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 .


Tom

"wwsjr" wrote in message
. net...
Bruce L. Bergman wrote:
On Thu, 19 Jan 2006 11:54:46 GMT, wwsnot

wrote:


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.


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?

-- Bruce --

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.

wws