In-service oil tank welding

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So i was approached the other day by the owner of a local heating oil company.  He was interested in having some ladders welded to the sides of his tanks.  The tanks are pretty large.  They're 20,000 gallons each and are of the lay down variety.  Wall thickness is 1/2"  Now heres the kicker.  The tanks are FULL of #2 heating oil.  The owner wants a ladder welded to the end of each tank and a small cat walk welded to the top for acces to the hatches.  He is not the slightest bit concerned about welding on full tanks.  In fact a few years back, an old timer in town did a welded "in-service" tap on one of the tanks that was full.  I know its fairly common to weld on live pipelines but i wasnt aware that you could live tap a full tank of this sizeSo basically what i need to do is weld 1/4" brackets onto the tank end and a few on top of the tank.  The beads will only be about 2" long.  The rest will be bolted together.  I've welded on a bunch of tanks before (although not quite this large) but never on a tank containing #2 oil. I'm a little concerned with welding on a full tank.  The owner isnt exactly a welder but he has had the tanks welded on before and isnt too concerned.Has anyone done any welding like this before?  I would love to hear your thoughts
Reply:Tough call for the faint of heart. Do get an experienced reply.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:I wound up doing a bit of "in-service" work a couple of years ago on light shade crude. Same geneal properties (Flammability, flashpoint, specific temp, etc) as #2. Never crossed my mind it would be dangerous. There again, I have been around the oil fields since I was big enough to walk. Of course, this is just me.Trust your own judgement. If you are uncomfortable with it, pass it on. It's as simple as that. If you don't feel safe doing the job, by all means, don't. YOUR comfort with a job is of the utmost importance.
Reply:"The owner isnt exactly a welder but he has had the tanks welded on before and isn't too concerned."The owner wants this done--cheap-period. I wouldn't weld below the fluid line-ever, due to the possibility of hot crackingthru the tank wall.A repair like this should be done with the tanks, drained and purged with inert gas,purge plan, monitoring, inert gas pressure test/or hydrostatic test for leaks.Be aware that this form of repair, may require post repair inspection and testing perASME, API, etc.---if one plays it by the book. If this job is pursued the 'owner's way', it will make for an interesting readin the Chemical Safety Board's findings and the Lawyers Forums. Be awarethat any subsequent problems with these tanks, will be placed in your lap.The CSB's site already has some instructional reads on storage tank repairsgone wrong, including items from the Oil Patch.1-Are the tanks in an enclosed area?Located in a populated area? (some locales  and states haveordinances regarding tanks, repairs, inspections, permitting, etc. I suspect Conn.is one that has stringent tank registration, inspection, permitting, etc.)2-Verify the tank wall thickness, I'd be surprised if they're 1/2".Inspect the weld areas on tank outside for corrosion and pitting.Do the tanks have any mfr. data/tank registration plate on them?(if not, these may be boot leg tanks)3-Welding with liquid on the opposite side of the weld, can producecracking/ heat affected zone that will not be apparent after welding,but after in-service use. The parent tank head and walls are under some degree of stress, prior to welding. This extreme hot/cold stress condition induced by welding with fuel on the inside can produce immediate cracking, fuel fire, etc.Additionally the welding heat will generate pressurized vapor that will leave the tank,creating an immediate fire/explosion hazard to personnel. 4-Welding doubler plates to the tank outer wall--THEN weldingthe brackets, etc. will stop in-service, stress cracking at the weld to tank wall juncture.275# fatties can produce lots of stress on ladder mounting points.Blackbird
Reply:Are they single or double wall tanks. If they're double you're going to have a time with the intersistal space as they're usually under vacuum. (I was going to say filled with vacuum but that didn't sound right).Like Dave said, I can't imagine them being 1/2", probably more like 1/4" i would guess. Would I do it? Nope the profit you're going to make could be swallowed up in a second should the wrong authoroties find out....Mike
Reply:I would pass on that one.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:In the lawsuit-happy States, I'd pass. $hit rolls down hill. If he didn't know your name, address, town you live in, and payed cash up front...maybe but you'd have to show up with a stolen truck with no plates and always keep your helmet down. 200amp Air Liquide MIG, Hypertherm Plasma, Harris torches, Optrel helmet, Makita angle grinders, Pre-China Delta chop saw and belt sander, Miller leathers, shop made jigs etc, North- welders backpack.
Reply:The tanks look to be rather old.  Im not sure of a date of manufactor but the cradles that they sit on are rivited together.  Another interesting tid-bit, these used to be underground tanks that were relocated a number of years back...
Reply:Originally Posted by KevD815The tanks look to be rather old.  Im not sure of a date of manufactor but the cradles that they sit on are rivited together.  Another interesting tid-bit, these used to be underground tanks that were relocated a number of years back...
Reply:Refer the job to a competitor, someone you don't like very much.CWI, CWE, CST for Miller, Lincoln, Thermadyne, Hypertherm & ESABMillermatic 350PLincoln Invertec 205 AC/DCVictor combo torchESAB PCM 1125
Reply:Thanks very much for the input guys!  Yes Dave, i was paying attention and i beleive you're correct!  I got a call today asking if i could "Weld a patch over a rusty spot on the bottom of tank 4".  WHAT THE F***!!!!  I bet there has been no record of these tanks since they made it out of the ground if there was any to begin with.  A "rusty spot"?  Who knows if these things are rotting from the inside out.Im going to propose a self supported access system.  Something i can bolt together on site so i can do all the welding at my shop.  Im primarily a structural guy anyway so im going to stick to what i'm completely comfortable with!  Thanks again guys.
Reply:Originally Posted by KevD815Thanks very much for the input guys!  Yes Dave, i was paying attention and i beleive you're correct!  I got a call today asking if i could "Weld a patch over a rusty spot on the bottom of tank 4".  WHAT THE F***!!!!  I bet there has been no record of these tanks since they made it out of the ground if there was any to begin with.  A "rusty spot"?  Who knows if these things are rotting from the inside out.Im going to propose a self supported access system.  Something i can bolt together on site so i can do all the welding at my shop.  Im primarily a structural guy anyway so im going to stick to what i'm completely comfortable with!  Thanks again guys.
Reply:Good decision and good plan, you still get a job out of it and no risk from welding on the tank.  Good call.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:I like Maedars thoughtLincoln Power MIG 215Lincoln WeldPak 3200HDLincon ProCut 25Lincoln WeldanPower 225 AC/DCIf all else fails... buy more tools
Reply:Okay i didnt like the idea of welding the tank....but how about welding new legs onto the flanges?Tank and flanges are good legs were on concrete ...need I say more?
Reply:For your first post, you find a thread from April of 2010..................."Where's Stick man????????" - 7A749"SHHHHHH!! I sent him over to snag that MIC-4 while tbone wasn't looking!" - duaneb55"I have bought a few of Tbone's things unlike Stick-Man who helps himself" - TozziWelding"Stick-man"
Reply:Spammer go home!American by birth Southern by the Grace of God
Reply:Originally Posted by Stick-manFor your first post, you find a thread from April of 2010...................
Reply:NO WAY IT AIN'T WORTH TAKING THE CHANCE SO THAT GUY CAN SAVE A FEW PENNIES!TELL HIM YOU WILL DO IT THE RIGHT WAY IF HE STILL WANTS YOU TO DO IT!    good luckAEAD 200LE, Lincoln precision tig 185, Millermatic 251, Spectrum 625 extreme, Victor torch , Smithy 1220LTD. and  Do all C-4 band saw ,  Always adding.