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
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James Johnson wrote:

It powered an AC emergency generator for a 7,000 ton missile sub

Oh, a nuke. I wasn't aware that they used Clevelands on the nuke boats.
All I ever saw on them was the little FM's.

Real subs 8-)like I sailed on used 268's or short FM's as there wasn't
enough width for the 278's in the engine room lower level.

Rick

On Thu, 18 Dec 2003 19:29:00 GMT, Rick wrote:

James Johnson wrote:

It powered an AC emergency generator for a 7,000 ton missile sub

Oh, a nuke. I wasn't aware that they used Clevelands on the nuke boats.
All I ever saw on them was the little FM's.

Real subs 8-)like I sailed on used 268's or short FM's as there wasn't
enough width for the 278's in the engine room lower level.
The SSN-585's (Skipjack class) and the SSBN-598's (George Washington class) had
the diesels in the lower level machinery space on the centerline aft of the
reactor, pretty much filled the whole level. Lighting them off while snorkeling
was a contortionists nightmare - simultaneously operating controls and
monitoring gages that were in front and in back of you. The human engineering
of pretty much everything on those old boats was non-existant. They were rush
through designs from the height of the cold war. The 598's were 585's with a
missile compartment added. The George Washington was originally going to be the
Scorpion (which sank in 68), they cut it apart on the ways and added the missile
compartment.

JJ


Rick


James Johnson
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