Best fix for rust hole in air tank?

[oldtiffie]

I wonder what your insurance company would have to say if you put in a claim and they found that you were using a pressure vessel other than for its rated and designed purpose and/or that was "Out of Test" (date) and/or over pressure and not either modified by a certified shop or certified by an Engineer?

My compressors are destroyed as soon as or before the 10-year test is required. A new compressor every 10 years is good going.

Same with all pressure vessels here - LPG included.

My oxy-acet and MIG bottles are rented and tested by the owner as required by Law. I just take them (LPG too) in and swap for new filled (and if required, re-tested and re-certified) as required. I have at least 4 oxy-acet and MIG bottle distributors/agents within 10 or so Km of here. I have a "Trade" account, so I just book it to the account.

There are at least two LPG re-fillers/bottle-swap in every town here.

I don't take chances with high-pressure gases or liquids.

Perhaps its (still?) more "Wild West" in the US than it is here.

[Evan]

At least in Canada there is no requirement to test a compressor receiver every ten years or ever at all in a home shop setting with no employees. 20 lb propane tanks also do not require such testing. Only the valve must be replaced every ten years, not the tank, nor is the tank recertified or tested, just the valve body.

Tanks for industrial gasses such as CO2, acetylene, oxygen etc are a different matter as the pressures are much higher.


Drilling extra holes in a propane tank is just fine as long as the holes are in the end bell and not the less curved body. The more curved the section is the higher the hoop stress it can withstand. It is best to braze fittings in place than to weld but if welding is desired then the use of either mig or low hydrogen rod is appropriate.

As for air pressure vessels in general air receivers with a diameter of 4 inches or less are exempt from certification and testing in the first place in the US and Canada. That is why you see so many of the import compressors with double air tanks, each just 4 inches in diameter as well as some that use large diameter tubing as the frame and receiver as one.

The steel used in propane tanks is low carbon aluminum killed deoxidized fine grained steel made specifically for pressure vessels. This type of steel is much less likely to fail by brittle crack propagation than regular mild steels.

[John Stevenson]

I have just cut a propane bottle open for the curved sections to make a trolley and can confirm they are not coated inside.
However think about this, Modern trucks have anything from 3 to 5 air tanks on them for their split braking systems, none of these are coated as I have cut many open, over an 8 or 10 year operating period these must cycle far more times than a normal compressor and the cycling is the factor with pressure vessels.

I have never seen one of these blow up or damaged other than the vehicle being involved in an accident and if there was a problem the Road Transport Board would have something to do about liaising with manufacturers about design.

.

[derekm]

[QUOTE=Evan]

...

Drilling extra holes in a propane tank is just fine as long as the holes are in the end bell and not the less curved body. The more curved the section is the higher the hoop stress it can withstand. It is best to braze fittings in place than to weld but if welding is desired then the use of either mig or low hydrogen rod is appropriate.
...
[QUOTE]
I'm afraid I would be just plain lazy and use the tank upside down

[airsmith282]

you know this is an idea , most are saying the tanks will rust form out side in and iam not going to say no to that what iam saying is whati f you repainted your compresser thank every year, this would prevent any rust up on the out side and should make the tank last like forever.. wooks for wood ,, i repaint my shop akak 8x12 shed every year and so far not one spec of rotten wood it still just like new , i also repaint my floor as well every year inside the shed as well to prevent swelling and rot from all the snow and water and crap that gets on the floor as well so far no problems, now iam not saying either to strip the paint off the tank but just respray it with a coat of paint every year and it shouldnt ever have a problem..

i have leaned now to leave my tanks full of air all the time and it is a blessing expecially to not have to hear the noise out of my 3 gallon tank every morring , i love my 8 gallon tank its so quiet ..

ya in know but i needed the 3 gallon one for its size and its job is to blow off the lathe and mill thats all its good for and it does the job..

propane tanks are cool to use as a portable sprayer, never heard of them used for use as a compressor , sounds like a cool idea, persoanly id just go out and get a new tank or a new compressor there getting so cheap now its crazy,, but if you get a new one then just paint it every year thats my idea ,, sorry for such a long post hear

[Ron of Va]

I repaired a pin hole in a compressor tank with a large sheet metal screw. One installed with a 3/8 socket. I ran the screw in half way, then slathered the shaft of the screw with hot glue, and ran it in all the way while the glue was still hot. I was surprised to find the repair lasted for over 10 years, until I disposed of the entire unit.

[pcarpenter]

That's sure lucky, Ron. Otherwise, you could have ended up with that screw imbedded in a body part.

The trouble with on-line forums is that you get information on what worked....but often those solutions depended on a lot of luck. This is a great example....that same screw could have become a projectile.

Pressure vessel failures can be pretty catastrophic. It's the very reason that they have to be hydro-tested from time to time in commercial environments. This is not an exercise that is done for the fun of it.

Want a new air compressor tank (small)? Go to www.surpluscenter.com and search on air tank. There are several small ones there with wheels, handles and mounting points for the motor and compressor.

Paul

[Willy]

One thing I learned a loong time ago...you can't weld rust!

[Evan]

Pressure vessel failures can be pretty catastrophic

That is particularly true of the large sizes and less so of the sizes used in the home shop. The type of strain the metal undergoes is directly dependent on the size of the tank. That has a direct influence on the failure modes.

Incidents involving catastrophic failure of small compressor receivers are very rare and incidents involving serious injury are nearly unheard of. The only real hazards involve operation in very cold conditions which should be avoided especially if a charged tank is left to cool to ambient and then moved. This applies to any size compressor or storage tank in cold climates. At a temperature of -40 the steel is close to a total transition to glassy metal behaviour and will shatter under fairly mild impact. If thinned by corrosion it may fail due to pressure alone.

The other cause for concern has nothing to do with the materials of the compressor or receiver but is caused by the use of improper compressor lubricant. If the wrong type or viscosity of oil is used it can cause a buildup of carbon in the compressor outlet and a buildup of oil in the tank. When air is compressed to 5 bar the partial pressure of oxygen is equivalent to a pure oxygen atmosphere. It takes only the sightest source of ignition from hot carbon particles to ignite excess oil in the compressor tank which will cause an immediate deflagration explosion and will violently rupture the tank regardless of what it is made from.

[sidegrinder]

Like Ron, I filled a pinhole with a sheet metal screw and then brazed it in place. It's been 4 or 5yrs now with no problems. It was near the bottom of the tank, so if it ever would break loose there wouldn't be much in the line of fire anyway. YMMV, Sidegrinder.