On Wed, 24 Feb 2016 08:45:56 -0500, Keith Nuttle
wrote:

On 2/24/2016 12:49 AM, -MIKE- wrote:
On 2/23/16 9:30 PM, DJ Delorie wrote:

.


Broken record: the concentration would have to be so high that you
couldn't see across the room, let alone breathe.

I think Darwinism would do us all a favor and explode the shop of any
woodworker who would let that kind of "cloud" be produced is his
shop. Lord know, I wouldn't want to see any of his work if he's that
reckless.

I can't even imagine a normal woodworking scenario in which that high
a concentration of wood dust could occur.

Broken record or not. There is a very low probability of people being
stuck by lightning, but they are. There is a very low probability of
people being struck by a meteorite but there is a recent story in the
news about that happening.

There is a very low probability of a person being killed by a falling
tree, but there are people who are cutting down their trees every day so
they do not fall on them and kill them.

Low probability means exactly that, it can happen but infrequently.

Remember Murphy's law. Why tempt Murphy.

Durn Irishmen!

On Wed, 24 Feb 2016 14:02:07 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 1:28 PM, -MIKE- wrote:
On 2/24/16 1:06 PM, Leon wrote:
On 2/24/2016 12:34 PM, Keith Nuttle wrote:
On 2/24/2016 12:52 PM, -MIKE- wrote:
On 2/24/16 7:45 AM, Keith Nuttle wrote:
On 2/24/2016 12:49 AM, -MIKE- wrote:
On 2/23/16 9:30 PM, DJ Delorie wrote:

.


Broken record: the concentration would have to be so high that you
couldn't see across the room, let alone breathe.

I think Darwinism would do us all a favor and explode the shop of any
woodworker who would let that kind of "cloud" be produced is his
shop. Lord know, I wouldn't want to see any of his work if he's that
reckless.

I can't even imagine a normal woodworking scenario in which that high
a concentration of wood dust could occur.

Broken record or not. There is a very low probability of people being
stuck by lightning, but they are. There is a very low probability of
people being struck by a meteorite but there is a recent story in the
news about that happening.

There is a very low probability of a person being killed by a falling
tree, but there are people who are cutting down their trees every
day so
they do not fall on them and kill them.

Low probability means exactly that, it can happen but infrequently.

Remember Murphy's law. Why tempt Murphy.


The point is, there's a low probability in everything. If you want to
worry about everything that is technically "possible" happening to you,
go for it. Enjoy that life.

That's the kind of severely flawed logic that inhabits the brains of
people who will never fly on an airplane but have no problem driving on
the interstate, even though the chances of injury or death are almost
unbelievably, exponentially higher when driving a car.

If people want to live in fear of everything that "might" or "could"
happen to them, well... let's just say they make lots of pills for that
condition. :-)


There is a difference between worrying about the probabilities of
accident, and taking steps to avoid a potential for an accident. You
do not spend a lot of money installing things to prevent an 1 in a
million probability of accident. However you don't ignore the
possibility that it can happen. Sort of like walk under a ladder, the
probability of something falling off of the ladder is remote, it is just
good practice not to get in the habit of doing it.

There are other places where this applies. You buy home owners insurance
even though there is a small probability that your house will be damaged
or broken into. You make sure there are not children in the area where
you are mowing even thought the probability you will hit something that
will fly our and hit a child. Most people modify there behavior or
make purchases based on low probability events.

And yet there are really no reasonable steps to take to keep saw dust
from exploding because of static electricity in your DC, which is what
this thread is about.


I ground my dust collector duct-work to fend off the mind control rays
from outer-space.
It also helps disperse those pesky chemtrails the gummint is using to
make me more subservient.


I simply don't worry about it. There are numerous other things in the
shop that make sparks and on a continuous basis. Like "any" electric
tool or machine that has a universal motor. Yes damn near any hand held
power tool. ;~)

Speaking of which, any motor with brushes, spark. It is the nature of
the beast, and capacitor start motors had a switch which opens up when
a certain RPM is reached, and it too sparks.

One has to have a TEFC IIRC or an explosion proof motor to contain
sparks on failure of a motor.

I am afraid this threads becoming a bit irrational.
As many times as a saw blade has hit a nail, especially on a TS and
thrown the spark into the dust bin below if it were a serious problem
we'd of heard about it the day the women who invented the TS operated
it.

On Wed, 24 Feb 2016 16:08:56 -0600, Markem
wrote:

On Wed, 24 Feb 2016 13:06:45 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 12:34 PM, Keith Nuttle wrote:
On 2/24/2016 12:52 PM, -MIKE- wrote:
On 2/24/16 7:45 AM, Keith Nuttle wrote:
On 2/24/2016 12:49 AM, -MIKE- wrote:
On 2/23/16 9:30 PM, DJ Delorie wrote:

.


Broken record: the concentration would have to be so high that you
couldn't see across the room, let alone breathe.

I think Darwinism would do us all a favor and explode the shop of any
woodworker who would let that kind of "cloud" be produced is his
shop. Lord know, I wouldn't want to see any of his work if he's that
reckless.

I can't even imagine a normal woodworking scenario in which that high
a concentration of wood dust could occur.

Broken record or not. There is a very low probability of people being
stuck by lightning, but they are. There is a very low probability of
people being struck by a meteorite but there is a recent story in the
news about that happening.

There is a very low probability of a person being killed by a falling
tree, but there are people who are cutting down their trees every day so
they do not fall on them and kill them.

Low probability means exactly that, it can happen but infrequently.

Remember Murphy's law. Why tempt Murphy.


The point is, there's a low probability in everything. If you want to
worry about everything that is technically "possible" happening to you,
go for it. Enjoy that life.

That's the kind of severely flawed logic that inhabits the brains of
people who will never fly on an airplane but have no problem driving on
the interstate, even though the chances of injury or death are almost
unbelievably, exponentially higher when driving a car.

If people want to live in fear of everything that "might" or "could"
happen to them, well... let's just say they make lots of pills for that
condition. :-)


There is a difference between worrying about the probabilities of
accident, and taking steps to avoid a potential for an accident. You
do not spend a lot of money installing things to prevent an 1 in a
million probability of accident. However you don't ignore the
possibility that it can happen. Sort of like walk under a ladder, the
probability of something falling off of the ladder is remote, it is just
good practice not to get in the habit of doing it.

There are other places where this applies. You buy home owners insurance
even though there is a small probability that your house will be damaged
or broken into. You make sure there are not children in the area where
you are mowing even thought the probability you will hit something that
will fly our and hit a child. Most people modify there behavior or
make purchases based on low probability events.

And yet there are really no reasonable steps to take to keep saw dust
from exploding because of static electricity in your DC, which is what
this thread is about.


Remember an accident is a chain of unlikely events aligning. Now if
and when someone has a dust explosion from saw dust, the cause will
not be static. The water heater, furnace or other open flame in the
room yep that would do it. But what did "you" do to suspend that much
dust in the air? Sugar on the other hand burns great and fast,
powdered is best (do not try in a confined space).

Mark

Mark, that's called Caramelization.

Now have the little woman dump a 5lb bag into her Mixer bowl on Hi
-speed.....naw.

On Wed, 24 Feb 2016 18:30:20 -0600, "SnA Higgins"
wrote:


"OFWW" wrote in message
.. .
http://www.woodshopnews.com/news/fea...s-of-wood-dust

Nice article.

How OSHA currently judges with a paper clip.

