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Thread: Overfilled propane tank

  1. #1
    Join Date
    Feb 2005
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    Mont. Co. MD
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    Overfilled propane tank

    A week or two ago, I set out to get my 20 lb propane tank filled. I took it to our local "Southern States" to this, as usual.
    We had a hard time getting it to take the liquified gas, until I discovered that the Weber grill adapter (quick connect fitting) wasn't screwed in tight enough.

    Well I was chatting with the ole guy while it was filling, and he ended up stuffing around 4.6 gallons in that tank. Now 20 lb tanks are only suppose to be filled to 3.4 gallons when they are totally empty. No big deal I thought.

    Later on, either that night or the next, I hooked up the newly filled tank as the other tank was getting low. Things were going fine initially until I noticed the temperature dropping. I looked at the tank and the regulator and the hose line were totally frosted over. The main gas valve on the grill was also stiff with cold. Ultimately the flame did go out.

    That extra LP in the tank caused such a big pressure differential that there was an enormous temperature drop. I wish I had a non-contact IR thermometer to measure how cold that regulator got. Ambient temperature was about 60-70 deg. F, and the relative humidity was down in the 30% range. It was so cold and iced over that touching it would stick your skin to it. Who says propane doesn't make a good refrigerant.

    Anyway, to be able to use the grill, I've had to keep dowsing the regulator with water to keep it thawed out. I've had to do this for several weeks now in order to use the grill. The last couple of times it hasn't been icing up very much, and last night it didn't ice up at all (higher ambient temp probably helped too). So I think I've finally run enough gas out of the bottle. Moral of the story: don't talk to the fill-up guy, or use charcoal.
    Last edited by Bill Lewis; 05-12-2005 at 9:14 AM.

  2. #2
    Join Date
    Jun 2003
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    Portsmouth, VA
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    Bill, it sounds like you have an old propane tank. I'm not sure how you got it filled if you do. It's illegal to have them filled now. All tanks must now have a OPD installed (overpressurization device). Basically it only allows so much to go into the tank and then trips a vent. If you shake an empty tank you can hear it rattle around in there, it's a float valve.

    It was about 3-4 years ago when they passed the law. I found out when I took 2 tanks to be filled and the filling station (on base) confiscated them. I was stationed in Washington at the time and they gave me a $10 each credit toward a new OPD equipped tank (which cost about $30).

    I checked a list of states that enforce OPD laws and Maryland is one. Here's the complete list: http://www.npga.org/i4a/pages/index.cfm?pageid=535

    Be well,

    Doc

  3. #3
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    Feb 2005
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    Mont. Co. MD
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    Nope all my tanks are OPD. I did a Rhino exchange to get a new tank when I could no longer get my old tank filled. My Weber tank has been OPD since I bought it 6 or 8 years ago.

    I forgot to mention this in my original post. It did occur to me that OPD might be brought up. This just goes to show that these tanks really can be overfilled. So much for this technology.

    FYI to tell if a tank is OPD, look at the valve knob. If it is OPD the knob is "tri-shaped" vs. the older non-OPD "star-shape" knob. I guarantee you can't get a non-OPD tank filled around where I live.

  4. #4
    Bill,

    The valve inside an OPD tank is very similar to a level indicator for a fuel tank in that it is a hinged float switch. I haven't heard of one sticking but given that it is made of rather thin metal I guess the tank could have been bumped hard and bent the float.

    If your doing Rhino tank exchange that means you always use someone elses tank, right?....and don't know how its been treated....I own three tanks for my barbeque as I like to keep track of these little bombs. I've conducted damage inspections on boats that have experienced propane explosions and whereas the amount of fire has been less that expected, the explosive force is incredible!!!

    If it happens again I would suggest just releasing the gas before use.

    KP

  5. #5
    Join Date
    Feb 2005
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    Mont. Co. MD
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    Kent I hear ya.

    I actually considered releasing the gas, but really couldn't do so without removing the quick connect fitting. You just can't open the valve and release the gase without that fitting.

    I thought, briefly, about coming up with a way of connecting the over-full tank to the near empty tank and bleeding pressure from one to the other. I just didn't put that much effort in to it. It was more of a nuisance than a safety issue. The regulator was keeping the burner pressure no higher than the required level. I would get some surge when I "thawed" it out, but not much. I knew over time it should correct itself, and it did.

    I have only done blue-rhino exchanges a couple of times. Once to get rid of a tank that needed painting, and then once to get a tank with the OPD valve. I really don't like using them that much. It's really less conveinent to use them.

    One day, maybe this summer, I'll get around to building my deck. Then I can hook my grill directly to the 1000 gallon LP tank that I have for the house. Then I won't have to worry about those litte tanks at all.

  6. #6
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    The dangers of overfiling

    Id' suggest you get that tank replaced. The danger is much greater than a little inconvenience of frosted delivery lines.

    Our company made a machine for assembling and testing OPD's automatically. During the development of the machine we had a talk with our customers who pointed out the inherit danger of over filling and why OPD's were mandated. Wwhen the tank is overfilled it becomes all liquid in the tank, there is no (or very little) head space. When the liquid warms up it is already compressed, so the pressure in the tank gets extremely high very quickly. Tanks are known to either pop the safety or explode when this happens. Neither condition is desireable because the tank becomes surrounded by a highly flammable cloud. Any spark can set off a potentially devastating explosion.
    Lee Schierer
    USNA '71
    Go Navy!

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  7. #7
    Join Date
    Feb 2004
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    Odessa, Texas
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    Quote Originally Posted by Lee Schierer
    Id' suggest you get that tank replaced. The danger is much greater than a little inconvenience of frosted delivery lines.

    Our company made a machine for assembling and testing OPD's automatically. During the development of the machine we had a talk with our customers who pointed out the inherit danger of over filling and why OPD's were mandated. Wwhen the tank is overfilled it becomes all liquid in the tank, there is no (or very little) head space. When the liquid warms up it is already compressed, so the pressure in the tank gets extremely high very quickly. Tanks are known to either pop the safety or explode when this happens. Neither condition is desireable because the tank becomes surrounded by a highly flammable cloud. Any spark can set off a potentially devastating explosion.
    Another thing that is Dangerous about bleeding off the extra propane, is that Unlike Natural Gas, it does not rise, and dissipate easily, but will flow out to the lowest level and just hang there for quite a long time, and ANY SPARK (including a car's ignition) will set it off. This happened in South Texas when a Propane Transmission line sprung a leak, and someone started a vehicle to go for help, and the vehicle was almost 1/2 mile away, But, in a low area. It was a tremenduous fire.

    My Local Vendor, absolutely hates the new valves and said they have experienced a very high Problem Rate with them that will not let them fill, and you cannot fill them til you install another New Valve. I still liked the Old Method that we had on the Tractor and Vehicle tanks when I was a kid. You just opened the little vent valve and turned the indicator handle/pointer, til liquid poofed out and you knew exactly how much liquid you had in the tank.
    "Some Mistakes provide Too many Learning Opportunities to Make only Once".

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