prv
Well-Known Member
It still can’t generate an absolute pressure less than hard vacuum - what would that even mean? Since the absolute pressure on the other side is 1 bar, that’s the most that the differential can be.
Pete
Runaway diesel
- Thread starter webcraft
- Start date
It still can’t generate an absolute pressure less than hard vacuum - what would that even mean? Since the absolute pressure on the other side is 1 bar, that’s the most that the differential can be.
Pete
rogerthebodger
Well-Known Member
I have a number of wood tapered bungs intended to hammer into a broken seacock.
One of these could also be used to hammer into the air intake of a runaway engine to stop the think.
Note to self to check the size of my biggest bung is large enough to fit my engine intake.
One of these could also be used to hammer into the air intake of a runaway engine to stop the think.
Note to self to check the size of my biggest bung is large enough to fit my engine intake.
webcraft
Well-Known Member
a) I'm not trained (well, not on diesel engines, anyway)
b) The suction was not in any way threatening
c) What does an air inlet have in common with an unguarded belt? #puzzled
d) Why has no-one commented on my suggested use of a CO2 extinguisher, is it a daft idea?
- W
black mercury
Well-Known Member
Regarding the co2 extinguisher, it all depends on what rpm the engine is running at. The engine may be consuming more air than the extinguisher can produce co2. The average co2 extinguisher can produce about 2000 ltrs of co2. It may work if directed straight down the air intake, or at least slow the engine down, but if the engine can get hold of any air it will still run. My question is who is going to be brave enough to try a restart on that engine! Would be interesting to know if it immediately took off after it was started, or did it idle ok then take off after it was revved? The governor or rack could be jammed.
SteveGorst
Well-Known Member
Funnily enough this happened to me as well yesterday. I started the engine and it immediately took off at well over 4000rpm with loads of black smoke. We managed to stop it by holding the stop button for a while as it was reluctant to stop. When we restarted it it started normally and did so with a few repeated starts. Then it did it again. I also noticed that when it started normally if I moved the throttle when in gear the engine was slow to increase its speed and didn't reach anywhere near its normal power. However if I did the same in neutral it was fine. I've got an engineer coming to look at it this week and we suspect the governor or rack are jamming for some reason. Perhaps this is the same as your mates engine.
sgr143
Well-Known Member
I've used a teatowel balled-up and put inside a thick plastic bag to seal off the air intake (with the air filter removed) to stop an engine that wouldn't stop as the solenoid had burnt out. But that was at idling revs ... even then it really didn't want to stop; it took about 10-15 seconds for it to die. Maybe I should rename the engine "Desdemona".
black mercury
Well-Known Member
You could install a ball valve in the exhaust, closing it will suffocate the engine in its own exhaust fumes. I believe it will stop before the exhaust has a chance to fill with water if its installed after the waterlock. Or turn the water inlet off at same time if worried about engine taking in water.
Stemar
Well-Known Member
IIRC, fuel tankers used to have a spring loaded air shut-off valve to prevent runaway; nowadays, I expect they're controlled by electronics.
A fuel leak or spill at a refinery has provided enough fuel vapour in the air to cause runaway and the Texas City Refinery explosion in 2005 was probably set off by an idling diesel near leaking equipment.
A fuel leak or spill at a refinery has provided enough fuel vapour in the air to cause runaway and the Texas City Refinery explosion in 2005 was probably set off by an idling diesel near leaking equipment.
Old Bumbulum
Well-Known Member
That would be sensible to avoid with an intake big enough to swallow a hand or arm but a little yacht engine with an inlet diameter of 50p bit isn't going to harm you - except for the bits of conrod, pistons, crank-case and boiling oil you're likely to collect in the face or goolies when it lets go.
Dan Tribe
Well-Known Member
An elderly uncle was an engineer on submarines pre-war. He used to have a battered tin tea tray proudly displayed on his mantle piece.
He claimed it was used several times to clap over intakes to stop runaway diesels. He said he saved the ship several times but never got a medal for it!
He claimed it was used several times to clap over intakes to stop runaway diesels. He said he saved the ship several times but never got a medal for it!
