On Wed, 24 May 2006 09:27:01 -0400, Joseph Gwinn
wrote:

In article , "AL"
wrote:

I'm afraid I don't understand why the tank would go airborne. When I open
the drain valve with air still in the tank, my compressor doesn't hit the
ceiling. I'm thinking about a weak spot maybe 0.5 to 1" in diameter, sized
appropriately for the pump.

What does the assembly weigh and what is the burst pressure? If the
burst pressure is 300 psi and the disk is one inch in diameter, the
thrust at the moment of burst will be (Pi (0.5)^2)(300)= (0.785)(300)=
236 pounds. The impulse (integrated thrust) will be proportional to
tank volume.

Anyway, this thrust is enough to make most compressors move.

Joe Gwinn

Indeed.

Gunner


"The importance of morality is that people behave themselves even if
nobody's watching. There are not enough cops and laws to replace
personal morality as a means to produce a civilized society. Indeed,
the police and criminal justice system are the last desperate line of
defense for a civilized society. Unfortunately, too many of us see
police, laws and the criminal justice system as society's first line
of defense." --Walter Williams

"William B Noble (don't reply to this address)" wrote
in message ...
wasn't the A300 with the composite vertical stabilizer that separated
when the pilot over=reacted to a wake vortex - all on board died -
that's carbon composite



I saw a show on Discovery (I think) about this. The pilot hit some
turbulence shortly after takeoff and the nose started to drift so he went
full left rudder and then when it was coming back he went full right rudder
and the tail snapped off. Airbus said "Yeah, it will do that". Every pilot
in the world went "How in the &*^$^% can you build a plane where normal
pilot input will break it?!!!!!". Nothing in the pilot's manual about this
little "feature" so Airbus got the big hit in the lawsuits.

Steve.

"Bob Engelhardt" wrote in message
. ..
Dave Lyon wrote:
How is the rocket thrust figured?

IIRC, it's basically conservation of momentum: the exiting mass times
its velocity is conserved by the containers mass times its velocity in
the opposite direction. Calculitically, of course - rates of change
very much involved.

In this case, the mass of the exiting air is very small, but the
velocity is high, so who knows. My guess is a rupture plug's blowing
would not lift the compressor. This is not inconsistent with the OP's
case mainly because the plug's relief pressure would be a lot less than
the failure pressure of the tank. For example, a propane tank's
observed rupture (failure) pressure is in excess of 1200 psi, and it's
operational pressure is about that of a compressor. Kind of hard to
believe that the compressor's motor/pump has enough oomph to get the
pressure that high, but what do I know.

Bob

I've had my 3000 psi compressor to 4500. It never changed tone, or seemed to
bog down the motor. Of course that's only .5 over designed pressure, and
you're talking about 10 times over.

On Thu, 25 May 2006 15:02:01 GMT, John Husvar wrote:
In article 2Iidg.2429$1i1.808@attbi_s72,
"Dave Lyon" wrote:

I've had my 3000 psi compressor to 4500. It never changed tone, or seemed to
bog down the motor. Of course that's only .5 over designed pressure, and
you're talking about 10 times over.

Oooh! Ya wanna fill some tanks for me?

Your local fire department probably has a cascade system for air, or a
compressor system. Worth calling to see if they do side-job fills.
The smaller the town the more likely they are to be receptive.

SteveF wrote:

"William B Noble (don't reply to this address)" wrote
in message ...

wasn't the A300 with the composite vertical stabilizer that separated
when the pilot over=reacted to a wake vortex - all on board died -
that's carbon composite




I saw a show on Discovery (I think) about this. The pilot hit some
turbulence shortly after takeoff and the nose started to drift so he went
full left rudder and then when it was coming back he went full right rudder
and the tail snapped off. Airbus said "Yeah, it will do that". Every pilot
in the world went "How in the &*^$^% can you build a plane where normal
pilot input will break it?!!!!!". Nothing in the pilot's manual about this
little "feature" so Airbus got the big hit in the lawsuits.

OTOH, if you turn the steering
wheel of your car lock-to-lock
at 70 mph, some bad things are
gonna happen as well....

"John Husvar" wrote in message
...
In article 2Iidg.2429$1i1.808@attbi_s72,
"Dave Lyon" wrote:



I've had my 3000 psi compressor to 4500. It never changed tone, or
seemed to
bog down the motor. Of course that's only .5 over designed pressure, and
you're talking about 10 times over.

Oooh! Ya wanna fill some tanks for me?



Sure, but I can't mail them, and I can only fill to 9000 psi.

"Jim Stewart" wrote in message
.. .
SteveF wrote:

"William B Noble (don't reply to this address)"
wrote in message ...

wasn't the A300 with the composite vertical stabilizer that separated
when the pilot over=reacted to a wake vortex - all on board died -
that's carbon composite




I saw a show on Discovery (I think) about this. The pilot hit some
turbulence shortly after takeoff and the nose started to drift so he went
full left rudder and then when it was coming back he went full right
rudder and the tail snapped off. Airbus said "Yeah, it will do that".
Every pilot in the world went "How in the &*^$^% can you build a plane
where normal pilot input will break it?!!!!!". Nothing in the pilot's
manual about this little "feature" so Airbus got the big hit in the
lawsuits.

