Welding a used gas tank

[rjardy]

Hey guys, I am looking to upgrade my fuel system and considering an in-tank pump. My tank is all but new but has had gas in it. Id like to weld the fuel return and the sump into this tank but have reservations about welding to a tank that has had fuel in it. Any recommendations on how to purge this and weld it safely?


Regards,

Rob

[raustinss]

It's like trying to take a s**t with your pants on. Can be done might be messy.cleaning it out and letting it air dry for a week obviously remove any and all parts that you can. Then be brave lol... Honestly take it to a shop and let them do it..if they will

[rjardy]

It's like trying to take a s**t with your pants on. Can be done might be messy.cleaning it out and letting it air dry for a week obviously remove any and all parts that you can. Then be brave lol... Honestly take it to a shop and let them do it..if they will

Sounds like I may be better off just buying a new tank. I like your analogy though!

[Vince@Meanstreets]

yep, they are so cheap now. Welding galv steel sucks.

[Build-It-Break-it]

Most radiator shops will clean them out and sometimes weld in what ever you desire. It's been done and isn't a big deal. Call a few and ask if they'll do it and pricing.

Galvanized is toxic when welded so just take proper precautions. Proper respirator etc.

[bigkarz]

fill the 1\5 way with water and dawn dish soap blow air in tank to mix repeat if still smells like gas poor it out and cut and weld
i did my tank and worked great

[Musclerodz]

If you have a plain stock tank, then just replace it. If you got a high doller tank like ricks then modifying may be something to consider. I purge my tanks with argon, but even then the pucker factor is high.

[rjardy]

fill the 1\5 way with water and dawn dish soap blow air in tank to mix repeat if still smells like gas poor it out and cut and weld
i did my tank and worked great


Lots of great info here. Thanks for all the input. It's just a stocker so getting another one is only a $200 affair. On the same note, whats the best place to put a sump? Lowest point sounds right?

[Musclerodz]

they are cheaper than that. You can buy a tanks inc tank already ready to go very reasonable.

[rjardy]

they are cheaper than that. You can buy a tanks inc tank already ready to go very reasonable.


Ill look in to that. Thanks

[Vega$69]

Looks like this guy is welding on his. He also has a 2 post lift. Lol

http://i103.photobucket.com/albums/m158/Johnthaxton/photo.jpg

[MeanMike]

Wash with soapy water a few times, then fill it with argon. Then say a prayer before striking an arc. I've done it twice and that first arc always makes you pucker.

[DBasher]

Looks like this guy is welding on his. He also has a 2 post lift. Lol

http://i103.photobucket.com/albums/m158/Johnthaxton/photo.jpg

Speaking of stupid....Years ago my brother picked up an early 60's Lincoln for cheap. After getting it running on a gas can we decided we needed to drop the tank and clean it out. Problem was it was full....solution, suck it out with a shop vac! My dad wasn't real proud of us that day.

:sieg:

[GregWeld]

Hey guys, I am looking to upgrade my fuel system and considering an in-tank pump. My tank is all but new but has had gas in it. Id like to weld the fuel return and the sump into this tank but have reservations about welding to a tank that has had fuel in it. Any recommendations on how to purge this and weld it safely?


Regards,

Rob



Rob -- Depends on what kind of tank -- Stainless Steel? Aluminum?

Don't bother if it's galvanized stamped steel.


I wash my tanks with Simple Green and water - about three times..... making sure to slosh this mixture around so it gets in the corners etc.

Then I rinse with plain water.... and sniff the tank... I don't want anything that even remotely smells like gas. IF the tank sniffs okay -- then I set it in the sun to bake and dry out. I've also done this with standing them up and directing some heat on them.... just to evaporate the water.

Before welding -- I get some dry ice and put that in side the tank -- I wait until the vapors are pouring out of all the openings. The dry ice turns into CO2... and purges the air out.

Add more dry ice if you need to as you weld and reposition etc.

What you don't want is any air in the tank -- it's the gas fumes that are explosive! If you've done your job washing... remember GAS is an oil so needs some soap of some kind to get it clean.... and you've got an inert gas -- then the fumes can't ignite.

