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Morgan
01-18-2006, 07:17 PM
I have a broken broken flange weld on my cars exhaust system. The broken weld is on the flange which has the pipe that connects to the catalytic converter side of the exhaust system. Therefore, removing the exhaust system would be difficult. Also, the broken flange that needs welding is about 8 inches from the gas tank. My question is, if I weld near the tank do you think the sparks from the welder will cause the gas tank to expode? :confused:

81Malibu
01-18-2006, 07:27 PM
as long as you have no leaks your fine but to be safe try putting some sort of shield between the exhaust and gas tank if your that worried about it...ie, sheetmetal, maybe even a few layers of tin foil or something.

MDuke
01-18-2006, 07:36 PM
I agree with Malibu your best bet I think is to put some kind of barrier up to try to aviod any problems. You may be better off waiting until the tank almost empty to start welding on it. Just my thoughts. MDuke

Manny
01-18-2006, 07:46 PM
Mduke,
It's the vapors in gas that are worrisom to work around, full fuel tank is better to minimize vapors. A shield would be needed, make sure have no leaks or contained area for vapor accumulation.
Manny

Hotfoot
01-18-2006, 08:40 PM
Yup on heat shield. If you have to improvise, I'd put an oven mitt behind that sheet metal...and watch it for burning...which it shouldn't unless you direct heat to it....then, I'd venilate , with fan blowing TOWARDS gas tank (so fumes are not transported to the weld), I'd also be doing it outside. If MIG, you'll have to use flux cored wire in order to use the fan. If all fails and it explodes, be sure to let us know! :p

djb
01-18-2006, 09:12 PM
You didn't mention what kind of vehicle this is. For all we know this may be a plastic gas tank. Careful.

Bowtieman31
01-18-2006, 10:30 PM
You may be better off waiting until the tank almost empty to start welding on it. MDuke

Wrong, Wrong, Wrong! The more vapor space in the tank, the more likely you WILL have an explosion. It's the gasoline vapors that ignite, not the liquid itself. If you've ever seen a flammable liquid burn, you will notice that the flame is actually a short distance above the liquid. The liquid does not burn, as it heats up it produces more vapors and sustains the fire.

If you're welding in close proximity of the fuel tank and it is a metal tank, not plastic, and you do not have any leaks. You will do fine. You can use a heat shield if you'd like just for an extra measure of safety. Also, make sure there are no rubber fuel or brake lines that are close. If there are, shield them also. :D

Charley H
01-18-2006, 11:11 PM
hi. this is just for a little information. when my dads garage burned down,his almost new car was sitting in it. a 1979 dodge aspen that he bought new for a retirement car. he had just filled up the gas tank. the gas tank never blew up or burned. Dad started to go in to start car and back it out. before he got to the door some boards from overhead fell down on the car and he decided not to do it. the state fire marshall said lighting stuck the roof. i have read before that it is not so much the gas that will get you but the fumes. the lower the gas level the more fumes. good luck. charley.

Morgan
01-18-2006, 11:27 PM
I have a broken broken flange weld on my cars exhaust system. The broken weld is on the flange which has the pipe that connects to the catalytic converter side of the exhaust system. Therefore, removing the exhaust system would be difficult. Also, the broken flange that needs welding is about 8 inches from the gas tank. My question is, if I weld near the tank do you think the sparks from the welder will cause the gas tank to expode? :confused:

Once again I would like to thank everyone for their comments. The gas tank in the car is about 3/4 full, and I have some scap sheet metal that I will be using for a shield. However, if there are something else that some would like to add, please keep the comments going.

Morgan
:)

bfmaloney
01-18-2006, 11:54 PM
Once again I would like to thank everyone for their comments. The gas tank in the car is about 3/4 full, and I have some scap sheet metal that I will be using for a shield. However, if there are something else that some would like to add, please keep the comments going.

Morgan
:)

If its not completly broken it might be benificial to go to the car wast to get the undercarrage wast. If its completely broken that might not be the best idea. In that case id clean it off by hand. Either way i say clean it to get off the grease and grime. the last thing you need is a pocket of greese and road grim catching fire.

Id also make sure there are no rubber hoses near by. Im prone to melting stuff thats "not that close"

Just my 2 cents

Wild Turkey
01-19-2006, 12:22 AM
Wrong, Wrong, Wrong! The more vapor space in the tank, the more likely you WILL have an explosion. It's the gasoline vapors that ignite, not the liquid itself. If you've ever seen a flammable liquid burn, you will notice that the flame is actually a short distance above the liquid. The liquid does not burn, as it heats up it produces more vapors and sustains the fire.:D

We used to use small drums of scrap steel as heaters in the stock water tanks. Once or twice a day we'd dump a couple gallons of diesel into the drum, then light a tin can of gasoline and pour it in to start the fire.

I've seen many a match go out when it hits the liquid gasoline without starting a fire. If it's cold enough the gas won't vaporize -- makes lighting the fire a challenge.

On welding near gas tank -- make sure the heat as well as sparks don't hit the tank. We used a water-soaked rag laid over the tank to help with both.

calweld
01-19-2006, 12:40 AM
If all fails and it explodes, be sure to let us know! :p

Don't worry, it'll only hurt for a little while . . .

