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