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    Default gasoline tankers explosions???

    I'm confused. From what I've been taught and reading what explosions are, I didn't think that a MC306 could explode. I thought to have an explosion you would have to have a pressurized container and the results of an explosion would be a pressure/shock wave and pieces of the container being expelled. There have been several 306 tankers on fire in the Dallas area and the news and civilians all report that there was an explosion. I think that they are getting confused with a large amout of fuel lighting off and having the "Woosh" factor they are hearing. Someone please shed some light on this issue.

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    Quote Originally Posted by hotjob View Post
    I'm confused. From what I've been taught and reading what explosions are, I didn't think that a MC306 could explode. I thought to have an explosion you would have to have a pressurized container and the results of an explosion would be a pressure/shock wave and pieces of the container being expelled. There have been several 306 tankers on fire in the Dallas area and the news and civilians all report that there was an explosion. I think that they are getting confused with a large amout of fuel lighting off and having the "Woosh" factor they are hearing. Someone please shed some light on this issue.
    I think you are absolutely correct. The EXPLOSION comments are from the inept reporters in the media. Notice that nearly every story today is BREAKING NEWS...to get the viewers attention. Most reporters/commentators and eye witnesses are not experts...especially with the FACTS, therefore the stories get somewhat twisted as to what REALLY happened.

    I think the woosh factor comes from the rapid ignition of the flammable liquid, like when we used to pour petro on a pile of brush to get it started fast, or when some moron pours too much starter on the barbie.
    Last edited by TFMBob; 11-18-2007 at 10:30 PM.
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    Quote Originally Posted by hotjob View Post
    I'm confused. From what I've been taught and reading what explosions are, I didn't think that a MC306 could explode.
    There's no inherent reason why an MC306/406 tank can't "explode" from simple internal ignition of a flammable mixture or from an externally induced BLEVE just like any other closed containter. I'm not sure why someone would try to teach anyone otherwise.

    Quote Originally Posted by hotjob View Post
    I thought to have an explosion you would have to have a pressurized container...
    Maybe this is what's confusing the issue. MC306/406 tanks are nominally "atmospheric tanks" in normal use. That's doesn't mean that they can't develop explosive pressures when conditions aren't "normal."

    Remember, any closed container with any flammable/combustible liquid in it is subject to explosion under the right conditions. For a BLEVE to occur, the liquid doesn't even have to be combustible. (i.e. even a tank containing just water can BLEVE)

    All that being said, I have no doubts that many media reports of "explosions" are questionable. Just don't think for a moment that an MC306/406 tank can't explode.
    "Nemo Plus Voluptatis Quam Nos Habant"

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    Deputy Marshal makes a good point. An empty or partially full compartment could be the explosive trigger due to a better chance of having a vapor to air ratio in the explosive range.

    The Air Force used to use 2500 and 5000 gal fuel trailers for props in the live fire training areas. These were the same type trailers used for road transport but they were built in the 1950s and were all steel construction. The fuels shop purged and cleaned the inside of the tanks before we got them.

    We had a ‘Fire Protection Engineer” design the piping for fuel delivery to the mock up. It consisted of 500’ of black iron pipe from the storage tanks to a manifold at the trailer. The manifold fed individually controlled lines to the area under the trailer (front, middle, rear) and two lines that dumped fuel on top of the trailer over open hatches to the tanks.

    We objected to the top lines as we felt we could easily create an explosive atmosphere in the tanks but were overruled.

    I was the Asst Chief for the first burn and it was spectacular. We pumped about 50 gal of JP4 (jet fuel) into the rear and the front compartment and about 500 gal on the ground under the trailer. We all set back 1000’ and did a remote light off.

    At about two minutes into the burn the front and rear compartments had explosions. The front bulkhead blew open but stayed attached at the bottom. The rear bulkhead did the same but the baffle blew out of the opening and traveled 180’ feet as a Frisbee no one wanted to catch. The top lines were removed after that.

    In my experience most of the “Explosions” reported by the media are in fact the “Whoosh” factor and other pressurized things such as tires, hydraulic lines, air conditioning lines, etc failing.

