Machinist's Workshop Article
 

Just got the Dec/Jan Copy . In the article titled"Shop compressed air for in
house tire service" The author describes in detail a coil of copper tube he
installed in his air line, but doesn't tell us why. Am I missing something?
Is it obvious why? All I can see is it adds volume to the system and might
be a good way to camoflage a still from the revenuers.

Anybody have any ideas?

John

"John Hall" wrote in message
...
Just got the Dec/Jan Copy . In the article titled"Shop compressed air
for in house tire service" The author describes in detail a coil of
copper tube he installed in his air line, but doesn't tell us why. Am
I missing something? Is it obvious why? All I can see is it adds
volume to the system and might be a good way to camoflage a still from
the revenuers.

Anybody have any ideas?

John

Expansion and cooling.

Bernd

John Hall wrote:
Just got the Dec/Jan Copy . In the article titled"Shop compressed air for in
house tire service" The author describes in detail a coil of copper tube he
installed in his air line, but doesn't tell us why. Am I missing something?
Is it obvious why? All I can see is it adds volume to the system and might
be a good way to camoflage a still from the revenuers.

Anybody have any ideas?

This is commonly done to act as a heat exchanger. The hot air leaving the
compressor is cooled somewhat by being passed through the copper tube
where some of the heat is radiated to the air. Presumably this cools the
air enough so that the water vapor contained in it turns to little drops
which can be collected by a filter. I always thought of putting a copper
coil in a bucket of water, into which one or more bags of ice could be
dumped for peak need if necessary. Perhaps a coil in ambient air would
be enough.

I thought his construction (the coil mounted up under a workbench) was
well done, and the article was well done and interesting too.

GWE

John Hall wrote:
Just got the Dec/Jan Copy . In the article titled"Shop compressed air for in
house tire service" The author describes in detail a coil of copper tube he
installed in his air line, but doesn't tell us why. Am I missing something?
Is it obvious why? All I can see is it adds volume to the system and might
be a good way to camoflage a still from the revenuers.

Anybody have any ideas?

John


I used to ride bikes (dirt) with a machinist named John Hall...??

Jack

"John Hall" wrote in
:

Just got the Dec/Jan Copy . In the article titled"Shop compressed air
for in house tire service" The author describes in detail a coil of
copper tube he installed in his air line, but doesn't tell us why. Am
I missing something? Is it obvious why? All I can see is it adds
volume to the system and might be a good way to camoflage a still from
the revenuers.

Anybody have any ideas?

John




It is used as a cooling coil for the air, to aid in water
removal/condensation.




--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

OK, I understand the cooling, but still wonder if this is overkill. Why
don't any of the shops I have been in need to do this? My compressor does
collect water, which I drain periodically from the tank. I use it for
painting and driving nailers. When I use it, it's working steady. I never
sensed there was a problem. Is cooling of the air that big a deal?

John

"Jack" wrote in message
news:C_hGd.6657$sF5.4302@okepread06...

I used to ride bikes (dirt) with a machinist named John Hall...??

Jack

Nope. just another one of the thousands of us.

John

John Hall wrote:
OK, I understand the cooling, but still wonder if this is overkill. Why
don't any of the shops I have been in need to do this? My compressor does
collect water, which I drain periodically from the tank. I use it for
painting and driving nailers. When I use it, it's working steady. I never
sensed there was a problem. Is cooling of the air that big a deal?

Some geographical locations have air that contains much more moisture
than others. Also, some guys have applications that are much more
moisture-sensitive than others. If you want to spray paint, for example,
you need *dry* air.

If you blow air do you see a mist of water? If you direct the stream against
a piece of metal plate, do you see water "piling up"? If so, then you
have a lot of water in your air.

GWE

On Sat, 15 Jan 2005 17:51:24 -0800, Grant Erwin
wrote:

John Hall wrote:
OK, I understand the cooling, but still wonder if this is overkill. Why
don't any of the shops I have been in need to do this? My compressor does
collect water, which I drain periodically from the tank. I use it for
painting and driving nailers. When I use it, it's working steady. I never
sensed there was a problem. Is cooling of the air that big a deal?

Some geographical locations have air that contains much more moisture
than others. Also, some guys have applications that are much more
moisture-sensitive than others. If you want to spray paint, for example,
you need *dry* air.

If you blow air do you see a mist of water? If you direct the stream against
a piece of metal plate, do you see water "piling up"? If so, then you
have a lot of water in your air.

GWE

Here in the Central Valley of California, during the summer months, I
drain my compressor maybe once a month, sometimes even less. I go to
Newport Beach or similar places to service machines, and the guys are
using the air hoses like squirt guns, spraying long streams of water.

Climate makes a HUGE difference.

Gunner

"At the core of liberalism is the spoiled child -
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosphy of sniveling brats." -- P.J. O'Rourke

We have refrigerated drier systems through which we pump the
pneumatic control air for the building(s). Different application,
same principle.

(top posted for your convenience)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Keep the whole world singing . . . .
DanG (remove the sevens)




"John Hall" wrote in message
...
OK, I understand the cooling, but still wonder if this is
overkill. Why don't any of the shops I have been in need to do
this? My compressor does collect water, which I drain
periodically from the tank. I use it for painting and driving
nailers. When I use it, it's working steady. I never sensed
there was a problem. Is cooling of the air that big a deal?

John

I missed the staff meeting but the minutes show Gunner
wrote back on Sun, 16 Jan 2005 05:01:27 GMT in
rec.crafts.metalworking :

If you blow air do you see a mist of water? If you direct the stream against
a piece of metal plate, do you see water "piling up"? If so, then you
have a lot of water in your air.