"So is the sawdust in my facility a hazard? It depends, Scott says.
The really dangerous stuff is so-called "wood flour" - fine particles
500 microns or smaller."

It appears to be a very small chance.

However as far as I am concerned the breathing of the "wood flour" is
my concern, so I will be paying attention, to this for my sake.

Steel wool catches fire easily, just so as you are aware of it. I like
to bet that I can set steel on fire. Haven't lost yet.

When I was an 8th grader, a buddy of mine and I were hired by the local
CO-OP to broom out the corn dust in the head houses of the grain elevators
in my home town. They wanted it done because they feared a buildup of the
dust might cause an explosion given the right conditions. We liked the job
because no one came to look in on us because it was such a dirty job: after
about five minutes of pushing brooms the headhouses would have so much
powder in the air you couldn't see across the room. We also liked it
because we could stand outside the headhouse and smoke cigarettes without
fear of being caught.
An additional elevator was built when I was a sophomore. It was about 60
feet taller than the old one so the design was to build a 24" diameter auger
up to the head house on the new structure from the old one. One Saturday
after the new elevator had been slipped and had been cured enough to drill
concrete anchors into it, the engineers came up to the top of the old
elevator where we had started cleaning. Of course we were smoking. It was
cold outside so we were inside. They got off the man lift just as my buddy
took a deep drag on his cig. They saw the glowing coals through the corn
dust cloud and nearly trampled each other getting the hell back on the man
lift to escape what they were sure to be a huge explosion.
They apparently didn't squeal on us. But a few minutes later the elevator
operator came up and said to stay up there until the dust cleared then come
down.

When I was a Junior I told the story to my science teacher. Without
profanity he called my buddy and I a couple of dumb asses and then explained
spontaneous combustion. For the class he made an example. He took a 2
pound coffee can. He drilled a hole on the side near the bottom where he
attached a length of tubing. He put a votive candle inside near the center
of the bottom. Then he poured a ring of cornstarch around the candle. He lit
the candle and put a lid on the can. He blew a short puff of air in the
tube. The ball of fire was big enough to scorch the ceiling tiles!

Stupid is as stupid does.

Steve


Great story, I was waiting for the punch line. And that is why
reasonable precaution should not be thrown into the wind.

I'm glad neither of you were hurt, I have heard stories of elevator
explosions.

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.


IOW's how many inches of vacuum required before all oxygen is boiled
off, and that includes the oxygen from moisture.

Even in the highest CFM DC systems the air pressure is only a minimal
amount below atmospheric pressure; yes it's a big "vacuum" cleaner, but
there's really not a lot of vacuum, it's just slightly lower pressure
air moving at a pretty high velocity. Hence, there's not going to be
any strange things happening owing to anything other than that there is
a concentration of dust created and given a large enough ignition
source, one could potentially cause a boom. But, static electricity
from PVC for at least home-shop-sized duct work simply doesn't have
sufficient energy to do so. Metal hitting an iron impeller, _maybe_,
but still unlikely. More likely would be an overheated bearing or
another open ignition source like a steaming tube or the like that gets
away but getting it into the necessary location is the trick there...

An overheated bearing would have to be above 425 degF as I recall to
burn wood. A spark is a different animal. A spark hitting a muffler
packed with steel wool sets it on fire which sets the sawdust on fire
and minor implosion in a vacuum system, and hey! It was my imagination
so don't be a party pooper, K?


And I am not trying to argue with you at all here but there are a lot
other considerations to worry about that can make your DC combust aside
from static spark.

I cant tell you how many times I have cut through a finishing nail with
my TS. Surely there was a really hot spark that traveled into the
collector hose.

AND with marginal powered table saws or those with dull blades it is not
at all uncommon, at times, for the wood to actually get hot enough to
smolder and for the dust from that to go into the DC.

I totally believe the static spark thing is a threat with any DC if the
DC is used to clean up something other than wood saw dust. I think the
caution labels are a blanket statement for what ever the DC might be
used for. Maybe some one uses them to clean up grain elevators. ;~)
I know I use mine to suck up anything that is on my shop floor including
my son's hair when my wife cuts his hair. Yeah is is 28 but sometimes
this is the only way we get to see him. LOL

On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.


IOW's how many inches of vacuum required before all oxygen is boiled
off, and that includes the oxygen from moisture.

Even in the highest CFM DC systems the air pressure is only a minimal
amount below atmospheric pressure; yes it's a big "vacuum" cleaner, but
there's really not a lot of vacuum, it's just slightly lower pressure
air moving at a pretty high velocity. Hence, there's not going to be
any strange things happening owing to anything other than that there is
a concentration of dust created and given a large enough ignition
source, one could potentially cause a boom. But, static electricity
from PVC for at least home-shop-sized duct work simply doesn't have
sufficient energy to do so. Metal hitting an iron impeller, _maybe_,
but still unlikely. More likely would be an overheated bearing or
another open ignition source like a steaming tube or the like that gets
away but getting it into the necessary location is the trick there...

An overheated bearing would have to be above 425 degF as I recall to
burn wood. A spark is a different animal. A spark hitting a muffler
packed with steel wool sets it on fire which sets the sawdust on fire
and minor implosion in a vacuum system, and hey! It was my imagination
so don't be a party pooper, K?


And I am not trying to argue with you at all here but there are a lot
other considerations to worry about that can make your DC combust aside
from static spark.

I cant tell you how many times I have cut through a finishing nail with
my TS. Surely there was a really hot spark that traveled into the
collector hose.

AND with marginal powered table saws or those with dull blades it is not
at all uncommon, at times, for the wood to actually get hot enough to
smolder and for the dust from that to go into the DC.

I totally believe the static spark thing is a threat with any DC if the
DC is used to clean up something other than wood saw dust. I think the
caution labels are a blanket statement for what ever the DC might be
used for. Maybe some one uses them to clean up grain elevators. ;~)
I know I use mine to suck up anything that is on my shop floor including
my son's hair when my wife cuts his hair. Yeah is is 28 but sometimes
this is the only way we get to see him. LOL

On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.


What you said brought back memories, old ones. Like the vacuum gauge
in inches of water column. Trying to use it for economy runs to save
gas for a race. Watching that sucker jump around made it all
pointless. In order to set injectors, or multiple carbs you had to use
a manometer to sync them up. On motorcycles and their smaller engines
and High rpms it was cortical, if a valve failed to seat or your fuel
system flooded out, it was a definite boom time in the intake
manifold. I've had more than one engine go up in flames, especially
with stromberg 97's.




IOW's how many inches of vacuum required before all oxygen is boiled
off, and that includes the oxygen from moisture.

Even in the highest CFM DC systems the air pressure is only a minimal
amount below atmospheric pressure; yes it's a big "vacuum" cleaner, but
there's really not a lot of vacuum, it's just slightly lower pressure
air moving at a pretty high velocity. Hence, there's not going to be
any strange things happening owing to anything other than that there is
a concentration of dust created and given a large enough ignition
source, one could potentially cause a boom. But, static electricity
from PVC for at least home-shop-sized duct work simply doesn't have
sufficient energy to do so. Metal hitting an iron impeller, _maybe_,
but still unlikely. More likely would be an overheated bearing or
another open ignition source like a steaming tube or the like that gets
away but getting it into the necessary location is the trick there...

An overheated bearing would have to be above 425 degF as I recall to
burn wood. A spark is a different animal. A spark hitting a muffler
packed with steel wool sets it on fire which sets the sawdust on fire
and minor implosion in a vacuum system, and hey! It was my imagination
so don't be a party pooper, K?