[bigkarz]

dish soap works the radiator shop showed me

[rjardy]

dish soap works the radiator shop showed me

Perfect! Thank you. The tank is a stamped one. I'm thinking it is probably galvanized. I have had good luck with muruatic acid to remove the galvanizing, any other tips on removing it? I know what happens when you weld it. (Ask the 20 year old me about that) so ill do my diligence in removing it.

Rob

[T_Raven]

I used the pump out of a 98 Camaro tank in my 67 GMC. I just needed a quick, cheap way to get the truck running so I put the Camaro pump in the stock, in cab GMC tank.

I filled the Camaro tank with water and cut the ring out

http://i.imgur.com/Ae6WGqz.jpg

I filled the GMC tank with water and welded it in. It works fine until I get around to putting a tank under the bed.

http://i.imgur.com/NqgLNH0.jpg

A lot of people are really concerned about welding on a gas tank. It can't explode if water is displacing any fuel vapor. If there's a cheap option to just buy the tank you need, then that's not a bad idea, but I wouldn't be afraid to weld on a used tank.

[raustinss]

I used the pump out of a 98 Camaro tank in my 67 GMC. I just needed a quick, cheap way to get the truck running so I put the Camaro pump in the stock, in cab GMC tank.

I filled the Camaro tank with water and cut the ring out

http://i.imgur.com/Ae6WGqz.jpg

I filled the GMC tank with water and welded it in. It works fine until I get around to putting a tank under the bed.

http://i.imgur.com/NqgLNH0.jpg

A lot of people are really concerned about welding on a gas tank. It can't explode if water is displacing any fuel vapor. If there's a cheap option to just buy the tank you need, then that's not a bad idea, but I wouldn't be afraid to weld on a used tank.
As someone who is a fabricator I must say you are retarded !
-there is still air space in the tanks
-Water and electricity don't mix
-Metal fume fever is not cool
-Just because you have done it and it's worked ok doesn't mean it always will, why do you think that professional shops are leary about welding them. Not only that just because you have a "good" looking weld (which look terrible and just a bunch of tacks) on the tank I must ask
-Was the tank pressure tested after welding ?
-Did you use a mirror to inspect the other side of the welds to ensure proper penitration ?
-Was the tank "regalvinized "?
-If the tank wasn't pressure tested were the welds tested with liquid dye pen.?
Mag particle ?
-If it was pressure tested to what pressure and what was your process for finding potential leaks?
So please go ahead and fill my mind with your profound knowledge as you are now a professional gas tank welder and are teaching others how to endanger their own and possibly others lives

[Vega$69]

Right Stuff sells a new tank for $120

Not worth the risk. You'll spend more on Argon, Dry Ice and/or all the other misc. and still may blow your ass up.

[GregWeld]

Like most things --- the fact that people don't understand or know how to do something - doesn't make the practice inherently dangerous... People that are willing to learn, and listen, can be quite successful.

Simply understanding the process is critical. Cleaning the gas out of the tank is not overly complicated. Smelling the tank for fumes is not rocket science... and making sure you have an inert gas (of choice) so that fumes are not able to ignite is not hard or expensive either.

The naysayers probably have never welded something like this - and there's nothing wrong with saying "I don't want to do this". Many shops don't or won't work on this stuff because they either A) can't make money doing it or B) their insurance won't cover it.

Like most things - there's the right way and the "I think I know what I'm doing.... the wrong way".

Just FYI -- Antifreeze is flammable and when heated in a tank will also ignite with explosive results.... and there's millions of radiators worked on.

[Build-It-Break-it]

I'll say this much, when tanker trucks that previously had diesel, gas, lng or cng get cracks, leaks or damaged they're getting repaired period. They're not buying a new tanker ,they're fixing the damage. It can be done.

I worked at a place that repaired lng/cng tankers. Look up how explosive those are.