Sberry
01-19-2006, 12:42 AM
Do not arc strike or melt vapor or fuel lines.

abtanner327
01-19-2006, 02:35 AM
If ya gotta head-ache take an Asprin, if ya got Cancer see an Doctor.
When's the last time ya heard of a "Muffler Shop" burning down?They are the "Pros".
Leave the "rust to Midus" or sumpin like dat.Be safe, Al

miestro_jerry
01-19-2006, 06:54 AM
The guys at Midas do this work everyday. So why not go over and watch them for a bit then maybe another muffler shop.

HF has welding blankets that would be a good and not too expensive "fire proof" padding you can protect yourself and the car with.


Jerry

bfmaloney
01-19-2006, 07:26 AM
The guys at Midas do this work everyday. So why not go over and watch them for a bit then maybe another muffler shop.



Jerry

How does Midas work?

I was under the impression they have prefab cat backs and only clamp them on.

TJJ
01-19-2006, 08:01 AM
I had Midas do a job on my old F150 years ago. All they used was a Victor wrench. Cut off and install. Scared the **** out of me but I guess they knew what they were doing. I'm still here. :p :D


.

SurffKatt
01-19-2006, 09:32 AM
an observer helps too weldin the frame on a backpack blower in my ols shop didn't see the flames from the gasoline grass mix (overflow hose pumped out fuel in hot weather) till i flipped my lid up decided moving the machine right quick was a good idea

J Hall
01-19-2006, 10:17 AM
I worked in a custom exhaust shop years ago. We did a lot of cutting and welding under vehicles. All the joints were OA welded. It will get your heart rate up if you melt a gas line with a torch, but it only happened one time when I was working there. We never did anything special, just used common sense.

mopakel
01-19-2006, 11:10 AM
I would also make sure you have a good clean ground connection close to the welding area as possible.

Conrad_Turbo
01-19-2006, 01:38 PM
Mostly regurgitated info...but whenever I do welding near a gas tank or lines, I always make sure the tank is over 3/4 tank, use an oven mitt or one of those mats you use to put a hot pot on. I'd put one of those against the gas tank and then put a piece of stainless steel (lower thermal conductivity than mild steel or aluminum) to deflect any sparks from burning the oven mitt and provide a larger barrier of heat protection.

fyoung
01-19-2006, 02:31 PM
I'd try to do it on a very cold day so there would be less vapor. Try to see if you can locate the vent hose coming from the tank and then stay away from it..as that's like a fuse going to dynamite.
Be very careful and look around and see what all you're going to be welding close to.
Regards!

Mr_mechanic
01-19-2006, 06:31 PM
Worry more about vapors, they are what can catch on fire, good idea to use a welding blanket if you can for a barrier.

Laiky
01-19-2006, 06:58 PM
I never work on a fuel system in my garage, that includes welding near it too. It's one thing to lose a car, another to lose a home or shop.

big rig guy
01-19-2006, 09:56 PM
I have all the welding equipment, and can lift up the car say about three feet, but for the 20 bucks or so the local muffler shop would charge for a little weld, saving me from welding on my back and getting sparks in my ears in a tight area. Not worth doing for myself. Been there and done it too many times to learn that it is not worth doing. Metal is likely thinned out as well, burn holes, now go in with o/a and make a bigger mess.

Sberry
01-19-2006, 11:33 PM
Well, I figure my 175 class machine has way more than paid for itself with simple exhaust repairs. Its not for everyone thats for sure but I even have a system, 2 sizes muffler cover most of my units, I keep some pipe in stock, out comes the sawzall in goes a new muffler, welded on.

Sberry
01-19-2006, 11:47 PM
I have only caught a couple things on fire over the years,,, ha but one day my mechanic Buds comes over about 3/4 jagged up and wants a quickie weld on a car frame, his wifes ride. It was under the rear, near the fuel and I realize this so I clean off the undercoat and do the repair best as I can. So, he peels out and about 30 mins later he calls and says,,, hey,,, you burnt my car up as on the way home it catches on fire as he is pulling in the drive. I agree with it all, didnt get to excited, figure I wait till he sobers up so I pass it off till the next day and finally he calls, finds out that something dropped out of a harnass, a hose or wire loom, something like that, sheer coincidence.

TOMWELDS
01-19-2006, 11:56 PM
I had a coincidence today too....while rewiring a steel shop, one of the lifting hoist goes out. First thing..yell at the electrician! Found out the cord was bad..LOL....still waiting for the **** apology..L

Cronatron Rep
01-21-2006, 11:19 PM
The guys at Midas do this work everyday. So why not go over and watch them for a bit then maybe another muffler shop.

That I could go watch a doctor for a few hours and then go start practicing medicine ?

Or should I go out and watch a PGA tour event, then I could play golf like they do ?

Sberry
01-21-2006, 11:42 PM
There is no doubt that there has been a fair mount of shoddy, shady work in exhaust shops over the years. The guy that actually works on your car may not always resemble the pro you see in the TV commercial, could always be his first week on the job,,, ha.

IRON TO ART
01-22-2006, 09:13 AM
I'm with Sberry. I use to avoid exhaust work but have started trying my had at it. Recently mt wife ripped the exhaust from the cat back off her Ranger. I had to start by making a new flange from some plate in the shop and welding that on. I then bought a couple fittings from the local Canadian Tire and their cheapest muffler. I fab the whole exhaust up on the bench then bolted it to the cat. Works great looks custom. Sounds stock. Plus it saed my a couple hundred bucks.