And I am not trying to argue with you at all here but there are a lot
other considerations to worry about that can make your DC combust aside
from static spark.


that's ok, I meant it as a joke, "in my imagination" just letting it
go wild to conjure up something. I believe that was first in response
to Mikes comment on using imagination. Guess it didn't come across
that way, sorry.

I cant tell you how many times I have cut through a finishing nail with
my TS. Surely there was a really hot spark that traveled into the
collector hose.

AND with marginal powered table saws or those with dull blades it is not
at all uncommon, at times, for the wood to actually get hot enough to
smolder and for the dust from that to go into the DC.


I've had that happen with skil saws, actually had glowing embers from
a dull blade.

I totally believe the static spark thing is a threat with any DC if the
DC is used to clean up something other than wood saw dust. I think the
caution labels are a blanket statement for what ever the DC might be
used for. Maybe some one uses them to clean up grain elevators. ;~)
I know I use mine to suck up anything that is on my shop floor including
my son's hair when my wife cuts his hair. Yeah is is 28 but sometimes
this is the only way we get to see him. LOL


As long as he doesn't ask for money too.

I finally picked up an 1 1/2" hose for some of my small stuff, then
realized I should cut that into smaller pieces and buy a few more
fittings for it. I mistakenly had my hand holding the 2 1/2 hose when
I hit to button to start the vac and boy did that hurt. that flex hose
slammed closed in a hurry, pinching my skin and gave me instant blood
blisters with that small hose hooked up. WOWEE! Then the small hose
started whistling and stuff. I'm not sure how long that hose is, but
it is so restrictive that I want to shorten it some to increase the
air flow and cut down on the whistling at the same time. I'm thinking
I am going to Rockler for those. they seem much better prepared with
the fittings and hose then woodcraft where I picked up the hose on a
whim. Where I am at there is only a woodcraft, and it is an
independent store. Rockler is about 50-60 miles away.

"So is the sawdust in my facility a hazard? It depends, Scott says.
The really dangerous stuff is so-called "wood flour" -- fine particles
500 microns or smaller."

Check this out:
https://www.youtube.com/watch?v=u2Fa1ESqGeE

It's worth watching all the way through ....

On 2/24/2016 9:18 PM, krw wrote:
On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.




IOW's how many inches of vacuum required before all oxygen is boiled
off, and that includes the oxygen from moisture.

Even in the highest CFM DC systems the air pressure is only a minimal
amount below atmospheric pressure; yes it's a big "vacuum" cleaner, but
there's really not a lot of vacuum, it's just slightly lower pressure
air moving at a pretty high velocity. Hence, there's not going to be
any strange things happening owing to anything other than that there is
a concentration of dust created and given a large enough ignition
source, one could potentially cause a boom. But, static electricity
from PVC for at least home-shop-sized duct work simply doesn't have
sufficient energy to do so. Metal hitting an iron impeller, _maybe_,
but still unlikely. More likely would be an overheated bearing or
another open ignition source like a steaming tube or the like that gets
away but getting it into the necessary location is the trick there...

An overheated bearing would have to be above 425 degF as I recall to
burn wood. A spark is a different animal. A spark hitting a muffler
packed with steel wool sets it on fire which sets the sawdust on fire
and minor implosion in a vacuum system, and hey! It was my imagination
so don't be a party pooper, K?


And I am not trying to argue with you at all here but there are a lot
other considerations to worry about that can make your DC combust aside
from static spark.

I cant tell you how many times I have cut through a finishing nail with
my TS. Surely there was a really hot spark that traveled into the
collector hose.

AND with marginal powered table saws or those with dull blades it is not
at all uncommon, at times, for the wood to actually get hot enough to
smolder and for the dust from that to go into the DC.

I totally believe the static spark thing is a threat with any DC if the
DC is used to clean up something other than wood saw dust. I think the
caution labels are a blanket statement for what ever the DC might be
used for. Maybe some one uses them to clean up grain elevators. ;~)
I know I use mine to suck up anything that is on my shop floor including
my son's hair when my wife cuts his hair. Yeah is is 28 but sometimes
this is the only way we get to see him. LOL

On 2/24/16 10:43 PM, wrote:

"So is the sawdust in my facility a hazard? It depends, Scott says.
The really dangerous stuff is so-called "wood flour" -- fine particles
500 microns or smaller."

Check this out:
https://www.youtube.com/watch?v=u2Fa1ESqGeE

It's worth watching all the way through ....


How much you want to bet they didn't use a static spark for the ignition
source?


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

-MIKE- wrote in
:


Broken record: the concentration would have to be so high
that you couldn't see across the room, let alone breathe.

I think Darwinism would do us all a favor and explode the
shop of any woodworker who would let that kind of "cloud"
be produced is his shop. Lord know, I wouldn't want to see
any of his work if he's that reckless.

I can't even imagine a normal woodworking scenario in which
that high a concentration of wood dust could occur.



DAMHIK but... You ever seen the bag blow off of a dust collector
while you were planing a 10" wide board?? That SOB will make a
mess in a couple of seconds that will take you hours to clean
up. Particles from the planer would be much larger than dust but
the built-up dust in the bag that escapes would certainly come
close.

Larry

On Wed, 24 Feb 2016 23:07:33 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 9:18 PM, krw wrote:
On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...




IOW's how many inches of vacuum required before all oxygen is boiled
off, and that includes the oxygen from moisture.

Even in the highest CFM DC systems the air pressure is only a minimal
amount below atmospheric pressure; yes it's a big "vacuum" cleaner, but
there's really not a lot of vacuum, it's just slightly lower pressure
air moving at a pretty high velocity. Hence, there's not going to be
any strange things happening owing to anything other than that there is
a concentration of dust created and given a large enough ignition
source, one could potentially cause a boom. But, static electricity
from PVC for at least home-shop-sized duct work simply doesn't have
sufficient energy to do so. Metal hitting an iron impeller, _maybe_,
but still unlikely. More likely would be an overheated bearing or
another open ignition source like a steaming tube or the like that gets
away but getting it into the necessary location is the trick there...

An overheated bearing would have to be above 425 degF as I recall to
burn wood. A spark is a different animal. A spark hitting a muffler
packed with steel wool sets it on fire which sets the sawdust on fire
and minor implosion in a vacuum system, and hey! It was my imagination
so don't be a party pooper, K?


And I am not trying to argue with you at all here but there are a lot
other considerations to worry about that can make your DC combust aside
from static spark.

I cant tell you how many times I have cut through a finishing nail with
my TS. Surely there was a really hot spark that traveled into the
collector hose.

AND with marginal powered table saws or those with dull blades it is not
at all uncommon, at times, for the wood to actually get hot enough to
smolder and for the dust from that to go into the DC.

I totally believe the static spark thing is a threat with any DC if the
DC is used to clean up something other than wood saw dust. I think the
caution labels are a blanket statement for what ever the DC might be
used for. Maybe some one uses them to clean up grain elevators. ;~)
I know I use mine to suck up anything that is on my shop floor including
my son's hair when my wife cuts his hair. Yeah is is 28 but sometimes
this is the only way we get to see him. LOL

On 2/25/2016 9:00 PM, krw wrote:



Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...


I think he meant inches of Hg, a common measure on a vacuum gauge.
29.92 is perfect vacuum at 1 atmosphere.

