Reason for marine diesel engines runaway

Hi,

Any brand of diesel engine can suffer a runaway.

The conditions have to exist for the engine to produce enough Oil Mist to get going uncontrolled or the introduction of a fuel source via the air inlet such a a gas rich environment will result in the same.

Turbocharger seal failure is probably the most common reason.

Governor failures or problems such as a stuck or bent control rod can make it impossible to shut down the engine via the normal methods. While not as spectacular as a failed turbo seal or a serious case of fuel dilution, it is still considered a runaway.

I was under the impression that this was a phenomenon unique to two cycle diesels, that is till the other day when I watched a 16v2000 run away...

It's just more spectacular when it happens to a 2-stroke.

But not always, years ago we had a Fairbanks-Morse OP run on lube oil for over 6 hours before we could shut it down. It was running slowly but it just wouldn't quit. That was caused by a failure of several upper piston oil control rings.

Hi,

A note of advice for anyone reading this is do not lean over a run away engine trying to do something.

I know of a very experienced Mechanic who was called to a customers 3306 genset that had some problems, he checked it over and started it up , it ran away and a rod came out through the block. His leg was nearly torn off by the big chunk of Cast Iron coming out of the block.

He said it happened in seconds, as soon as it fired up it was away uncontrolled.

The underlying reason given for the uncontrolled acceleration was the work done by another mechanic working for the same dealer. The stop control is used on those for speed control, the incorrect fitting of the stop solenoid wouldn't allow the control to be pulled backwards at all.

My first action if confronted with one and no ESD working would be a C02 Fire Extinguisher in the Air Inlet.

Thankfully in more than 30 yrs of being around running diesel engines I have never had one run away whilst I was in attendance.

I have however seen an 8V 71 run backwards in a truck for a minute or so at idle - looked kinda strange sucking the smoke back down the exhaust pipes.

With larger engines the issue isn't so much overspeed and throwing metal around the engine room it is running out of lube oil followed by a crankcase explosion from a hot bearing.

The last one (runaway - not CC explosion) I had was due to a bent control injector control rod that locked one bank of a very large (by yacht standards) V-12 in a low speed setting after the governor was in stop. It ran for what seemed a long time until the reason was discovered and then for a longer time until the fuel piping drained enough to stop it.

Had one very minor CC explosion when a fool opened a CC door after evidence of a hot bearing ... despite a clearly legible label warning not to do that sort of thing. It was a very frightening WHOOOSH and a bunch of smoke accompanied by near heart failure and weak legs.

Morning all,
Thanks very much K1W1 for that CO2 fire extinguisher tip for stopping a run-away.
Peter

The FM engine mentioned earlier consumed several hundred pounds of CO2 from portable extinguishers from 20 pounders on up to 100 pound wheeled units on the dock. I will admit they slowed it down but it was a combination of blocking off the air and CO2 plus generally loading up the cylinders with so much lube oil that it finally choked itself to death.

The first few 20 pounders were consumed like it was laughing gas.

In 2001 in Dania Florida M/Y Frosty's Sliegh lost control while docking. One engine went in gear and 100% full throttle. They ran over a small boat in front of them and landed on some bridge pilings before crew could emergency stop engine and take control.
I met the captain a few years later who had the unfortunate experience and he was nice enough to share with me exactly what went wrong for my interest in learning. To sum it up in a few words, the engines were MTU (2000's if I remember right). MTU's have a junction box near the engine containing the can/can bus from throttle controls. Inside the box, from vibration, something came loose falling creating metal connection between to wires causing the run away.

Loss of bridge control is not equivalent to a "runaway" diesel.

Marine engineers define a "runaway" as a condition in which the engine overspeeds or cannot be stopped due to a source of fuel other than the fuel system; or a failure associated with the governor where local engine control is no longer available.

Are you going to tell us what happened? It was like your phone rang and...Wait... I would like to guess... The throttle control was accidentally pushed fwd by a deck hand securing the wing station as a capt left the controls live after docking with engines still running.
I know that has happened more than once in yachting and it is another form of engine run away.

Hi,

C4ENG, While the engine still runs at it's designed speed and there is any sort of control of this it is not a runaway as such which is what I believe the OP was asking about.

Take the time to read this if you think I am pulling your leg.

Diesel engine runaway - Wikipedia, the free encyclopedia

So let me see if I get this straight..
If an engine runs out of control from the operator and goes to full throttle for any other reason other than what Wikipedia describes as a run away, than that uncontrolled engine at full throttle is not then a run away engine?

Hi,

The Wiki Article was given as an example of what is meant by the term runaway in this context.

If an engines goes to it's maximum governed speed by receiving an erroneous signal from the engine controls it is still not running away but running at WOT.

A runaway engine is usually running on something other than what it left the factory designed to run on.

That technique, along with an "astern test," is normally called a "pre-arrival check" and, is what the prudent mariner does at a time and place where a surprise doesn't immediately precede a disaster.

Having a bridge control fail or an uncommanded high rpm signal that puts the engine on the governor stops is not a "runaway."

On larger boats that is one of the reasons an engineer is supposed to be in the engine room during close quarters maneuvering. An engineer who knows the difference between a runaway diesel and a control problem can easily take local control to shut down the engine or move the gear to neutral.

For most of the history of mechanical propulsion, that is how it was done anyway.

I think this is what is meant by "Runaway Engine"?
detroit 4-71 in gmc 650 running away start after the 30 years - YouTube

I like the way the young guys RUN like heck while the old mechanic just strolls over with a 4 by 2 asking for a rag!

I think this is also the on and off highway engineers definition.

Full throttle implies the fuel source is diesel and the throttle is functional. Out of control and goes to full throttle an engine will still operate as designed to run on diesel- it should not go past it's top RPM. An "uncontrolled" engine at full throttle is not a runaway. A runaway's fuel source is usually lube oil and since the fuel source is not governed the runaway's rpm's will normally exceed the designed upper rpm limits. The preferred method of stopping a runaway is to block it's air access.

]A runaway engine is usually running on something other than what it left the factory designed to run on.


I think most of us would agree that this is the classic definition for a run away, not some mechanical malfunction or operator error - though they may have the same practical effect.

Anybody. If fire extinquishers don't work, would activating the Halon do it?