners and developers in evaluating buildings' life safety and property protection goals. Fire protection engineering is a high tech design engineering involving experience and knowhow of chemistry of different industries products and related international codes. Fire Protection Engineering mostly deals on macro level while portable fire extinguishers deals on micro scale. Pakistan, though a large population with more than 200 million people and having industrial base lacks Safety and Fire prevention awareness at public level.
Even our high-rise buildings, commercial plazas and several major industries are poorly equipped with regular fire suppression systems and are mostly dependent on only a few different short range fire extinguishers, resulting in heavy loss of property and human lives in case of fire accidents. Industrial accidents and fire incidents are a routine in most of our industrial cities. Absence of precautionary measures and lack of robust regulatory framework have put the lives of employees in a permanent danger.
Occurrence of these industrial disasters and subsequent loss of human lives is attributed to insufficient safety precautions on the part of factory owners. Since there is a large number of process industries, textile industrial units and others are not well equipped with latest Fire Suppression system thus most of them are dependent on a small number of different fire extinguishers. In some cases, very old systems are installed and they are not workable. 70% of the fire deaths occur at home in Pakistan.
As reported in our local newspapers in 2012, fire incidents kill 16,500 people and leave 164,000 injured or disabled every year across the country causing property losses and insurance claims of worth 400 billion. The metropolises like Islamabad, Rawalpindi, Lahore and Karachi have been witnessing frequent fire incidents. There exists no Fire and Safety Act or Code in Pakistan. Neither is there any clear policy or guidelines to avoid, prepare for or effectively avoid and respond to such emergencies which often lead to a total chaos.
Recently the Pakistan Engineering Council (PEC) has prepared and notified "FIRE SAFETY PROVISIONS 2016", based on the National Fire Protection Association (NFPA) Fire Code 2015 through SRO No 1073 (1) 2016 by the Ministry of Science and Technology (SandT). It has mentioned that the implementation and enforcement of this Bye-law shall vest with the authority having jurisdiction (AHJ) within their respective jurisdictions and circles. It has given names of 12 bodies responsible for implementing this S.R.O.
It is worth mentioning here that most of these bodies lie under provincial jurisdiction and hence these provisions are not applicable in the present status. FIRE the self-sustaining process of rapid oxidation of a fuel which produces heat and light. Fire is an exothermic chemical reaction between Oxygen and fuel at certain temperature. Three things essential for the combustion of fire are:
1. FUEL (Any combustible material)
2. OXYGEN (A concentration above 23%, the situation becomes dangerous due to increased fire hazard)
3. TEMPERATURE CLASSIFICATION OF FIRES
CLASS A FIRE
Fires involving ordinary combustible materials such as paper, wood, rubber plastics and textile fibers where a cooling, blanketing or wetting extinguishing agent is needed.
"A" class fire is extinguished by water. Small fires may be extinguished with sand and clay. Professional fire extinguishers also use water "MIST" or converting water into "FOG" for extinguishing fire by cooling the fuel to a temperature that is below the ignition temp. Water and other extinguishing agents are effective.
CLASS B FIRES
Fires involving flammable liquids such as gasoline, thinners, oil based paints and greases. Flammable liquids (burn at room temperature) and combustible liquids (require heat to ignite).
Petroleum greases, gasoline, thinners, tars, oils, oil-based paints, solvents, lacquers, alcohols, kerosene, diesel, Mobil oil and flammable gases. Extinguishing this type of fire requires Carbon Dioxide, Dry Chemical and Halogenated Types. Foam or Dry Chemical Powdered DCP is used to extinguish this fire. Small fires may be extinguished by clay, sand or CO2 fire Extinguishers:
CLASS C FIRES
Fires involving energized electrical equipment where a non-conducting gaseous clean agent or smothering agent is needed. The most common type of extinguisher for this class is a Carbon Dioxide extinguisher.
DCP, CO2 and Halotron are used for extinguishing electrical fires. Special techniques and agents are required to extinguish most commonly carbon dioxide or dry chemical agents. Use of water is very dangerous because water conducts electricity.