OTOH, if you turn the steering
wheel of your car lock-to-lock
at 70 mph, some bad things are
gonna happen as well....


Yeah, you are going to spill your coffee and leave some nice skid marks.
But the front wheels aren't going to come off.

My Mom did that when she fell asleep at the wheel on I-95 coming South out
of Washington - woke up and spun the wheel, skidded across 4 lanes of
traffic and wound up on the shoulder facing North. No damage to her or the
car although I'm sure some underwear changes were needed by the folks
watching her pass across their front bumpers.

Steve.

In article 36odg.2813$1i1.168@attbi_s72,
"Dave Lyon" wrote:

"John Husvar" wrote in message
...
In article 2Iidg.2429$1i1.808@attbi_s72,
"Dave Lyon" wrote:



I've had my 3000 psi compressor to 4500. It never changed tone, or
seemed to
bog down the motor. Of course that's only .5 over designed pressure, and
you're talking about 10 times over.

Oooh! Ya wanna fill some tanks for me?



Sure, but I can't mail them, and I can only fill to 9000 psi.

IIRC European SCUBA divers could get tanks for 4500 psi years
ago.(smaller physical size for equivalent air volume)

I've been away from diving for a while, so I don't know what the current
systems are using. Guess I'm gonna have to google.

There was a move toward getting European tanks approved for use in the
US, but I don't know how that came out.

9000 psi? Bet that first-stage regulator is something.

--
Bring back, Oh bring back
Oh, bring back that old continuity.
Bring back, oh, bring back
Oh, bring back Clerk Maxwell to me.

Sure, but I can't mail them, and I can only fill to 9000 psi.

IIRC European SCUBA divers could get tanks for 4500 psi years
ago.(smaller physical size for equivalent air volume)

I've been away from diving for a while, so I don't know what the current
systems are using. Guess I'm gonna have to google.

There was a move toward getting European tanks approved for use in the
US, but I don't know how that came out.

9000 psi? Bet that first-stage regulator is something.

--
Bring back, Oh bring back
Oh, bring back that old continuity.
Bring back, oh, bring back
Oh, bring back Clerk Maxwell to me.


Sorry, I was misleading.

My 3000 psi compressor is indeed a scuba compressor. It is very old, heavy,
and military issue. The filters haven't been changed since I've owned it, so
it's probably not safe for breathing. I use it to fill paintball tanks, or
scuba tanks for paintball use only.

When I first got the compressor, I would sometimes use it to fill my 4500
psi tank, but I was getting some pressure blowing past the rings, so I
bought a booster pump. Now I fill my scuba tanks to 3000 with my compressor,
and use the booster to top off the paintball tanks. The booster claims it
will go to 9000 psi, but I've never even heard of a cylinder that could
handle that pressure. The highest I've had it is 4700 psi.

"Dave Lyon" wrote in message
news:a0Edg.3889$No1.2576@attbi_s71...

Sure, but I can't mail them, and I can only fill to 9000 psi.

IIRC European SCUBA divers could get tanks for 4500 psi years
ago.(smaller physical size for equivalent air volume)

I've been away from diving for a while, so I don't know what the current
systems are using. Guess I'm gonna have to google.

There was a move toward getting European tanks approved for use in the
US, but I don't know how that came out.

9000 psi? Bet that first-stage regulator is something.

--
Bring back, Oh bring back
Oh, bring back that old continuity.
Bring back, oh, bring back
Oh, bring back Clerk Maxwell to me.


Sorry, I was misleading.

My 3000 psi compressor is indeed a scuba compressor. It is very old,
heavy,
and military issue. The filters haven't been changed since I've owned it,
so
it's probably not safe for breathing. I use it to fill paintball tanks, or
scuba tanks for paintball use only.

When I first got the compressor, I would sometimes use it to fill my 4500
psi tank, but I was getting some pressure blowing past the rings, so I
bought a booster pump. Now I fill my scuba tanks to 3000 with my
compressor,
and use the booster to top off the paintball tanks. The booster claims it
will go to 9000 psi, but I've never even heard of a cylinder that could
handle that pressure. The highest I've had it is 4700 psi.


In certain circles 6000 psi tanks are common for emergency air, nitrogen
etc. Funny thing the 6000psi large nitrogen tanks I have used don't ever
have to be hydrostatically or volumnmetricly tested. I have never cut one up
but they say they steel walls are close to two inches thick. I can't say if
this is true or not, but they are some heavy mothers. A lot heavier than the
similar sized tanks that come with other gases at 2000/2200/3000/3600 psi.

DJ