On 2/25/2016 8:00 PM, krw wrote:
On Wed, 24 Feb 2016 23:07:33 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 9:18 PM, krw wrote:
On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...

OK, My mistake, not PSI, inches of vacuum. I was trying to recall what
the vacuum gauge on my first car indicated. I thought it was between
15~30 "inches".. apparently inches on the gauges are double actual PSI.

On 2/25/2016 8:21 PM, Ed Pawlowski wrote:
On 2/25/2016 9:00 PM, krw wrote:



Well hopefully there is no combustion inside of the manifold and
having
said that, typically the fuel is combusted when it is under higher
than
atmospheric pressure. And engines work better when the fuel
bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...


I think he meant inches of Hg, a common measure on a vacuum gauge. 29.92
is perfect vacuum at 1 atmosphere.



Yes! Precisely, I was mistaken. Inches not PSI, although the actual
PSI is half the reading on the gauge.

On Thu, 25 Feb 2016 23:01:34 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/25/2016 8:00 PM, krw wrote:
On Wed, 24 Feb 2016 23:07:33 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 9:18 PM, krw wrote:
On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...

OK, My mistake, not PSI, inches of vacuum. I was trying to recall what
the vacuum gauge on my first car indicated. I thought it was between
15~30 "inches".. apparently inches on the gauges are double actual PSI.

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

On Fri, 26 Feb 2016 19:59:32 -0500, krw wrote:

On Thu, 25 Feb 2016 23:01:34 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/25/2016 8:00 PM, krw wrote:
On Wed, 24 Feb 2016 23:07:33 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 9:18 PM, krw wrote:
On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...

OK, My mistake, not PSI, inches of vacuum. I was trying to recall what
the vacuum gauge on my first car indicated. I thought it was between
15~30 "inches".. apparently inches on the gauges are double actual PSI.

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

1ATM = 14 PSI = 0" Hg

In article ,
lid says...

In article
Keith Nuttle wrote:

On 2/24/2016 12:52 PM, -MIKE- wrote:
On 2/24/16 7:45 AM, Keith Nuttle wrote:
On 2/24/2016 12:49 AM, -MIKE- wrote:
On 2/23/16 9:30 PM, DJ Delorie wrote:

.


Broken record: the concentration would have to be so high that you
couldn't see across the room, let alone breathe.

I think Darwinism would do us all a favor and explode the shop of any
woodworker who would let that kind of "cloud" be produced is his
shop. Lord know, I wouldn't want to see any of his work if he's that
reckless.

I can't even imagine a normal woodworking scenario in which that high
a concentration of wood dust could occur.

Broken record or not. There is a very low probability of people being
stuck by lightning, but they are. There is a very low probability of
people being struck by a meteorite but there is a recent story in the
news about that happening.

There is a very low probability of a person being killed by a falling
tree, but there are people who are cutting down their trees every day so
they do not fall on them and kill them.

Low probability means exactly that, it can happen but infrequently.

Remember Murphy's law. Why tempt Murphy.


The point is, there's a low probability in everything. If you want to
worry about everything that is technically "possible" happening to you,
go for it. Enjoy that life.

That's the kind of severely flawed logic that inhabits the brains of
people who will never fly on an airplane but have no problem driving on
the interstate, even though the chances of injury or death are almost
unbelievably, exponentially higher when driving a car.

If people want to live in fear of everything that "might" or "could"
happen to them, well... let's just say they make lots of pills for that
condition. :-)


There is a difference between worrying about the probabilities of
accident, and taking steps to avoid a potential for an accident. You
do not spend a lot of money installing things to prevent an 1 in a
million probability of accident. However you don't ignore the
possibility that it can happen. Sort of like walk under a ladder, the
probability of something falling off of the ladder is remote, it is just
good practice not to get in the habit of doing it.

There are other places where this applies. You buy home owners insurance
even though there is a small probability that your house will be damaged
or broken into. You make sure there are not children in the area where
you are mowing even thought the probability you will hit something that
will fly our and hit a child. Most people modify there behavior or
make purchases based on low probability events.

Is it just me or have we become a nation of pussies? And where was I
when this cosmic shift took place? Let me explain "cosmic shift"
through example. When I was a baby we did not have a car seat, no one
did. When I got older I would sit in the front seat without a seat
belt, everyone did.

Just a note on that one, but the gummint decided too many people were
getting killed in car crashes and decided to Do Something. So they
passed a law that all cars have to have seat belts. Nobody used the
seat belts. They they required that the cars be rigged so that they
wouldn't start without the seat belts being fastened, so everybody
fastened the seat belts permanently and sat on them. So then the airbag
makers came along and lobbied Congress to solve this problem by forcing
the car manufacturers to put air bags in all cars. So all cars have air
bags. Then they found out that people below a certain height were
likely to get killed when the air bags went off. Most of the people
below that height are kids, althought many women and Asians are also
below that height. So they passed laws that kids had to sit in the back
where there were no air bags--apparently the lives of Asians and small
women don't count. Then someone pointed out that pickup trucks,
Corvettes, and a variety of other vehicles don't have back seats, so
they rethought this and without changing the back seat law they passed
car seat laws that basically require that the kid be in a box that's
armored against the air bags. Along with way it was discovered that
regardless of your size, if you are not exactly where the air bag
designers thought you would be when they designed the air bag, the air
bag could kill you anyway, so now it's back to seat belts, this time not
to protect you from the crash, but to protect you from the GOVERNMENT
MANDATED AIRBAG. Because letting people actually have a choice is,
like, unthinkable.

I did not own or wear a bicycle helmet as a kid -
I still don't. In any event, somewhere along the line a cosmic shift
took place where only lunatics would put a baby in a car without a car
seat or drive without seat belts. The same sort of cosmic shift is
nearly completed with bicycle helmets. It's a strange sort of
phenomenon that sometimes makes sense but at other times it doesn't.

Another cosmic shift has taken place in America but this one is
repugnant in all ways. I'm talking about the pussification of American
men. The seat belts and the bike helmets are all part of this and the
cosmic shift really accelerated after 9-11. Fear began to trump sex on
Madison Avenue. The metrosexual has become the symbol of American
masculinity. Hugh Grant has replaced Cary Grant as a Hollywood icon of
masculinity. I was at a party recently and some hag was blathering on
about how hot David Schwimmer is. He's the guy that was on Friends
always blubbering on about his feelings or something. Can you imagine
this guy playing along side of John Wayne in the Sands of Iwo Jima?

I was really struck by this pussification at my son's t-ball game last
summer. It was warm and sunny but nothing unusual. A mother came out
of the stands and asked me, the coach, if I had sun screen and water
for the kids. I just sort of looked at her in a mystified state. I
said we have hats and a bubbler behind the back stop. T-ball is not
really known for making kids sweat much at all and I figured sun tan
lotion is for the beach. I'm not opposed to a kid running over to the
bubbler for a drink. She then proceeded to spray sun screen on all 15
kids and practically forced them to gulp some bottled water. Parents
in the stands literally cheered her for her safety first approach.

I just sort of shrugged it off but later I heard one boy comment to
Mrs. Worrywart's kid, "Why was your mom spraying us with that stuff.
You're mom's stupid." A few other kids chimed in as well and Mrs.
Worrywart's son just sort of sat there in a state of slumped
resignation. It pretty much ended at that but I was just a little
inspired to know that masculinity is still inherent in boys. Its
society and people like Mrs. Worrywart that beat it out of them.