CLASS D FIRES
Fires involving combustible metals such as magnesium, titanium, zirconium, sodium, lithium and potassium Aluminum. Special Dry Powder extinguishing agents are required for this class of fire and must be tailored to specific hazardous metals.
This fire is extinguished using "SAND" or special chemical powders. This fire is never extinguished through water.
CLASS K FIRES
According to the National Fire Protection Association (NFPA), Kitchen Fires are included in "K" Class Fire. Fires involving commercial cooking appliances with vegetable oils, animal oils or fats at higher temperatures. A wet Potassium Acetate, low pH based agent is used for this class of fire.
FIRE DANGER RARINGS
1. BLUE COLOR - Low fire hazard, controlled burning, allowed with care.
2. GREEN COLOR - Medium fire hazard, take extreme care with controlled burning.
3. YELLOW COLOR - Dangerous
4. LIGHT BROWN - Very Dangerous
5. DARK BROWN - Extremely Dangerous.
COMMON CAUSES OF INDUSTRIAL FIRES AND EXPLOSIONS.
1. Combustible dust.
2. Hot work.
3. Flammable liquids and gasses.
4. Equipment and machinery.
5. Electrical hazards.
6. Use of flammable conveyor belts at hot materials transportation.
GENERAL CAUSES OF FIRE
1. Careless cooking
2. Use of Ordinary extension cords
3. Placement of electric heaters and open heaters too close to combustible.
4. Cooking oils left unattended or burning stoves
FIRE EXTINGUISHER is an active fire protection device used to extinguish or control small fires often in emergency situations. It is not intended to use on an out-of-control fire, such as the one which reached the ceiling. Fire extinguishers are further divided into handheld and cart-mounted (also called wheeled extinguishers). Handheld extinguishers weigh from 0.5 to 14 kilograms (1.1 to 30.9 lb.), and are hence, easily portable by hand. Cart-mounted units typically weigh more than 23 kilograms (51 lb.).
These wheeled models are most commonly found at construction sites, airport runways, heliports as well as docks and marinas.
TYPES OF FIRE EXTINGUISHERS
DRY CHEMICAL - extinguishers are either stored-pressure models or cartridge-operated models. The stored-pressure models have a lever above the handle for operation. The cartridge-operated models require two steps: Depress the cartridge lever, and then squeeze the nozzle at the end of the hose. The dry chemicals leave a residue that must be cleaned up after use.
(i) AMMONIUM PHOSPHATE - dry chemical can be used on Class A, B, and C fires, but should never be used on a fire in a commercial grease fryer because of the possibility of reflash and because it will render the fryer's automatic fire-protection system less effective
(ii) SODIUM BICARBONATE - dry chemical, suitable for fighting Class B and C fires, is preferred over other dry-chemical extinguishers for fighting grease fires. Where provided, always use the extinguishing system first. This also shuts off the heat to the appliance.
(iii) POTASSIUM BICARBONATE, UREA-BASE POTASSIUM BICARBONATE, and POTASSIUM CHLORIDE - dry chemical are more effective and use less agent than sodium bicarbonate on the same fire.
2. CARBON DIOXIDE - extinguishers contain pressurized liquid carbon dioxide, which turns to a gas when expelled. These models are rated for use on Class B and C fires, but can be used on a Class A fire. Carbon dioxide does not leave a residue.
3. FOAM or (AFFF and FFFP) EXTINGUISHERS - coat the surface of a burning flammable liquid with a chemical foam. When using a foam extinguisher, blanket the entire surface of Fire
4. PRESSURIZED WATER Extinguishers - are appropriate for use on Class A fires only. These must never be used on electrical or flammable-liquid fires.
5. CLEAN AGENT FIRE EXTINGUISHER: Gaseous fire suppression is a term to describe the use of inert gases and chemical agents to extinguish a fire. Also called Clean Agent Fire Suppression.
