Runaway Diesel-gctid812874

[Mariner156]

I just read about Carters Cove very unfortunate boat fire and a few folks brought up runaway diesels. Can someone educate me on how this happens, how I can prevent it and what the hell do I do if it happens?

Thanks.

Jamie

[smitty477]

In the big scheme of things its I not going to happen and the likelihood of a fast fire is also very low.

Runaways on diesels were more 'common' with 2 stroke diesels.

It could happen a couple of ways but the most common was when the fuel was shut down but continued to run on lube oil.

We have been posting on the BIOC for over 25 years now - only seen one fire and never a runaway on a 4 stroke 6 cyl diesel.

Unfortunately we have seen drownings, electrocutions and great injuries due to hard falls - those are the areas I would focus on first before spending too much time on these.

[grey.wilfong]

I work with electronics on large Diesels in the gas industry. ..Imagine having a runaway diesel shooting flames right by large volumes of natural gas.

Basically a runaway diesel is usually sucking a combustible vapor or fluid directly into the air intake. Since a diesel relies on the pressure of the cylinder to create the "spark" of combustion, killing power to the engine may not actually kill it like it would with a gasoline engine. As long as the engine is turning it'll keep firing.

In this industry, natural gas is of course the most worrisome source of combustible vapor, but most fires I've known of were actually caused by hydraulic fluid spraying into a mist and getting sucked into the air intake.

All our engines are out fitted with an emergency stop circuit that 1. Kills all voltage to the engine and its control module & 2 .(Most Importantly) activates an electromagnet that releases a spring loaded flapper open in the air Intake. When the emergency button is pressed the spring loaded "air kill" slams shut starving the combustion process of air and combustible vapor or fluid and killing the engine.

An ounce of prevention is worth a pound of cure.....always be sure your cooling system and fuel system is functioning properly, always inspect and pressure test hydraulic lines etc. that could allow a leak or spraying fluid to enter the air intake. make sure no sources of combustible vapors are near your engine compartment(gasoline, ether, etc.) and keep the compartment clean of oil and grease. Inspect and tend to any leaks as soon as you find them.. Always be sure to test any emergency kill system on a regular basis to ensure it functions properly.

[Norton_Rider]

Another cause of runaway diesels is excessive blowby and the engine sucking oil and fuel from the breather.

[Solandri]

"grey.wilfong" post=812880 wrote:
(Most Importantly) activates an electromagnet that releases a spring loaded flapper open in the air Intake. When the emergency button is pressed the spring loaded "air kill" slams shut starving the combustion process of air and combustible vapor or fluid and killing the engine.

Make sure the flapper is pretty substantial (should be able to support at least 14.7 psi x its surface area. These guys tried to block the intake with what looks like a plastic clipboard. The engine just sucked it in (2:00 into video).

https://youtu.be/vbiNndfNNKI?t=2m

[smitty477]

There are no flappers, there are no internal fuel lines, scavenging is much less an issue.

The possibility of runaway on one of these is remote.

But if you cannot shut it down at idle it is more common that the fuel shutdown solenoid is not working - that is not too hard to solve for.

[freedre]

"smitty477" post=812966 wrote:
There are no flappers, there are no internal fuel lines, scavenging is much less an issue.

The possibility of runaway on one of these is remote.

But if you cannot shut it down at idle it is more common that the fuel shutdown solenoid is not working - that is not too hard to solve for.

I had that problem.

[Centerline2]

on ANY marine diesel engine, severe over filling with oil can cause a a very real threat of a runaway engine.... as has already been said, sucking oil thru the intake will cause it and when over filled, the over filled oil gets splashed up into the crankcase blow-by tube and sucked into the intake . when a runaway happens the only way to stop it is by cutting of the intake of air....

[dmcb]

As said over filling with oil will cause it to get its fuel from the crankcase. If that happens you cannot shut it down via the fuel route. The only way is to shut off its air. A plastic bag over the air intake will do it. But not if the filter has been removed. It will eat the bag in that case. Anything that will shut off the air will do it but you better be quick as the governor will not work and it will destroy it self quickly.

Doug

[p91473]

I was there when my buddy's port DD12v71 run away. That's 1200 HP. I was in the engine room when he started it just after resetting the fuel rack. Sucker immediately when to WOT with no load. Very scary as we had no control. I thought it was going to blow up. We shut the fuel valves, but it took nearly 4 minutes to run dry and shut down. It was just screaming for 4 minutes straight. I felt very helpless. The cause was a stuck fuel rack. Basically he put it back wrong. I agree this is very rare for a 4 stroke diesel.

[Guest]

I got called to deal with a control problem on a 30L Cummins in a test cell. Got it started and then it started to run away. Killed the main fuel line coming in and it took another minute or so for it to run out of fuel (no way to kill the air coming in). Called the mechanic in and turns out there was a missing spring in the HP pump. The engine redline was 2.5k, and it ran out of fuel at 3k. Not a good feeling. But in all the testing we do, that's the only one I know of that 'ran' away from us. Cummins dug in right away as to why this spring was missing.