    Stay Safe
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    Exclamation Product "remaining" in Tank Vehicles:

    Since the late 1970's when they started bottom loading/sealed vapor recovery loading of tank vehicles, a hidden danger was created. AFTER the loading of the tank, the lines leading to the various compartments [usually four]...remain completely full of product when the vehilcle is in transit.
    --------------------------------------------------------------------------
    note:
    I attempted to measure this amt. years ago, volume/length, etc., and it varies, however it is safe to say that at minimum 30 to 40 gallons are contained in these 3 to 4 in. lines.

    --------------------------------------------------------------------------
    The product is sealed in the compartments by the bottom and top [compartment] safety valves, but if the lines are severed in an accident...you have an immediate, automatic discharge/flow of product...separate from the tank itself.

    The is no way of draining/relieving these lines after loading at the terminal, as the product is metered [measured when loading], and the customer would always come up short in the amt. delivered if it were drained off. At $3 gal., this is a considerable amt.

    It is important to consider this when responding, as what is actually burning, may [?] only be what was discharged from the bottom lines [from the loading process], with the tank itself NOT discharging product at first...unless of course it was ruptured in the incident.

    Every solution is guaranteed to create a new problem.
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    Last edited by TFMBob; 11-18-2007 at 10:28 PM.
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    Quote Originally Posted by DeputyMarshal View Post
    There's no inherent reason why an MC306/406 tank can't "explode" from simple internal ignition of a flammable mixture or from an externally induced BLEVE just like any other closed containter. I'm not sure why someone would try to teach anyone otherwise.
    Actually I am under the impression that they can not explode as wel. I thought that the material they were made of would melt ... thus not allowing for pressure to build up in the tank.

    I have seen several pictures of tankers that were involved in bad accidents and caught fire. The one I most recall was a picture of a 1/2 a tanker. The top half was gone, the bottom portion was still there holding gasoline and a layer of foam!

    It has been a while since I dealt with gas tankers but ...


    Still learning,
    Anthony

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    Quote Originally Posted by gdsqdcr View Post
    Actually I am under the impression that they can not explode as wel. I thought that the material they were made of would melt ... thus not allowing for pressure to build up in the tank.
    Aluminum tanks have different failure modes than steel tanks. They're arguably less likely to explode than steel tanks in many fire scenarios but it would be a potentially grave mistake to think that it can't happen.[/QUOTE]
    "Nemo Plus Voluptatis Quam Nos Habant"

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    Quote Originally Posted by DeputyMarshal View Post
    Aluminum tanks have different failure modes than steel tanks. They're arguably less likely to explode than steel tanks in many fire scenarios but it would be a potentially grave mistake to think that it can't happen.
    Older steel transport tanks [which are seldom used anymore by any of the carriers], did not have Vapor Recovery Systems, with the only thing preventing product release in a rollover, being the dome lids themselves. Today the mostly aluminum or stainless steel tanks, are all required to have USDOT approved Vapor Recovery Systems.

    A line connects each compartment via a sealed connection to the overturn rail, which connects to a 4 in. line running down the back of the tank. Thus, the vessle is sealed, and probably will not release any product...unless of course it is punctured. Melting would occur only if enough fire was present to completely consume the tank.

    Often overlooked and not considered is; an EMPTY tank trailer, is as hazardous as a loaded one, as it contains all the VAPORS which are SEALED [from the previous delivery]...by the Vapor Recovery System. Gasoline will not burn unless it has oxygen...right, but VAPORS will cause an IGNITION/EXPLOSION. The possiblity of any given VAPOR igniting at distances in OPEN AIR, will largely depend on the properties of the vapor and...atmospheric conditions at the time. Staic electricity must also be considered when the EMPTY tank is uprighted by the salvage crew.

    It was stated years ago, that THE VAPORS from one gallon of gasoline, is equal to eight (8) sticks of dyanmite! An EMPTY transport will NOT have any product [only vapor] in the lines UNDER the tank.

    All this being said...I cannot stress enough [on a LOADED transport] to consider the product remaining in the loading lines...UNDER the vessle when you arrive on the scene of ANY tank transport vehicle accident...even though there is no fire present...YET!

    (see post/photos below...)
    "we learn from history...that we do not learn from history"

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