Leon wrote:
"dpb" wrote in message
...
Again, I don't think it is impossible, only highly improbable.



Ok, and I'll end with this, I think. What keeps the improbable scenario
from exploding? Those improbable scenario's actually do not explode.

They would. That the don't is indicative of just how improbable they
are (because they simply don't happen).

--

"dpb" wrote in message
...

Again, I don't think it is impossible, only highly improbable.



Ok, and I'll end with this, I think. What keeps the improbable scenario
from exploding? Those improbable scenario's actually do not explode.

"dpb" wrote in message
...
Leon wrote:
...

If there is a hole in the bottom of the tank, it is absolutley below the
pick up level. ...

But are the pumps mounted in a well?

No. They are typically flat and generally tilt towards a low end of the tank
for all the gunk to collect at. The pump is suspended by the tank unit up
from that position. There are ridges for rigidity on some tanks but those
ridges generally run in a direction so as to drain to the low spot of the
tank and the low spot is typically the forward end facing towards the front
of the vehicle. This allows for more ground clearance under the back of the
vehicle. That area is also the most vulnerable and typically will be the
damaged/ruptured area when a driver drives over an obstacle.




Are there not formed
hollows/ridges for structural rigidity in the tanks? Even if it leaks to
the point of not running, I'd expect there to be a little gas in almost
all cases left in such areas. If the tanks were a perfect sphere and you
punched a hole at the very bottom, all the liquid would run out, yes. But
there still wouldn't be air intrusion in most cases, only almost pure
vapor.

I would say that a pint of fuel could collect, maybe depending ont he
damaged area but if the damage is located on the front bottom it is likely
very very little will remain. Keep in mind a puntcture on the bottom of the
tank will act exactly like a can of juice. Hold the juice can and poke a
hole in it from the bottom. Juice will come out and as it comes out air
will replace the leaking juice otherwise the fluid would not drain.
Gasiline works the same way.





Added to that that the brushes are undoubtedly built to be non-arcing so
that there really isn't a continuous ignition source, the conditions
just aren't satisfied.

That may be the case. Non arcing brushes and again the brushes were in a
strongly built contained steel enclosure behind a steel ball check ball.

So, there's the design feature(s) you're after which are simply part of
the design. I'm not saying the pumps are built w/ no thought of
preventing an ignition source; only that I'm convinced there's no
secondary protective device or system other than the base design and the
physics of gasoline combustibility.

Yeah I am sure there is a secondary back up measure there are countless
others in the fuel lines and in the old days the carburetors had
preventatice features to limit fuel flow.

"litteratuer" takenonotice@all wrote in message
...
"dpb" wrote in message
...
--


It may also be that even when the fuel/air ratio conditions for combustion
are met, the arcing from the brushes may not provide a high enough
temperature to instigate ignition. (The article in the url below gives an
ignition temperature of 600F for gasoline vapor.)

And there in lies the probable answer as a fowled spark plug will spark but
not necessarily ignite the fuel mixture. Gasoline running past the brushes
keeps every thing cooled down under normal operating conditions. And with
electrical wiring running into the fuel tanks even for the tank units to
measure the level of fuel you have to know that sooner or later there is
going to be a short and that does not seem to present a problem either.
that has veen a fact long before electric fuel pumps wer even being used.
There is absolutely air in the tank otherwise the tanks would colapse or
fuel would not exit. Fuel vapor may be too dense to burn unless the
conditions are right. Vapor literally does not exist with out air, vapor is
simply difused matter suspended in air.

Either way I believe your explanation that the spark in not hot enough is
the stop gap safety measure. That is indeed a constant vs air and vapor
conditions around the fuel pump.





http://tinyurl.com/yanzowk

Leon wrote:
....

... Vapor literally does not exist with out air, vapor is
simply difused matter suspended in air.

Not necessarily--there are other gaseous materials other than O, N,
etc., that are the constituents of air.

--

"Leon" wrote in message
...

Vapor literally does not exist with out air, vapor is simply difused
matter suspended in air.

It might seem so, but that is not the case.

Gasoline vapor is heavier than air. With air given a vapor density of 1, the
vapor density of gasoline is between 3 and 4.

In an undisturbed tank, vented to the outside, as gasoline evaporates, the
vapor will displace the air.
In the case where all of the gasoline has been drained and air has entered
the tank, the remaining vapor will be concentrated at the bottom.

