One of my first welding projects is to repair a hole in a hydraulic fluid resevoir on a backhoe. The tank is part of the frame and cannot be removed. It apparantly has been welded in the past, but still leaks ? i guess a bad job ?. Anyway, i sincerely do not want to damage the machine or myself in the process of this repair. I also seem to have a little nervousnesss about it being a tank, probably having a thick film of oil on its interior even if it is drained. My thoughts are to disconnect the battery on the machine, drain the tank, remove the filler cap, and weld up the hole. Are there any safety concerns I am overlooking? I was also thinking about filling the tank with carbon dioxide, to prevent any oil residue from igniting ?? is this a concern. Maybe I am thinking too much, but I dont want to do something stupid.

 

I won't say it can't explode, because as we all know, s--t happens. I've welded cracks in quite a few hyd. tanks without a problem. If it will make you feel safer, hook a garden hose to the tail pipe of a good running engine and let it run in the tank for a half hour before starting the job. Keep it running while doing the job. I've brazed leaks in gas tanks with this method. This last sentence will probably create a real s--tstorm, but I guess I'm lucky 'cause I'm still here to talk about it.
Mike

 

toolboy,

You certainly did the right thing in looking for answers when you could see a risk in doing the job at hand.
I did a search to see if I can find an officially accepted method of welding a used hydraulic tank but could not find anything.

I have heard of Mike's method of excluding oxygen to prevent combustion but I think that you need to find the method that is officially accepted.
I'm sure you will get a few suggestions but I would use them in balance with information from your employer AND your industry standards people.

I myself have used nitrogen and have also filled a vessel with water as my own means to reduce a fire or explosion hazard but would suggest you get the official scoop.

What is your work situation?
Are you an experienced welder doing this for the first time or an apprentice and what type/size of shop are you working for?

 

I agree with you,Greg. The gas tank repairs were done on my own time. Toolboy should check with his supervisor to get the "official" word on how best to do it.
Mike

 

hi guys, and thanks for responding to my post. to answer some of your questions, I am a novice welder doing this for the first time. I need to do this repair for myself on my own machine. I recently bought it and this is the last of the repairs to be done. I cant really afford to pay for a low boy to transport it to a repair shop, nor could i even begin to imagine what they would charge. To have a professional come on site with mobile equipment i fear would also be outrageous. Last year i had to pay a guy well over a weeks salary to do about 15 minutes of welding. So, in the true (hard core) do-it-yourself fashion i have decided it better to spend that money on equipment and be set for all the future welding i see on the horizon. as for equipment, i have a small generator and am probably going to buy a Miller Passport (based on lengthy advice i recieved from an engineer at Miller) Its light (fairly) so i wont kill myself moving it around; it appears to have the capability of weldng anything i plan to run into; and aparently, its designed to have the living crap beaten out of it on a daily basis (constant transport, bad power sources, etc, etc) ( he also said they recently had one returned for repair that was dropped from a 150 ft scaffold; other than a damaged face plate and torn cables it was functionally OK; ?? i was impressed) As for experience, i am neither a profesional nor apprentice, i am a novice, green as grass. i do however have desire, inspiration and stubornness. As for training, i got some scrap sheet at the junkyard yesterday the same gage as the tank, and plan to drill and patch several holes in it before letting myself loose on the expensive equipment. well, im really running at the mouth (or keyboard?), sorry. you probably didnt want THIS much info. but oh well, thats part of the fun of this internet stuff

thanks, toolboy

 

Good luck, toolboy. When practicing, weld in the same position as the crack in tank ie: vertical, overhead, etc. If the tank has been empty for a day or two, you shouldn't have much trouble with oil running into the weld. If you have to drain it immediately prior to welding, heat area of tank above crack to get rid of oil clinging to inside of tank.
Hope this helps,
Mike

 

What about a fuel tank? How can I neutralize the vapors inside? I've heard that sometimes you can rinse them out and let water sit in them and still have a flash. I've also heard that if the gas cap is open and so is the petcock, then if anything _does_ flash, it will just blow through once and be done.

Mathius

 

Good news! my tank repair is complete. It took two attempts though.

First try: I drained the tank, filled it with CO2, ground down the affected area, found two small small hairline cracks in the steel, and welded over them. when i refilled the tank it still leaked. I was most depressd.

Second try: began grinding down area again. this time with the tank filled. aaah! it was very easy to find the leak with the tank full. As it turned out, there was one aditional tiny tiny crack above where I had welded before. I didnt see it the first time. I re-drained, filled with CO2 and welded again. This time on full power because I was on the 1/2 " portion of the tank. I was much more comfortable with the welder the second time, an got much nicer welds. no leaks, looks good, very happy.

well thanks for all the advice, I'm off to look for more welding projects!

 

Glad it worked out.