[MeanMike]

As someone who is a fabricator I must say you are retarded !
-there is still air space in the tanks
-Water and electricity don't mix
-Metal fume fever is not cool
-Just because you have done it and it's worked ok doesn't mean it always will, why do you think that professional shops are leary about welding them. Not only that just because you have a "good" looking weld (which look terrible and just a bunch of tacks) on the tank I must ask
-Was the tank pressure tested after welding ?
-Did you use a mirror to inspect the other side of the welds to ensure proper penitration ?
-Was the tank "regalvinized "?
-If the tank wasn't pressure tested were the welds tested with liquid dye pen.?
Mag particle ?
-If it was pressure tested to what pressure and what was your process for finding potential leaks?
So please go ahead and fill my mind with your profound knowledge as you are now a professional gas tank welder and are teaching others how to endanger their own and possibly others lives


If he is retarded, then there are a lot of successful retarded hot rodders and fabricators out there. Most mustangs get sumps welded in when they start getting faster than the stock style pump will support. Lots of low budget guys do it themselves. They don't buy new tanks and they don't tig weld them. They mig weld used tanks just like this guy did. And unlike his, they are welding where fuel leaks are more likely (under the level of fuel) Most all of them work fine. They don't re-galvanize them and they don't MPI them. Tig welds can look good and suck too, so don't get all judgemental about looks. And nobody pressure tests them because it's not a pressure vessel. Pressure testing a fuel tank would actually be quite dangerous.

Water and electricity are fine the way he is using it. Minimal air/fuel mix in the tank is the goal and water does it just as well as CO2 and Argon, it's just harder to work with.

Don't be a fabricator snob. This is hot rodding, there are many ways to do things if your smart about it. If your not, the tank explodes and natural selection does it's job.

[Che70velle]

I've had two tanks welded on, and both times the shop filled them both with water, and welded away. I did the clean out work, as Greg talked about, myself, before I took it to them.
I wasn't confident in my welding skills at the time, so I used a local shop.

[raustinss]

First I am definitely not a fabricator snob I mentioned that so some people know that I do have knowledge.
Second yes there are lots of people who do weld used tanks with success, that by no means that he should be telling someone else who doesn't quite know what to do or how to do it, ways to weld and possibly hurt himself
Third there were previous suggestions on much safer ways to do this eg. Try local shops, purge with argon,
Fourth clearly you aren't thinking correctly either a fuel tank IS a pressure vessel. Iill let you figure out that one
Fifth anyone who has welded anything galvanized will know how it can "pop" and "spit" unless you use a galvanizing wire which quite often is expensive and not easy to find.
I absolutely welcome hot rodding and everything which comes with it, I do have a problem with things when there is a solid 50/50 chance of someone getting hurt over a couple hundred dollars and some questionable advice

[rjardy]

Kinda bummed out that this thread turned to personal insults. Not cool, especially if you consider yourself a professional fabricator by trade. Any how... Ive got a lot of good info here. I think that I will give this a shot when the time comes. I'm all but settled on the dish soap method. I'm probably smart enough to run the tig near a tank full of water and not electrocute myself.

[raustinss]

Kinda bummed out that this thread turned to personal insults. Not cool, especially if you consider yourself a professional fabricator by trade. Any how... Ive got a lot of good info here. I think that I will give this a shot when the time comes. I'm all but settled on the dish soap method. I'm probably smart enough to run the tig near a tank full of water and not electrocute myself.

I should not have called him retarded...i was rude and wrong, it really gets me though when people open the opportunity to hurt themselves for absolutely no reason other then questionable advice. Having said that I think most people also missed something I should have stated but I thought it was obvious. If someone has a welder and the ability to weld the tank.....then why in gods name would you not purge the tank with argon. I have welded probably 15-20 transport truck tanks after road salt has been trapped by the straps. A simple aluminum strip is welded in place and then pressure test the tank at 10 psi with a soapy water solution. Back to the purging...the tanks were purge with a tank of argon, regulator and, hose. Dial the regulator down jam the hose in the tank and open the argon tank,after a few minutes the argon will push out the oxygen when possible just continue to let the argon flow while welding as it can also aid in weld penitration. If you can't then tape off the opening and weld away
Good luck and please play safe

[rjardy]

