Aluminum Bung (TIG) Tanks Pressure Test ?

admin

Hello.I've been working on putting together an Aux fuel cell for my off road vehicle.  SundownIII was a HUGE help with the settings on my Dynasty 200.  The 80-85% balance and 120 Hz on the AC was big help.Also went to a 3/32 Zirconiated tungsten electrode and 3/32 filler.  The rest is On-ARC time to lay down consistent  dimes.   I get a few.Below is a slide show of where I am.  This is my first real AL project.I've got another 12" to lay down and everything will be done except for putting on the lid and adding some Bungs.  (There is the issue)I tried to put a bung on a cast AL tranny pan about 18 months ago and it was a disaster.  But I'm a much better welder now.Plus I'm working with 6061-T6  .125 rather than cast.  But I'm still very nervous about turning the whole thing into scrap.Any tips on welding on an Aluminum Bung.  It's a Male AN -10 fitting.Also.  Tonight I'm going to float the tank to check the bottom and sides for leaks.  (Wish me luck) After I get the  bungs and the lid on, I will pressure test it.Any tips on the psi I should use?ThanksLukeNote.  Photos below show me tacking the tank together using my Miller Passport Plus and a Spoolmate 100.http://www.flickr.com/photos/radrod5...65052981/show/Just a Ham 'n Egger.Dynasty 200DX (Pre B. Lightning)Spectrum 375 ExtremePassport Plus
Reply:Ive done a few tanks like that, always tested to 5ish psi.  On a thin tank like that you will start to bulge out the sides if you go higher.  Plus it wont see pressure during use so no need to go any higher.As for the fittings, if your nervous about it then get your hands on some al tube about the size of the fittings your working with.  Practice on that just to get the feel of keeping your torch angle consistent as you move around the piece.  You can also experiment to find out how far around you can get in one start/stop, and plan out your starts accordingly.  This is where you will most likely have problems if any.  Make sure to fill in your craters and overlap your starts well.Also make sure your not overheating the fitting.  Its not likely, but you could melt through and damage the threads on the inside.Heres one I made, fittings are welded to the sump.Have we all gone mad?
Reply:Rad,First off, let me say you're definitely making progress.Don't get too impatient.  Tig, in addition to learning the principles, takes time to develop the "motor skills/timing/coordination" necessary to lay down a good consistent bead.Looking at the tank, I don't see a lot of consistency in torch movement and adding filler.  Looks to me like a few things were happening here.  You could have used a few more amps (beads too humped) and moved faster while still adding filler at a consistent pace.For someone new to the game, freehanding those seams is probably somewhat overwhelming.  I would recommend that you use a guide to steady your torch hand.  Doesn't have to be anything fancy, just something to help you keep a consistent angle of attack to the puddle.  Try moving the torch (no arc) along the entire seam you intend to weld.  If you find yourself reaching a point where you're "not comfortable" then rethink how you want to approach the weld.As far as the bung in the tank.  I'd definitely recommend practice on scrap before you attempt the "real thing".  I'd recommend just picking up some scrap (if available) aluminum tubing and cutting it into about 2" pieces.  Then take a holesaw (dia of the OD of the tubing) and punch some holes in scrap aluminum.When learning, I'd recommend tacking the tubing in 4 spots with a 90 deg offset.  Then tig weld from one tac to the other.  Move to the opposite side and weld from one tack to the other.  Kinda like tightening lug nuts on a drum brake.  You're welding as far away as possible from the previous weld.  This will minimize pulling/warpage as the aluminum shrinks.  (Yea, aluminum shrinks about 6% when going from a liquid state back to a solid).As far as pressure testing, we used to pressure test our fuel cells (filled with water) at 8 PSI for about 8 hours.  Viking yachts tests their aluminum fuel tanks (heavier gauge than you're using) at 12 PSI for 12 hours.  For that tank, I wouldn't recommend more than about 8 PSI.  If it's going to leak, it won't take much pressure to show you where.You're getting there.  