I have a secondhand, homemade aircompressor that uses a small tank
with a platform welded to the tank for the motor and compressor.

Is it safe to weld to an air tank?

At first I thought this was crazy to do, but then I thought of
the very high pressure welded pipes on gas wells, and so forth.


So, is it safe if welded properly? And second, if it does have a bad weld
on it, will it just pop out the weld and then fiz off, or is it
and explosion hazzard?

It's a homemade small air compressor set at about a 100 psi.


Thanks

"stone" wrote in message
om...
I have a secondhand, homemade aircompressor that uses a small tank
with a platform welded to the tank for the motor and compressor.

Is it safe to weld to an air tank?

At first I thought this was crazy to do, but then I thought of
the very high pressure welded pipes on gas wells, and so forth.


So, is it safe if welded properly? And second, if it does have a bad weld
on it, will it just pop out the weld and then fiz off, or is it
and explosion hazzard?

It's a homemade small air compressor set at about a 100 psi.



Let's assume that the tank is a small one. For talking purposes, let's take
a sphere about 18" in diameter. That's got 339 square inches of interior
surface in each of the two hemispheres. If your weld should fail and the
two halves separate, each half flies off with over 28 thousand pounds of
force behind it -- that's 85 psi x 339 square inches (because standard
atmospheric pressure is ~15 psi). It would probably put a serious dent in
any surface it hits even if it doesn't penetrate it. Any surface. even a
human body. If it were me, I'd leave it to the professionals who have the
equipment to test their welds at pressures much higher than you'd ever
subject them to.

Norm

stone wrote:

I have a secondhand, homemade aircompressor that uses a small tank
with a platform welded to the tank for the motor and compressor.

Is it safe to weld to an air tank?

At first I thought this was crazy to do, but then I thought of
the very high pressure welded pipes on gas wells, and so forth.


So, is it safe if welded properly? And second, if it does have a bad weld
on it, will it just pop out the weld and then fiz off, or is it
and explosion hazzard?

It's a homemade small air compressor set at about a 100 psi.


Thanks

If it's welded properly it should be safe. A bad weld
could just leak or if the structure is weakened it could
explode. I've welded 1000's of hydraulic cylinders and
not a one has exploded. They are subject on average to
25000psi. Of course I welded them "properly". We even
built an explosion chamber and tried to blow some of them
up. Never saw a weld fail. Usually the rod end would
flare out causing the lock wire to pop out and the whole
rod/sleeve/piston would shoot out.

Sure, for small welds to stick the tank to a frame etc. An inch or
two of faulty weld here and there won't cause an otherwise sound tank
to fail catastrophically.






On 17 Aug 2004 16:37:26 -0700, (stone) wrote:

I have a secondhand, homemade aircompressor that uses a small tank
with a platform welded to the tank for the motor and compressor.

Is it safe to weld to an air tank?

At first I thought this was crazy to do, but then I thought of
the very high pressure welded pipes on gas wells, and so forth.


So, is it safe if welded properly? And second, if it does have a bad weld
on it, will it just pop out the weld and then fiz off, or is it
and explosion hazzard?

It's a homemade small air compressor set at about a 100 psi.


Thanks

I think you're wise to defer to professionals, Norm.


On Wed, 18 Aug 2004 00:59:05 GMT, "Norm Dresner"
wrote:


Let's assume that the tank is a small one. For talking purposes, let's take
a sphere about 18" in diameter. That's got 339 square inches of interior
surface in each of the two hemispheres. If your weld should fail and the
two halves separate, each half flies off with over 28 thousand pounds of
force behind it -- that's 85 psi x 339 square inches (because standard
atmospheric pressure is ~15 psi). It would probably put a serious dent in
any surface it hits even if it doesn't penetrate it. Any surface. even a
human body. If it were me, I'd leave it to the professionals who have the
equipment to test their welds at pressures much higher than you'd ever
subject them to.

Norm

"stone" wrote in message
om...
I have a secondhand, homemade aircompressor that uses a small tank
with a platform welded to the tank for the motor and compressor.

Is it safe to weld to an air tank?

At first I thought this was crazy to do, but then I thought of
the very high pressure welded pipes on gas wells, and so forth.


So, is it safe if welded properly? And second, if it does have a bad weld
on it, will it just pop out the weld and then fiz off, or is it
and explosion hazzard?

It's a homemade small air compressor set at about a 100 psi.


Thanks

This is one of those cases where if you have to ask, you really shouldn't do
it.
Admittedly this is UK but similar rules probably apply in US. To weld a
pressure vessel the welder has to be coded. That means that he passes a
practical welding test every few years. where the results are X rayed. These
guys are GOOD welders. Despite this, every welded pressure vessel is
subjected to a hydraulic test well above normal working pressure before the
vessel is certified for use. This test applies if the vessel is repaired or
modified as well.
The problem with compressed air is that gasses are compressible. That means
that there is a huge amount of energy stored in the cylinder. If something
fails, that energy will be released. If the cylinder breaks, the shrapnel
will fly like a grenade.
In short, don't do it.

John

i had a customer do that to some cylinders on a 300 ton low boy trailer,
they were driving it without the pins engaged to hold the trailer part up
just riding on the oil in the 10 inch bore cylinders , a few bumps down the
road and shock poped the 10.250 x 12tpi glands right out of the tubes taking
the threads with them , wish i could have seen it , dropped the loaded
trailer on the highway at 45 mph!


but back to topic , weld it then fill it with water and pressurize it with
50 pounds more pressure than you will operate it at and yuou should be ok

or , go down to the local pawnshop and buy one with a blown up pump or motor
just for the tank

How do you think they make them in the first place...
All tanks are welded... Just do a good job...

"Tim Williams" wrote in message
...
"Norm Dresner" wrote in message
...
each half flies off with over 28 thousand pounds of
force behind it -- that's 85 psi x 339 square inches

But what of the force vectors pointed around the rim? The only forces
that
matter are directed parallel to the travel, in other words, the effective
area is ALWAYS a circle of the inner diameter.

Still 254 square inches, but I wanted to correct you...

Tim


Tim. Worst case, assume my calculations are off by a factor of 10 (very,
very unlikely). That's still 2,800 pounds of force propelling the
fragments. That'd make quite a dent in your chest, wouldn't it?

Norm