This is an example of busybodyism gone mad. I suspect that if you knew
a cop with enough sense of humor to be willing to pay the paperwork
costs of ruining Mrs. Busybody's day you could have had her arrested for
something or other--spraying noxious substances on her kid is one thing,
spraying it on a bunch of other people's kids without the permission of
their parents is quite another.

Of course in a less pussified time one could have just grabbed her
sunscreen and dumped it on her head, but now she'd come back with a
lawyer.

I have been blessed with three sons and counting. It's my mission in
life to see that they don't become metrosexuals. My wife can harp on
them about washing their hands and not farting at the dinner table but
I'm in charge of what they do out of the house. They're boy's boys
complete with dirty faces and skinned knees. They jump, wrestle and
horse play at every opportunity. They are not and will not be pussies.

Of course this will be a challenge in this day and age of hand
wringing and anti-anxiety medications. I was called into school for
one of my kids this year. A kid cut in front of him in line and he
corrected the punk. I didn't see the big deal but the principle did so
we took our licks. I still instructed him to stand up for himself, not
be punked by a punk and to choose his battles wisely.

At this juncture many of you are proving my point with your thoughts.
Those of you that think I'm an awful father for not telling my son to
ignore the bully, to tell the teacher or run away have bought into the
pussification of American men lock, stock and barrel.

I never understood this attitude of coddling bullies. The bully's the
one who did wrong and he's going to keep on doing wrong. Unfortunately
bullies apparently do well in later life--one wonders how many
Congresscritters were bullies in school.

The 4th of July weekend last year, some punks were blowing of
fireworks in the park behind my house. I had no problem with this
until they started launching **** into my backyard. I marched over
there and gave them two choices. I guess that makes me pro-choice.
They had the choice to launch their **** at my house or away from my
house. The consequences of course would be different for each choice.
They chose to launch away from my house- the correct choice. My
neighbors chastised me for being so rash and challenging the punks.
"What if they would have had a gun?" My response was that we would
have had a gun fight. You see I'd rather do something and take the
chance than to have my sons see me cower behind the curtains like half
a fag.

There was a time in this country when most men would have acted just
like I did. When I was kid the adult men were all WWII vets and those
guys put up with no ****. Consequently we had little crime in our
neighborhood. A lot of fist fights but little crime. In that exact
same neighborhood we now have the opposite. No fist fights but a ****
load of bull**** crime and good men that do nothing. They have all the
excuses down about having kids, fearing lawsuits and guns but all this
is simply caving into cowardice.

Maybe I'm an anomaly but I was taught that it's my job as the man of
the house to put his balls on the line from time to time. This means
protecting my home and neighborhood. I don't have problem with this
and it comes quite natural but I learned this throughout a childhood
and adolescent of rough play and risk taking. I'm not talking about
foolishness here. I'm talking about bravery, toughness and balls.
These used to be cherished traits among men and women admired these
qualities in men as well. Nowadays we are all confused about these
things. Being a hard dude doesn't mean you are misogynistic piece of
**** that we see glorified in rap videos. A real man has a big heart
that he reserves for his family and friends. For the assholes in the
world he has his balls, big ones.

We have a lot of social problems in our country these days and
everyone has their pet theory that explains the reasons for the
proliferation of these problems. Conservatives blame big government
and welfare. Liberals think we don't have enough big government and
welfare. It's the Koch brother's fault! Blame it on the Clintons!
Bull****. I blame it on men who have ceased to be men. Behind ever
battered woman, every knocked up teenage girl and every punk firing
off guns indiscriminately are millions of men that won't do their jobs
as fathers or simply as stand up guys that won't abide by bull****.
Men have become pussified in America but I won't have any part of it.

Can't really disagree with any of the rest of this, except to say that
the fear of lawyers is valid---when in doubt sue.

On 02/27/2016 12:48 AM, OFWW wrote:
On Fri, 26 Feb 2016 19:59:32 -0500, wrote:
....

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

1ATM = 14 PSI = 0" Hg

You've mixed reference -- 1 atm is ~760 mm Hg (29.9"), 0" Hg _gauge_
pressure relative to atmospheric. Negative is then vacuum, positive is
pressure like 28 psi for tires is 28 psig(auge) or 28 psi _above_
atmospheric.

--

On Fri, 26 Feb 2016 22:48:18 -0800, OFWW wrote:

On Fri, 26 Feb 2016 19:59:32 -0500, krw wrote:

On Thu, 25 Feb 2016 23:01:34 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/25/2016 8:00 PM, krw wrote:
On Wed, 24 Feb 2016 23:07:33 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 9:18 PM, krw wrote:
On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...

OK, My mistake, not PSI, inches of vacuum. I was trying to recall what
the vacuum gauge on my first car indicated. I thought it was between
15~30 "inches".. apparently inches on the gauges are double actual PSI.

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

1ATM = 14 PSI = 0" Hg

No, you've got absolute and relative pressure measurements mixed
together. 0" Hg (absolute) is a vacuum. 0" Hg relative to 1ATM is,
well, 1ATM.

On 02/27/2016 8:17 AM, dpb wrote:
....

... Negative is then vacuum, positive is
pressure like 28 psi for tires is 28 psig(auge) or 28 psi _above_
atmospheric.

Or, when in "inches (mm) vacuum" then the negative sign is discarded but
numeric value is same of course.

--

On Sat, 27 Feb 2016 08:17:44 -0600, dpb wrote:

On 02/27/2016 12:48 AM, OFWW wrote:
On Fri, 26 Feb 2016 19:59:32 -0500, wrote:
...

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

1ATM = 14 PSI = 0" Hg

You've mixed reference -- 1 atm is ~760 mm Hg (29.9"), 0" Hg _gauge_
pressure relative to atmospheric. Negative is then vacuum, positive is
pressure like 28 psi for tires is 28 psig(auge) or 28 psi _above_
atmospheric.

Possibly, I didn't verify what ATM stood for, just accepted it as one
Atmosphere at sea level. I almost made the mistake of typing psig but
caught myself since that would be 14 above atmospheric pressure.

Now 0" is the equivalent to the air pressure at sea level. And yes, it
is gauged vacuum. since everything above 30" is actually positive
pressure.

The air pressure at 20,000 feet is 6.8 Psi equivalent to 13.6" hg.
And yes, there is oxygen at that level. Maybe not enough to keep us
functional, but it is still there.

So if you want to dry out wood quickly run it up the mountain it would
be less expensive than pulling a vacuum on it.

On 02/27/2016 12:32 PM, OFWW wrote:
On Sat, 27 Feb 2016 08:17:44 -0600, wrote:

On 02/27/2016 12:48 AM, OFWW wrote:
On Fri, 26 Feb 2016 19:59:32 -0500, wrote:
...

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

1ATM = 14 PSI = 0" Hg

You've mixed reference -- 1 atm is ~760 mm Hg (29.9"), 0" Hg _gauge_
pressure relative to atmospheric. Negative is then vacuum, positive is
pressure like 28 psi for tires is 28 psig(auge) or 28 psi _above_
atmospheric.

Possibly, I didn't verify what ATM stood for, just accepted it as one
Atmosphere at sea level. I almost made the mistake of typing psig but
caught myself since that would be 14 above atmospheric pressure.

Now 0" is the equivalent to the air pressure at sea level. And yes, it
is gauged vacuum. since everything above 30" is actually positive
pressure.
....

But you can't drop the reference from the units-- 0" Hg _vacuum_ is
equivalent, yes, but _NOT_ just 0" Hg. The units are important, not
just the number.