D
Deleted member 36384
Guest
For your own boat web you need a Positive Air Shut off Device. It could be as simple as a bung shoved into the air inlet or a bit more sophisticated and automatic. I fit these to small diesel engines / power packs on rigs where the risk of combustible gas in an air intake greatly affects the potential consequences: -
http://www.chalwyn.com/tenants/chalwyn/documents/Brochure-D-Valve-Eur-Chin-0716-Rev1.pdf
They cost less than £100 and fit in the air intake line, after the filter housing. As the engine speed increases, the air velocity increases which trips a flap and isolates the air supply. I witnessed a boiler suit disappear into the air intake of a large, temporary diesel powered generator many moons ago; it took another boiler suit to stop the thing. On the big rig engines the devices are manufactured usually by a company called "Rigsaver", the name is now associated with all Positive Air Shut ff devices, like Hoover is with vacuum cleaners.
What you are trying to prevent is the catastrophic failure of something heavy punching a hole in the boat or smashing your head open as you look inside. Have a plan, set up the mechanism (soft wood plug or rubber bung), test it will fit, tie it off near the air intake, make sure you take the fire blanket with you if you have to do an emergency shut down.
http://www.chalwyn.com/tenants/chalwyn/documents/Brochure-D-Valve-Eur-Chin-0716-Rev1.pdf
They cost less than £100 and fit in the air intake line, after the filter housing. As the engine speed increases, the air velocity increases which trips a flap and isolates the air supply. I witnessed a boiler suit disappear into the air intake of a large, temporary diesel powered generator many moons ago; it took another boiler suit to stop the thing. On the big rig engines the devices are manufactured usually by a company called "Rigsaver", the name is now associated with all Positive Air Shut ff devices, like Hoover is with vacuum cleaners.
What you are trying to prevent is the catastrophic failure of something heavy punching a hole in the boat or smashing your head open as you look inside. Have a plan, set up the mechanism (soft wood plug or rubber bung), test it will fit, tie it off near the air intake, make sure you take the fire blanket with you if you have to do an emergency shut down.
lw395
Well-Known Member
Maybe injuries from the suction are a folk story. I don't know. Maybe it's a from big diesels where 15psi x several sq in = enough force to hurt.
Regarding the CO2, I suspect you'd have to be sure the engine was breathing near pure CO2? An unloaded diesel engine will run fast using much less than full fuelling, so it's only using a fraction of the normally available oxygen. If you don't actually stop it, then it will rev again as the CO2 runs out.
But on our engine, the air filter inlet would be hard to get the nozzle to, and you're not going to be dismantling the air filter housing when the motor's thrashing around on its rubber mounts.
Luckily we have an old Yanmar with decompressor levers.
dom
Well-Known Member
That’s a great piece of kit - will definitely purchase one :encouragement:
AntarcticPilot
Well-Known Member
If the engine is hot, there must be a chance that it could continue to run on CO2, by reducing it to CO. If that happened, the exhaust would be a mixture of Carbon Monoxide and steam (and probably a lot of incompletely burnt fuel)! I don't think it would run well on CO2, but we're already in an abnormal situation and I wouldn't discount the possibility of it running. Just to help, if you poke the CO2 nozzle into the air intake, you're effectively applying a turbo boost to the engine!
Even in a normal flame there are places where CO2 is being reduced to CO, and then oxidized to CO2 - that's why a badly adjusted gas burner can emit CO. In the hot, high pressure environment of a misbehaving diesel engine, I don't see why the same shouldn't happen.
Old Harry
Well-Known Member
I bet you €0,05 you will use your L/R before needing to deploy this device :encouragement:
Resolution
Well-Known Member
What ever happened to the chap who had been wearing the boiler suit??????
Resolution
Well-Known Member
We had a Desdemona last year when our solenoid packed up. I did try hammering a soft wood bung into the air intake but it did not stop the engine even from tickover. Just sounded like it was being strangled, thumped and banged but kept on. Must have been some other air leaks.
D
Deleted member 36384
Guest
He took it off!
oldharry
Well-Known Member
Its on You Tube so it MUST be true.
Probably just a bit of fluff?
Probably just a bit of fluff?