Fir Eek

FIRE AND EXPLOSION HAZARDS AND PROTECTION Michael Liu Dominic Malicsi Mark Mariano Mary Irene Pollicar

FIRE - combustion process - Chemical reaction between fuel, oxygen, and ignition sources - Rapid pressure rise results to explosion

Fire Triangle • illustrates the three elements needed to ignite and burn • Removing one of the elements will extinguish fire

Fire Tetrahedron • Chain or chemical reaction is needed to sustain fire • Water cannot stop fires involving metals due to its role in metal combustion (class-D fires)

FUEL - Hydrocarbons in gaseous state • alkane, alkene, alkyne • influence state of matter, vapor pressure, vapor density, flash point, and boiling point • Flammability is affected by halogens

- Flash point – minimum temperature for flammable liquid to ignite

Example: Presence of Halogen COMPO UND

FLAM MA BIL IT Y

Methane (CH4)

Highly Flammable

Chloromethane (CH3Cl) Dichloromethane (CH2Cl2) Chloroform (CHCl3)

Flammable

Carbon Tetrachloride (CCl4)

Fire Extinguisher

Less Flammable Not Flammable

NPFA Flammable and Combustible Liquid Classifications

CLASS

DEFINIT ION

Flammable IA

Flash Point < 73°F, Boiling Point < 100°F Flash Point < 73°F, Boiling Point >= 100°F 73°F < Flash Point < 100°F 100°F < Flash Point < 140°F 140°F < Flash Point < 200°F Flash Point >= 200°F

Flammable IB Flammable IC Combustible II Combustible IIIA Combustible IIIB

FLAMMABLE LIMITS - Maximum gas or vapor in air w/o occurring FLAME PROPAGATION - Upper and Lower Flammable Limits (UFL, LFL)

FLAMMABLE PROPAGATION - Reproduction of flames - Vapor-oxygen ratio - Mixture above UFL produce explosion - Mixture below LFL produce no ignition - Inert gases, Carbon Dioxide and Steam can stop fire

IGNITON SOURCES -

Electric Sparks Smoking and Matches Frictional Heat Hot Surfaces Overheated Materials Open Flames Spontaneous Heating Welding and Cutting Combustion Particles

NFPA 704 SYSTEM FOR HAZARD IDENTIFICATION

Red Flammability 0-4 Yellow Reactivity 0-4

Blue Health 0-4 White Special 0-4

EXPLOSIVE HAZARDS • Rapid oxidation • Causes structural damage • Size of the vessel does not affect the magnitude

FLAMMABLE VAPOR CLOUDS • Results from release flammable liquid • Flammability region depends on the vapor release state • Occurs due to leaking gasliquids pipelines

DUST EXPLOSION • Solid particles ≤ 10μm • If combustible, flammable dustair is formed • Enormous energy release • Moisture can prevent ignition

Spontaneous Combustion • Chemical process of oxidation – an exothermic reaction, where considerable heat is generated. • Examples: burning of flammable & combustible fuels.

Spontaneous Combustion • Ignition happens when.. heat generation rate > the heat removal rate

Products of Combustion • 4 Types of products of Combustion: 1. 2. 3. 4.

Flame Heat Fire gases Smoke

Products of Combustion Usually produced in fire: • Carbon dioxide • Carbon Monoxide

Products of Combustion • Water • Smoke

Products of Combustion • Hazardous fire gasses may include: • • • • • •

Sulfur dioxide Nitrogen dioxide Hydrogen chloride Hydrogen sulfide Hydrogen cyanide ammonia

Fundamentals of Fire Prevention • The first principle of fire control is to prevent the formulation of a fuel-air mixture that is within the appropriate flammable limits. • Effective fire prevention must consider all possible potential fire causes and provide design & operating features to reduce

Fundamentals of Fire Prevention • Large industrial fires often begin with an explosion. • In fire prevention at facilities that process large quantities of flammable materials, a great deal of emphasis should be placed on preventing explosions, thereby preventing a resultant fire.

Fundamentals of Fire Prevention • An explosion produces an outward pressure waves. • The damage effects are influenced by the peak overpressures, measured in pounds per square inch gauge.

Fundamentals of Fire Prevention • Detonations usually involve unstable or highly reactive materials. The pressure wave from a detonation is much higher, ranging up to 50,000 atm or more.