--

On Sat, 27 Feb 2016 10:10:41 -0500, krw wrote:

On Fri, 26 Feb 2016 22:48:18 -0800, OFWW wrote:

On Fri, 26 Feb 2016 19:59:32 -0500, krw wrote:

On Thu, 25 Feb 2016 23:01:34 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/25/2016 8:00 PM, krw wrote:
On Wed, 24 Feb 2016 23:07:33 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 9:18 PM, krw wrote:
On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...

OK, My mistake, not PSI, inches of vacuum. I was trying to recall what
the vacuum gauge on my first car indicated. I thought it was between
15~30 "inches".. apparently inches on the gauges are double actual PSI.

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

1ATM = 14 PSI = 0" Hg

No, you've got absolute and relative pressure measurements mixed
together. 0" Hg (absolute) is a vacuum. 0" Hg relative to 1ATM is,
well, 1ATM.

No, 0 psi is absolute. Vacuum is always relevant.

Atmosphere

Unit

The standard atmosphere (symbol: atm) is a unit of pressure defined as
101325 Pa (1.01325 bar). It is sometimes used as a reference or
standard pressure. In 1954 the 10th Conférence Générale des Poids et
Mesures (CGPM) adopted standard atmosphere for general use and
affirmed its definition of being precisely equal to 1,013,250 dynes
per square centimetre (101325 Pa).

Therefore 1 atm is equal to 14.69595 psi

There is no such thing as a vacuum, per se' it is always a relative
measurement.

At 250,000 feet above sea level it is 0 PSI Absolute. Imperial
measurements.

Using a moisture indicator on any wood, it would register "0"

Microns is also used in measurement of a vacuum to tell when certain
physical properties are no longer there.

On Sat, 27 Feb 2016 12:40:24 -0600, dpb wrote:

On 02/27/2016 12:32 PM, OFWW wrote:
On Sat, 27 Feb 2016 08:17:44 -0600, wrote:

On 02/27/2016 12:48 AM, OFWW wrote:
On Fri, 26 Feb 2016 19:59:32 -0500, wrote:
...

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

1ATM = 14 PSI = 0" Hg

You've mixed reference -- 1 atm is ~760 mm Hg (29.9"), 0" Hg _gauge_
pressure relative to atmospheric. Negative is then vacuum, positive is
pressure like 28 psi for tires is 28 psig(auge) or 28 psi _above_
atmospheric.

Possibly, I didn't verify what ATM stood for, just accepted it as one
Atmosphere at sea level. I almost made the mistake of typing psig but
caught myself since that would be 14 above atmospheric pressure.

Now 0" is the equivalent to the air pressure at sea level. And yes, it
is gauged vacuum. since everything above 30" is actually positive
pressure.
...

But you can't drop the reference from the units-- 0" Hg _vacuum_ is
equivalent, yes, but _NOT_ just 0" Hg. The units are important, not
just the number.

True, but I don't 0" should be understood as 14 psi since I know of no
zero measurement for board feet, etc. Since any identifying mark would
be larger than zero. Or maybe I am just used to say 0" as meaning no
vacuum in my old trade.

On 02/27/2016 1:24 PM, OFWW wrote:
On Sat, 27 Feb 2016 12:40:24 -0600, wrote:
On 02/27/2016 12:32 PM, OFWW wrote:
....

Now 0" is the equivalent to the air pressure at sea level. And yes, it
is gauged vacuum. since everything above 30" is actually positive
pressure.
...

But you can't drop the reference from the units-- 0" Hg _vacuum_ is
equivalent, yes, but _NOT_ just 0" Hg. The units are important, not
just the number.

True, but I don't 0" should be understood as 14 psi since I know of no
zero measurement for board feet, etc. Since any identifying mark would
be larger than zero. Or maybe I am just used to say 0" as meaning no
vacuum in my old trade.

If you don't say it's 0" vacuum, then it isn't a complete specification.
Granted, if one is working within an environment where vacuum is the
norm it'll become a shorthand and will be understood
_in_that_environment_. But, it's still a shorthand and isn't precise
without the qualifier.

--

On Sat, 27 Feb 2016 14:08:16 -0600, dpb wrote:

On 02/27/2016 1:24 PM, OFWW wrote:
On Sat, 27 Feb 2016 12:40:24 -0600, wrote:
On 02/27/2016 12:32 PM, OFWW wrote:
...

Now 0" is the equivalent to the air pressure at sea level. And yes, it
is gauged vacuum. since everything above 30" is actually positive
pressure.
...

But you can't drop the reference from the units-- 0" Hg _vacuum_ is
equivalent, yes, but _NOT_ just 0" Hg. The units are important, not
just the number.

True, but I don't 0" should be understood as 14 psi since I know of no
zero measurement for board feet, etc. Since any identifying mark would
be larger than zero. Or maybe I am just used to say 0" as meaning no
vacuum in my old trade.

If you don't say it's 0" vacuum, then it isn't a complete specification.
Granted, if one is working within an environment where vacuum is the
norm it'll become a shorthand and will be understood
_in_that_environment_. But, it's still a shorthand and isn't precise
without the qualifier.

If you say so, "0" is neither pressure nor vacuum.

So, we can extend that out to making sure one specifies PSIA or PSIG
in all instances, and as there is no absolutes in vacuums it will need
to be specified in PSI? or PSI? if you know what I mean.

An interesting time wasting discussion. Along these lines I have
thought about the possibility of creating a near impossible large
diameter pipe. With the right diameter inside, and if it was created
with and interlock say 100 ft from its base. And a large door at its
base, one could put something inside, open the interlock and open
another door lower than the object and launch the object into space
with no energy consumed.

The only drawback would be if someone opened the door and left it open
all of the earths atmosphere would be sucked into space.

So that will be the last of my craziness for now.

Of interesting note for this topic, I found an addon for sketchup
which works with both Pro and Make.

It is like some add on libraries for AutoCAD and my understanding is
that it is free. There is an offline version, for downloading.

It has softwood libraries with the "finished " sizes, S4S, it has HVAC
and ductwork fittings and stuff.

It has various piping fittings for plastic, steel, copper, etc.

http://sketchup.engineeringtoolbox.com/

Multi language

The wood sizing list is to me a bit on the weak side, but at least on
designs if you were to say a 4x4 it would give you the real s4s
measurements.

Could be valuable for vacuum piping design.

On Sat, 27 Feb 2016 14:08:16 -0600, dpb wrote:

On 02/27/2016 1:24 PM, OFWW wrote:
On Sat, 27 Feb 2016 12:40:24 -0600, wrote:
On 02/27/2016 12:32 PM, OFWW wrote:
...

Now 0" is the equivalent to the air pressure at sea level. And yes, it
is gauged vacuum. since everything above 30" is actually positive
pressure.
...

But you can't drop the reference from the units-- 0" Hg _vacuum_ is
equivalent, yes, but _NOT_ just 0" Hg. The units are important, not
just the number.

True, but I don't 0" should be understood as 14 psi since I know of no
zero measurement for board feet, etc. Since any identifying mark would
be larger than zero. Or maybe I am just used to say 0" as meaning no
vacuum in my old trade.

If you don't say it's 0" vacuum, then it isn't a complete specification.
Granted, if one is working within an environment where vacuum is the
norm it'll become a shorthand and will be understood
_in_that_environment_. But, it's still a shorthand and isn't precise
without the qualifier.

