"DaveC" wrote in message
news.net...
I've got an old 20 gal (?) compressor tank in which I want to install a
drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is rated
to
125 psi.

Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a
"plug"
welded to it that I can drill & tap?


I'd be totally surprised if your tank has the wall thickness you speak of.
They typically are thinner, especially if it's rated for 125 PSI. If it
has, it would be adequate for a 1/4" pipe thread, but marginally. Best
policy is to weld in a bushing, assuming you have the capability.

Are there rules to follow for such stuff?

Pressure vessels are generally built to the pressure vessel code, so, yes,
there are rules. Ernie is our chief cook and bottle washer where welding
is concerned. With luck, he'll chime in.

Is there a better n.g. to ask this
question in?

The one he frequents most, which I don't recall. I think it's scientific
welding and joining, or some such. Others will probably provide the proper
group for you.

Harold

"DaveC" wrote in message
news.net...
I've got an old 20 gal (?) compressor tank in which I want to install a
drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is rated
to
125 psi.

Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a
"plug"
welded to it that I can drill & tap?

Are there rules to follow for such stuff? Is there a better n.g. to ask
this
question in?

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

Dave

Since this is a drain, and you are concerned about the integrity, maybe
you'd be less concerned with a 1/8th pipe valve, or petcock.
But, if the tank pressure never gets higher than 125 psi, the force on 1/2
inch diameter area is only about 25 pounds. Besides, the valve is on the
bottom so there is minimal probability of any failure injuring anyone.

Jerry

"Harold and Susan Vordos" wrote: (clip) Others will probably provide the
proper group for you.
^^^^^^^^^^^^^^^^
It's sci.engr.joining.welding Ernie follows this group pretty closely as
well--he will probably read your post.

On Thu, 25 Aug 2005 20:24:29 -0700, DaveC wrote:

I've got an old 20 gal (?) compressor tank in which I want to install a
drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is rated to
125 psi.

Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a "plug"
welded to it that I can drill & tap?

Are there rules to follow for such stuff? Is there a better n.g. to ask this
question in?

Thanks,

It is nowhere near 1/4" thick. Probably less than 1/8". I don't
recommend welding on it. But if you're going to anyway, why not just
weld on a coupling that is already threaded?

"Andy Asberry" wrote in message
...
| On Thu, 25 Aug 2005 20:24:29 -0700, DaveC wrote:
|
| I've got an old 20 gal (?) compressor tank in which I want to install a
| drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is
rated to
| 125 psi.
|
| Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a
"plug"
| welded to it that I can drill & tap?
|
| Are there rules to follow for such stuff? Is there a better n.g. to ask
this
| question in?
|
| Thanks,
|
| It is nowhere near 1/4" thick. Probably less than 1/8". I don't
| recommend welding on it. But if you're going to anyway, why not just
| weld on a coupling that is already threaded?

If the coupling stuck up inside the tank, there'd be a puddle that the
drain could not get to. I wonder how well a flange would work brazed to the
tank. Drill the hole, shape the flange to match very closely, then braze in
place. The low heat of brazing will not affect the heat treatment of the
tank wall that much. The flange ought not to be small, though. Weld a
coupling to the flange before brazing and connect that to the drain valve.

Does this sound safe?

"carl mciver" wrote in message
k.net...
snip----

The low heat of brazing will not affect the heat treatment of the
tank wall that much.

Not true, Carl. Anything above 700 F will change any heat treat present in
carbon steel for the worse, but I'm not convinced tanks are heat treated, so
it's a non-issue. Brazing, even silver brazing, occurs at a temperature
over 1,000 F.

Harold
coupling to the flange before brazing and connect that to the drain valve.

Does this sound safe?

On Thu, 25 Aug 2005 20:24:29 -0700, DaveC wrote:

I've got an old 20 gal (?) compressor tank in which I want to install a
drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is rated to
125 psi.

Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a "plug"
welded to it that I can drill & tap?

It won't be thick enough to tap. Have a plumbing fitting welded or
brazed in. I'd braze it. That's what I did on my tank.
Plumbing fittings are often cast iron which can be welded to steel --
but brazing is a lot easier, would have ample strength and is less
likely to have pinhole leaks or cracks.

