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  1. #1
    Join Date
    May 2012
    Location
    chilliwack BC
    Posts
    38

    Question Welding on a diesel alum slip tank?? help?

    I'm a red seal journeyman welder, but have never run into this before. A buddy wants a crack welded on his aluminum diesel slip tank, the crack is on the top, so when the tank moves around it leaks diesel, I was thinking fill the slip tank up almost all the way with diesel and then purge the rest with argon before I tig it up? I know diesel is not as explosive as reg gas, but a few little tips and tricks might go a long way here. Thanks

  2. #2
    Join Date
    Dec 2011
    Location
    TN
    Posts
    79

    Default

    I wouldn't take the chance with it full of diesel not to mention the contamination hat could occur. It is discussed here: http://www.thecombineforum.com/forum...el-tank-2.html

  3. #3
    Join Date
    Dec 2011
    Posts
    388

    Default

    I've heard all kinds of methods for welding tanks but your ultimate goal is your safety. I haven't done one in a while but my method was (is) to fill the tank as full as possible with water. Be aware that some filler pipes extend below the top of the tank so as to prevent complete filling of the tank and leave room for expansion of the fuel. This may demand innovative methods to overcome the air trapped in that space-could be that inert gas purge would work??. DO NOT be fooled by anyone saying diesel fuel is not that flammable--it can be. We have seen a number of seemingly innocuous materials burn or explode including but not limited to motor oil(blew the pan gasket out), liquid fertilizer(burned like gasoline) and molasses(2500 gallon tank blew when we were cutting the end out but it was full of water,resulted in a wet worker but no other damage) All we could figure was that the molasses had fermented into alcohol? I know the whole water thing is a pain in the butt but dead is forever!! I have also heard of welders filling tanks to the top of the filler spout and setting it on fire to burn off any fumes while they weld(see problem with filler extensions above) but it scares the **** out of me. Recognize that just because someone got away with it in the past doesn't mean it is safe. Whatever you do think it though completely before you start,choose a method you are comfortable with and above all BE SAFE!
    good luck.--Meltedmetal

  4. #4
    Join Date
    Feb 2010
    Location
    YOUNGSTOWN, OHIO
    Posts
    172

    Default

    I have repair-welded numerous aluminum diesel fuel tanks with great success. Some were full, some half full, and some empty. Don't get caught up in all the horror stories out there floating around. 99 out of 100 of those stories were because stupid people were doing stupid things. With minimal basic knowledge, and following a couple basic common sense rules, you will be fine.

    First, understand the difference between FLAMMABLE and COMBUSTABLE.
    Second, understand what FLASHPOINT is.
    Third, understand VAPOR PRESSURE and EXPLOSIVE RANGE.

    The diesel fuel that you buy at the pump "no.2" diesel is an NFPA Class-II combustible liquid. It has a closed cup flashpoint of 125 deg. F. It has an AUTOIGNITION Temp. of >489 deg. F. And an LFL AP 0.6% and a UFL AP 7.5%.
    The LFL and UFL have to do with the "sweetspot" of when a vapor is too lean or too rich to ignite.
    I have attached a RUPATABLE link to help clarify the info that I have posted.
    http://www.osha.gov/dte/library/flam...e_liquids.html

    By the way, your idea is the right way to go as long as you are not making really long welds. It is the vapor mixed with oxygen that will ignite, not the liquid.
    Last edited by jpence38; 05-23-2012 at 04:40 PM.
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  5. #5
    Join Date
    May 2012
    Posts
    215

    Default Welding on a diesel alum slip tank?? help?

    I have done this many times I will only do a weld job like this two ways one filling tank up with water or a nitrogen purge no exceptions I saw a guy blown thirty feet off a boat luckily he hit the water bounced and rolled into the beach not usually that lucky oh yeah and he totaled the boat

  6. #6
    Join Date
    May 2012
    Location
    chilliwack BC
    Posts
    38

    Default Thanks for the help

    Thanks for all the help. I think I'll just empty the tank and fill it with water. The little extra time seems like its worth it.

  7. #7
    Join Date
    Oct 2009
    Posts
    305

    Default

    I have seen a diesel tank bulge and rupture when filled with water and welded. The diesel vaporized that was clinging to the walls of the tank than flash ignited. I'll only weld gas tanks purged with inert gas now. The diesel tank was a write off, blew up like a balloon then split.
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  8. #8
    Join Date
    Dec 2011
    Posts
    388

    Default

    Quote Originally Posted by jrscgsr View Post
    I have seen a diesel tank bulge and rupture when filled with water and welded. The diesel vaporized that was clinging to the walls of the tank than flash ignited. I'll only weld gas tanks purged with inert gas now. The diesel tank was a write off, blew up like a balloon then split.
    Did you by any chance have that fuel tank capped? If the tank is completely full of water there is no oxygen to fuel an explosion that I can see? However if the tank is completely full and capped the heated water has to have a place to expand into and something has to give. Just a thought. I am not claiming that a water fill is the only possibility but it has worked for me in the past and I am comfortable with it and an inert gas purge of the top air space seems like a really good idea. That said "properly" disposing of a couple hundred gallons of lightly contaminated water in B.C. these days could cause a national incident.(There is just no winning here) If you can prevent the "window"(sweetspot) that jpence refers to(informative link btw) from opening with inert gas it looks like a neater way to go. I haven't used that method so I can not speak to it's efficacy though it may well be fine. I'm a chicken and the idea that if the tank was to pop and splash me with fuel, turning me into the human torch, has kept me from welding on tanks filled with flammable/combustible material. Others are quite comfortable doing this but I'm not. Water also will absorb considerable energy. When our molassses tank blew it shot water up 50 or 60 feet as I recall, all energy moving water and not the guy cutting it although he was wet when the dust settled. Part of the point here is that explosions occur in unlikely places not just fuel tanks and some things have a flammable(explosive) range that you may not readily recognize so be careful and aware not only of what you are working with and on but also what is in the surrounding area cause "Dead Sure" trumps "Sure Dead" every day of the week.
    Meltedmetal

  9. #9
    Join Date
    Dec 2011
    Posts
    388

    Wink

    [QUOTE=jpence38;286605] Don't get caught up in all the horror stories out there floating around. 99 out of 100 of those stories were because stupid people were doing stupid things. With minimal basic knowledge, and following a couple basic common sense rules, you will be fine.

    Just for the sake of clarity-what you describe are ignorant people, the stupid ones are the ones who do it the second time for no better reason than the first wasn't fatal.
    Meltedmetal

    Enjoy the long weekend everyone and take a few minutes to think about the people who gave all that they could to make what we all have possible.MM

  10. #10
    Join Date
    Mar 2012
    Posts
    12

    Default

    I weld gas tanks all the time. I use pine-sol floor cleaner and mix it with water and clean the inside of the tank. The pine sol will cut the fumes completely. It realy works I was a little scared at firstbut this really works.

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