Welding tanks and steam myth .

[Redneck in training]

This brought back memories of an old timer who welded up the leaky seams in a motorcycle gas tank for me. When I went back to pick it up I asked how he had purged the tank. He told me he kept it 100% full of water so there was no space for an explosive atmosphere. I still think his torch could have boiled gas vapors out of the leaky seam and ignited them.

But outside of the tank. It would just burn without an explosion.
Tanks explode due to reaction speed. They start as burning but quickly escalate due to pressure increase speeding up the chemical reaction (oxidation).

 

[greenmule]

Well,don't know about that now,?I'm not going to be welding up a hole in a gas tank.

 

[Egon]

I apologize if I came across as miffed earlier. I was frustrated at not being able to get through with my point.

I understood perfectly do not fear.

But how do you get as safe environment for the welding. Get rid of the source of combustibles would seem to be one plausible explanation.


! [expandable plugs. vented plugs, circulated plugs, eductor drawing tank fumes to a flare stack or just a safe location downwind, clay packs, vented plug injecting nitrogen into tank and being drawn out at another location to safe environment or stack and the list could go on. And yes steam could be used to drive the eductor.

If piping configuration is know there may be other ways.

By the way, no comment on the welder being on top of the tank. Was he on a walkway, supported platform or just standing on the top of the tank. Most reputable operations rather frown on standing on a tank top.

 

[polo1665]

I understood perfectly do not fear.

But how do you get as safe environment for the welding. Get rid of the source of combustibles would seem to be one plausible explanation.


! [expandable plugs. vented plugs, circulated plugs, eductor drawing tank fumes to a flare stack or just a safe location downwind, clay packs, vented plug injecting nitrogen into tank and being drawn out at another location to safe environment or stack and the list could go on. And yes steam could be used to drive the eductor.

If piping configuration is know there may be other ways.

By the way, no comment on the welder being on top of the tank. Was he on a walkway, supported platform or just standing on the top of the tank. Most reputable operations rather frown on standing on a tank top.

I believe the only way to get and absolutely safe environment would be to clean the tank in the ways prescribed by yourself and "Wis Bang" . You may be able to fudge your way through by blasting an inert gas through the tank while welding, but this is where my knowledge runs aground.
In my application a purge is only necessary in an emergency, not as a matter of daily doings. I became interested in this matter when I heard that steam was used as an oxygen purge. It did not seem like a good choice to me and I wanted to know what drove the decision to use it. It does not sound to me like these people had a clue IMO. Too bad, sorry for his family.

Mark

 

[Redneck in training]

My thinking is steam was most likely used because of availability. To use steam effectively to purge the tank it has to have sufficient velocity trought the vesel and constant positive pressure during the welding. Once the flow is lowered it starts condensing faster than it is supplied lowering pressure inside the tank drawing air back onto it.

 

[Egon]

You may be able to fudge your way through by blasting an inert gas through the tank while welding,

Depending on the piping configuration there may be other perfectly acceptable ways in which to produce a safe welding environment.

I also feel sorry for the individual and his family for a situation that should not have happened.

 

[Stimw]

Over 30 years ago I used to weld cracks and other repairs in semi gasoline tankers. I worked for Fruehauf Trailers. We used a steam cleaner to clear the tanks. We ran the steam in all sections of the tank and let the valves open and the condensed water would run out. Usually they would be cleaned for a day before trying to repair. We used what was called an Explosimeter to test for flameable material. The tank was checked every 30 minutes while being repaired. We even climbed inside to weld. There was a dedicated vent system and a safety man used at all times.
The mistake from reading the article is they didn't clear the tank they just tried to purge the air. The steam in their situation would have only made things worse by heating the flameables up to their flash point.
I've cut, welded, soldered or brazed on hundreds of fuel and diesel tanks through the years and I've walked away from a few.

 

[Wis Bang]

Over 30 years ago I used to weld cracks and other repairs in semi gasoline tankers. I worked for Fruehauf Trailers. We used a steam cleaner to clear the tanks. We ran the steam in all sections of the tank and let the valves open and the condensed water would run out. Usually they would be cleaned for a day before trying to repair. We used what was called an Explosimeter to test for flameable material. The tank was checked every 30 minutes while being repaired. We even climbed inside to weld. There was a dedicated vent system and a safety man used at all times.
The mistake from reading the article is they didn't clear the tank they just tried to purge the air. The steam in their situation would have only made things worse by heating the flameables up to their flash point.
I've cut, welded, soldered or brazed on hundreds of fuel and diesel tanks through the years and I've walked away from a few.

Exactly, you followed a set procedure and monitored the tank atmosphere to insure your safety. Fruehauf & Heil built the Best tankers in my opinion...

A previous poster questioned why the explosion occured inthe open atmosphere atop the tank. The report says the welder was welding a flange to the top of the tank, a tank filled with fumes in the explosive range. He was welding on a bomb with spectacular results,

 

[tommu56]

Reading this thread is why cutting open old barrels scares the bejesus out of me. A few years back a local guy had his garage go up because he got his torch too close to the gas tank.

I resemble that one careless mistake!

Back in 85 I was cutting some drums in half at work I was working alone on a Saturday I had 20 or so laying in the field. I took the bungs out of them all (or so I thought) I use to put torch on the side and would blow a hole in side put torch in the hole and burn out the residue out the bungs.

Well I put the torch on one and as I was heating it up it started to blow out like I had the oxygen on but it wasen't on.

The next thing I knew I was 20 feet away from drums against the side of my truck my right knee had been cut and my stomach had a 8" gash in it.

I got up turned off the gases to the torch an hobbled to a neighboring plant for some help.

The drum head unrolled when it exploded I got hit by the head and the drum went 65' the other way.

Laying in the hospital 3 days later the evening news had article on a guy doing the same thing I was and got killed, then I realized how lucky I was!

or maybe I wasn't alone?
Needless to say I am really careful with the torches / welding after that.

tom

 

[Scooby074]

I resemble that one careless mistake!

Back in 85 I was cutting some drums in half at work I was working alone on a Saturday I had 20 or so laying in the field. I took the bungs out of them all (or so I thought) I use to put torch on the side and would blow a hole in side put torch in the hole and burn out the residue out the bungs.

Well I put the torch on one and as I was heating it up it started to blow out like I had the oxygen on but it wasen't on.

The next thing I knew I was 20 feet away from drums against the side of my truck my right knee had been cut and my stomach had a 8" gash in it.

I got up turned off the gases to the torch an hobbled to a neighboring plant for some help.

The drum head unrolled when it exploded I got hit by the head and the drum went 65' the other way.

Laying in the hospital 3 days later the evening news had article on a guy doing the same thing I was and got killed, then I realized how lucky I was!

or maybe I wasn't alone?
Needless to say I am really careful with the torches / welding after that.

tom

Glad you made it thru that. It can happen all too quick.