Are there rules to follow for such stuff? Is there a better n.g. to ask this
question in?

There are rules for damned near everything, but if it's for your own
use I wouldn't worry about it. As Jerry noted, there isn't much
hydrostatic force on a small fitting like that at 125 PSI.

"DaveC" wrote in message
news.net...
I've got an old 20 gal (?) compressor tank in which I want to install a
drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is rated
to
125 psi.

Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a
"plug"
welded to it that I can drill & tap?

Are there rules to follow for such stuff? Is there a better n.g. to ask
this
question in?


I got a great find last year in a nice two-stage pump that only needed the
valves re-seated to make it cherry again. I was also given a beautiful,
hot-dip galvanized upright propane tank of 100gal capacity. Hmmmm..... I
think I see a picture here.

I didn't want to compromise the tank's integrity because I'm NOT a good
weldor. So, I looked at things from a Rube Goldberg point of view.

Here we fill port, output port, and gauge port. The fill and output were
both 1" NPT bosses in good shape. The gauge port was a huge 2-1/4" machined
flange with the gauge bolted down onto a gasket.

Ok... fill will be fill; just screw in a check valve. Output was output;
natch. Took off the gauge and extracted the float assembly. Machined a
manifold that sat where the gauge used to.

In the manifold is a: Pressure relief port (tested... it does keep ahead of
the pump), a pressure gauge port, and... and... a dip-tube drain. It's just
a copper pipe that kisses the bottom of the tank, and a petcock valve to
open it to ambient pressure. Air pressure pushes the water up the tube.

I welded the pump base to the top flange and the feet to the bottom
flange -- never once touched a torch to the tank itself.

Since I'm not a weldor, I feel safer, and I've got a perfectly servicable
upright that has a drain valve I can actually reach without aggravating my
knees.

LLoyd

"DaveC" wrote in message
news.net...
I've got an old 20 gal (?) compressor tank in which I want to install a
drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is rated
to
125 psi.

Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a
"plug"
welded to it that I can drill & tap?

Are there rules to follow for such stuff? Is there a better n.g. to ask
this
question in?

Thanks,

don't all compressors already have a drain, unless this is a homebrew job?

"DaveC" wrote in message
news.net...
I've got an old 20 gal (?) compressor tank in which I want to install a
drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is rated
to
125 psi.

Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a
"plug"
welded to it that I can drill & tap?

Are there rules to follow for such stuff? Is there a better n.g. to ask
this
question in?

Thanks,
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.

DaveC

This is an invalid return address
Please reply in the news group


Are there rules for such stuff? I would hope there are, in your country.

If you don't know the answer without asking don't mess with air or gas
filled pressure systems.
There are some very scary answers to this question.

In article .net,
DaveC wrote:

I've got an old 20 gal (?) compressor tank in which I want to install a
drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is rated to
125 psi.

Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a "plug"
welded to it that I can drill & tap?

Are there rules to follow for such stuff? Is there a better n.g. to ask this
question in?

Thanks,

You could try avoiding modifying the tank altogether. Get a pipe
cross, mount the tank above so the pipe has to go up to get into the
tank, then have a six to eight inch (assuming it's 3/4 or 1"--longer for
thinner pipes unless you don't mind draining more often) leg of pipe go
out the bottom of the cross to collect water and gunk. Stick a drain at
the bottom of that pipe. Then use the remaining two sides of the cross
for inlet and outlet.
Not pretty or very mobile, but works OK.

--
B.B. --I am not a goat! thegoat4 at airmail dot net
http://web2.airmail.net/thegoat4/

DaveC wrote:
I've got an old 20 gal (?) compressor tank in which I want to install a
drain. I'm guessing it to be 1/4-inch (6.3 mm?) thick steel. Tank is rated to
125 psi.

Can I drill and tap this for 1/4 or 3/8-inch pipe? Or should i get a "plug"
welded to it that I can drill & tap?

Are there rules to follow for such stuff? Is there a better n.g. to ask this
question in?

A welded iron half-coupling is the correct way to go. Do it yourself if
you can. Your tank isn't worth what a shop would have to charge--about
$80 or their one hour minimum.
good luck,
Boat_dreams