GWE

Here in the Central Valley of California, during the summer months, I
drain my compressor maybe once a month, sometimes even less. I go to
Newport Beach or similar places to service machines, and the guys are
using the air hoses like squirt guns, spraying long streams of water.

And sometimes, mist when you blow off the part is the sign you need to
go double check the blasted "automatic" drain on the tank. And check the
various water traps. And then come back and drain the air line.

Climate makes a HUGE difference.

Oh yeah.

--
pyotr filipivich.
as an explaination for the decline in the US's tech edge, James
Niccol wrote "It used to be that the USA was pretty good at
producing stuff teenaged boys could lose a finger or two playing with."

I haven't read the article, but I have quite a bit of experience
installing copper air systems. My personal system is 3/4" and over
200 ft of tubing (shop is 38x26). I've read the advice from TP Tools
that says you should only use black iron but respectfully disagree.
Their concern is that a soldered joint might separate under pressure -
the soldered surface area is over 1" sq. I have yet to have one come
apart at 125 or 175 psi and I've been running them for years. Note:
Use a flexible connection between any air system and the compressor to
isolate compressor vibration from the piping system.

When air is compressed the temperature rises (aka PV=nRT) and so does
the amount of entrained water vapor. The purpose of a long run
between the compressor and the outlet is to provide air travel
distance allowing the heated air to cool. As the air cools the water
vapor condenses. Copper is an excellent conductor and is perfect for
this purpose. The piping should be running slightly uphill away from
the compressor allowing the water to run back away from the outlet.
Usually drops are provided in the piping system to catch water with
valves at the bottom to drain the system. Think of the anti-water
hammer risers in your home, but in reverse - pointing down instead of
up. The system I installed in my shop has 7 such drains plumbed out
through the walls so I can just crack the valves and drain each
collection point.

The copper coil you reference is probably in the system to add cooling
distance in a relatively small amount of space. A coil can also be
placed inside a refrigerator or in an ice chest to provide a larger
temperature differential to speed condensation. This is also how
commercial air drying systems work - they are heat exchangers removing
the heat from the high pressure compressed air side and dumping it
into the environment. A coil also works well to "sling" the water out
of the air stream as it condenses - takes advantage of angular
velocity.

Any air system should have a water separator and a filter at the end
of the stream. No matter the pipe selected you will get particles in
the compressed air that can contaminate your air tools, especially
painting.

Ryan Reid
Systems Engineer

On Sat, 15 Jan 2005 21:13:54 GMT, "John Hall"
wrote:

Just got the Dec/Jan Copy . In the article titled"Shop compressed air for in
house tire service" The author describes in detail a coil of copper tube he
installed in his air line, but doesn't tell us why. Am I missing something?
Is it obvious why? All I can see is it adds volume to the system and might
be a good way to camoflage a still from the revenuers.

Anybody have any ideas?

John

On Sun, 16 Jan 2005 21:45:45 GMT, Ryan and Diana Reid
wrote:

I haven't read the article, but I have quite a bit of experience
installing copper air systems. My personal system is 3/4" and over
200 ft of tubing (shop is 38x26). I've read the advice from TP Tools
that says you should only use black iron but respectfully disagree.
Their concern is that a soldered joint might separate under pressure -
the soldered surface area is over 1" sq. I have yet to have one come
apart at 125 or 175 psi and I've been running them for years. Note:
Use a flexible connection between any air system and the compressor to
isolate compressor vibration from the piping system.

When air is compressed the temperature rises (aka PV=nRT) and so does
the amount of entrained water vapor. The purpose of a long run
between the compressor and the outlet is to provide air travel
distance allowing the heated air to cool. As the air cools the water
vapor condenses. Copper is an excellent conductor and is perfect for
this purpose. The piping should be running slightly uphill away from
the compressor allowing the water to run back away from the outlet.
Usually drops are provided in the piping system to catch water with
valves at the bottom to drain the system. Think of the anti-water
hammer risers in your home, but in reverse - pointing down instead of
up. The system I installed in my shop has 7 such drains plumbed out
through the walls so I can just crack the valves and drain each
collection point.

The copper coil you reference is probably in the system to add cooling
distance in a relatively small amount of space. A coil can also be
placed inside a refrigerator or in an ice chest to provide a larger
temperature differential to speed condensation. This is also how
commercial air drying systems work - they are heat exchangers removing
the heat from the high pressure compressed air side and dumping it
into the environment. A coil also works well to "sling" the water out
of the air stream as it condenses - takes advantage of angular
velocity.

Any air system should have a water separator and a filter at the end
of the stream. No matter the pipe selected you will get particles in
the compressed air that can contaminate your air tools, especially
painting.

Ryan Reid
Systems Engineer

On Sat, 15 Jan 2005 21:13:54 GMT, "John Hall"
wrote:

Just got the Dec/Jan Copy . In the article titled"Shop compressed air for in
house tire service" The author describes in detail a coil of copper tube he
installed in his air line, but doesn't tell us why. Am I missing something?
Is it obvious why? All I can see is it adds volume to the system and might
be a good way to camoflage a still from the revenuers.

Anybody have any ideas?

John

I'm not so sure about the water flinging to the sides of the coils as
the air travels through it. I do know that having the pipe cool the
air is good. Also, the larger the pipe the better. This is because the
larger pipe lowers the velocity of the air. Fast moving air will pick
up water that's on the bottom of the pipe. At the spots where you tap
the pipe for air a tee should be installed with the outlet UP. Then,
use a U shaped of pipe to bring the air down to the shop. Having the
air outlets on the top of the pipe helps to prevent water from
becoming entrained in the air.
ERS