Welding question for tanks

[JohnEd]

I will be making a steel tank in the near future and doing the welding myself.  Failing eyes make it largly iffy but my fallback is a welder friend.  He is not what you would call the repository of diverse information.  Fact is he told me to do my own brazing cause he was never good at it and I did better than he.  Regardless of how good I or he may be I want to go over all welds with either silver solder or brass.  The welds will be mig and near perfect if he does it or really crude if I am left to my own device.  My question is "will silver solder do as good a job of seeking and filling pin holes as brass would?  Silver runs from "spendy' for some types to "impossible" for others.  Even if you aren't a certified welder I am interested in your thoughts.  One of my tanks will be for the bus and I hope to get the total capacity up to 400 gallons.  Max utilization of available space will require a strange and complicated tank shape to get that capacity and not write off a entire compartment.

Thanks,

John

[Blacksheep]

John mig welding mild steel is a good way and any competent welder should be able to weld your seams without the need to go over them by brazing!
To do an even better job and much cleaner would be to tig the seams! This takes a. Little longer but the results are far superior!
You can do it but it just takes practice! Lots of it!
Ace

[junkman42]

John Ed, if You are fabricating Your own tanks if You will bevel all the joints or faying surfaces and then dry pass them with a tig torch before welding either mig or tig You will have a much better chance of a long trouble free tank.  I would also suggest that You purge the tank with argon gas or carbon dioxide while You are welding to reduce both pinholes and other anomolies.  A little money will be well spent on a tank project.  By bevel I mean a v groove.  John

[NJT 5573]

John, If you can see what your doing, you should be able to do as good as anyone. Welding shield glass comes in prescription grinds just like reading glasses. Get the right lens and do it yourself. Prescription lens for your helment are not expensive.

[Chaz]

John,
MIG-ing it would be your best bet. And then put a little air pressure in it - but not much!! - and then go around it with a soapy water spray bottle. (your shielding gas would work fine for this also.) Mark any holes, wipe it off and then touch it up with the MIG. If you use brass or silver, you almost have to use that from then on or get it all out of there.
I typically TIG all the tanks I do, but then, I can. It can take a little longer, but works best.....I think.

Good luck ol'buddy. Wish I could help more.
  Chaz

[JohnEd]

Ace,

Thanks for the encouragement.  I have access to mig but not tig.  I would rather tig it.  The "need" as you put it is anticipated as a result of my most recent experience.  I ain't no friggen good anymore...no way.  Sad but true.  If I ever was, actually.

Chaz,

I have had bad experience trying to weld steel that was impregnated with rifle bullet lead.  It blew the weld back in my face.  Even though it made me "better" looking it hurt and i didn't like it.   Point being that I understand what you are saying about brazing although I hadn't heard it before.

NJT,

I have those lens in a tournament selection.  I currently use a lens and my trifocals in unision.  I am diabetic and my vision changes by the minute...it seems.  The least stress associated with setting up a weld and my vision blurs.  Bitch to work with but I manage and then there is plan B....my buddy.   Thanks for you suggestion and this isn't a sympathy suck.

Junk,

Thanks a bunch!!!  I had forgotten about backgassing.  OI have a friend that does stainless and he says it is a must.  I will do anything to reduce those pinholes.  I plan to make this out of heavy sheet metal and not sheet steel.  1/16 of an inch at most unless someone here tells me I am nuts.  My welding is so poor I think I must back up the job with brass or silver.  Just reality for me.  You are all correct that is "shouldn't" be needed.

Nobody said which, brass or silver, was preferred....please.

John

PS: maybe I "NEED" a tig welder.  Wadauthink?

[Len Silva]

John,

Not to discourage you from fabbing steel tanks if that's what you want, but...... Have you considered plastic tanks?  Tons of great info on Craig's website http://www.gumpydog.com/bus/MC9_WIP/Plumbing/Holding_Tank_Fabrication/holding_tank_fabrication.htm

I did fiberglass on plywood with good results that have lasted for years but next time around I would do plastic.

Len

[bottomacher]

Since you are using carbon steel, I assume you are making a fuel tank. Four hundred gallons is over a ton, and pressures within the tank will be pretty stiff for 16 gauge stock. Baffles will help hold the sides together, but it is still going to be under a load. Instead of double welding, you might consider a tank sealant liquid applied inside the tank- cheap, effective, and a lot less work.

[jjrbus]

   
                              Try asking here.  A quick web search will bring up several sites like this.  
                                                          HTH Jim

http://weldingweb.com/this is a clickable link:

http://weldingweb.com/

Richard
Thats interesting, I wonder why it was not clickable the first time

[wrench]

 I went over the welding of a 100 G. tank few years back(test for leak & touch up pin hole & seal), here what I did:  Hooked the blowing side of a large shopvac to the filler neck( you get 1-1.5PSI) but lot of volume. Spray with soapy water, mark the spot & touch up the worse spot. After that I spread urethane (used to glue windshield) on all joints with a (like trowel bended smaller then 90 degree) so you get a gap of 1/4-3/8" between the bottom of the V on the trowel & the top of the corner on the tank. It make like plastering a corner on drywall.
RESULT:  After 5 years I inspected the tank, & no seepage at all can be detect, this was a diesel tank made from scratch= 2 sheet of 4X8' bend 90deg & welded together & the end caped. It would have been easier if the 2 half been put together offset so you get 1/8" inside corner to weld instead of welding on the outer edge where you get only the tickness of the sheet metal to weld.
 Hope you understand my explanation & it help any.
           wrench

[JohnEd]

Len,

These will hold BioD.  While there are plastic tanks that are said to hold up "well", the Fire D said minimize their use due to failure.  Most in the BioD arena agree that plastic has a lifespan.  Not a good fuel tank.  Still, the new D trucks come with a pastic tank??

John

[Blacksheep]

John Prevost installs plastic tanks in their seated coaches used for diesel fuel. Since mine is a 1992, it has some years on it. Only thing you shouldn't do is drill anywhere near it! Don't even ask how I found that out! Same time I found out it was plastic!

Oh it was very easy to repair though!
Ace

[TomC]

Why do you want to carry 400 gallons (of fuel?).  That's 2,800lbs when full.  There are so many Diesel stations now, I don't see the need for more than 150 gal.  Personally, I would save the space to use for else things.  Good Luck, TomC

[CraigC]

We always built our tanks with the end bent over in a break or if round rolled the lid. That way we were never butt welding. We were welding to a over lap joint. It was more work to form. I always thought we have a stronger joint, easier to weld, looked nicer as we had less metal distoration. All of our mild steel and Stainless work back then was with a generator type machine and not a buzz box, but still stick welding. We had a tig welder, I had not heard of a tig welder at that time. A  leak for us was almost unheard of, if we did, we would  grind out section and reweld. Some of these tank are still in service 35 years later. I would install a of more then one baffle for added strength.

Just another way of skinning the putty kat.

[jjrbus]