I should not have called him retarded...i was rude and wrong, it really gets me though when people open the opportunity to hurt themselves for absolutely no reason other then questionable advice. Having said that I think most people also missed something I should have stated but I thought it was obvious. If someone has a welder and the ability to weld the tank.....then why in gods name would you not purge the tank with argon. I have welded probably 15-20 transport truck tanks after road salt has been trapped by the straps. A simple aluminum strip is welded in place and then pressure test the tank at 10 psi with a soapy water solution. Back to the purging...the tanks were purge with a tank of argon, regulator and, hose. Dial the regulator down jam the hose in the tank and open the argon tank,after a few minutes the argon will push out the oxygen when possible just continue to let the argon flow while welding as it can also aid in weld penitration. If you can't then tape off the opening and weld away
Good luck and please play safe


Great tips, very helpful. Thank you. I understand your frustration. Thanks for clearing the air.

Rob

[Vince@Meanstreets]

Im not saying it stupid, turbo timing, dangerous or a waste of time to do. Its just so much easier for me to buy a new tank and ones that are already converted.

I have modded a few tanks in the past, you have to take it down, clean it out, prep it, prep i again, weld it up, pressure test and repair if the weld didn't hold. Sound like an easy afternoon, sure but you still have that dented scruffed up old gas tank.

For less than 4 hours of labor time you can have a new tank that is sealed right and does what its supposed to do... and it looks new. But....if they are not available for your car then have at it. Dry ice in the tank and go.

[T_Raven]

As someone who is a fabricator I must say you are retarded !
-there is still air space in the tanks
-Water and electricity don't mix
-Metal fume fever is not cool
-Just because you have done it and it's worked ok doesn't mean it always will, why do you think that professional shops are leary about welding them. Not only that just because you have a "good" looking weld (which look terrible and just a bunch of tacks) on the tank I must ask
-Was the tank pressure tested after welding ?
-Did you use a mirror to inspect the other side of the welds to ensure proper penitration ?
-Was the tank "regalvinized "?
-If the tank wasn't pressure tested were the welds tested with liquid dye pen.?
Mag particle ?
-If it was pressure tested to what pressure and what was your process for finding potential leaks?
So please go ahead and fill my mind with your profound knowledge as you are now a professional gas tank welder and are teaching others how to endanger their own and possibly others lives

I'm well aware of the fumes from welding galvanized metal. I did it in a ventilated area and had no problems.

The air space is minimal. Maybe what little fumes are in there could cause a problem but nothing like an empty tank full of fumes. Nothing happened so oh well.

I know the welds look bad. I never said they didn't. The piece from the Camaro tank was much thinner and it was hard to make tacks without it just making a bigger gap. I'm sure a pro could do it better.

I pressurized the tank and used soapy water to find pin holes.

People like you really need to calm the heck down. I never said I was a professional or sharing my profound knowledge. The point of what I did was to make my truck run with what I had on hand until I decide on a better tank. It's not professional quality but it works. The point of sharing it was to show that I welded on a tank with no catastrophic damage done, not to show what a pro gas tank welder I am.

[Vince@Meanstreets]

I'm well aware of the fumes from welding galvanized metal. I did it in a ventilated area and had no problems.

The air space is minimal. Maybe what little fumes are in there could cause a problem but nothing like an empty tank full of fumes. Nothing happened so oh well.

I know the welds look bad. I never said they didn't. The piece from the Camaro tank was much thinner and it was hard to make tacks without it just making a bigger gap. I'm sure a pro could do it better.

I pressurized the tank and used soapy water to find pin holes.

People like you really need to calm the heck down. I never said I was a professional or sharing my profound knowledge. The point of what I did was to make my truck run with what I had on hand until I decide on a better tank. It's not professional quality but it works. The point of sharing it was to show that I welded on a tank with no catastrophic damage done, not to show what a pro gas tank welder I am.

not baggin on you but your debating safety. whats safer? welding on a cleaned out tank that previously had fuel in it or having a 16 gallon fuel tank with potenial for leaking welds? :sarcasm_smiley:

[T_Raven]

not baggin on you but your debating safety. whats safer? welding on a cleaned out tank that previously had fuel in it or having a 16 gallon fuel tank with potenial for leaking welds? :sarcasm_smiley:

Well the OP's question was about the safety of welding on a tank that has had fuel in it.

