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Metro CNG bus PRD's release in South Los Angeles

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  • Metro CNG bus PRD's release in South Los Angeles

    Metro bus in South LA was T-boned by a BMW and the resulting fire resulted in the roof tank pressure relief devices (PRD's) operating as designed. The gas release was described by witnesses in a TV news spot - link not available - as "an explosion." News story found here:

    http://abc7news.com/news/good-samari...-car-/1267526/
    .

  • #2
    Maybe the linked article is not complete but it doesn't suggest any CNG leak or involvement.

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    • #3
      Witness video posted of the early evening March 28 2016 crash at intersection of South Western Ave and Martin Luther King Jr Blvd in South Los Angeles:

      http://www.autoblog.com/2016/03/29/g...n-los-angeles/
      .

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      • #4
        After streaming the video, I now see the journalist at the scene said "explosions" and, in fact, two bursts are heard in the last 5 seconds of the clip. Quite a hot fire, too. Safety systems all seem to have worked fine. Don't know if there is anything to be learned here. But none of the reporters led on show they even knew what fuel was burning . .
        .

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        • #5
          News article was updated to say the bus was not carrying passengers at the time. Article also states something which probably was not factually correct about the bus CNG tanks - because bystanders were not burned and windows were not broken in the area:

          The victims were pulled from the burning car before a natural gas tank on the Metro bus exploded, shooting flames into the air.

          http://abc7ny.com/news/dramatic-resc...o-bus/1267590/
          .

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          • #6
            Other examples of CNG transit buses safely releasing fuel during a fire surfaced while checking as to when Sun Metro of El Paso TX plans to open (answer, not likely) the public CNG portion of the $1.5M CNG station they opened in Jan 2015 of which half of the funding was from a public Federal Transit Administration grant.

            It is evident in this first clip of an April 2013 Sun Metro CNG bus fire that the photographer was holding the camera very steady until the tank pressure relief device (PRD) released. The numbing, ear shattering noise then caused him to run to a safer distance before regaining control of the camera. The noise release must have made things uncomfortable for the fire crews, unless they had prepared by putting in ear plugs:

            https://www.youtube.com/watch?v=78fxV71GsTA


            This next clip from 2012 was made in a foreign country given the foreign language heard toward the end. An instructive comment was included with the video - Tank is functioning as designed. This prevents an explosion. All CNG vehicles have a vent for the fuel. The vent runs sideways because it could potentially clog (gravity) and cause an explosion. Most Ive seen point to the side and slightly downward actually. This is why for firefighting purposes you approach at a 45 degree angle to a CNG vehicle. Standard protocol and, while, it shot a nice flame out the side and anything in its path would be burned, this was the safest scenario imaginable. A gasoline tank just explodes immediately with no warning. CNG tank fires are really pretty predictable and extremely rare. And the other commenter is correct. BLEVE doesnt apply CNG is a gas, not a liquid. If the tank were filled with propane, that could result in a BLEVE situation because its liquefied.

            https://www.youtube.com/watch?v=BPllyKsN3C4


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            • #7
              CNG bus T-boned by a pickup truck this time. No gas release. No fire:

              http://kval.com/news/nation-world/tr...ic-transit-bus
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              • #8
                The CNG tanks are probably under that white cover on top of the bus, in which case, they were untouched.

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                • #9
                  CTIF 10 Mar 2019 - CNG propelled bus exploded in central Stockholm

                  A city bus propelled by natural gas has exploded and started burning in central Stockholm. Photos and videos show a massive fire ball with flames reaching 40 to 50 meters tall. According to Swedish media, 20 % of all public buses in the country now run on some form of natural or bio gas.

                  "The incident involves a CNG bus that has hit the top of the Klara Tunnel and subsequently exploded", says Björn Westerdahl, communicator at the Greater Stockholm Regional Fire Department. Keolis Sweden, the company operating the buses, recently equipped their fleet with MAN Lion’s City Articulated Buses fueled by CNG.

                  A spectacular eye witness video in Swedish media - filmed by a dash cam from a vehicle driving right behind the bus - shows a rapid fire development, almost like a detonation, when the bus hits something in the ceiling of the tunnel. The gas bottles hit an obstruction and were damaged. According to the police, the bus has probably hit the pontoons which hang down as height indication warnings in the opening of the tunnel.

                  No passengers were on the bus, but the driver was injured. The bus company Keolis announced that the driver was taken to hospital in an ambulance with only light facial burns.

                  Patrik Åberg at Keolis says that the buses are not allowed to be driven through the tunnels. "They must never go that way because the buses are too tall. The driver went the wrong way and entered the barrier before the tunnel", said Patrik Åberg at Keolis to Aftonbladet.se.

                  https://www.ctif.org/index.php/news/...reason-unknown
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                  • #10
                    CTIF 6 Dec 2018 - CNG accident discharge with no fire in Holland

                    An incident in the Franeker region of the Netherlands on December 6, 2018 involved a transit bus where the bio gas tanks caught the top of a road tunnel and were torn off the vehicle, landing on the street. The gas bottles started leaking heavily, but there was no explosion or fire. The accident occurred around half past eight and by ten o'clock, gas was still leaking from one bottle.

                    There were no injuries in the incident in the Netherlands incident. In this accident there was no explosion, because the tanks were not damaged. Only the vents of the fuel bottles were damaged, and by the time the fire services had arrived, almost all of the gas had escaped. Luckily, there was no source of ignition nearby, and the gas was diluted with fresh air and reached inflammable mixture before any ignition could occur.

                    https://www.ctif.org/index.php/news/...reason-unknown
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