Has anyone heard of filling the diesel tank with water before welding??

[Cadence]

It sounds like opinions from a bunch of know nothing, my self included.

[Kita]

Originally Posted by Cadence

Yep! carbon monoxide and lots of unburnt gas vapor. I'd take my chances with a little diesel vapor.

Can you say BOOM!

[Kita]

Originally Posted by groundtackle

Oxygen/gas analyzer and know how to use it... no other way than safe. Go to a pro.

I never had one,but that's how we do ship tanks you can get in,sometimes it may take days to get it ...on a big tank,we are talking smaller here,no 1 way was inert gas like what I use for TIG ,,argon,that's best for me,next is co2 like a car ex,this is usually what I do because it's cheep & easy,vent tank & pipe an ex hose in & move the tank around if you can or a small something to move a small amount of co2 around so as to completely fill tank & have it flowing while you are welding. .....I seen a guy die cutting the bottom of an empty gas tank with a grinder cutoff wheel...tank blew up!

[Reefmagnet]

Originally Posted by Cadence

It sounds like opinions from a bunch of know nothing, my self included.

I've forgotten more than most people know about welding yet still no more about welding then most people.

My particular favs in this thread are the use of car exhausts (inside a boat, no less) and horribly embrittled welds on low carbon steel caused by rapid cooling.

Funny enough, welding on a full tank of oil (which diesel is) isn't as stupid as it seems (google "hydrostatic testing" for one reason it's not as dumb an idea as it first sounds). In fact, the biggest problem encountered with welding cracks in tanks containing oil is weld porosity caused by the gassing from the oil as it's burnt. Mind you, it's probably not a good idea to burn through the parent material whilst welding either.

[Kita]

Originally Posted by Reefmagnet

I've forgotten more than most people know about welding yet still no more about welding then most people.

My particular favs in this thread are the use of car exhausts (inside a boat, no less) and horribly embrittled welds on low carbon steel caused by rapid cooling.

Funny enough, welding on a full tank of oil (which diesel is) isn't as stupid as it seems (google "hydrostatic testing" for one reason it's not as dumb an idea as it first sounds). In fact, the biggest problem encountered with welding cracks in tanks containing oil is weld porosity caused by the gassing from the oil as it's burnt. Mind you, it's probably not a good idea to burn through the parent material whilst welding either.

Wouldn't matter if you used argon or co2 or car ex in the matter of small environment like a boat ,they ALL have a similar Danger removing oxygen so that the fire won't burn and well you still got to have enough to breathe so ventilation is important but you gotta remember we're talking about a fuel tank that is going to be a thin layer unless it is not a normal tank,water oil or anything other than inert gas will contribute to a very poor quality weld...so a tube Goin in & outside that will leave the welder air,that's just welder common sense any welder that will be welding a tank should have no problem working with this if he doesn't have a problem and doesn't care where the fumes are then let me know when he is going to weld I want to be someplace else....somebody said underwater welding, this is totally different, that uses a Flux that removes the contaminant from the weld area it is a completely different situation with water on the other side of a thin piece of metal that you are trying to weld. Been there done that some of it I learned the hard way sometimes I even listened and learn the right way sometimes I just hate to see someone get hurt.

[Uncle Bob]

Originally Posted by Make_My_Day

We are having some welding done on our boat as recommended by the surveyor. Along the way the bottom was sandblasted and some additional places that needed attention came to light.

One of these is the back of the keel where diesel was visible after the sandblasting. The keel is our 200 liter diesel tank.

We drained the tank completely and left it open to ventilate. This was good for the welding on the transom and on the bow, but now the welder wants to fill the tank with water prior to welding on the places that showed leaks. This is to prevent explosion.

This seems strange to me because I would never want to have water by diesel. In addition to worrying about how to get it completely dry before refilling, I am also concerned about corrosion. There is no access port from above the tank only a drain port on the bottom of the keel.

I spoke to the surveyor and he thought it was strange as well. He thinks that an inert gas like nitrogen should be used in the tank to displace the oxygen.

