welding explosion

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Would like to understand the cause of an explosionCar was an chromemoly tube chassis car, with electroic fuel injection and a front mounted aluminum fuel cell (in grill area) that was full of alcohol.  The guy was welding on the intake (aluminum) throttle linkage area, not sure where his ground was but the aluminum fuel tank exploded and split apart a the seams and caught fire. Would like some opinions was this could have happenedthanks
Reply:Ever heard of vapors?  Alkyhol evaporates quite rapidly.Esab Migmaster 250Lincoln SA 200Lincoln Ranger 8Smith Oxy Fuel setupEverlast PowerPlasma 80Everlast Power iMIG 160Everlast Power iMIG 205 Everlast Power iMIG 140EEverlast PowerARC 300Everlast PowerARC 140STEverlast PowerTIG 255EXT
Reply:I'm not sure but I do believe the vent was not anywhere near the weld area. I am well aware of vapors that would be my first guess but I was wondering if welding ac on the aluminum could have produced a spark/arc in the fuel cell (bad welding ground)
Reply:Maybe the cap wasn't on the fuel cell very tight or there was some other way that fumes were escaping.
Reply:The fuel cell had to be vented.  A spark could have got near the vent, OR the vapors could be around.  Alcohol burns like crazy.Hope no one was hurt.  No way we could tell from here, just speculation.  I am not a fireman, just a weldor.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Don't know about alcohol, but a lot of vapors/fumes from explosive gasses and liquids wind up around floor level eventually.  Sparks wouldn't have had to be anywhere near the tank to ignite the vapors if they pooled on the floor around the shop."Any day above ground is a good day"http://www.farmersamm.com/
Reply:A charging battery vents explosve hydrogen and all fuel cells are vented somehow.Yes hopefully noone got hurt.Co-Own CNC shop:Miller :1251 plasma cutter, MaxStar 700 TIG/Stick, & XMT 456 Multiprocess Welder.&  2 Hypertherm HPR260's Plasma CutterSorry I had a bad stroke but now I am back.
Reply:Unless you know where that work lead was clamped, there's not much to talk about. Just wild guesses. Then you would also need to know the real facts as to how the chasis, engine block, fuel cell and other components were (if at all) all bonded together. After all that it could be all you have done is eliminate his method of hook up. Simply said one would really need to have the have the car right there in front of them for inspection and know the details of his connection as well as the conditions that existed at the time the work was being done. An accurate assessment isn't going to happen over the internet.
Reply:Just an idea. How was the fuel cell mounted? Could it have been loose in one area just enough to cause a hot spot between the cell & the mount?Kind of like when you lay a piece of steel on a steel table to be welded & a good ground is not immediate? Gets a small arc in between.Sorry guys, just me thinking out loud again!Flash
Reply:Ya I would say the tank may have somehow been used to complete the ground circuit, maybe the ground clamp was pulled over to the tank and it provided a better ground and arced. But he would have to have been tig welding, don't know what achohol flashes at but it must be near 30 deg.
Reply:How full was the fuel cell.  Alcohol is very volatile and will fill its container rapidly with vapors.  Every vapor has a lower and upper explosive limit.  It will only explode if the air/fuel ratio is within a certain range.  Generally, alcohol and gasoline in tanks give off enough vapor to maintane an athmosphere above the upper explosive limit.Also, when welding, electricity sometimes finds interesting routes to ground.  It seems a simple electrical short circuit on one of our boats found its way to ground through a strain gage on the brake pin for the winch on one of our boats.  This pin tells us how hard we are pulling.  That was a $7000 short circuit which was completely unrelated to the strain measurement system.  The point is, an arc may have formed in the tank if the tank for some reason had the least potential to ground.
Reply:My 2 cents....I will bet there was steel braided fuel lines involved.   Current passed down the fuel line through the tank to seek the frame ground.    Ka-pow...
Reply:I'm not trying to be a wise guy here, just trying to learn.  The lesson I'm getting from this thread is that because you just don't know what can happen with 'trons and fumes, the piece that was being worked on should have been removed and worked on separately.  Is that correct?Hobby welder with MIG, stick and gas experience.  Just got a Miller 250 TIG that I hope to use with some degree of expertise someday
Reply:If the ground was not very solid, there is a chance for arcing. Very likely, the tank may have some loose section on it, or the tank is isolated but very close to the chassis, and you can get an arc that way. I was just welding on an old aluminum boat last week and I was seeing arc marks all over, and my ground lead was actually easting some aluminum as the electricity was passing through the ground clamp. Nasty high speed corrosion!!And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Strangest thing I ever saw was when all of the chains securing my pasture gates were actually welded to the steel gate posts.  Apparently there was a lightning strike somewhere along the fenceline, and it traveled to the gates.The strike could have been far away too.  Most landowners fences are interconnected at the corner posts on the edge of ther property.I've seen cows electrocuted this way, when they have their heads through the barbed wire trying to get to grass on the other side of the fence.It's generally not a good idea to touch field fences during lightning storms."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by pigpenI'm not trying to be a wise guy here, just trying to learn.  The lesson I'm getting from this thread is that because you just don't know what can happen with 'trons and fumes, the piece that was being worked on should have been removed and worked on separately.  Is that correct?