Fire & explosion hazards in welding -Safety

Fire and Explosion Hazards in welding and safety measures to be taken are discussed..

1. Fire & Explosions in welding-Safety

2. 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

3. Welding Hazards Electric Shock Fumes, Gases Fire and Explosions Ergonomic Radiation Noise

4. 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.

5. The Fire Triangle Oxidizers Liquids Gases Oxygen, fluorine, chlorine hydrogen peroxide, nitric acid, perchloric acid Solids Metal peroxides, ammonium nitrate AIR ( OXYGEN ) FUEL IGNITION SOURCE 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

6. 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.

7. 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

8. 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 .

9. 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  

10. 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 .

11. Fire Hazards with gases used in welding Oxygen: 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.

12. Acetylene: Decomposition of the acetylene is triggered by heat when it is involved in a fire scorched by flames from a blowtorch Decomposition can be triggered more easily and proceed more rapidly if the porous mass has been damaged by repeated flashbacks the cylinder has been mishandled or dropped the cylinder valve is leaking the acetylene in the hoses is above the pressure recommended by the supplier

13. 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.

14. 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.

15. Control Measures Isolate 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.

16. 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.

17. 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.

18. 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

19. Case study PARTRIDGE-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.

20. 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.

21. 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