Welding 2000 gal Hyd tank full of Hyd oil

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Have a tank that i have to weld on. This tank is 2000 gal Hyd tank full of hyd oil. A bottom weld is leaking around the bead. I know that i have to grind it, but how much. There is a lot of weight there with all that oil. I am going to attempt to weld this full. I would like to just mig it after i grind it out. Am i going to chase this crack in the weld when i start to grind it out? Any ideas from someone that has done this before?? Aaron
Reply:I think you're going to have to drain it and thoroughly clean the weld area after grinding to get any kind of a good weld on it.  Welding up a crack/hole through a stream of leaking oil is not going to be conducive to a good water-tight (or oil-tight) weld.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:I agree if not completely clean you will fight pin holes as the crack opens up while welding250DXMM251MM175225G plus 251D-1
Reply:From what i was told, draining the oil is out of the question. I think i am going to go and sandblast the area and see how fast the oil is coming through the crack and go from there. I shouldn't have to worry about any fires????? I might shoot some pictures and post on here. I will keep you postedAaron
Reply:Is draining out of the question because the unit can't be taken out of service at this time?  If so, clean it off and slap some of that two-part miracle epoxy stuff that HAZMAT guys use to seal fuel/chemical tanks and such.  Then when the unit can be taken out of service and drained you can fix it right.As for a fire hazard, welding and oil usually equals smoke and flames.  Good way to get the unit taken out of service I guess.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:how thick is the tank wall, is it possibly double wall?what about welding a patch on with tig at very low amps, clean the surrounding area and leave the crack alone.  Maybe use epoxy to help it.  Then just weld the patch on with tig and be sure to keep the heat low.Have we all gone mad?
Reply:ehh, if you try and weld on it with any kind of oil near there, you are only going to make things worse..  might as well duct tape it.. lol.. epoxy is a good idea.. epoxy a pail to the place were the crack is, wait for it to be able to be taken out of use, and fix it properly.
Reply:You won't seal it with a mig.  6010 or 6011 is gonna be your only option.  I have welded many of  them before, and they can be tough, but it is doable.  As far as grinding goes it all depends on how thick the tank is.  It may be an easier option to plate over the crack instead of trying to weld it.  What I have done in the past is clean the area well.  Duct tape or silicone over the crack.  Stick the plate over it, and don't waste anytime welding around it to seal the patch.  Believe it or not the tape/silicone will usually hold the oil from leaking long enough that you can have time to seal it.  Good luck.   ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Double post;first one seemed lost so I rewrote it. Is the site slow tonight?Last edited by Oldiron2; 02-15-2009 at 11:36 PM.
Reply:Is the tank sealed so you can hook a vacuum pump to its top and suck in air, to keep any oil from leaking while you work? Then just patch the area without welding the actual crack, as sn0border88  suggested above?Seems like a permanent fix to me.
Reply:I had to weld up a hydraulic cylinder that leaked (because I didn't do a good job welding the new street elbow on, long story).  It was the PITTTTTTTS.You can do it, but you'll be chasin' leaks around the edge of the weld.  I think it has something to do with cooling the weld off too rapidly with the crap leakin out.  I finally got it sealed, but I had to keep piling metal on.  It looked like rat crap, but it's held.I'll try to find a pic, and if I can't, I'll go out and take one."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by Oldiron2Double post;first one seemed lost so I rewrote it. Is the site slow tonight?
Reply:do not grind it!!! you will make it leak more if you do so...i have tried the whole stick on low amps trick before and blew a hole in the side of the tank...then i had to drain it. best bet is to put a patch over the crack and weld around it... like everyone else has said on here you will be chasing air holes the whole time if you try to weld the crack.AWS CWI/CWEASNT NDT Level 2 PT/MTAWS Certified Welder(aerospace)
Reply:Went out and got a pic.This was my only experience welding something that had oil in it.  The oil wasn't under operating pressure, but it was under residual pressure.  Scared the hell outta me.  And started a little fire at my feet while welding.Hobart Handler 135.  .030 flux core, and a lot of prayin'   I thought the damn cylinder would explode in my face with all that oil in itIt took 3 tries before I got it sealed Attached Images"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by Oldiron2Is the tank sealed so you can hook a vacuum pump to its top and suck in air, to keep any oil from leaking while you work? Then just patch the area without welding the actual crack, as sn0border88  suggested above?Seems like a permanent fix to me.
Reply:Would that keep the joint dry?  I've inadvertantly tried to weld a joint that had liquid in it and it got all bubblegummy(is that a word?).  The moisture seems to super cool the puddle I think.  I'm not sure"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by farmersammWould that keep the joint dry?  I've inadvertantly tried to weld a joint that had liquid in it and it got all bubblegummy(is that a word?).  The moisture seems to super cool the puddle I think.  I'm not sure
Reply:I see.'Nother case of my 40watt noodle tryin' to understand a 100watt questionSo, what happens when the vaccum tries to suck the gun into the tank??Just kiddingI better get to bed before I destroy the known universe"Any day above ground is a good day"http://www.farmersamm.com/
Reply:What concerns me is that the weld that is leaking is on the very bottom of the tank. It doesn't leak that fast. I wiped it down last night and this morning you can see just a little bit of oil coming through the crack.  I am going to put a patch on it tomorrow morning. I don't think i have to worry about that oil getting to hot and starting a fire. All that oil on top and i am guessing that it is 1/4 plate. I will keep you posted.
Reply:Don't be so hard on yerself, Samm. Some of us won't ask the simple questions, but we enjoy seeing the answers. I better get to bed before I destroy the known universe.   You don't have to worry, you'd need MILLER POWER to pull that off. 9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:The FL DOT folks have a two part epoxy that they use when catch leaking tanks on truck inspections. I would suggest somthing like that until that tank can be drained, steam cleaned, properly ground down, and welded. Other wise you'll be chasing leaks unitl properly done. An the owner will be facing alot of HazMat violations.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.