Right. Context is everything. One has to mentally add (or subtract)
the absolute reference if the context requires it.

On Sat, 27 Feb 2016 11:19:14 -0800, OFWW wrote:

On Sat, 27 Feb 2016 10:10:41 -0500, krw wrote:

On Fri, 26 Feb 2016 22:48:18 -0800, OFWW wrote:

On Fri, 26 Feb 2016 19:59:32 -0500, krw wrote:

On Thu, 25 Feb 2016 23:01:34 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/25/2016 8:00 PM, krw wrote:
On Wed, 24 Feb 2016 23:07:33 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 9:18 PM, krw wrote:
On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...

OK, My mistake, not PSI, inches of vacuum. I was trying to recall what
the vacuum gauge on my first car indicated. I thought it was between
15~30 "inches".. apparently inches on the gauges are double actual PSI.

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

1ATM = 14 PSI = 0" Hg

No, you've got absolute and relative pressure measurements mixed
together. 0" Hg (absolute) is a vacuum. 0" Hg relative to 1ATM is,
well, 1ATM.

No, 0 psi is absolute. Vacuum is always relevant.

No, it is not. Your tire gauge will read 0PSI when the absolute
pressure is 14PSI. The tire gauge is a *relative* measurement but
this is understood by its context.

Atmosphere

Unit

The standard atmosphere (symbol: atm) is a unit of pressure defined as
101325 Pa (1.01325 bar). It is sometimes used as a reference or
standard pressure. In 1954 the 10th Conférence Générale des Poids et
Mesures (CGPM) adopted standard atmosphere for general use and
affirmed its definition of being precisely equal to 1,013,250 dynes
per square centimetre (101325 Pa).

All irrelevant.

Therefore 1 atm is equal to 14.69595 psi

....either relative or absolute.

There is no such thing as a vacuum, per se' it is always a relative
measurement.

Nonsense.

At 250,000 feet above sea level it is 0 PSI Absolute. Imperial
measurements.

OK, but the sky is blue.

Using a moisture indicator on any wood, it would register "0"

Microns is also used in measurement of a vacuum to tell when certain
physical properties are no longer there.

What *are* you jabbering about now?

On Sat, 27 Feb 2016 20:23:07 -0500, krw wrote:

On Sat, 27 Feb 2016 11:19:14 -0800, OFWW wrote:

On Sat, 27 Feb 2016 10:10:41 -0500, krw wrote:

On Fri, 26 Feb 2016 22:48:18 -0800, OFWW wrote:

On Fri, 26 Feb 2016 19:59:32 -0500, krw wrote:

On Thu, 25 Feb 2016 23:01:34 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/25/2016 8:00 PM, krw wrote:
On Wed, 24 Feb 2016 23:07:33 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 9:18 PM, krw wrote:
On Wed, 24 Feb 2016 20:39:08 -0600, Leon lcb11211@swbelldotnet
wrote:

On 2/24/2016 8:06 PM, OFWW wrote:
On Wed, 24 Feb 2016 10:04:59 -0600, dpb wrote:

On 02/24/2016 1:38 AM, OFWW wrote:
...

In a vacuum strange things happen, given a spark, and a whoosh of dust
already suspended in the pipe (your cloud) and I can see things happen
that wouldn't happen in a positive pressurized pipe.

If it were a vacuum, there'd be no oxygen, hence no combustion.


At sea level the air pressure is 15PSI. Every 2" of vacuum is
equivalent to a 1 PSI drop in pressure. So at what point do you
consider a vacuum a vacuum? And how does a gasoline engine operate
when its intake manifold is in a vacuum if there was no oxygen?

Well hopefully there is no combustion inside of the manifold and having
said that, typically the fuel is combusted when it is under higher than
atmospheric pressure. And engines work better when the fuel bypasses an
intake manifold altogether and is atomized, by an injector, at the
optimum location and time inside the cylinder. BUT YES you need a
vacuum inside the manifold to draw fuel into the heads and cylinders
from a throttle body or carburetor. IIRC sometimes up to 15~30 lbs of
vacuum in the manifold at idle, considerably less during full throttle
with the butterflies fully open.

15-30lbs.?? Atmospheric pressure is only ~14psi.

Vacuum, not pressure.

Exactly the problem. You can't pull a vacuum higher than the outside
atmospheric pressure. That is, once you suck all the air out of the
room (14psi), you can't suck any more. Well, The Donald can, but...

OK, My mistake, not PSI, inches of vacuum. I was trying to recall what
the vacuum gauge on my first car indicated. I thought it was between
15~30 "inches".. apparently inches on the gauges are double actual PSI.

I questioned it because you said it and it was repeated. I didn't
know if you were talking about in.Hg, or what. Yes, PSI is half in.Hg
(though I hadn't thought of it that way) by the simple fact that
1ATM = ~14PSI = ~30"Hg.

1ATM = 14 PSI = 0" Hg

No, you've got absolute and relative pressure measurements mixed
together. 0" Hg (absolute) is a vacuum. 0" Hg relative to 1ATM is,
well, 1ATM.

No, 0 psi is absolute. Vacuum is always relevant.

No, it is not. Your tire gauge will read 0PSI when the absolute
pressure is 14PSI. The tire gauge is a *relative* measurement but
this is understood by its context.

Smiling,
http://www.engineeringtoolbox.com/st...ere-d_604.html

The tire pressure gauge reads 0 PSIg "g" is for gauge pressure. Not
absolute.

Look at a low side refer gauge sometime. "0" on it is the divide
between PSIg and hg


Atmosphere

Unit

The standard atmosphere (symbol: atm) is a unit of pressure defined as
101325 Pa (1.01325 bar). It is sometimes used as a reference or
standard pressure. In 1954 the 10th Conférence Générale des Poids et
Mesures (CGPM) adopted standard atmosphere for general use and
affirmed its definition of being precisely equal to 1,013,250 dynes
per square centimetre (101325 Pa).

All irrelevant.

Therefore 1 atm is equal to 14.69595 psi

...either relative or absolute.

There is no such thing as a vacuum, per se' it is always a relative
measurement.

Nonsense.

At 250,000 feet above sea level it is 0 PSI Absolute. Imperial
measurements.

OK, but the sky is blue.

Using a moisture indicator on any wood, it would register "0"

Microns is also used in measurement of a vacuum to tell when certain
physical properties are no longer there.

What *are* you jabbering about now?

Well I was making a pitiful comment about wood to try and bring this
around, back to wood, then I unfortunately through in the comment
about microns used to gauge vacuum below a certain point for the
purposes of ridding systems of H20 and other properties. Which I knew
you would be clueless about. That was stupid of me and I am sorry.

So, please forgive me, and lets get back to WW'ing or should we be
going to some gym and duke it out? LOL

On 02/27/2016 1:24 PM, OFWW wrote:
....

... Or maybe I am just used to say 0" as meaning no
vacuum in my old trade.

Yes, apparently you are. That, as noted above, would be a shorthand
within that context that would be understood but is incomplete and
potentially misunderstood if translated to another context wherein the
missing reference units would not be automagically inferred.

--

On Wednesday, February 24, 2016 at 8:12:52 AM UTC+5:30, OFWW wrote:
http://www.woodshopnews.com/news/fea...s-of-wood-dust

Nice article.

How OSHA currently judges with a paper clip.

"So is the sawdust in my facility a hazard? It depends, Scott says.
The really dangerous stuff is so-called "wood flour" -- fine particles
500 microns or smaller."