If you stay with tig, in a couple years you'll look back at that tank and say, "man, I can't believe I let that out of the shop".  Looks strong enough to hold the fuel as long as it doesn't leak.  Pretty beads will come with arc time.  Remember, with tig, there's a lot more going on at the same time than it is with pointing a squirt gun welder and  pulling the trigger.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by SundownIIIRad,First off, let me say you're definitely making progress.Don't get too impatient.  Tig, in addition to learning the principles, takes time to develop the "motor skills/timing/coordination" necessary to lay down a good consistent bead.Looking at the tank, I don't see a lot of consistency in torch movement and adding filler.  Looks to me like a few things were happening here.  You could have used a few more amps (beads too humped) and moved faster while still adding filler at a consistent pace.For someone new to the game, freehanding those seams is probably somewhat overwhelming.  I would recommend that you use a guide to steady your torch hand.  Doesn't have to be anything fancy, just something to help you keep a consistent angle of attack to the puddle.  Try moving the torch (no arc) along the entire seam you intend to weld.  If you find yourself reaching a point where you're "not comfortable" then rethink how you want to approach the weld.As far as the bung in the tank.  I'd definitely recommend practice on scrap before you attempt the "real thing".  I'd recommend just picking up some scrap (if available) aluminum tubing and cutting it into about 2" pieces.  Then take a holesaw (dia of the OD of the tubing) and punch some holes in scrap aluminum.When learning, I'd recommend tacking the tubing in 4 spots with a 90 deg offset.  Then tig weld from one tac to the other.  Move to the opposite side and weld from one tack to the other.  Kinda like tightening lug nuts on a drum brake.  You're welding as far away as possible from the previous weld.  This will minimize pulling/warpage as the aluminum shrinks.  (Yea, aluminum shrinks about 6% when going from a liquid state back to a solid).As far as pressure testing, we used to pressure test our fuel cells (filled with water) at 8 PSI for about 8 hours.  Viking yachts tests their aluminum fuel tanks (heavier gauge than you're using) at 12 PSI for 12 hours.  For that tank, I wouldn't recommend more than about 8 PSI.  If it's going to leak, it won't take much pressure to show you where.You're getting there.  If you stay with tig, in a couple years you'll look back at that tank and say, "man, I can't believe I let that out of the shop".  Looks strong enough to hold the fuel as long as it doesn't leak.  Pretty beads will come with arc time.  Remember, with tig, there's a lot more going on at the same time than it is with pointing a squirt gun welder and  pulling the trigger.
Reply:Originally Posted by sn0border88
Reply:You mean a rosebud to heat for bending?  Ive never annealed aluminum to bend it and its never been an issue.  No jig either, just bent and tacked.  I forgot to mention but if you look at the picture of the sump on the right hand fitting you can see a little spot on the top where it leaked at a crater I didnt fill in.  Thats why I stressed making sure your cover them well.  Other than that aluminum is fairly easy to make watertight if its clean.Have we all gone mad?
Reply:Originally Posted by sn0border88You mean a rosebud to heat for bending?  Ive never annealed aluminum to bend it and its never been an issue.  No jig either, just bent and tacked.  I forgot to mention but if you look at the picture of the sump on the right hand fitting you can see a little spot on the top where it leaked at a crater I didnt fill in.  Thats why I stressed making sure your cover them well.  Other than that aluminum is fairly easy to make watertight if its clean.
Reply:Yes, our shop has an 80 something ton mechanical press brake.Have we all gone mad?
Reply:Don't get discouraged on the tranny pan, ESPECIALLY if it was used.  I can weld on fresh cast aluminum no problem and plate no problem.  Last bung I welded on a used cast pan was a nightmare.  COULD NOT get that sucker clean enough to make a pretty weld, had to pump enough heat into it to where I could break under the **** at the surface and feed filler in beneath it.  It was ugly, but it worked.
