Tank repairs

P

paulincayman

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Location
Cayman Islands
I straightened out a small crease in the area of the front gas tank frame mounts , 77 3cl gas tank , have now found a near invisible leak close to or at the right hand front mount bracket .it is very small but definitely a leak . For the experts...will a gas braze with brass/ bronze rod be sufficient or do I have to go with steel .
We have a new machine at work that can do mig, tig etc. Recalling my metal shop school class days was
Thinking gas brazing ought to do it
thanks
 
Not an expert welder, but have a little knowledge of metals. I'd prefer to go with whatever welding system they used to attach the fuel tank mounts in the first place. If it was fusion welded (spot welds?) then stick with a steel filler rod type. If it was originally brazed then go with that.

Reason being that introducing a new metal into a welded assembly limits future repair options if it fails.
 
as always Cam is offerring good advise but as a welder all my life I would say that silver solder would be the best option, the capilliary "creep" into and under the bracket (is it the U shaped one) will do lots of good, but before the process is started, gas free the tank (obviously) and VERY GENTLY heat the area all around and including the bracket to dull cherry, then, when cold, use an air line jet and a brush to get all the scale away before the silver solder float jobbie. It doesnt hurt to put a patch of steel over the crack and float that on as well, because cracks usually dont last long if s/s of braze is used, that is why but welding is not possible with either method. Cam is correct once you have used this method, its that or nothing (sort of)
CLEM
 
CLEMTOG said:
as always Cam is offerring good advise but as a welder all my life I would say that silver solder would be the best option, the capilliary "creep" into and under the bracket (is it the U shaped one) will do lots of good, but before the process is started, gas free the tank (obviously) and VERY GENTLY heat the area all around and including the bracket to dull cherry, then, when cold, use an air line jet and a brush to get all the scale away before the silver solder float jobbie. It doesnt hurt to put a patch of steel over the crack and float that on as well, because cracks usually dont last long if s/s of braze is used, that is why but welding is not possible with either method. Cam is correct once you have used this method, its that or nothing (sort of)
CLEM
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I’ve done just that but with a copper patch on a Guzzi nuovo Falcone tank where the metal had pin pricks, been good for five years.
 
And depends how much metal is left. When I had my '76 tank cleaned up for repainting in some areas there had obviously been more paint than metal. Required major patching and an epoxy liner to ensure no leakage.
 
Probably obvious, but worth mentioning just to be sure: Make sure there's no fuel vapour in the tank before hitting it with any kind of welder.
There are various methods of achieving that.
 
one of the best ways to get the tank gas free is to leave it outside, cap removed and invert the tank so the cap is on the bottom, leave it in free air for a month, (petrol is heavier than air) a few good blasts inside it with an air line is good thing prior to testing your process is good. a quicker way is to use a hair dryer (not a heat paint strip gun) and blow warm air into the tank until its so hot that you cant handle it with bare hands, put gloves on and heat some more, that works, I have done a similar process in a race paddock a couple of times, using the exhaust pipe from a car (we chose a petrol engined one) and with it at a fast idle, the same system worked well. For the DIYer the testing is the hard thing, and needed for your own safety and that of others nearby, I invert the tank outside, and "wave"a soft oxy/acet flame, at full arms length, under the cap, about 3 feet away, and getting progressively closer, all should be good, if the flame reaches the outlet without drama, but be prepared for a "woof" which has happened to me, you dont want to be in its way! this method is of course totally UNOFICIAL and cannot be condonned and should never be used, always get a chemist out to test for explosive gas (which I have had to do many times when cutting/removing welded in situ diesel tanks for commercial heating systems, they earn a months pay in a single day, and your insurance remains valid, no test cert= no insurance, take head.
CLEM
 
Thaks for all the advice. The tank have been sat for ages so little chance of a big bang ..been there done that many moons ago .
I have silver solder experince and access to a sandblaster so will go that route.
Thanks again
Paul
 
The tank sitting for ages will not rid it of petrol vapour, unless it is upside down and the vapour can run out of the filler hole, as petrol vapour is considerably heavier than air. Clem´s advice is what I have always used, however I say that it doesn't matter how you heat it, as long as there is no ignition source for the heavy vapours to reach. We used to sit the tank in the Australian sun for a couple of hours, and you can see the vapours falling out of the tank, until there was no visible vapour and then you couldn't even smell any in the tank. Here in Norway the hot season is short so we have just aimed a fan heater at the outside of the tank to achieve the same result. Clem´s idea of filling the tank with exhaust from a car is what is used on ships to prevent an explosive atmosphere in tanks and should also work fine though I have never tried it.
 
