Found small leak in 80 gallon tank. I've seen posts about tanks exploding etc. Anyone done it, know of the proper way to repair, or is it scrap? Safety is an issue, but I would believe that there is an appropriate way to fix.
How you repair the tank depends on if it is rivetted or welded, a certified welder can repair your tank properly and then it must be recertified by your local government agency, Manpower certify's tanks here in Manitoba.
Recertification involves filling the tank with water and then pressurizing the tank with a hand pump (with attached gauge) to one and a half times the listed max pressure on the side of the tank and then letting the tank sit at the rated pressure for three days, it should not lose any pressure during this time.
Of course if this is a small garage style tank buying a new one is a heck of a lot cheaper.
I have designed ASME pressure vessels for 13 years. It most probably can be repaired at a reasonable price. I think most of the tanks you read about blowing up in this forum are gasoline tanks. Obviously, if you have hydrocarbon fumes in the tank, you will have problems. And you have to be a good welder with some common sense.
Tell us about the leak. Does it look like it came from partially drilled hole? Some fabricators machine a shallow hole so the remaining wall thickness is the amount of the corrosion allowance. A leak indicates your tank is corroded to the max and should be replaced. Is it in a weld? If it is Code stamped, I would contact the manufacturer and advise. If one of our Code stamped vessels leaked in a weld, I would repair it for free.
One final thought. If the tank is Code stamped and you want to keep it that way, you must have the repair work done at an ASME Sect. VIII Div. 1 shop that has an R stamp. While this would drive up the cost of the repair, it would still probably be cheaper than an new Code stamped tank.
My intention was to sell my "old" compressor, 5hp, single stage, Sanborn 60 gallon up right, to recover the money I spent on the other compressor. Now it seems that I have a few choices.
1) Purchase a new tank - just under $400 is the best price I can find. I'm not totally against, but its probably going to cost another $100+ to ship.
2) Repair the leak.
3) Cut the mount off the 2 stage compressor and plumb it into the 60 gal tank. Problem is the inlet on the 60 gal tank is 3/8" and the 80 gal tank is 3/4". Seems to me that I would be stifling the performance, and potentially causing more moisture by necking down the inlet into the tank.
Thanks for the replies.
Redsdad - It looks like the previous owner had a problem with one of the legs, and gobbed some weld on to fix the leg and potentially a leak. I ground a lot of the weld out last night to see exactly where the leak is, but still can't locate visually. So I am going to back fill the compressor to 15 or 20 psi from my pancake compressor to locate exactly where the leak is. Using a pick hammer, I found one softspot about 1/4" in diameter between some of the weld, but the balance of the tank is solid. I'll grind & hammer a little more tonite, and hopefully find the leak. If the tank can be repaired, will the hole be welded over, or will a piece of metal be welded over top, or both?
I agree about your comment on the tanks exploding also. I've seen a few of the "pictures", and none of them were asme compressor tanks. I firmly believe that the tank would spring a leak at a weak spot before it would explode like a bomb, but anything is possible. Anyway, this is a hobby shop where the compressor is used 3 or 4 times a month, and I have the pressure cutoff at 125 psi - no need to go to 175. I definetly want to be safe, but I also take the cost/benefit approach to things. If I can locate the leak, get it repaired and use it safely, that's what I'll do. Again thanks to everyone for the responses.
If it is built like my tank, the legs are welded to the bottom head. At our plant, we would probably check the price of a new head and do a cost evaluation. ASME 2:1 ellipsoidal heads made from carbon steel are fairly cheap. If the hole were small, proper prep and weld fill would take place. If it needed a patch, the correct repair would be to weld in a piece of metal of the same contour using double butt welds or a single butt weld with double butt weld quality. In the long run, cutting the head off and welding on a new one may be cheaper.
Knowing what goes on in HCI and CPI plants, the pressures, chemicals, and temperatures involved, the longer I do this the faster I drive by chemical plants and refineries. LOL At 125 psi at slightly above room temperature, I would not be afraid of a cover patch filet welded to the tank, PROVIDED a qualified welder did it, you inspect it regularly, and you junk it when through with it (don't sell it to someone else).
Redsdad - The hole is very small. I ground out the weld last night & still can't find it visually. Once I pressurize the tank again, I'll be able to squirt some soapy water to find it. The legs are welded directly to the tank, the center portion. It is an old speedaire tank. Thanks for the info, I am going to have a certified welder take a look, and decide from there.
Willys - Those are the three reports I've seen. 1 non-asme tank and 2 scuba tanks. Not really an apples to apples comparison in my eyes. But safety should always be a concern.
It is apples and apples from the standpoint that as a tank ages, ASME or not, the internal condition degrades. I would be very concerned about the internal condition of a coded tank that springs a leak. These things are assembled and inspected by anal retentives so when a defect shows up, there probably is some much bigger problem lurking. And if a forged constantly inspected scuba tank can blow without apparent reason, an abused steel low pressure one can too! I posted those mainly to alert novice readers that compressed air can be as destructive as a combustible pressure tank when it decides to go. Just because there aren't many pictures showing up in a Yahoo! search doesn't mean that it isn't a common occurrence.