Odd Diesel Transfer Tank Situation

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  • Dawico

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    Oct 15, 2009
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    Lampasas, Texas
    I drive a company truck with a 95 gallon aluminum transfer tank in the bed. The tank has a filler cap on the drivers side and an electric pump on the passenger side. The cap is a radiator style cap with a rubber gasket and a hole for a padlock. The cap and pump both are locked. The truck is an '08 and I assume the tank and cap is about the same age.

    I also pull a box gooseneck trailer.

    I have been in Tucson, AZ for the past two weeks. Temperatures range from about 70° at night to as high as 115° during the day.

    Now my odd situation. Atleast four times since I have been here the cap has been popped off the filler pipe. The cheesy cap is pretty easy to pry off or even overturn and bend the ears open to remove. I have never done this but now that I look at it it is entirely and easily possible.

    I assumed somebody was stealing diesel. Not a far stretch really.

    So today I decide to remove the filler pipe and just put a plug in it. Not really lockable but harder to get through than the cheesy cap.

    When I took the filler pipe out I looked into the tank and it is still pretty full, like 90% full. It doesn't have any kind of gauge so I really have no idea if any is missing but I was surprised to see how full it is.

    If someone had stole some a few different times they didn't take much.

    It was about empty when I left Texas so I put some in at each stop. Again, no idea how full it was though. I do know if it is topped off it will spray diesel on the back window of the truck and it didn't do that.

    We don't use the tank much unless something comes up like needing fuel for a forklift or generator. I haven't used it since I have been here.

    My question is, do those caps go bad and not vent properly? Could pressure pop the cap off given how full the tank is and the temperature swing here?

    The cap is always in place just jumped off the rim. I have rebent the ears a couple times to make sure it locks on properly but it still happens.

    It is always loose in the morning, never the evening. I would assume it would have the most pressure later in the afternoon during the hottest part of the day but it is never popped off then.

    I have also thought about somebody maybe putting something into the tank to be destructive. I can't see any reason why but that doesn't keep if from happening.

    Anyways, any thoughts or experience with anything like this? I have replaced the filler with a Teflonned steel plug. If it is a pressure issue bad enough to damage the cap I hope that solid cap won't cause other damage.

    TIA
     

    Tx_Mark

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    It sounds like a ventilation issue, I think it would be safe to assume that if someone was stealing fuel, they would take as much as possible. You could try drilling a hole in it and putting a vent on the tank, or buy a new cap, and see if that fixes the issue.


    "Prepare yourself for the future,with what you've seen in the present"
     

    Dawico

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    I have also thought about running some of the fuel into the truck tank now that I know how full it is. Give the diesel a little more room to expand.

    Maybe when I have some time I will track down a new cap also.
     

    Tx_Mark

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    I have also thought about running some of the fuel into the truck tank now that I know how full it is. Give the diesel a little more room to expand.

    Maybe when I have some time I will track down a new cap also.

    Another option is to drill a hole in the top of the tank cap, and put a small tube into the top of it (like a dirt bike cap) and have a "vent tube" of some sort.

    Although Idk what DPS would say about that if you got curbed.


    "Prepare yourself for the future,with what you've seen in the present"
     

    Dawico

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    The cap should vent out the extra pressure, correct? Or is that not the case?

    I guess I will know here in a few minutes if there is a big bulge in the tank..............
     

    Das Jared

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    Friendswood
    The cap acts as a pressure relief device for when it gets warm outside. It also acts as one so you don't create a vacuum on the tank while pumping. You will lose material due to evaporation. Completely normal.

    sent from Jennifer Lawrence's bedroom
     

    Dawico

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    The cap acts as a pressure relief device for when it gets warm outside. It also acts as one so you don't create a vacuum on the tank while pumping. You will lose material due to evaporation. Completely normal.

    sent from Jennifer Lawrence's bedroom
    It is normal for the cap to jump it's tabs because of pressure? Literally just sitting on top of the filler pipe?

    That doesn't seem right. I am guessing that the cap needs to be replaced like any fuel filler cap. It just isn't breathing enough to relieve the pressure.
     

    Das Jared

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    It is normal for the cap to jump it's tabs because of pressure? Literally just sitting on top of the filler pipe?

    That doesn't seem right. I am guessing that the cap needs to be replaced like any fuel filler cap. It just isn't breathing enough to relieve the pressure.

    Anything is possible.

    sent from Jennifer Lawrence's bedroom
     

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