Reply:Supe:Thanks for the tip. In my home garage, I can be pretty hard on myself; thinking that I should be able to do some things better. If you guys have to settle for ugly sometimes, it makes it easier on me when something tough shows up. 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:Supe,Seen your work, so know if it was tough for you, it must have been a "problem" weld.Next time, you may want to try "bump" welding it.  Sounds kinda like the problem you face when welding anodized.  Set your amps much higher than you would normally use to make the weld (195-205) and use a torch mounted on/off button.  Hit it hard with the amps, add filler, let up.  Repeat.Not saying that it would work for sure, but may be something you want to try.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:radrod57:1-often those an fittings are anodized. The one shown in your pic may be clear anodized.Suggest you lightly file or sand the hex side to discern. (I'd just buff off the hex sides, anyway with a 3M pad). If it is anodized, you will readily know when begging to weld it.(yes, there's some guys, high experience tiggers that can weld anodized, but that takesa good amount of practice.)-The fitting will tend to tip from the first tack. This can be alleviated by very gently clampinga block of soft wood on the thin nose of the fitting, removing the block after the second tack. Another way is to use a thru bolt arrangement. In any case, you cannot damage this thin nose or the machined cone for the fitting to be seal tight. (I don't know why the experts didn't tell u this.)2-to strengthen, stiffen the area around the fittings and help limit weld distortion--a doublerplate can be fit and welded to the tank shell--first; then welding the fitting.3-putting a dummy fitting cap on--loosely, never tight to protect the machined sealing coneof the fitting--maybe. Forget using the cap as a heat sink, if you can't control your weldingthen the cap won't help you. It is possible for the threads to seize between the cap and the fitting, during welding, especially if the cap is tight.4-Pressure testing poker/roulette                          SN0BORDER88 sez "5#"       then......SundownerIII  Calls SN0BORDER88's 5#                                   and RAISES it to 8#!(I'll check the raiser; while bracing myself for the brick bats that will come flying in my directionfor this post. )This is just plain, dangerous advice and I'm surprised considering the parties who gave it. SundownerIII is a P.E., with other virtues.a-The  construction of this tank is not known--other than pics of  inconsistent welding, some lack of  edge fusion/wetting, unknown joint quality, no baffling, no interior fillet welds, no interior flanging----how 'much' pressure can SAFELY HOLD, without permanent deformation or rupture is also unknown.b-Pressure testing of thin wall, tanks of known and calculated design can be done--often inside a cradle to prevent pressure deformation (and provide testing safety)---but this is not the case at hand.c-In my own pressure testing of tank repairs or new builds---I use blowoff patch(es) one hand on the blowoff patch, sensitive air gauge on dedicated regulator. I watch and feel for the tank sidesbeginning to swell--then stop.d-Most leak problems are avoided, by good joint design and really watching what one's doing with the puddle. Not fading the torch output at the end of a weld (stopping abruptly) is a great way to make little craters in the bead--which are crack sensitive and usually leakers. Ibid for not wetting in starts and stops.Blackbird
Reply:Dave,I understand your concern regarding pressure in a small tank.  However, I think you need to go back and re-read my post.I stated that the tanks were filled with water (non-compressible) and then pressurized.  The volume of air involved was, in reality, very small.These tanks/fuel cells were much larger than the OP's tank but did have baffles to reinforce the tank.  These cells were used in race boats operating in excess of 100 MPH.  If they couldn't handle that water pressure then they sure wouldn't handle the stresses of fuel getting slammed around in them at those speeds.When considering the safety factors involved in dealing with compressed air, you not only have to look at the pressure but also the volume.  In this case the volume was very small.  In fact, we used a hand bicycle pump to pressurize them.Viking Yachts (one of the premier yacht builders in the US) tests their tanks in the same fashion.  These tanks are generally in the 400-500 gal range.  They fill with water and then pressurize to 12 PSI.  This pressure is left on for 12 hours.  