NTSB Report Engine E xplosion and F ire aboard Towing Vessel The Admiral


#1

July 14, 2016

National Transportation Safety Board
Marine Accident Brief
Engine Explosion and Fire aboard Towing Vessel The Admiral
(pdf)

First Engineer killed, second Engineer badly burned.’

After the accident, the company hired a forensic engineer to determine the cause of the
engine explosion. He concluded that the engine had been in a runaway condition and likely used
its own lubricating oil as an uncontrolled fuel source for combustion. The white smoke that the
pilot saw was an indicator of lubricating oil combustion. The forensic engineer determined that the ticking sound likely was a sticking hydraulic lash adjuster, which functioned to maintain the timing of the opening and closing of the exhaust valves on the cylinder head. The engineer’s report concluded that a misfiring cylinder, with pressurized exhaust gases and combustion products entering the airbox, could have caused the lubricating oil in the airbox to reach a combination of pressure and temperature necessary for an explosion to occur.


#2

I think they should hire a new forensic engineer. A lash adjuster? The ticking noise could have been the chiefs sphincter clacking open and closed.


#3

I don’t think anyone takes a company hired forensic engineer seriously. Reading the report indicates maintenance was dictated by the company based from shore, even down to changing filters. Nah…nothing could go wrong with that plan. The engineers, if the report is to be believed, were clueless.
"Investigators asked the vessel engineers about the operation and maintenance of the governor and the engine-mounted mechanical overspeed trip device. The chief engineer stated that he did not know much about either device and he was not aware if they were ever tested. The second engineer indicated that he was not aware of any maintenance performed on the governor or overspeed trip device during the time he was aboard"
Lord…


#4

Sounds like a normal old fashioned runaway scenario to me.

“The first engineer subsequently grabbed onto the fuel rack lever in an attempt to stop the fuel supply to the engine, but this made no difference in the engine speed”

Gee, anyone think that might be a clue.

Did this forensic genius think the governor or overspeed trip would stop the lube oil that he said was fueling the runaway? I guess he needed to cover all the bases, bad governor, bad OS trip … I wonder if he asked about governor and OS trip maintenance because he didn’t know himself how a governor works.


#5

If they were using the Old Version of Lash Adjusters this could cause One Injector stuck in the open position to hold the entire rack open causing a runaway. If this happens, the Overspeed does NOTHING because the other Injectors are being held open by the hung Injector and Old Lash Adjuster.

The Old Style Adjuster was a solid design, the updated Adjuster had a spring that would allow the rack to operate the rest of the Injectors, leaving only the one stuck open, in the open position. In this case the Overspeed Trip would do it’s job.

Back when I was first starting out it was beat into me, to check the rack on each and every vessel that I came onboard to see which Adjusters were installed. The School that EMD used to hold even talked about them and the problems that could happen.

The last time that I saw the Older Lash Adjusters in use was in the Mid 80’s on a 16-567-c. As soon as I found them they were replaced with the new type and all the “Old but Good” spares dumped.


#6

Excuse my ignorance (I’m a deckie); is this known as dieseling?
If so it has just happened to a friend’s Landrover; they could only stop it by putting it in first gear, standing on the brakes and dumping the clutch. Stopped but trashed the transmission in the process
Also happened to another local car and a boat owner.
If it were possible to cut off the air supply would that stopping it running away?


#7

The lash adjusters are in the valve bridges actuating the exhaust valves. You seem to be describing the rack attachment link to the injectors. But yes with the solid type if stuck good enough it can require more force than the governor can apply. But in my experience this would not cause a run away condition only limit the engines ability to run at correct / commanded speed / load. For example on a diesel electric ship that engine will not share load correctly. Have performed many PM’s and found stuck(ish) lash adjusters with little affect on engine performance. Certainly not causing overspeeds or explosions. Hence my original comment.


#8

One cylinder was missfiring which started a runaway condition. Engineers tried to shut it down but couldn’t.

the ticking sound likely was a sticking hydraulic lash adjuster, which functioned to maintain the timing of the opening and closing of the exhaust valves on the cylinder head.

But also this:

the number seven fuel injector was stuck in the full-open position, and the fuel rack arm was in the off position.

If I have it right the engineers were running the at idle to listen to the ticking sound. How did the #7 get stuck on full-open?

Also this:

Neither of the engineers interviewed had any formal training; they stated that their training
was typically “on the job.” They did not have any Coast Guard-issued credentials, nor were they required to have them.

==============================================================

Probable Cause
The National Transportation Safety Board determines that the probable cause of the engine
explosion and resulting fire aboard the towing vessel The Admiral was a misfiring cylinder that
ignited lubricating oil in the sump of the engine.