What should I expect to leak? After fixing a couple pin holes it held pressure fine, and 9 months later doesn't leak. I'm not saying the quality of my tank is good for a long term mod, all I'm saying is I welded on a gas tank and didn't die.

[raustinss]

You missed the part where I stated that If you can get or have access to welder.... . Probably have access to argon and jamming a hose in the tank to purge isn't hard. Leading me to say why not. I'm glad that you were able to weld it and not hurt yourself but when there is a easier way why not do it

[GregWeld]

You missed the part where I stated that If you can get or have access to welder.... . Probably have access to argon and jamming a hose in the tank to purge isn't hard. Leading me to say why not. I'm glad that you were able to weld it and not hurt yourself but when there is a easier way why not do it



Because we're "hot rodders" and "Do-It-Yourself" people...


I can afford to buy anything I like... but I also have a lot of tools and a very nice shop... so I can do things myself or for others. Sometimes it has nothing to do with buying. The saying "built not bought" comes to mind.

[MeanMike]

Fourth clearly you aren't thinking correctly either a fuel tank IS a pressure vessel. Iill let you figure out that one


You apologized, so I'm not going to get into any heated debate here. But I want to discuss this so no-one tries anything dangerous here. I'll assume you are talking about head pressure. 12" of fuel is about as deep as you'll get in any fuel tank in a car. 12" is about .5psi of head pressure at the bottom of the fuel tank and it gets lower as you go up. Pressure testing to .5 psi is fine, but that's not really considered a pressure vessel.

Factory tanks are resistance welded around the edge sometimes with some seam sealer in there to help seal it. It's not the best weld. Just bending the weld joint is sometimes enough to make it leak.

Let's assume you have a 3' x 2' tank (36" x 24") That's 864 in^2. If you pressurize that tank to 5 psi that's 4300lbf trying to rip that weld apart. If it were a round tank like a tanker it would withstand that pretty easily. But, since it has corners, those are the weak points and as it deforms puts some really bad stress on those welds. It's not safe to pressure test that high because it was never meant for that.

Just filling it with water and letting it sit is usually good enough to find a leak.

[T_Raven]

You missed the part where I stated that If you can get or have access to welder.... . Probably have access to argon and jamming a hose in the tank to purge isn't hard. Leading me to say why not. I'm glad that you were able to weld it and not hurt yourself but when there is a easier way why not do it

What I did was mostly an experiment and my first time welding a gas tank. I thought about purging it with argon, but since I can't see argon and fuel vapor, having water I can actually see and know for certain how much vapor had been displaced, I did it that way. I do need to set up my tig to be able to back purge for welding stainless in the future, but with my current regulator set ups, it was easy enough to grab the water hose.

Again, I'm not saying anything I did was the best way. I was just sharing to show that welding on a used tank isn't the explosion hazard a lot of people think it is. :)

[rustomatic]

This seems like a really (or at least potentially) expensive and stressful way to save money/be creative. I get the thrust of the venture, but over the summer, I found out how ridiculously difficult it is just to get all of the gas out of my Falcon's former gas tank. I gave up and threw it in the truck headed for the dump . . .

Stay safe!:peepwall:

[Vince@Meanstreets]

Well the OP's question was about the safety of welding on a tank that has had fuel in it.

What should I expect to leak? After fixing a couple pin holes it held pressure fine, and 9 months later doesn't leak. I'm not saying the quality of my tank is good for a long term mod, all I'm saying is I welded on a gas tank and didn't die.

just sayin, you brought it up not me. :stirthepot:

no dog in this fight if you can't see that. :lmao:

[raustinss]

You apologized, so I'm not going to get into any heated debate here. But I want to discuss this so no-one tries anything dangerous here. I'll assume you are talking about head pressure. 12" of fuel is about as deep as you'll get in any fuel tank in a car. 12" is about .5psi of head pressure at the bottom of the fuel tank and it gets lower as you go up. Pressure testing to .5 psi is fine, but that's not really considered a pressure vessel.

Factory tanks are resistance welded around the edge sometimes with some seam sealer in there to help seal it. It's not the best weld. Just bending the weld joint is sometimes enough to make it leak.