6. WET CHEMICAL FIRE EXTINGUISHER: Wet chemical fire extinguishers are essential for tackling cooking oil fires and fat fires. Unlike other fire extinguishers, wet chemical extinguishers react with the oil to create a cooling film on the surface which will extinguish the fire.
TYPES OF COLORS OF FIRE EXTINGUISHERS
1. Dry Chemical Powder. DCP. RED and BLUE
2. Foam-RED and CREAM
3. Carbon Dioxide CO2. RED and BLACK
4. Halotron. RED and GREEN
STAGES OF FIRE
There are four stages of fire (Combustion).
Stage 1. INCIPIENT.IGNITION: Initial stage Fuel, oxygen and heat join together in a sustained chemical reaction. At this stage, a fire extinguisher can control the fire.
Stage 2. SMOLDERING.burns slowly with smoke but no flame.
Stage 3. VISIBLE FLAMES. GROWTH: With the initial flame as a heat source, additional fuel ignites. Convection and radiation ignite more surfaces. The size of the fire increases and the plume reaches the ceiling. Hot gases collecting at the ceiling transfer heat, allowing all fuels in a room to come closer to their ignition temperature at the same time.
Stage 4. INTENSE HEAT. FULLY DEVELOPED: Fire has spread over much if not all the available fuel; temperatures reach their peak, resulting in heat damage. Oxygen is consumed rapidly.
DECAY (Burnout): The fire consumes available fuel, temperatures decrease, fire gets less intense. The length of time a fire remains in each stage depends on the class of fire and properties of available fuels.e.g In a Class A fires 1 and 2 stages are of relatively long duration. It takes several minutes, hours or days for the fire to reach STAGE 2 and 3.
For Class B Fires, stages 1 and 2 are extremely short. The fire enters Stage 3 almost immediately and rapid progresses to stage
4. PRINCIPLES OF FIRE EXTINCTION STARVATION
Removal of unburnt material from fire area.
Cut off the supply of Oxygen from the area.
Removal of heat from burning the material from fire area.
Removal of fuel
BREACHING OF CHAIN REACTION
Extinguishing mechanism of multipurpose mono ammonium phosphate dry chemical
COLOR OF FIRE SMOKES
1. Hydrocarbons, Rubber, Oil fires -BLACK / ORANGE/NARANGI
2. Metals Fires REDDISH/SURKH
3. Wood, Cloth, Gatta, Jute-LIGHT BLUE
5. Common Fire-Yolk/Zardi
Usually smoke is 18 inches above the earth
SMOKE COLOR: Smoke Color can depict fuel type. Thick black smoke indicates heavy fuels that are not being fully consumed. At times, black smoke can be an indicator that a man made material is burning such as Tires, Vehicles .As a general rule, the darker the smoke, the more volatile the fire is.
COLOR SMOKE WHEN A FIRE IS PUT OFF
White smoke is mostly moisture. As a material dries out and breaks down, the color of the smoke changes. Wood material changes to TAN, or BROWN whereas PLASTICS and painted /sustained surfaces emit a gray smoke as a result of mixing of moisture (White) and Carbons/Hydrocarbons BLACK. Fire can be controlled or extinguished, either manually (firefighting) or automatically.
Manual control includes the use of a fire extinguisher or a standpipe system. Automatic control means can include a fire sprinkler system, a gaseous clean agent, or firefighting foam system. Automatic suppression systems would usually be found in large commercial kitchens or other high-risk areas. Fire sprinkler systems are installed in all types of buildings, commercial and residential. They are usually located at ceiling level and are connected to a reliable water source, most commonly city water.
A typical sprinkler system operates when heat at the site of a fire causes a glass component in the sprinkler head to fail, thereby releasing the water from the sprinkler head. This means that only the sprinkler head at the fire location operates - not all the sprinklers on a floor or in a building. Sprinkler systems help to reduce the growth of a fire, thereby increasing life safety and limiting structural damage. (The writer is a senior plant engineer and trainer)
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|Publication:||Pakistan Engineering Review|
|Date:||Sep 22, 2017|
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