Agenda

Introduction

Fire and Explosion Causes

Fire and Explosion Hazards

Hazards from gases used in welding

OSHA regulations

Control Measures

Protection of personnel

Case study

Welding Hazards Electric Shock

Fumes, Gases

Fire and Explosions

Ergonomic

Radiation

Noise

An explosion is detonated. A fire cannot be detonated. An explosion occurs

after compounds are exposed to heat or shock. A fire is initiated after being

exposed to a heat source only.

Because of how quickly the reaction occurs in an explosion, shock waves

are produced. A fire does not produce shock waves.

Differences between Fire and Explosion:

Similarities between Fire and Explosion:

•Both require oxygen.

•Both create heat and light.

•Both usually will damage the environment in which they occur.

The Fire Triangle Oxidizers

Liquids

Gases

Oxygen, fluorine, chlorine

hydrogen peroxide, nitric acid, perchloric acid

Solids

Metal peroxides, ammonium nitrate

Fuels:

Liquids

gasoline, acetone, ether,

pentane

Solids

plastics, wood dust,

fibers, metal particles

Gases

acetylene, propane,

carbon monoxide,

hydrogen

• Ignition sources

• Sparks, flames, static

electricity, heat

Fire The effect of fire on people is due to exposure to thermal

radiation

The severity of burns depends on heat intensity and

exposure time

The secondary effects of fire can be depletion of oxygen

or generation of toxic fumes.

Explosion Explosions are characterised by a shock wave or pressure

wave

Cause damage to buildings, Equipment and breaking of

windows

Effects of over pressure can directly result in fatality but

only in close vicinity

Causes Flying sparks are the main cause of fires and explosions in welding and

cutting. Sparks can travel up to 35 feet from the work area. Sparks and

molten metal can travel greater distances when falling.

Sparks can pass through or become lodged in cracks, clothing, pipe holes,

and other small openings in floors, walls, or partitions which can cause fires

to start.

Welding and cutting can cause explosions in spaces containing flammable

gases, vapors, liquids, or combustible dusts, and tanks and vessels that

contain or have held flammable substances

.

Hot Work Hazards Combustible Materials are anything that is

combustible or flammable and is susceptible to ignition by cutting and

welding. The most common materials likely to become involved in fire

are

1. Floors, partitions, and roofs

2. Wood, paper, textiles, plastics, chemicals, and flammable liquids and

gases, and dusts.

3. Ground cover such as grass and brush

Fire and Explosion Hazards

Intense heat and sparks can cause fires or explosions if in the vicinity of

combustible or flammable materials

Welding and cutting should only be performed in areas free of combustible

materials such as trash, wood, paper, textiles, plastics, chemicals and flammable

dusts, liquids and gases.

Never weld or cut on containers that have held a flammable or combustible

material unless the container is thoroughly cleaned or filled with an inert gas.

A fire inspection should be performed prior to leaving a work area and for at

least 30 minutes after the operation is completed

Fire extinguishers should be nearby, of proper size,type and number for the

hazards involved.

Fire Hazards with gases used in weldingOxygen:

Oxygen enrichment from leaking equipment

leaks from damaged or poorly maintained hoses, pipes and valves

leaks from poor connections

opening valves deliberately or accidentally

Use of materials not compatible with oxygen

“O” rings and gaskets, Metal components, Pressure regulators

Use of oxygen in equipment not designed for oxygen service Replacing air or inert gas ,inflating vehicle tyres

Incorrect or careless operation of oxygen equipment.

Acetylene:

Decomposition of the acetylene is triggered by heat when it is

1) involved in a fire

2) scorched by flames from a blowtorch

Decomposition can be triggered more easily and proceed more rapidly if

1) the porous mass has been damaged by repeated flashbacks

2) the cylinder has been mishandled or dropped

3) the cylinder valve is leaking

4) the acetylene in the hoses is above the pressure recommended by

the supplier

Argon Helium Gas mixture:

• This gas mixture does not burn; however, cylinders, when involved in a fire,

may rupture or burst in the heat of the fire.

• These are not so sensitive when subjected to mechanical impact

• Fire extinguishing materials- Use extinguishing materials appropriate for

surrounding materials involved in the fire. Water spray should be used to

cool fire-exposed containers.

Occupational Health and Safety Act Regulations Regulation 52: A person conducting a business or undertaking must

manage risks to health and safety associated with ignition sources in a

hazardous atmosphere at the workplace that are not part of a deliberate

workplace process or activity.

Regulation 53: A person conducting a business or undertaking must ensure

that flammable or combustible substances kept at the workplace are kept at

the lowest practicable quantity.

Control MeasuresIsolate fuel sources from ignition sources.

Purge all traces of flammable or combustible materials from drums, vessels

and tanks which are to be welded prior to welding, and preferably fill with an

inert substance such as nitrogen gas or water.

Use fire resistant barriers to prevent welding sparks accidently reaching

flammable and combustible materials.

Check work areas are well ventilated to prevent accumulation of flammable

vapours in the work area.

Check work area is free from rubbish, paper or dust that could be potential

fuel sources or produce dust explosions.

Control Measures(contd.)Use flash back arrestors on gas hoses to prevent the flames travelling back

and igniting the gas in cylinder.

Drain and purge equipment, such as gas hoses, and lock the gas off at the

valve immediately after use.

Do not store flammable and combustible materials near welding area.

Keep and maintain fire fighting equipment near welding area.

Protection of Personnel Eye protection should be used for all welding operations to protect

the eyes from bright light, Fire and explosions

For the best protection, wear face shields, helmets or goggles

Protective clothing which should be worn during welding (by welders and nearby workers) includes:

fire-resistant gauntlet gloves

high-top hard-toed shoes

leather apron

Face shield

flame-retardant coveralls

safety glasses

helmets

leggings or high boots.

Protection of Personnel

•Safety harness should be worn when working on heights

•Keep working surfaces clean and unobstructed

•Safe use of welding equipment

•Personnel need to be aware of surroundings

•Inspection of containers when welding near by containers

•Fire proofing should be there wherever it is required

•Radiations shields protect against heat effect from fire incidents

Case studyPARTRIDGE-RALEIGH SMITH COUNTY OILFIELD

Three contractor workers died and a fourth was seriously

injured.

The explosion occurred when flammable vapor inside two

tanks was ignited by welding activities on a nearby tank.

Welding sparks ignited flammable vapor escaping from an

open-ended pipe about four feet from the contractors’ welding

activity on tank 4.

Case study(contd.) To connect the piping from tank 3 to tank 4, the workers had to weld a pipe

fitting onto the side of, and a few inches below the top of, tank 4.

To prepare for the welding operation, they removed the access hatch at the

base of tank 4 and entered the tank to remove the crude oil residue. Then

they flushed the tank with fresh water and allowed hydrocarbon vapor to

evaporate for several days. They did not clean out or purge tanks 2 and 3.

On the day of the incident, the welder inserted a lit oxy-acetylene welding

torch into the hatch and then into the open nozzle on the opposite side of

tank 4 to verify that all flammable vapor was removed from the tank before

welding began.

The welder was not aware that this act, called “flashing” the tank, was an

unsafe practice.

Reference American Petroleum Institute (API), 2001. API Recommended Practice 74-

Recommended Practice for Occupational Safety for Onshore Oil and Gas

Production Operations, Washington

Welding Hazards Safety Program :Division of Worker’s Compensation

HS04-044A

Fire Precautions for Welding by Kris Bancroft

Health safety and Executive website: http://www.hse.gov.uk/welding/fire-

explosion.htm