The only difference between what they do and what I did, is that they use a small, about 6 gal, air reservoir tank to maintain a "bank" of air.  The reservoir tank is certified for 135 PSI.Heck, shake up a coke bottle.  I suspect you'll get more than 8 PSI.All comes down to "stored energy".  Water, being non-compressible, doesn't "store" energy.  The small volume of air involved doesn't store much.I haven't heard lately about anybody getting hurt/killed when their garden hose (generally 45-60 PSI) burst.  Nor have I heard of many people getting hurt/killed when the tire on their bicycle blew out.  Dirty britches maybe, but seldom life threatening.If you look back at my posts (maybe you have), if I err (guess we all do at times), it will be with a lean toward safety.PS,  I'd dang sure rather have the tank piss on me (leak) in the shop, than bust a seam coming out of a turn in Marine Stadium (Miami, FL).Last edited by SundownIII; 06-26-2009 at 10:34 PM.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by SundownIIIDave,I understand your concern regarding pressure in a small tank.  However, I think you need to go back and re-read my post.I stated that the tanks were filled with water (non-compressible) and then pressurized.  The volume of air involved was, in reality, very small.When considering the safety factors involved in dealing with compressed air, you not only have to look at the pressure but also the volume.  In this case the volume was very small.  In fact, we used a hand bicycle pump to pressurize them.Heck, shake up a coke bottle.  I suspect you'll get more than 8 PSI.All comes down to "stored energy".  Water, being non-compressible, doesn't "store" energy.  The small volume of air involved doesn't store much.I haven't heard lately about anybody getting hurt/killed when their garden hose (generally 45-60 PSI) burst.  Nor have I heard of many people getting hurt/killed when the tire on their bicycle blew out.  Dirty britches maybe, but seldom life threatening.If you look back at my posts (maybe you have), if I err (guess we all do at times), it will be with a lean toward safety.
Reply:Dave,Read the PS I just posted to the thread.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:DAMN,Don't you just love it when someone tries to take a "poke" at you, and his whole premise "blows up in their face".FWIW:  I didn't get my PE certs. for being stupid.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by SundownIIIDAMN,Don't you just love it when someone tries to take a "poke" at you, and his whole premise "blows up in their face".FWIW:  I didn't get my PE certs. for being stupid.
Reply:Well Dave I guess your experiences and mine differ.It will test his welds, which you seemed so concerned about.As I said earlier, I'd prefer to have the tank split or leak in the shop (I can fix it there), than I would have the tank fail (full of gas) from dynamic loading coming out of a turn in Marine Stadium or charging across the desert in his off-road vehicle.The "bulging" you seem so concerned about can easily be solved with the addition of a baffle or two, but just based on what he described, I don't think it will be needed.  If there's a problem to be found, I suspect it will be more likely a crack in one of the welds that may have left a slight crater.I've been welding aluminum fuel cells/tanks since 1966 and I've never had one fail in it's intended use (probably being overdesigned had something to do with it).  I've had them crushed in a blowover and cut in half when run over by another boat, but they didn't "leak" or "bulge".Maybe the OP will keep us posted on his progress.PS,  As far as where the 8 PSI came from.  It came from an engineer (not me) who worked for Hercules Powder Company (munitions manufacturer) in Hopewell, VA.  He was one of the members of our race team.  Had to do with what stresses the tank would be subjected to during an actual race.  Back in those days we didn't have a lot of sophisticated equipment to do proper strength of materials testing.  Worked for us.  BTW this is the same guy who got me into the welding shop at Hercules to fabricate the tanks in the first place.  They had one of the first of those "newfangled heliarc welders".  One of their welders was good enough to teach me how to use it (old Linde machine if I remember correctly).  I've used those numbers ever since.Last edited by SundownIII; 07-01-2009 at 01:46 AM.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by radrod57Do you just put it in a Brake?
Reply:for bungs I usually just weld in a piece of round stock with a small center hole.  After welding, I drill and tap it with pipe thread then buy an adapter that screws in.  Don't have to worry bout hurting the fancy fittings then.