Fundamentals of Fire Prevention • Disastrous results of detonation can be minimized by carefully controlling and limiting the quantities of the unstable materials involved.

System Design and Layout • Once a fire is initiated it may spread through a combination of factors such as heat transfer, direct burning and the release of flammable vapor or liquid may contribute to spreading. • Proper selection of construction materials can reduce the damage from an industrial fire

System Design and Layout

• If combustibles are avoided as construction materials, less fuel is available to sustain fire. • Fire resistant materials of construction provide additional time to control and extinguish the fire. • Commonly used in many critical construction applications. ex: control rooms, enclosed exit stairways, walls and barriers that separate hazardous storage and process areas

System Design and Layout • Water. A reliable water supply and piping distribution system must be capable of delivering water to the fire protection equipment and system.

FIRE DETECTION AND CONTROL • Early detection • Must be planned for • Minimize injury and property damage • Detection through fastest and most reliable means

• Isolate equipment / processes that are hazards • Proper location of detectors (arrangement, distance limitations, point of origin, air movement pattern)

TYPES OF FIRE DETECTORS • Smoke detectors – concentration • Heat detectors – temperature • Flame detectors – light spectrum • Fire gas detector - combustion

FIRE DETECTION AND ALARM DEVICES • Horns and bells • Light • Control system

STORAGE TANKS • Vapor reduction is the best fire safety technique • Potential for flammable emissions is reduced • Nitrogen as an insulation and vapor space

TYPES OF STORAGE TANKS • Standard cone roof tank • Floating roof tank – eliminates large vapor space that is present • Floating diaphragm tank

• Best is Floating roof tank • Disadvantage is potential leaks around seal • Therefore higher maintenance

FIRE EXTINGUISHMENT • Water is most preferred fire extinguisher • Smaller water particles has better heat absorption (more water per volume) • Water spray / steam

TECHNICAL SPECS • Water supply for a minimum of 4 hrs • Water line made of cast iron steel pipe with 175 – 225 psig cold pressure design • Centrifugal pumps – constant pressure and flow rate

DISADVANTAGE OF WATER • Damage products, materials, equipments • Electrical conductivity

CARBON DIOXIDE • Dilute air-vapor mixture below flammable limit • Stored in cylinders • Lasts for years • Minimal maintenance • Local application or total flooding

DISADVANTAGE OF CO2 • • • •

May cause freezing Ineffective for class A fires Class B fires flashback Effective only in contained areas • Loss of consciousness / possible death when air concentration reaches 35%

ADVANTAGES OF CO2 • Will not conduct electricity • Will not harm sensitive electrical equipments • Vaporizes w/o residue

DRY CHEMICALS • • • •

Sodium Bicarbonate Potassium Bicarbonate Potassium Oxalate Discharges by compressed CO2 or N2 • Most effective for electrical hazards • Leaves no residue

FOAMS • Effective extinguishing agent for flammable liquids • Contains closed cell bubbles that creates a barrier to separate flammable liquid from air • Prevents flammable vapors to meet with fire

EMERGENCY PROTECTION SYSTEM • Fuel, oxygen, ignition source and chain reaction • Eliminate one or more • Fire plugs strategically located • Looped main water line 4 in diameter

• • • •

500 gal/min at 125 psig Min 4 hrs water supply Min 150 gal liquid foam supply Polyester hose instead of cotton hose • Fire truck hoses must be compatible with fire plugs of facility • Portable handheld fire extinguishers

Fire Class • Class A - SOLIDS such as paper, wood, plastic etc • Class B - FLAMMABLE LIQUIDS and GASES such as paraffin, petrol, oil etc • Class C - energized ELECTRICAL EQUIPMENT, such as appliances, switches, panel boxes, power tools, and stirrers.

Fire Class • Class D - METALS such as aluminium, magnesium, titanium etc • Class K - also known as Kitchen Fire - kitchen oil

Types of fire Extinguishers •

Water – for Class A only

• •

CO2 – effective Class B and C Dry Chemical (3 types)

• •

• • •

Regular - effective on Class B and C ABC - effective on Class A, B, and C Purple K - effective on Class B and C

Combustible Metal – for Class D Wet Chemical – for Class K