"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

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?

"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?

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.

"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?

"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...

This sounds like a very creative idea, but I'm having difficulty picturing
what your set-up is. (A compressor with a "float assembly"? Water actually
accumulates enough to require a float?)

It was a propane tank in real life. It had a float-actuated gauge. The
gauge port was BIG, so it was a nice place to combine some functions.


I've got 2 ports on this tank: input (small boss fitted with 1/4 copper
tube
connecting to compressor output), and output (large (2-inch?) threaded
boss
with 1/4ntp threaded adapter (plug) connecting to 1/4 pipe with tees for
gauge and quick disconnect hose fitting).

Hmm... I could adapt the input to also act as output, and put the dip-tube
drain on the large boss.

How, exactly, is a dip-tube drain constructed? How do you fit a tube
internally and connect that to the backside of a 1/4ntp (or such) output?

The manifold had two holes straight through into the top of the tank: one
for the relief valve and one for the new pressure gauge. It had a THIRD
hole that had a petcock on the outside, and a copper compression fitting on
the inside to accept the dip tube.

LLoyd

"DaveC" wrote in message
news.net...
Thus spake DaveC:

In the manifold is a: Pressure relief port (tested... it does keep ahead
of
the pump)

What's the purpose of a pressure relief port? Is this an "open at x psi"
valve to keep pressure below the tank's limit? But this is what an
electrical
pressure switch does.

Dave, pressure switches weld shut in storms, or with age, or with mud-dauber
nests inside them.

EVERY compressor must have a pop-off valve to protect the tank from
over-pressure.

LLoyd

In article .net,
DaveC wrote:
Thus spake Charles Spitzer:

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

no, this one doesn't. Craftsman brand, old.

That sounds very strange. I have an old Craftsman -- horizontal
tank, belt-driven pump, two wheels at one end and a handle at the other.

Between the wheels, on the underside, is the drain valve. It
was rather small -- perhaps 1/4" NPT thread. It had a T-handled valve,
which was hollow for the water to flow out. It was rather prone to jam,
so I replaced it with one with a knurled knob on the end, and a silicone
rubber-gasketed seat on a wider portion on the inside. That one remains
controllable with just my fingers.

If there were room, I would replace it with a timer controlled
solenoid valve, but there is not on this one.

You might consider looking up the parts list for your model on
Sears' website, to see whether it lists a drain valve as part of what it
should have.

I could imagine taking the output fitting and replacing it with
a concentric fitting, with the inner part being a dip tube to drain from
near the bottom, and the outer part passing air to the regulator.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"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.

DaveC wrote:
So I guess without some custom "manifold" or such, there's no way to fit a
dip tube, internally. All I have is threaded holes in the tank for 1/4 inch
input, and 3/8 inch output ...

I assume that your 3/8 threaded hole is NPT. In which case, use a
npt-compression adapter/union, 3/8 NPT to 1/4 (OD) compression. Such as
McMaster-Carr #50915K316:
http://www.mcmaster.com/
But also generally hardware-store available.

Drill out the adapter to 1/4" to allow the tube to pass through it. The
fitting has plenty enough "meat" to do this, but as-made it stops the
tube for ease of assembly.

Screw the adapter to the tank, pass the tube through it, tighten the
compression sleeve/nut, add a compression-fitting valve to the tube. If
you file a notch on the in-tank end of the tube, you can lower it all
the way to the bottom and still have an opening for the water.

If you first fit a 3/8 NPT tee to the tank, with the straight-through
vertical, you can take your tank output from the horizontal leg, while
fitting the dip tube adapter to the top. The dip tube will be co-axial
with part of the output path, but with enough room for air flow.

HTH,
Bob

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

A 'Pressure relief port or valve' is a redundant safety feature. (Required
by most codes for any pressure vessel.) Electrical pressure switches do
fail.


--
$.02
Chipper Wood
useoursatyahoodotcom

"DaveC" wrote in message
news.net...
Thus spake DaveC:

In the manifold is a: Pressure relief port (tested... it does keep ahead
of
the pump)

What's the purpose of a pressure relief port? Is this an "open at x psi"
valve to keep pressure below the tank's limit? But this is what an
electrical
pressure switch does.

What's a relief port?
--
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




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