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
still only 1/8'' thread. Will weld in a bushing for 3/8" pipe to fit a
Question is: does anyone here have an idea what the silver filler is? It
seems too hard for solder.
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
Be VERY Carefull
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.
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?
Thanks Bruce, et al.
The as art option is something that probably would not cross my mind
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.
Stop! NOW! Do not pressurize this tank. Have you ever seen an air
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
dangerous, because a pipe bomb will only kill people in the room with
a burst air tank can bring the entire building down on you after the
If the drain plug is rusted out, what is the condition of the bottom of
If it is significantly rusted, it is dangerous.
I just would not use anything this old without at least a hydro test.
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
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
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.
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.
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...