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Gas Explosions

Gas Explosions. Ireland Chapter IAAI By Jamie Novak Saint Paul Fire and Safety services Novak Investigations. Properties of natural and Propane gas. Natural gas LEL lower explosion limit 5%-45,000pp Natural gas UEL upper explosion limit 15%100,000ppm Propane gas LEL 2.15% 22,500 ppm

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Gas Explosions

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  1. Gas Explosions Ireland Chapter IAAI By Jamie Novak Saint Paul Fire and Safety services Novak Investigations

  2. Properties of natural and Propane gas • Natural gas LEL lower explosion limit 5%-45,000pp • Natural gas UEL upper explosion limit 15%100,000ppm • Propane gas LEL 2.15% 22,500 ppm • Propane gas UEL 9.60% 95,000 ppm • Vapor density -Natural gas 0.6 -Propane 1.5 • Ignition Temp Natural gas –900-1170 Propane-920-1120 • Heating Value –BTU/FT3-Nat-1000 Propane-2488

  3. Odorant • Mercaptans are generally used to odorize fuel gases • Natural and propane are to be odorized so they can be detected at 20% of the lower explosive limit. • 1.4 lbs per 10,000gallons

  4. Odorant • Since ethyl mercaptan does not vaporize as readily as propane, the concentration of odorant in a propane tank may increase as the tank is depleted . Consequently , the potential for insufficient odorant in the vapor may be higher when the tank is full.

  5. Explosive force • Explosive force is dependant on the concentration of the gas in air. • Most violent explosions occur at approximately twice the LEL where there is enough air for complete combustion. This concentration is called the Stochiometric concentration. • Nat. gas- 10% Propane – 4%

  6. Odorant detecting Factors • Age,Health-colds, allergies • Competing odors • Some people cannot detect the odorant • People sleeping nose shuts off when sleeping • Odorant fade-new steel piping or steel tanks can absorb odorant! • Soil can absorb odorant!

  7. Gas Fire/Explosion Investigations Important considerations and guidelines to follow

  8. Conditions leading to Fire/explosion • What happened? • Was anyone home and what where they doing? Should always try to interview victims some die later! • Any gas or appliance work done lately? • Any gas valves turned off or on? • Was someone trying to light an appliance? • Gas service disconnected or reconnected? • Any appliances running or any problems? • Anyone smell gas?

  9. Conditions leading to Fire/explosion • Last time tank filled? Anyone home? • Was tank out of gas? • Did gas company light pilots or check for leaks? • What was weather like? Rain, snow, melting freezing temps, Flooding? • If cylinders ,location and when last filled?

  10. Scene Examination • Walk entire scene • Follow entire gas system, source,piping, appliances,etc. • Look at all gas valves and connections used and unused. • Examine all appliances and note position of controls. • Measure , sketch, photograph all equipment, piping before moving or testing. • Photograph everything!!!!!!!!

  11. Examine Gas System • Start at gas meter or tank, then regulators etc. • Note connections, valves, piping. • Document all manufacturers, model , serial numbers. • Look for breaks, holes, tears, etc. • Check system for leaks before disturbing. • Test should be at normal working pressure or less! Anymore can cause new leaks! • Remember spoliation, might want to inform all potential parties before conducting any tests!

  12. Special Propane Considerations • Was this an out of service call? • If tank empty gas company is suppose to check entire system for leaks. • Including appliances , lines and valves. Gas company also to relight pilots for homeowner.

  13. MYTHS ABOUT GAS EXPLOSIONS • Propane explosions blow walls out at the bottom and natural gas blows out at the top! • Propane exlosions are more destructive than natural gas explosions! • Natural gas explosion presssures and flame fronts are as not as high or as fast as propane.

  14. Explosion Investigations

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