Welding a compressor tank

[Mr Fro]

My father-in-law lent me a little compressor the other week so I could pop the beads on my bike tyres. He told me when he dropped it off that there was a small leak from *somewhere* and it slowly lost pressure.

I tracked the leak down to the check valve which had a crack in it. "No bother" I thought and ordered a new one. However, when I went to take the old one out it disintegrated leaving the thread stuck in the tank - looks like it had been stuck in with epoxy or something.

I've tried getting it out but it's totally shagged. The only thing left is to chop the lug off the tank and weld in a new one. Is this a fantastically bad idea? I'm happy to do the job but don't know whether the heat will make that area of the tank brittle - don't rally want it failing when it's pressurised...

What do you think?

 

[MCKDAVID]

tried easy outs, or chiseling out the old fitting, then running a tap through it to clean up the threads. I would definitely persevere with that first before even contemplating welding the tank. On high pressure vessels you really need to know what you're doing.

try heating the fitting first, they're usually pretty tight on there with thread lock / pipe sealant. Had to give mine a good blast with the propane torch before they'd come out.

 

[Cobbler]

When I removed the end plug in my compressor tank, it would not come out with normal means. I don't know what the sealant was, but it wouldn't shift, it was bending & deforming the tank, but still wouldn't come. I ended up drilling through the plug & splitting it with a hacksaw blade, even then I had to make two cuts & lever it out in two pieces.

I dropped one of the blades in the tank when doing it & I couldn't get it out, it's still in there now!

 

[rtbcomp]

Heat is definitely the first thing to try. I had a tank and none of the unions would shift. After heating they came out easily.

Could you drill & tap the existing boss?

 

[grim_d]

The first half of this video will show you how to remove the remainder of the fitting.

In your case as mentioned, add heat to soften the epoxy.

 

[Bill Edwards]

There are some very strong theadlockers available, heat is the answer to removing them.

However in answer to the original question of whether you can weld a new fitting in then provided you're competent with a welder (and have a suitable machinem a tiny MIG perhaps wouldn't be suitable) there's nothing to worry about. The tank will be fine afterwards (bear in mind they're already welded) and a single run of stick weld round a fitting takes 2-3000 psi with no bother, although the consequences of air systems failing is serious 150 psi isn't demanding.

 

[Mr Fro]

That's a good vid Grim, 'ta very much!

The fitting crumbled to dust when I first tried to get it out - it was more like ricotta than metal!

I've already tried drilling it, tapping it round with a chisel and slitting the remnants with a hacksaw blade and no dice.

I'm going to try and cut a few more slots in it and give it a bash before I get the grinder out.

 

[Bill Edwards]

I don't know what material yours was made of but on most DIY to semi professional compressors the fittings are usually made appallingly weak. It's very common for them to break well before the thread sealant/locker gives! Chinese monkey-metal, nasty stuff as you've discovered.

 

[the snooper]

That's a good vid Grim, 'ta very much!

The fitting crumbled to dust when I first tried to get it out - it was more like ricotta than metal!

I've already tried drilling it, tapping it round with a chisel and slitting the remnants with a hacksaw blade and no dice.

I'm going to try and cut a few more slots in it and give it a bash before I get the grinder out.

try the heat before the grinder

 

[Mr Fro]

Quick update...

A few more cuts with the hacksaw blade and a healthy dose with the blowtorch and the cheese metal was finally persuaded out!

I've picked out as much crud from the threads as I can - can't get a tap in there as the tank aperture is smaller than the boss.

Thanks very much for the help guys!

 

[rtbcomp]

Thanks for letting us know.

A bottoming tap should do the job, or you could make a makeshift tap by getting a fitting with a parallel male thread and cutting a groove with a hacksaw along its length (across the threads).

 

[Mr Fro]

I don't have one of those! I'm pretty sure I've got a n appropriately size bolt somewhere though...

Thanks again!