It appears to be a very small chance.

However as far as I am concerned the breathing of the "wood flour" is
my concern, so I will be paying attention, to this for my sake.

Steel wool catches fire easily, just so as you are aware of it. I like
to bet that I can set steel on fire. Haven't lost yet.

On 02/27/2016 1:24 PM, OFWW wrote:
On Sat, 27 Feb 2016 12:40:24 -0600, wrote:
....

But you can't drop the reference from the units-- 0" Hg _vacuum_ is
equivalent, yes, but _NOT_ just 0" Hg. The units are important, not
just the number.

True, but I don't 0" should be understood as 14 psi since I know of no
zero measurement for board feet, etc. Since any identifying mark would
be larger than zero. Or maybe I am just used to say 0" as meaning no
vacuum in my old trade.

0 "Hg Vacuum _is_ 14.7 psia by definition. It has to be else't the
weather measurements for barometric pressure would have to 0" plus/minus
instead of 30" plus/minus with fluctuations...and that isn't so.

Or another way to say it which I know you know innately is that no
vacuum is one atmosphere pressure.

You conflate two things of different relative measurements by comparing
to bd-ft (and yes, I know you were trying to somehow get it back to
w-working and that's a noble attempt) but there can be 0 bd-ft; you just
don't have any wood. But the difference is that you can't have negative
board-feet but you can have negative pressure or temperature or any of
several other physical measurements. It is simply what the definition
of the units reference point is.

Consider temperature, there are at multiple common scales, one of which
is absolute and the two other of most familiarity each have positive and
negative values but their zeros are at different absolute temperatures.
For pressure, simply for convenience, units were developed
historically from a mean atmospheric pressure and hence, are positive
and negative around that value. That was purely convenience as it's
nice when doing the ordinary things like tire pressure, etc., to not
have to worry about that background 14.7 psi. Similarly for vacuum
work, it was/is convenient to define a new zero at that point and
measure how far away from that point one is and in fact "inches of
vacuum" throws away the negative sign and speaks of less as
more...kinda' like scoring in golf!

So, currently barometric pressure is heading up and is about 30" Hg,
_not_ 15!!!

http://www.weatherlink.com/user/dpboz

--

-MIKE- wrote in :

The point is, there's a low probability in everything. If you want to
worry about everything that is technically "possible" happening to you,
go for it. Enjoy that life.

That's the kind of severely flawed logic that inhabits the brains of
people who will never fly on an airplane but have no problem driving on
the interstate, even though the chances of injury or death are almost
unbelievably, exponentially higher when driving a car.

SWMBO has a friend who completely refuses to drive on interstate highways because they
terrify her, and instead drives only on secondary roads -- where of course the risk of fatality is
an order of magnitude higher.

Doesn't make sense to me.

On 02/28/2016 9:41 AM, dpb wrote:
.....

So, currently barometric pressure is heading up and is about 30" Hg,
_not_ 15!!!
....

Woops, dropped back into psi, not "Hg...


.... barometric pressure is ... about 30" Hg, _not_ 0!!!

--

On 2/28/2016 12:03 PM, Doug Miller wrote:

SWMBO has a friend who completely refuses to drive on interstate highways because they
terrify her, and instead drives only on secondary roads -- where of course the risk of fatality is
an order of magnitude higher.

Doesn't make sense to me.


Logic does not apply. I know someone like that too. Even with someone
else driving she does not like the highways. This is an otherwise
intelligent, educated person.

On 2/28/2016 11:03 AM, Doug Miller wrote:
SWMBO has a friend who completely refuses to drive on interstate highways because they
terrify her, and instead drives only on secondary roads -- where of course the risk of fatality is
an order of magnitude higher.

Doesn't make sense to me.

Married to one of those ... me either.

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://www.google.com/+eWoodShop
https://plus.google.com/+KarlCaillouet/posts
http://www.custommade.com/by/ewoodshop/
KarlCaillouet@ (the obvious)

On Sun, 28 Feb 2016 09:41:34 -0600, dpb wrote:

On 02/27/2016 1:24 PM, OFWW wrote:
On Sat, 27 Feb 2016 12:40:24 -0600, wrote:
...

But you can't drop the reference from the units-- 0" Hg _vacuum_ is
equivalent, yes, but _NOT_ just 0" Hg. The units are important, not
just the number.

True, but I don't 0" should be understood as 14 psi since I know of no
zero measurement for board feet, etc. Since any identifying mark would
be larger than zero. Or maybe I am just used to say 0" as meaning no
vacuum in my old trade.

0 "Hg Vacuum _is_ 14.7 psia by definition. It has to be else't the
weather measurements for barometric pressure would have to 0" plus/minus
instead of 30" plus/minus with fluctuations...and that isn't so.

Or another way to say it which I know you know innately is that no
vacuum is one atmosphere pressure.

You conflate two things of different relative measurements by comparing
to bd-ft (and yes, I know you were trying to somehow get it back to
w-working and that's a noble attempt) but there can be 0 bd-ft; you just
don't have any wood. But the difference is that you can't have negative
board-feet but you can have negative pressure or temperature or any of
several other physical measurements. It is simply what the definition
of the units reference point is.

Like you say Zero board feet is none existent. You cannot measure what
is not there. However,...

LOL, There is a negative board foot and no doubt you have seen it many
times. Ever pick up a piece of wood to use only to find out it is a
1/2 " too short, or 6" to short?

Barometric pressure is relative, and a far different usage. It is also
useful for altitude measurement.

Then here you now go into Temperature? There are a couple scales
alright, degF and degC then there is a scale from absolute 0 wherein
there is no molecular movement. But what is the point?

1 atmosphere equals 29.92 " hg positive pressure, not a vacuum.

..000024583 atmosphere equals .010 "hg positive pressure, not a vacuum.

As I have been saying, a vacuum is relative. There is in reality no
such thing as less than O PSI absolute.

Consider temperature, there are at multiple common scales, one of which
is absolute and the two other of most familiarity each have positive and
negative values but their zeros are at different absolute temperatures.
For pressure, simply for convenience, units were developed
historically from a mean atmospheric pressure and hence, are positive
and negative around that value. That was purely convenience as it's
nice when doing the ordinary things like tire pressure, etc., to not
have to worry about that background 14.7 psi. Similarly for vacuum
work, it was/is convenient to define a new zero at that point and
measure how far away from that point one is and in fact "inches of
vacuum" throws away the negative sign and speaks of less as
more...kinda' like scoring in golf!

So, currently barometric pressure is heading up and is about 30" Hg,
_not_ 15!!!

http://www.weatherlink.com/user/dpboz

You can never achieve 30" HG barometric pressure unless you use a
cheap gauge 29.92 is the best you can do, and it is not a vacuum.

but it was nice of you to explain why and how a vacuum is relative in
your next to last paragraph. So can we consider this subtopic closed?

On Sun, 28 Feb 2016 13:03:58 -0600, dpb wrote:

On 02/28/2016 9:41 AM, dpb wrote:
....

So, currently barometric pressure is heading up and is about 30" Hg,
_not_ 15!!!
...

Woops, dropped back into psi, not "Hg...


... barometric pressure is ... about 30" Hg, _not_ 0!!!

And not a vacuum either.

On 02/28/2016 1:38 PM, OFWW wrote:
....

1 atmosphere equals 29.92 " hg positive pressure, not a vacuum.
....

Precisely, what I've been saying all along. Thank you.

--