Steven Shelikoff wrote:

Why? Did you find somewhere that says an absolute zero/zero vacuum is
0.0049 psi?

I just made it up. Why don't you look it up and tell us, tell us
anything except -14.7 psi.

This thread is turning into a "How many angels can dance ..." argument
where you guys can't even define and angel.

This stuff isn't rocket science. To expand on Rod's contribution, the
real metrics are available, the standards used throughout the world and
their definitions are readily available to those who prefer to speak the
language of science and technology rather than technical pig latin.

All you accomplish by saying -14 psi is to sound very very ignorant of
how pressure is measured and its standard conversions.

Rick

On Fri, 12 Dec 2003 03:36:59 GMT, Rick wrote:

Steven Shelikoff wrote:

Why? Did you find somewhere that says an absolute zero/zero vacuum is
0.0049 psi?

I just made it up. Why don't you look it up and tell us, tell us
anything except -14.7 psi.

I did. I said you couldn't define it as -14.7 psig and that it was 0
psi. Do you have anything to suggest that absolute zero vacuum is not 0
psi?

This thread is turning into a "How many angels can dance ..." argument
where you guys can't even define and angel.

This stuff isn't rocket science. To expand on Rod's contribution, the
real metrics are available, the standards used throughout the world and
their definitions are readily available to those who prefer to speak the
language of science and technology rather than technical pig latin.

All you accomplish by saying -14 psi is to sound very very ignorant of
how pressure is measured and its standard conversions.

If by psi you mean psia, there is no such thing as -14 psia. If you
mean psig, all -14 psig means is that the pressure you're measuring is
14 psi less than the pressure surrounding it. That *could* be an
absolute vacuum *if* the pressure surrounding the gauge is 14 psia.

There are such things as vacuum gauges though, that read positive
numbers as the pressure they're reading decreases. Hell, I have 3 of
them on my boat. Of course, if the pressure they're reading is higher
than the surrounding pressure, they'll go negative until the needle hits
the stop that's just below 0.

All the stuff I've said above is actually pretty simple. What about it
don't you understand? Is it the fact that gauge pressure can be
negative? Is that what's throwing you for a loop?

Steve

(Steven Shelikoff) wrote in message ...
On Fri, 12 Dec 2003 02:08:36 GMT, Rick wrote:

I suggest you guys find a textbook or look up vacuum or metrology on Google.

Why? Did you find somewhere that says an absolute zero/zero vacuum is
0.0049 psi?

Steve

we can ask him this way, Steve: Since when does (zero) = 0.0049?

Well, that's as may be, but, my truck has an electric fuel shutoff valve. Most
modern diesels in truck (and I would think also boats) applications do.
Or how does turning the key to off stop the engine? A vastly complicated
mechanical linkage to a manual fuel shut off lever?
The fuel pumps that supply the engine are engine driven of course and require
no electrical power to operate.
The point I was tring to make is that though the engine may run with out
electrical power it requires it to start and stop.
Mike


Gould0738 said:
Most diesels, particularly older models, do not require electricity to supply
fuel to the engine.

In response to a previous post that went (in part):
Ummmm...the normal shutdown of a diesel (like my Cummins equipped Dodge) IS
to
kill the electrical supply. Thereby closing the fuel shut off valve.

Well, that's as may be, but, my truck has an electric fuel shutoff valve.
Most
modern diesels in truck (and I would think also boats) applications do.
Or how does turning the key to off stop the engine?

Your truck is designed to be started in the same fashion that people are
accustomed to use when starting a car.

A lot of diesel boats don't use the key to start or stop the engine. The key is
turned on to activate the electrical panel and the alternator, but a separate
push button is used to crank the engine. When the engine is shut down, another
push button
activates a solenoid that, yes, does actuate a mechanical fuel shut off
mechanism. Only after the engine comes to a complete halt is the key turned to
"off."

Depriving a gasoline engine of the electricity reuired for the ignition system
would shut down the engine. Unless your diesel needs a constant supply of
electricity to keep the fuel supply flowing,
cutting off electricity will have no effect. As the question was generic in
nature, a choice that applied only in very unique circumstances would not be
the best choice among the answers- even though in those unique circumstances it
would be entirely correct.

My new engine (going in next week, yeah!)
won't even have a key, just a switch. :-)

Steven Shelikoff wrote:
It would probably be better for you to define an absolute vacuum as 0
psi instead of -14.7 psig.

For extremely low pressures there is a measurement called a Torr. Much more
useful and it also shows (as with all properly used technical jargon) that
you know what you're talking about.



Rick wrote:
It is far better to describe it as it really is. An absolute vacuum (or
as close as we can get to one) is about .0049 psi.