Has anyone heard of or used this practice of filling the tank with water for welding? What about the use of inert gas? Any insight would be appreciated.

Originally Posted by Kita

Wouldn't matter if you used argon or co2 or car ex in the matter of small environment like a boat ,they ALL have a similar Danger removing oxygen so that the fire won't burn and well you still got to have enough to breathe so ventilation is important but you gotta remember we're talking about a fuel tank that is going to be a thin layer unless it is not a normal tank,water oil or anything other than inert gas will contribute to a very poor quality weld...so a tube Goin in & outside that will leave the welder air,that's just welder common sense any welder that will be welding a tank should have no problem working with this if he doesn't have a problem and doesn't care where the fumes are then let me know when he is going to weld I want to be someplace else....somebody said underwater welding, this is totally different, that uses a Flux that removes the contaminant from the weld area it is a completely different situation with water on the other side of a thin piece of metal that you are trying to weld. Been there done that some of it I learned the hard way sometimes I even listened and learn the right way sometimes I just hate to see someone get hurt.

Yeah, I guess that filling the internal fuel tank with an inert gas and then welding it from the OUTSIDE really places the welder at risk of asphyxiation.

[Kita]

Originally Posted by Uncle Bob

Yeah, I guess that filling the internal fuel tank with an inert gas and then welding it from the OUTSIDE really places the welder at risk of asphyxiation.

I was responding to someone's consern about flooding the tank with CO2 or whatever & have it also inside a boat & speaking from experience it could definitely happen so good ventilation is important but the co2 level inside of tank should be fine when saturated with car exhaust or whatever intert gas you're going to run,but yours is a very valid point! Hey I been known to run a fresh air line to my helmet! When you see someone get smoked it gets your attention. .

[bony]

Originally Posted by four winds

Indeed not an unknown technique. Have done it several times on old antique auto restorations to retain an original fuel tank.

Easy with the tank removed and the weld at the top, as mentioned.

Don't know about a tank in place with water dripping out, no experience there. But your welder is probably not an idiot as some might think.

Years ago I use to do interstate trucking in Australia and the old girl I drove had two 80 gallon diesel tanks. I was halfway between Melbourne and Perth on one trip when the right side tank developed a vertical crack about 10 inches long along the line of an internal baffle plate. Getting hold of someone with an arc welder out there was a story in itself but suffice to say that I managed to do that and repaired the tank myself. The tank was still about two thirds full of diesel and, not wanting to lose that precious fuel, I decided to tack weld the crack while gently playing copious amounts of water on it from a garden hose. The water did make welding more difficult but once I had the amperage right I soon had the crack tacked in several places. I then ran a series of vertical welds while still keeping the water flowing. In the end the repair was done successfully, no more fuel leaks, and I was able to hit the road again and had no further issues. I guess my methods may have been risky but in those days when things went wrong out there, you had to improvise.

[Alastair A]

Hi. A medical note about human biological interaction with various gasses, as I understand it.
1. Carbon-dioxide - small amount inside the tank ok. If excess escapes it is heavier than air. Don't breath from the bilge. If you breath excess CO2, it first causes rapid hyper ventilation and panic. Most people get out of this situation (if it is not deep in a confined space or bein lowered in).
2. Carbon-monoxide - small amounts cause drowsiness and lack of judgement. It blocks the bodies breathing reflex. Large amounts exclude blood born blood oxygen for the life of each blood cell. It is (of cause) often used for suicide. Don't go there please. If daylight seems pink, then you are affected and may soon die.
3. Argon and other inert gasses - these exclude oxggen that we need to breath, but they have little biological effect on human metabolism otherwise at normal atmospheric pressure. You just choke. They generally cause panic gasping and rapid escape (if possible). Most people get out of this situation, if it is not too deep in a confined space.

Please USE A PROFESSIONAL WITH EXPERIENCE. I have seen a huge explosion from a small tank. Cheers. A.