Let's assume you have a 3' x 2' tank (36" x 24") That's 864 in^2. If you pressurize that tank to 5 psi that's 4300lbf trying to rip that weld apart. If it were a round tank like a tanker it would withstand that pretty easily. But, since it has corners, those are the weak points and as it deforms puts some really bad stress on those welds. It's not safe to pressure test that high because it was never meant for that.

Just filling it with water and letting it sit is usually good enough to find a leak.

you are completely right lets stop the heated debate and insults (myself) and yes discuss this the right way, please see the next post

[raustinss]

What I did was mostly an experiment and my first time welding a gas tank. I thought about purging it with argon, but since I can't see argon and fuel vapor, having water I can actually see and know for certain how much vapor had been displaced, I did it that way. I do need to set up my tig to be able to back purge for welding stainless in the future, but with my current regulator set ups, it was easy enough to grab the water hose.

Again, I'm not saying anything I did was the best way. I was just sharing to show that welding on a used tank isn't the explosion hazard a lot of people think it is. :)

ok let me state here what i know and dug up ,
# 1 you cant see argon nor fuel vapour but you might not be aware that
argon is a inert gas that aids in welding as IS heavier then air which
is why alot of people will use it to purge tanks of flammable vapours
a fuel tank can be purged in just a few short minutes
#2 setting up your current TIG welder for back purging is quite simple of
course it depends on what you are welding but for the most part its as
simple as turning the tank on and set the regulator at barely open to flow
a few psi down a hose into the part being welded a little tape to hold it in
place and away you go . also tape off all openings except one
#3 i went out of my way to speak with my ex's step father he owns a local
radiator,AC,etc shop. he has welded thousands of tanks over the years
but whenever possible avoids it due to cost . his process is use a hotsy
hot water pressure washer getting the tanks to well over 100 degrees
immediately blows them dry with compressed air then lets them sit for a
day followed with whatever welding and then a pressure test in a water
tank. the way he pressure tests them is sets a regulator to approx 20lbs
then cracks a ball valve attached to it for 2-3 seconds .this will fill the
tanks to 1-3 psi after which he dunks them into his water tank but a soap
water mix will certainly work. any higher pressure will balloon the tanks
rendering them useless . i stated i had welded transport tanks earlier and
we pressure tested them at a higher pressure but this was due to the
much thicker material and construction (cylindrical) .
#4 PLEASE understand im not trying to be a fabrication snob i just couldnt
stand knowing that someone got hurt when i had the knowledge to help
guide them along safely and correctly
#5 Jim told me that the garage beside his rad shop was run by some italian
fella who used the water technique . his way after washing out a tank
dry it with a rag lit on fire on the end of a old fishing pole (needless to
say there was a few tanks that went up with a hell of a kaboom) he
then graduated to the water technique the problem with this is any
remaining vapours now get concentrated to the remaining airspace in the
tank with can increase the chances with a kaboom .

hopefully this can and will help anyone and everyone who is considering doing something such as this at home . FOR THE RECORD I WILL NOT TAKE ANY
RESPONSIBILITY FOR ANYTHING IF YOU BLOW YOURSELF OR YOUR HOUSE UP
when i asked jim what the best home made process is he said anything is doable the biggest thing is getting the tank clean he suggested a shop such as his,have the tank steam cleaned by someone else then weld it yourself, and last was the one i suggested clean it ,dry it ,air it out,argon purge , he did not suggest the water technique for the reasons i stated quite a bit earlier. i would also like to say that yes i chirpped about the appearance of the welds , i will say that im well aware some welds dont have to be good looking to be strong and vice versa . i have done quite a few over the years which landed on both sides of the fence it just goes with the territory of being a custom steel fabricator . what a poor attempt of my chirp was trying to state was it didnt look like the welder was not set up correctly for that thin of material and it looked like a bunch of tacks . a bunch of tacks can be strong when done right but can also cause weld faults in the form of inclusions and crater cracks. please if anyone has any constructive things to add or comment on chime away.
thanks guys Ryan

[T_Raven]

This seems like a really (or at least potentially) expensive and stressful way to save money/be creative. I get the thrust of the venture, but over the summer, I found out how ridiculously difficult it is just to get all of the gas out of my Falcon's former gas tank. I gave up and threw it in the truck headed for the dump . . .