"litteratuer" takenonotice@all wrote in message
...
"Leon" wrote in message
...

Vapor literally does not exist with out air, vapor is simply difused
matter suspended in air.

It might seem so, but that is not the case.

Gasoline vapor is heavier than air. With air given a vapor density of 1,
the vapor density of gasoline is between 3 and 4.

In an undisturbed tank, vented to the outside, as gasoline evaporates, the
vapor will displace the air.
In the case where all of the gasoline has been drained and air has entered
the tank, the remaining vapor will be concentrated at the bottom.


Disturbed, I suspect that a shaken tank would not qualify as undisturbed.
There is an awful lot of shoshing around going on in there when the vehicle
is moving and if there is a hole in the bottom of the tank from a damaging
impact the vapors will "grain out" after the fuel.

dpb wrote:
Leon wrote:
...

... Vapor literally does not exist with out air, vapor is simply
difused matter suspended in air.

Not necessarily--there are other gaseous materials other than O, N,
etc., that are the constituents of air.

Or, more visible way to think of it, if were to start w/ a liquid in a
closed container w/ a movable wall and if retract that wall creating a
vacuum there will become a new equilibrium of two phases--liquid and
gas. The concentration will be dependent on the specific liquid.
There's no air needed...

--

"litteratuer" takenonotice@all wrote in message
...
"Leon" wrote in message
...

Vapor literally does not exist with out air, vapor is simply difused
matter suspended in air.

It might seem so, but that is not the case.

Gasoline vapor is heavier than air. With air given a vapor density of 1,
the vapor density of gasoline is between 3 and 4.

In an undisturbed tank, vented to the outside, as gasoline evaporates, the
vapor will displace the air.
In the case where all of the gasoline has been drained and air has entered
the tank, the remaining vapor will be concentrated at the bottom.



And some fool will try to weld the 'empty' tank ....

"LDosser" wrote in message
...
"litteratuer" takenonotice@all wrote in message
...
"Leon" wrote in message
...

Vapor literally does not exist with out air, vapor is simply difused
matter suspended in air.

It might seem so, but that is not the case.

Gasoline vapor is heavier than air. With air given a vapor density of 1,
the vapor density of gasoline is between 3 and 4.

In an undisturbed tank, vented to the outside, as gasoline evaporates,
the vapor will displace the air.
In the case where all of the gasoline has been drained and air has
entered the tank, the remaining vapor will be concentrated at the bottom.



And some fool will try to weld the 'empty' tank ....


Sadly, it does happen.

Many years ago a young neighbor of mine was using an oxy-acetylene torch to
cut open a fuel tank which he had emptied some time beforehand and thought
was safe. It exploded, leaving him with serious permanent brain damage.

"litteratuer" takenonotice@all wrote in message
...
"LDosser" wrote in message
...
"litteratuer" takenonotice@all wrote in message
...
"Leon" wrote in message
...

Vapor literally does not exist with out air, vapor is simply difused
matter suspended in air.

It might seem so, but that is not the case.

Gasoline vapor is heavier than air. With air given a vapor density of 1,
the vapor density of gasoline is between 3 and 4.

In an undisturbed tank, vented to the outside, as gasoline evaporates,
the vapor will displace the air.
In the case where all of the gasoline has been drained and air has
entered the tank, the remaining vapor will be concentrated at the
bottom.



And some fool will try to weld the 'empty' tank ....


Sadly, it does happen.

Many years ago a young neighbor of mine was using an oxy-acetylene torch
to cut open a fuel tank which he had emptied some time beforehand and
thought was safe. It exploded, leaving him with serious permanent brain
damage.


How could anyone tell?

Sorry, that was thoughtless and cruel, but it's the mood I'm in at the
moment.

Friend of mine was working on a gas tank from a 1979 Ford Bronco washed
the gas tank out several times was trying to solder the tank and all of
a sudden there was a big bang what had happened the tank actually
expanded,he finished soldering it but we had a hellova time getting it
back onto the truck as it had expanded so much. Dan

On 27 Sep, 19:46, -MIKE- wrote:

Those giant electric turbine generators are cooled with direct water
immersion. Turns out pure H2O doesn't conduct electricity. It's all the
minerals and other stuff in water that does.

Trouble with that is that water is viscous.

Best thing for cooling them is an internal flow of hydrogen, but that
really is a pain to work with.