Runaway diesel

Many years ago an very large engine under test at Mirlees Blackstone ran away. The head blew off, went through the roof of the factory and parts landed up to a mile away.
 
Years ago I was working on a 2 cylinder Lister which had been fitted with a hydraulic pump to operate a Hiab crane. Started it up and tried the crane controls but nothing happened until suddenly the revs increased and I realised the engine was running away, I yanked off the air cleaner and slapped my hand over the inlet and the engine stopped. By this time the workshop was filled with acrid white smoke, had to open all the doors... The next day we discovered that the hydraulic pump had been supplied with the wrong rotation so as soon as the power was applied the seals blew and the sump filled with hydraulic oil and the engine ran away.
 
Rather more seriously than the fluffy girl, I would be reluctant to use anything like a rag to try and block the air inlet of a runaway. A taxi drivers know was cleaning round his engine, and had disconnected the air filter hose to clean it. He put his cleaning sponge down near the open manifold. The engine was only idling, but the suction was enough to suck the sponge in. He lost several days work stripping the engine to remove the debris which jammed the valves open so it would not start.
 
webcraft said:
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Was down the boatyard yesterday working on Avy-J. Across the yard a friend was trying to get an old Volvo engine running that had not run for 6 years.

I heard the engine fire into life and said to Catherine, let;s go and have a look. My pal seemed to be revving the nuts off the engine as we walked across, and there was a lot of smoke. Then I heard the shout for help.

Shot up the ladder to find my mate with a small headwound and a considerable panic on. The engine was a 3 cylinder and he only had two hands. He was crouched over the runaway beast with hands over two of the three air intakes but no way of blocking the third. The eninge must have been doing over 4,000 rpm with air only getting to one cylinder.

'Shove your hand over there' he shouted, removing his hand from the aftmost air intake. My hand was sucked hard onto the metal orifice an Robbie with his one now free hand ripped the air filter off the third intake then blocked it with said hand. The engine died almost immediately. I suspect no damage will have been done by the runaway, but now he needs to find what caused it. Immediate investigation was limited to checking the oil . . . up to the mark on the dipstick but somewhat emulsified. Further investigation was abandoned as the shocked owner went home and took whisky.

Made me think. The Yanmar in Avy-J has decompression levers, which would stop the engine in the event of this happening. It also only has a single air inlet even though it is two cylinder, so much easier to smother. But on Fairwinds the Beta has no decompression l;vers. I think I might get a CO2 extinguisher for precisely this eventuality.

Interesting . . .

- W
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Got to ask, I've read 5 pages of replies and still don't know what the head injury was caused by. I assume he didn't try to block one of the intakes with it.
 
I have been thinking about my particular air filter, which cannot be removed quickly, and have decided to use a heavy plastic bag-like a rubble bag,Cut to size, folded and taped so I can slip it over the round perforated intake grid. The suction should pull it-or rather atmospheric pressure push it-evenly into an effective seal.

Should my engine suffer a runnaway, I hope so!
 
I doubt that a runaway would be caused by sticking governor. After all, the fuel was shut off anyway. The most likely culprit would be the fact that the engine hadn't been run for years. The piston rings tend to get stuck in their grooves, gummed in with a mix of dried fuel and oil. They provide enough compression for the engine to start but not enough sealing to prevent the engine sucking sump oil up into the compression chamber, as this is uncontrolled the engine over revs and parts then subjected to sufficient stress for them to break up.

In the days when all engines were as agricultural as most boat diesels, the norm was to put a few squirts of Redex in each cylinder to soak overnight before attempting the first start. This usually freed the piston rings allowing normal function, although the clouds of smoke as the Redex burnt off were impressive!

Rob.
 
I reckon a CO2 extinguisher is a good idea on a boat anyway. People are put off because of the risk of suffocation (Pah! Do they not know the joys of the orange?), but you don't want some numpty to fill the saloon with powder (or foam) because the toast has got out of hand.

With the amount of stuff that needs looking at, I can't imagine I'd ever reach the point where I'll be worrying about special measures for a runaway diesel though, surely a bin bag duct taped over the filter will suffice?

I trust we all have duct tape and bin bags......
 
Balbas said:
Air pressure at sea level in a standard atmosphere is a smidge under 15psi. Unless my schoolboy physics has escaped me, you can't get lower than an absolute vacuum, so the maximum pressure differential is going to be what? 15psi? Should be alright.
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You are very close Balbas. 14.7 lbs per sq inch.
 
What is the likelihood of this happening on my boat engine, is it more or less than getting run down by a nuclear submarine?
 
Quandary said:
What is the likelihood of this happening on my boat engine, is it more or less than getting run down by a nuclear submarine?
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I wondered that too so I tried to answer it. A quick and dirty analysis of reports here found:

3 reports of "Own Boat" runaway
1 report of another boat
1 report of a non-boat runaway
4 hearsay reports

The problem is defining the size of population from which these reports have come.

32 different people have contributed to the thread which suggests a 1 in 10 chance of experiencing a runaway on your own boat. That's scarily high.

The forum front page reports that there have been 2465 views of the thread but I don't know if that's 2465 different individuals. If it were, then the probability of an own boat event is down to 1.3%, a lot more manageable.

I'm assuming that anyone who is aware of the thread and has experienced a runaway would let us know about it. I know I would.

I'm concluding that it's a more likely event than I had imagined and my own previous ill-considered contribution demonstrates that it's a bit late to work out how to deal with it after it's started.

Derek
 
Your 1 in 10 chance is drawn from a self-selecting sample with, most probably, a high proportion of people with an interest, which would likely include everyone here who's experienced it and a relatively small proportion of people for whom it's never been an issue. Personally, I'll be worrying more about that nuclear sub surfacing under me in the Solent
 
Not so much a threat in the Solent, but there have long been a string of disturbing incidents (often unproven) on the west coast of Scotland.

Rob.
 
No, if that's all it takes. However, given the state of my air filter, I rather suspect that any attempt to bung up the air intake would result in a cloud of rust and small bits of metal being inhaled by the engine.
 
rob2 said:
In the days when all engines were as agricultural as most boat diesels, the norm was to put a few squirts of Redex in each cylinder to soak overnight before attempting the first start. This usually freed the piston rings allowing normal function, although the clouds of smoke as the Redex burnt off were impressive!

Rob.
Click to expand...

Ah, that explains the motorway signs "RedX is mandatory".
 
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