Stay safe!:peepwall:

With as cheap as tanks are for the more popular models, I agree it's not worth the hassle if you have one of those cars. Especially now that there are EFI tanks as cheap as they are for some cars.

ok let me state here what i know and dug up ,
# 1 you cant see argon nor fuel vapour but you might not be aware that
argon is a inert gas that aids in welding as IS heavier then air which
is why alot of people will use it to purge tanks of flammable vapours
a fuel tank can be purged in just a few short minutes
#2 setting up your current TIG welder for back purging is quite simple of
course it depends on what you are welding but for the most part its as
simple as turning the tank on and set the regulator at barely open to flow
a few psi down a hose into the part being welded a little tape to hold it in
place and away you go . also tape off all openings except one
#3 i went out of my way to speak with my ex's step father he owns a local
radiator,AC,etc shop. he has welded thousands of tanks over the years
but whenever possible avoids it due to cost . his process is use a hotsy
hot water pressure washer getting the tanks to well over 100 degrees
immediately blows them dry with compressed air then lets them sit for a
day followed with whatever welding and then a pressure test in a water
tank. the way he pressure tests them is sets a regulator to approx 20lbs
then cracks a ball valve attached to it for 2-3 seconds .this will fill the
tanks to 1-3 psi after which he dunks them into his water tank but a soap
water mix will certainly work. any higher pressure will balloon the tanks
rendering them useless . i stated i had welded transport tanks earlier and
we pressure tested them at a higher pressure but this was due to the
much thicker material and construction (cylindrical) .
#4 PLEASE understand im not trying to be a fabrication snob i just couldnt
stand knowing that someone got hurt when i had the knowledge to help
guide them along safely and correctly
#5 Jim told me that the garage beside his rad shop was run by some italian
fella who used the water technique . his way after washing out a tank
dry it with a rag lit on fire on the end of a old fishing pole (needless to
say there was a few tanks that went up with a hell of a kaboom) he
then graduated to the water technique the problem with this is any
remaining vapours now get concentrated to the remaining airspace in the
tank with can increase the chances with a kaboom .

hopefully this can and will help anyone and everyone who is considering doing something such as this at home . FOR THE RECORD I WILL NOT TAKE ANY
RESPONSIBILITY FOR ANYTHING IF YOU BLOW YOURSELF OR YOUR HOUSE UP
when i asked jim what the best home made process is he said anything is doable the biggest thing is getting the tank clean he suggested a shop such as his,have the tank steam cleaned by someone else then weld it yourself, and last was the one i suggested clean it ,dry it ,air it out,argon purge , he did not suggest the water technique for the reasons i stated quite a bit earlier. i would also like to say that yes i chirpped about the appearance of the welds , i will say that im well aware some welds dont have to be good looking to be strong and vice versa . i have done quite a few over the years which landed on both sides of the fence it just goes with the territory of being a custom steel fabricator . what a poor attempt of my chirp was trying to state was it didnt look like the welder was not set up correctly for that thin of material and it looked like a bunch of tacks . a bunch of tacks can be strong when done right but can also cause weld faults in the form of inclusions and crater cracks. please if anyone has any constructive things to add or comment on chime away.
thanks guys Ryan

Good info, thanks.

The idea with what I welded was to just make a decent stitch weld around the ring. I had a hard time not burning through the thinner metal and had to weld up some holes. You mentioned galvanized can cause some popping so I wonder if that contributed as much as the metal being thin did.

[GregWeld]

I've seen welding and mods around here (and other sites) that are far more "dangerous".... and I've taken plenty of factory tanks out with lots of evidence of gas leakage around the fill connection and other ports. Gas fumes are heavier than air... the tanks exterior is "open to atmosphere" and therefore the fumes "should" fall away and not be in a confined space.

Scares me more to fill a plastic gas can where I can SEE the fumes rolling out the top and down the sides - and I'm standing right there with my face and hands close to this! Something as simple as static electricity could set it off. WTF

I don't think this is a big safety issue - and it's not at all if done correctly.