The emergency shutdown button on the governor did not stop the engine when the engineer
pressed the button. Also, the engine did not stop when the engineer attempted to shift the fuel rack arm to the off position. Furthermore, the overspeed trip device did not shut down the engine once the speed of the engine exceeded the setpoint, even though the overspeed trip device was found in the tripped position. Post accident inspection of the damaged engine by the port engineer revealed that the number seven fuel injector was stuck in the full-open position, and the fuel rack arm was in the off position. Despite attempts to shut off the fuel supply to the engine, the engine accelerated in an uncontrolled manner, indicating that an external fuel supply outside its normal diesel- injection system was present.

After the accident, the company hired a forensic engineer to determine the cause of the

engine explosion. He concluded that the engine had been in a runaway condition and likely used its own lubricating oil as an uncontrolled fuel source for combustion. The white smoke that the pilot saw was an indicator of lubricating oil combustion. The forensic engineer determined that the ticking sound likely was a sticking hydraulic lash adjuster, which functioned to maintain the timing of the opening and closing of the exhaust valves on the cylinder head. The engineer’s report concluded that a misfiring cylinder, with pressurized exhaust gases andcombustion productsentering the airbox, could have caused the lubricating oil in the airbox to reach a combination of pressure and temperature necessary for an explosion to occur.


#9

WTF?

I have had a single injector link stick and cause its injector to put fuel in the cylinder. But, the engine never even got close to an overspeed condition, it just idled roughly along until it used up the fuel downstream of the closest shut off valve. Maybe if the rack has siezed in some position where all the cylinders on that side were firing and overspeed would occur but the report said clearly that the rack was “off” and the overspeed was tripped. In that case it had to have been lube oil but the valve and airbox connection is hard to swallow.

Even if the valves never opened at all and the stuck injector continued to fuel, the amount of fresh air available to that cylinder would have so small as to make combustion a miracle after a few revs. How it could cause an airbox explosion and fire needs a bit more explanation. Where did “pressurized exhaust gases” come into play? How did the guy figure that could pressurize the airbox when any pressure above airbox pressure would simply flow into the inlet of an adjoining cylinder and out the exhaust. If hot unburned fuel ignited and caused an airbox fire it would be hard to cause an explosion. You can have airbox fires and never even know about them.

The report stated that it was a crankcase explosion which sounds a lot closer to the truth even though they didn’t mention crankcase doors. It also mentions “several” airbox doors blown off but a good CC explosion would probably shake a few loose. The report seems very light on engineering details and heavy on bubba lore.


#10

Was the engine opened up and checked for a dropped valve or holed piston?

New EMD Valve Bridge and Lash Adjuster
http://s7d2.scene7.com/is/content/Caterpillar/C10669467


#11

Related, the fire triangle is: heat - fuel - oxygen. Take one side of the triangle away and the fire stops.

The heat for fire in a gas car engine comes from the spark plugs. To stop the fire the ignition is shut off, no spark, no heat, fire goes out. Unless the engine is hot enough ignite the air/gas mixture from the heat of compression, then the car will “diesel” (run with the ignition off).

In the case of a diesel the heat comes from the heat of compression. So the source of heat can’t be cut off. So to stop a diesel the fuel supply is stopped.

In the case of a diesel running away the engine is burning fuel from another source, for example it’s own lube oil, so it runs out of control. To stop an engine in runaway condition the air supply is cut off. Either throwing something on the intake or pulling an emergency stop which cuts off the air.


#12

Thanks Kennebec.
I figured as much.
I’ve got an old wooden boat with an oldish diesel lump in it and have been wondering how to stop it in the event of it running away.
It’s not old enough to be able to have a decompression lever so I’ll have to figure how to fit a remote shut off to the air filter.


#13

Are these the new or old style adjusters? They look solid to me


#14

This is a newer style crab washer. The valve lash adjusters are hydraulic and the spring loaded rack are the same since the '70s.


#15

That’s correct, all that is shown is either a nicely updated Topdeck or a newer Engine. I’ll see if I can find a picture of the Older Injector Linkages.


#16

The older style, still in use here.


#17

Where are they still using them?


#18

Here’s a slightly tedious video that explains how (and where) the hydraulic lash adjusters are located. Since they are all but invisible on the engine it is easy to understand how a Navy trained expert might miss them and their function altogether, sort of like what a tell tale drain is for.

Regardless of where the guy was trained, it is still incredible that the “forensic engineer” would think a lash adjuster could cause an air box explosion.


#19

Maybe you’re not thinking creatively enough, as your actual experience and wisdom prevent you from putting forth ridiculous conclusions that these “experts” that get paid by the word compile. The qualifier “forensic” before engineer is supposed to make us all go ooooooooo–and----awwwwwwwwww. HAHA


#20

Hmmmmm, thanks for the comment, I think you might be right.

Creative thought of the day … go get some new business cards printed with “Forensic Engineer” under my name!

As soon as I get them I will work 90 percent less and probably make 110 percent more than I do now.