How Difficult Is a Fluid Tight Weld?

[Iplayfarmer]

Thanks for the replies. You've confirmed what I suspected...

A fluid tight weld doesn't require special skills, it just requires good basic skills.

I'm not sure I'm confident enough in my welding skills yet to count on it. If it were going to hold any kind of pressure I'd avoid it. Since it's a hydraulic reservoir with a vent to atmosphere, I may be willing to try it. The low pressure air test is a good idea I hadn't thought of. I guess I could weld up the piece and test it. If I can't fix all the leaks, then I can go with plan B, a bought reservoir. Are there any tricks to getting a good tight weld?... More heat? Multiple passes? MIG vs. Stick? (I have both.)

The discussion may be purely academic at this point since I calculated the volume of the space that I was thinking of using to be about 1.5 gallons. I'm using a 9 gpm pump.

 

[mbohuntr]

If your mig welding Hot Rolled Steel, it wouldn't hurt to grind off the mill scale first. Same with galvanised or rusty steel. Mig is pretty sensitive to dirty metal, worn tips and liners, as well as wind. If in doubt, run it a little hotter than you think you need. More penetration isn't a bad thing. Also, make your resevoir big enough so the fluid gets a chance to cool off. A small resevoir will get hot faster since you will likely be making an open center system. (The fluid is continuously pumped) Open (outside) corner joints are typically the easiest to make tight because you are exposing the most base metal to the arc. If you get a pinhole, hit it with the grinder, then spot it with a stick welder. Test with only water or air... Hydraulic fluid can flash when vaporized by welding. Lastly, make sure you put a filter before the pump so dirt doesn't ruin it.

 

[patrick_g]

While waiting to achieve the level of skill required to do air tight or water proof welds I found that a little flux and some brazing rod tended to make a leak go away.

Pat

 

[Iplayfarmer]

While waiting to achieve the level of skill required to do air tight or water proof welds I found that a little flux and some brazing rod tended to make a leak go away.

Pat

I had also thought about using the acetylene torch to touch up the pinholes.

...Also, make your resevoir big enough so the fluid gets a chance to cool off. A small resevoir will get hot faster since you will likely be making an open center system. (The fluid is continuously pumped)...

I will be using an open center system. That's why this reservoir will likely not work. I think the rule of thumb is to have the reservoir equal to the gallons per minute. I.e. my 9 gpm pump needs a 9 gallon reservoir.

 

[mbohuntr]

If memory serves, Mine had a 10 gal. reserve, a 2" cylinder, and a two stage barnes pump. I could run it on a hot day without worry. We did quit using snowblower engines as they burned up by running too hot.

 

[Car Doc]

I do it all the time its no big deal as long as you arnt welding upside down and backwards haha!

Its really a matter of getting the area clean and grind as necessary and make multiple passes where you can see what you are doing and air check with soapy water in a spray bottle.

That said why do it inside the structure I would be very worried about stuff happening or contaminants?

Steve

 

[Transit]

While waiting to achieve the level of skill required to do air tight or water proof welds I found that a little flux and some brazing rod tended to make a leak go away.

Pat

Yes, thinking along the same lines only with solder as a seal.:thumbsup:

 

[Scotty370]

IPlay- I built a tank for a log splitter years ago by O/A welding some 1/8" plate to each end of a 24" piece of 6" pipe. I also burned a couple 1" holes in one end of one of the plates, (side by side, at the six o'clock position) and cleaned and welded 3/4" pipe couplings, for inlet/outlet fittings. Worked fine after I ground and spot-filled some pin holes with brazing rod. In your application I'd be concerned that the flexing created in a 'structual' member would crack any weak spots, in short order! ~Scotty

 

[patrick_g]

Worked fine after I ground and spot-filled some pin holes with brazing rod.

Glad to see I'm not the only one brazing welds to get them pressure tight. I don't feel quite so inadequate now.

Pat

 

[Scotty370]

Glad to see I'm not the only one brazing welds to get them pressure tight. I don't feel quite so inadequate now.

Pat

Pat- My motto "If ya can't be perfect, learn how to cheat!" :laughing: