Woodland Hills CA - Hottest spot in Los Angeles City Limits
Re: Propane Fueled Disneyland Shuttle Explodes
Well, under the drivers' feet would be where they mount the Propane Vaporizer unit - the underhood space on these vehicles is at a premium, they would put it under the floor. The Vaporizer has lots of hoses and fittings and gaskets, places to spring a leak.
They just got it back from service - Anyone want to bet the mechanic left one of the hose fittings loose? And didn't double-check...
The Vaporizer takes coolant from the engine for a heat source, and heats the liquid Propane from the fuel tank so it goes from liquid into vapor faster. If they try drawing Propane as a vapor straight from the tank, the tank would ice over and the propane would stop flowing, especially in freezing weather - the Propane gets cold when it vaporizes, and the vapor pressure in the tank drops to near nothing as you get below appx. 30-F to 40-F. (Depending on the ratio of Propane to Butane and other trace gases like Methane.)
Go feel your barbecue Propane bottle get cold while in use, and the shuttle bus is using fuel 10X to 20X faster.
(And yes, one of the "Alternative Refrigerants" you can use for your car AC system is a blend of mostly Propane. Needless to say, the Fire Department doesn't think that's such a good idea for the obvious reason.)
Good thing is, the leak caught fire slowly. The driver had time to pull over and stop safely, and get out. Passengers on board would have only added another 30 seconds to the 'Time to get out' schedule.
The fire spreading back to the vehicle's Propane tank would have taken lots of time, and most likely it's just the pressure relief valve popping off from the fire heat. Once that valve gets cooked it won't seat closed tight again (the gasket melts), and you have to wait for all the gas to vent and burn off in a controlled manner.
And if a liquid Propane hose bursts under the vehicle, they have check valves at the tank that snap closed to choke off the majority of the gas - a trickle still gets out, but that's to automatically reset the check valve if it was an accidental trigger. (It happens.)
Underwriters Laboratories can't prevent fires - but they can insist on designed in safety features so that the fire stays small and controlled. (We deal with this every day in Electrical systems.)
Yikes. Now I'm getting nervous about my upcoming visit! I understand these explosions area rare..but- wow.
Can anyone help me understand the ART system? I saw the shuttle map on their website, and understand which route I would be on (route 6). I'm staying at the Doubletree. But the map doesn't say *when* it will pickup at my location, or how many hotels stops are left until we arrive at Disneyland.
Good lord, that's terrifying! I'm amazed the driver was able to get out safely.
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