Technical Pinhole leaks in tanks

Over the course of my less than notable welding career, I have welded up, or in many cases attempted to, leaks in various tanks, liquid or pressure, fuel, water, or in the case of this morning, my shop compressor, which rusted through at the bottom rear. Often the same result, I end up chasing pinhole leaks at the edge of the weld (MIG in this instance). I have heard that squirting shielding gas inside helps, what is the trick?

I had a leaky compressor tank years ago, poured I think some latex house paint in it! Did the trick. I'm thinking of maybe bars leak in this one, it has a couple of other rust spots on the bottom that are suspect. Don't want to contaminate the air for painting though..

 

Buy a new one!

 

Welding pressure vessels is a whole different aspect of the welding trade. Guys who do this are re certified regularly. Having sketchy welding skills and dealing with a potential bomb may be life altering. You may get away with it but if you are "chasing" pinholes you have more trouble than it's worth. I agree with scotty t.

 

We all deal with old rusty metal. Not uncommon for a old air compressor tank to rust through. They create water and sit in the bottom .... daily draining is important.

Imagine if you will, a weak spot and leaks, so you do get it fixed.
The whole bottom is compromised rusted metal.
Next time, It may just be another slow leak, or it has the potential of a 80 gallon tank with 150 psi, launch like a rocket and put a hole in your roof.
I would not want to be standing near it when it lets loose.

Cut 3" off the bottom of the tank, get rid of all the compromised metal, weld some 1/4" plate to it and add some legs and a drain ... might be cheaper/faster to just replace the tank and put your hardware on new tank.

Edit, Los goes and drains his tank

 

There is a guy here locally who gets the warranty returns on a certain well known brand of inexpensive compressors. A perfect condition 60 gallon is $60 and an 80 is $80. Surely in Kalifornia there is someone selling similar ones. Or look for one with a bad motor or pump on a reasonably new unit. I like to bolt them down too.......friend of mine had one go through his roof and land in his swimming pool. DON'T try to use it if it has pin holes.

 

If the tank is leaking it could be the tip of the iceberg. I went inside air tanks and condensate tanks as part of my work to inspect them and do thickness testing. Old tanks on the bottom inside can get seriously pitted where the deepest pit becomes the leak. The tanks were repaired by professional welders as mentioned that are regularly tested and the repairs are done with certified weld procedures for the tank. All the repairs were completed to pressure code standards. One consideration is that a pressure vessel can be sold at its minimum thickness with no corrosion allowance other than the few thousandths of an inch over the plates nominal manufactured thickness. The code minimum has a safety factor but as the metal corrodes away so goes away the safety factor. It may be reasonable to assume if the tank is beginning to leak that it is approaching the end of its service life. I have a 45 year old compressor tank that I checked the inside with a borescope to get some idea of its internal condition. My son has a pressure washer that has a pump that can have its pressure dialed down to zero. The tank was flooded and burped then the pressure washer adjusted until it was at 1-1/2x the working pressure then locked in with a ball valve. It was a confidence check to see if the tank is safe to use. Testing with water is safe so that if the tank fails it just pops and sprays water where as with air it will literally grenade at failure.

If a tank is repaired then there should be a hydrostatic test with water to ensure the safe integrity of the tank going forward. Never use air for a high pressure test.