Curtis Air Tank

Hi guys,
I am trying to re-hab an old Curtis air tank for home shop use @ 125 psi.
It is OLD, as in rolled plate, riveted, with the seam filled with a
silver color metal.
The drain bung is almost rusted out, so I drilled and tapped it for
1/2'' pipe,
still only 1/8'' thread. Will weld in a bushing for 3/8" pipe to fit a
drain cock.
Question is: does anyone here have an idea what the silver filler is? It
seems too hard for solder.
Thanks, wws.
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Long time lurker here, let me see if I can help.
1st: I don't know what the silver solder like stuff is.
2ond: If the tank is old and severely corroded (rusted out ) It would be extremely dangerous to use it for any pressurized application. I would use it for a water barrel or a burn barrel or scrap ect.
Compressed air (gases) can be extremely hazardous, when pressurized they store incredible amounts of energy and cause severe damage when released uncontrolled.
Be VERY Carefull
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Silver solder. Best bet, anyway.
Cheers Trevor Jones
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Trevor Jones
I just went through a similar situation. Ultimately I trashed an old tank for a new 26 gallon tank I purchased for $75 at Cummins with a drain cock and a check valve already installed. You really have no idea what condition the rest of your tank is in. Anything special about the tank that you just wouldn't replace it with a new tank? Seems like you're throwing a lot of time and good money at something that should be replaced for safety reasons anyway. -M
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Just a note that generally riveted lap-seam tanks and steam engine boilers are condemned on general principles for very little provocation - it's just impossible to tell what condition that seam and the rivets in it are in without destructive testing, and they can unzip without warning. Compressed air doesn't have the 'flash into steam' factor that a boiler does, but the tank rupturing still releases a whole lot of stored energy and can easily kill anyone in the area when it lets go.
And your note about the drain bung being almost rusted out is VERY troubling - old tanks like that can be repaired by cutting out the rusty spots, fabricating patches out of new plate and welding them up, but you are going to have a whole lot of time and money invested by the time you are done.
What's worse is, you know the metallurgy of the new steel in the patch, but the stuff the old tank is made of is questionable at best. Look at the Titanic - they sideswiped an iceberg that should have bounced off with a big dent, and the steel failed. Very brittle at low temps. They had no idea at the time what they were doing wrong.
They usually only invest effort like that into repairing rusted-out corners and low spots on antique steam engine boilers - and even at that, when they get too bad to patch they will start over and fabricate a brand new boiler out of modern materials to the same dimensions, just so they know it's safe for continued use.
I would err on the side of caution and get a new welded receiver that meets all the ASME codes. People restoring old equipment take a new tank and apply fake rivet heads to make it 'look right'. (They hide the modern inspection info plate on the back side.)
The old tank is worth more as an old tank than as an operating air receiver - There are lots of artsy places that will pay good money for an old riveted tank like that to use it as outdoor decoration, standing next to an old Fairbanks-Morse stationary steam engine...
If you really want to use that old tank (damn the expense), spend the money and find an expert Boiler and Pressure Vessel Inspector to check it over first. The life you save may be your own - or to be very crude in getting my point across: Do any other family members ever go into your shop? Do you want THAT on your conscience?
Reply to
Bruce L. Bergman
Thanks Bruce, et al. The as art option is something that probably would not cross my mind anytime soon. I'm quite leery of this tank as well. If my donor would like to dig a 2' hole 6' deep out in the backyard, I'll test it under pressure. A plumber suggested a water heater tank as a temporary replacement. Maybe I'll do that instead, my air tools only need 90 psi anyways.
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Stop! NOW! Do not pressurize this tank. Have you ever seen an air receiver explosion? I haven't, but have seen the remains of the exploded tanks! I'm glad I was spared the scene the paramedics and the coroner had to view. It isn't as bad as a pipe bomb, but it is DAMN close. Actually, it can be more dangerous, because a pipe bomb will only kill people in the room with it, but a burst air tank can bring the entire building down on you after the walls have blown out.
If the drain plug is rusted out, what is the condition of the bottom of the tank? If it is significantly rusted, it is dangerous.
I just would not use anything this old without at least a hydro test. I'm sure, however, that no one in their right mind would do the hydro test for you.
Please take my word for this, you are dealing with a SERIOUS safety issue here!
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Jon Elson
I'd scrap it, but if you insist that you want to use it,pressure test it with water to twice the pressure that you intend to use it. The water doesn't store much energy when you compress it so if it lets go, it will just squirt.
I've scrapped better sounding vessels, out of self preservation .
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Tom Miller
On a related note, a nearby testing facility got a contract to simulate a backhoe striking a 24" diameter high pressure natural gas line. The concern was that line high pressure lines would rip lengthwise until meeting a flange or valve. For the first simulation they buried a 20' long section of pipe, 6 foot down. It was then pressurized to 1000 psi. with nitrogen. The backfilled area was covered with several very heavy blasting mats that were covered with sand bags. A small shaped charge had also been attached to the outside wall of the pipe to make a small cut similar to what a backhoe bucket tooth would do. Everyone retired to a bunker about 500 feet away. What happened when the button was pressed amazed ...and then concerned everyone..the 2000 lb blasting mats were way up in the air..and starting to come down! Luckily they did not land on the bunker roof. Shreaded sand bags were hanging form trees.
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Holy Sheeeeit.
Now try it again, this time with 1000 PSI of real natural gas and enough volume to simulate a real pipeline, and a few ignition sources like an idling backhoe. But before you touch off that little squib, I'd stand WAY back. Like a half-mile or so...
Oh, another impressive KABOOM is to take a 30-gallon water heater, fill it to the top with water, and plug all openings. Disable the thermostat, and superheat the water to somewhere above 225F... Then take a .22 rifle and pop a small hole in the tank - again, this is another instance where you want to be WAY FAR BACK when you do it.
Watts Regulator (the people who make T&P Relief Valves) did this and filmed it back in the 1950's - rather impressive.
When we say "Kids, Don't try this at home!" we MEAN it.
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Bruce L. Bergman
Don't need an ignition source. The static electricity from the outpouring gas will take care of it. Karl
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I forgot to mention that the 24" pipe was neatly split from end to end as had been predicted. Looked just like a very large steel canoe. The rip stopped at the dished heads on each end and was very uniform. I have since heard of high pressure natual gas lines ripping for several miles after failing due to damage from impact or internal damage...evidently once a fracture starts, it can continue at very high speed with relatively low energy input until a flange or valve stops its progress. I wonder what precautions gas pipeline companies may or may not now use to prevent such scenerios where lines go thru populated areas? I know they do some internal testing with intrumented pigs for flaw testing and I guess they are usually buried fairly deep but...
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