Maybe a silly Q but - how does one stop a Diesel Engine running ?

Rogershaw said:
No one said to use your hand.

I was considering fitting a ball or butterfly valve into the air inlet as am emergency shutdown device.
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Seriously bad idea. Have you ever seen a diesel run away sucking the sump contents in for combustion? Its not something you want to happen,,,,,, ever,,,,,,, and this is the fastest way of achieving it.
 
Boater Sam said:
Seriously bad idea. Have you ever seen a diesel run away sucking the sump contents in for combustion? Its not something you want to happen,,,,,, ever,,,,,,, and this is the fastest way of achieving it.
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Seriously bad idea. Have you ever seen a diesel run away sucking the sump contents in for combustion? This will still need air for combustion to take place and continue.

I take your point, if the air inlet is blocked where is the air required for combustion going to come from

Are you saying that blocking the air intake of a diesel engine could cause the engine to run away ?
 
Rogershaw said:
Seriously bad idea. Have you ever seen a diesel run away sucking the sump contents in for combustion? This will still need air for combustion to take place and continue.

I take your point, if the air inlet is blocked where is the air required for combustion going to come from

Are you saying that blocking the air intake of a diesel engine could cause the engine to run away ?
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Certainly can. The vacuum created in the cylinders with the air supply cut of is massive, enough to pull the oil past the pistons and valve stems, as well as any crankcase breathers connected to the inlet manifold, into the combustion chambers where it will burn, powering the engine to unbelievable revs till it eventually either runs out of oil and seizes or grenades big time.
 
Boater Sam said:
Certainly can. The vacuum created in the cylinders with the air supply cut of is massive, enough to pull the oil past the pistons and valve stems, as well as any crankcase breathers connected to the inlet manifold, into the combustion chambers where it will burn, powering the engine to unbelievable revs till it eventually either runs out of oil and seizes or grenades big time.
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The vacuum created in the cylinders with the air supply cut of is massive

Ok so the is a vacuum in the cylinder that could/will suck oil into the cylinder from the sump.

For the diesel/sump oil to burn it need oxygen from the air and heat from the compression of the air.

As there i a vacuum in the cylinder there is not enough oxygen to allow the oil to burn and not enough heat as no compression.

So how will combustion be sustained?
 
Elessar said:
really bad advice except on tiny engines
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The bag idea needs more thought but flaps were/ are a requirement on commercial engines particularly in hazardous areas

My comments are basic principles to answer original question not a guide to finding the stop lever on a spec volmar unit
 
I’ve seen a mechanic mate stop a diesel generator with a magnetic parts tray (think tin plate) over the air box. Can’t see how this would get it to run away, unless the rings are shagged. I guess it could draw quite a vacuum inside the cylinders, but then there’s quite a lot of compression pressure in there normally, no?
 
jim.howes said:
How would you plan to get an air bag to the air intake by magic?
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What "air bag"

I was considering fitting a shut off valve in the between the air filter and the inlet manifold to stop air entering the engine thus preventing combustion either from diesel oil being injected or sump oil being burned in the cylinder.
 
Positive Air Shut-off devices are fitted from small single cylinder water pump diesel engines to massive power station diesel engines. Some manufactures are Pyroban, Amot, Rig Saver, Chalwyn. They operate via various techniques, overspeed sensors, high airflow or manual trip levers. They are there to prevent the diesel engine running away under gas in air intake or sucking up their own oil. Some countries require them by law e.g. USA on offshore vessels, many commercial diesel engines fit them as standard for oil and gas market.

Chalwin and Pyroban are very common on small diesel engines and can easily be retrofitted with no significant effort: -

Chalwyn-Categories
 
BlowingOldBoots said:
Positive Air Shut-off devices are fitted from small single cylinder water pump diesel engines to massive power station diesel engines. Some manufactures are Pyroban, Amot, Rig Saver, Chalwyn. They operate via various techniques, overspeed sensors, high airflow or manual trip levers. They are there to prevent the diesel engine running away under gas in air intake or sucking up their own oil. Some countries require them by law e.g. USA on offshore vessels, many commercial diesel engines fit them as standard for oil and gas market.

Chalwin and Pyroban are very common on small diesel engines and can easily be retrofitted with no significant effort: -

Chalwyn-Categories
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Exactly what I was thinking about.
 
Capt Popeye said:
Yep certainly silly question one might think; yea turn the Key Off, but Diesels do not have ignition do they ?

Are they starved of Fuel to the injectors or something like that ?

Are there various different ways to stop a Diesel running ?
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Diesel engines are normally stopped by bringing the fuel pump down to zero delivery. When you stop by turning the key then the relaxation of a solonoid achieves this and on older engines a pull cord does the same thing. Some times an engine will run away being driven by lube oil which has fuel contamination. As the fuel pump is having no part in this then the only way to stop the engine is to choke the air supply....BUT NOT WITH YOUR HAND!

It is bad practice to stop the engine using the decompressor as under these conditions there is revers airflow through the inlet valve and it is possible for loose carbon to find its way to the inlet valve seat,get trapped and initiate leaking valves.

Fuel contamination is the main reason for more frequent oil changes than we see on road vehicles. in the older engines with crankcase mounted fuel pumps it results from internal spill leakage from the fuel pump plungers. This is how the pumps are lubricated.. It can also be a problem on common rail diesel engines if a leakage occurs in the common rail system if it is internally fitted. Older diesel engines with external rotary fuel pums do not suffer from this problem but as with many diesel engines can also suffer from leakage from a faulty crankcase mounted fuel lift pump .
 
Boater Sam said:
Seriously bad idea. Have you ever seen a diesel run away sucking the sump contents in for combustion? Its not something you want to happen,,,,,, ever,,,,,,, and this is the fastest way of achieving it.
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The standard method of stopping an overrunning diesel engine is to block the air intake so, by definition, it cannot promote overrun.

Richard
 
I worked on offshore oil rigs and our diesel engines all had flaps to shut off the engine in the event of a gas escape allowing the engine to run-away on the gas - air mixture it sucked in. We were trained in these and how to engage them (it was a manual stop on my Cummins winch engine). No mention of it causing run-away, but, iirc, it didn't have a crank-case breather into the air inlet, it just vented, via a gauze, to the outside. Maybe this could be a factor.

On my comparatively tiny 50HP Beta on the boat there is a solenoid which did fail once; the pin came out of its hole - now held in with a bit of string - and a wooden spoon allowed me to push the lever as if the solenoid had engaged and easily stop the engine. It opens a bypass in the high pressure injection pump I believe; certainly it goes into the injection pump.
 
Rogershaw said:
What "air bag"

I was considering fitting a shut off valve in the between the air filter and the inlet manifold to stop air entering the engine thus preventing combustion either from diesel oil being injected or sump oil being burned in the cylinder.
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My typing error AIR TIGHT BAG as in post #15
 
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