The ally tank on the Motodd has been welded more times than I care to remember and always used the exhaust method to weld. Never really bothered venting the tank, just empty it and flush it with soapy water. Did the BM tank a couple of months ago at the front mounts. Mates son is a welder and while he migged it I held a hose from a 4 wheeler directly into the tank while he welded. Young guy and had never heard of that technique. Was taught in welding school never to weld tanks without a certificate of steam cleaning. Glad he listened to me over his instructor.
So glad I made the carbon fibre tank for the Motodd as it has been 100% reliable for more than 8 years now. Has saved me untold welds
 
The first time I heard about it some kids were mucking about with an old 44-gallon drum and matches, it was on the News. Made me very aware and the few times I have been involved with welding fuel tanks I have gone to extremes to avoid explosions. I have a similar apprehension about getting into any sealed environments after hearing about mass deaths. One bloke goes into some kind of tank and collapses its seen and the next bloke does exactly the same thing and then the next. Then they discover there is a heavier than air gas settled low in that tank.
 
Vince said:
The first time I heard about it some kids were mucking about with an old 44-gallon drum and matches, it was on the News. Made me very aware and the few times I have been involved with welding fuel tanks I have gone to extremes to avoid explosions. I have a similar apprehension about getting into any sealed environments after hearing about mass deaths. One bloke goes into some kind of tank and collapses its seen and the next bloke does exactly the same thing and then the next. Then they discover there is a heavier than air gas settled low in that tank.
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Over here, Northern France, kids, and adults, mess around with unexploded ordnance, including some with mustard gas. WW1 is still killing.
One idiot some time ago used a shell as an anvil.

Paul
 
Paul Marx said:
Over here, Northern France, kids, and adults, mess around with unexploded ordnance, including some with mustard gas. WW1 is still killing.
One idiot some time ago used a shell as an anvil.

Paul
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Hmm, sounds like a candidate for the Darwin awards. It is awful that dangerous relics of war remain in many countries.

bazzee
 
bazzee said:
Hmm, sounds like a candidate for the Darwin awards. It is awful that dangerous relics of war remain in many countries.

bazzee
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Unfortunately, it's impossible to clean up the rubbish of two world wars, from the North sea, to the Swiss border. Not to mention neighbouring countries.
Nearly every week, there's the funeral, with all the necessary pomp, of a man killed more than a century ago.

Paul
 
Vince said:
The first time I heard about it some kids were mucking about with an old 44-gallon drum and matches, it was on the News. Made me very aware and the few times I have been involved with welding fuel tanks I have gone to extremes to avoid explosions. I have a similar apprehension about getting into any sealed environments after hearing about mass deaths. One bloke goes into some kind of tank and collapses its seen and the next bloke does exactly the same thing and then the next. Then they discover there is a heavier than air gas settled low in that tank.
Click to expand...
Yeh true Vince. A few years ago a couple of brothers at Sarina who operated a Bio Dunder carting business were found dead inside one of their tanks which they had entered to clean the residue from the day before delivery! I know toxic fume specialists were part of the investigation however have never seen any outcome.
(Bio Dunder is a by product of molasses fermented at the Sarina distillery and widely used as a fertiliser and also stock feed supplement in various forms.)
 
Shajota said:
Yeh true Vince. A few years ago a couple of brothers at Sarina who operated a Bio Dunder carting business were found dead inside one of their tanks which they had entered to clean the residue from the day before delivery! I know toxic fume specialists were part of the investigation however have never seen any outcome.
(Bio Dunder is a by product of molasses fermented at the Sarina distillery and widely used as a fertiliser and also stock feed supplement in various forms.)
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Alcohol poisoning.

Paul
 
First job in the morning at a winery is to open all the doors and let the air flow through to disperse the CO2 made in the ferment process. Angle grinders or oxy torches have done for more than a few folk cutting up 44g drums.
 
I did a guided tour of a winery in Tassie a few years ago. In one of the fermentation sheds, I leaned over a pinot noir fermentation vat to get good whiff of the nice wine smell and nearly passed out from the CO2. I was aware that the gas was produced during fermentation but had no idea that it would be at such a high concentration above an open-top vat that was just inside a wide open roller door, or that one sniff would be enough to enough to pass out. I only just managed to stay on my feet and stand up straight again. The winemaker who was taking the group on the tour didn't say not to do it. Perhaps he thought it would be entertaining if someone passed out. There were enough people on the tour to drag any fainters back out into the fresh air.
 
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