Huh? 1 Pascal is .000145psi. There is off-the-shelf industrial equipment
that goes this low.

http://www.npl.co.uk/pressure/vacuum.html

By my figures, the evacuation pressure they are talking about here is
approximately
0.000000000725psi which is a LOT lower. You could probably could the air
molecules floating by....




There is no such thing as -X.X pounds per square inch.

Great. Next you'll be telling us that vacuum don't suck.

Regards
Doug Kng

On 13 Dec 2003 05:46:30 GMT, (Gould 0738) wrote:

Well, that's as may be, but, my truck has an electric fuel shutoff valve.
Most
modern diesels in truck (and I would think also boats) applications do.
Or how does turning the key to off stop the engine?

Your truck is designed to be started in the same fashion that people are
accustomed to use when starting a car.

A lot of diesel boats don't use the key to start or stop the engine. The key is
turned on to activate the electrical panel and the alternator, but a separate
push button is used to crank the engine. When the engine is shut down, another
push button
activates a solenoid that, yes, does actuate a mechanical fuel shut off
mechanism. Only after the engine comes to a complete halt is the key turned to
"off."

Or in my case, the engine is started just like a car. i.e., the "on"
position of the key activates the alternator, panel instruments, engine
hours meter, etc., and the "start" position activates the starter. But
to shut down, you pull a knob that is connected to a cable that is
mechanically connected (no solenoid) to a lever on the injector pump
that shuts off the fuel.

Steve

On 07 Dec 2003 15:30:50 GMT, ospam (F330 GT) wrote:

A paragraph in a book I've been sent to review seems to be in error.

Either that, or I'm not properly intuitice about this situation.

The paragraph poses a mulitple choice question. "What is the best way to shut
down a runaway diesel engine?"

One choice is a throw-away. "Cut off the electrical supply." Bzzzt! "Thanks
for
playing, and we do have some lovely parting gifts for you........"

The other two choices:

1. Cut off the fuel supply

2. Cut off the air supply

I immediately thought, "the fuel supply. You shut down a diesel by cutting
off
the fuel."

According to the author, the correct answer is supposed to be "Cut off the
air
supply." The author recommends "discharging a fire extinguisher into the air
intake."

Well, first off it would need to be the correct type of fire extinguisher.
Some
extinguishers are charged with halon (which is no longer legal to mfg in the
US
but is imported or recycled from other extinguishers) and a diesel will run
like crazy on halon.

And, I'm aware of emergency shut downs that have been accomplished with CO2
extinguishers, etc. I just thought those were cases where it was impractical
to
cut off the fuel supply.

Wouldn't putting a postive stop to the fuel supply from the injector pump be
a
more certain solution? "Some" air might get sucked into the air intake along
with the fire suppressant, maybe enough to allow the engine to cough past the
extinguisher discharge and keep running. But, the engine absolutely will not
run without fuel.

Shutting off the fuel very far upstream wouldn't be a good choice, as an
engine
can run quite a while on the fuel in lines, filters, etc.

Somebody care to agree, disagree, or show me why my preference for fuel shut
down would be wrong?




Happened to me in the Navy on a GM 278CD (Large 2 stroke V-8 emergency diesel
generator). The only way to shut it down was to close the ventilation for the
compartment and shut the induction valve - this was on a submarine. Turned out
a bearing seal on the Rootes blower had failed and was letting enough oil in to
keep it running (but it was not enough for it to overspeed). A runaway is a
rare occurrence but does happen and has been know to cause them to throw various
internal parts around.

JJ




I've been told that in certain circumstances diesel engines can run on the oil
in the crankcase being sucked into the cylinders, particularly Detroit Diesels.
If this is true, that would make the air shutoff the only correct answer.

Barry

James Johnson
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James Johnson wrote:


Happened to me in the Navy on a GM 278CD (Large 2 stroke V-8 emergency diesel
generator). The only way to shut it down was to close the ventilation for the
compartment and shut the induction valve - this was on a submarine.

An 8-278 as an aux? Must have been a heck of a squeeze down there.

Rick

On Sun, 14 Dec 2003 21:48:23 GMT, Rick wrote:

The compartments on a submarine are designed to be isolated for flooding
including the ventilation system. As I had posted it wasn't running away just
not shutting down. We evacuated the compartment, isolated it, and then shut the
induction valve. As soon as the diesel stopped we equalized pressures and
remanned watchstations.
It powered an AC emergency generator for a 7,000 ton missile sub (a small one as
these things go).

JJ

James Johnson wrote:


Happened to me in the Navy on a GM 278CD (Large 2 stroke V-8 emergency diesel
generator). The only way to shut it down was to close the ventilation for the
compartment and shut the induction valve - this was on a submarine.

An 8-278 as an aux? Must have been a heck of a squeeze down there.

Rick

James Johnson
remove the "dot" from after sail in email address to reply