Diesel engine overspeed

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Pengze
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Re: Diesel engine overspeed

Postby Pengze » Sun Sep 16, 2012 5:15 am

Dear Gents,
1.We found 2 pcs of broken bolts from the crankweb counter weights inside one of the cylinder units. I was wondering whether these broken parts caused overspeed or after overspeed , these bolts were then broken off.? Consequently, we had a sidekick causing damages to the cylinder block.
Or could it be due to crankcase explosion but to recall, the alarm indicated Overspeed.

2. FYI, the genset had been operating for the last 57 hours with all parameters normal and working at 50 % load only. There was no tripping of the MCB at the switchboard before Overspeed and engine failure. :roll:
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Pengze
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Re: Diesel engine overspeed

Postby Pengze » Sun Sep 16, 2012 5:23 am

Dear Gents,
Here are some more pictures for yr perusal.
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P1000005.JPG

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The Dieselduck
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Re: Diesel engine overspeed

Postby The Dieselduck » Mon Sep 17, 2012 5:55 am

Off the top of my head, I don't see how a bottom end failure could cause an overspeed at this time. However, if it was, it must have been some major overspeed to throw a connecting rod out / counter weight. or...

Could you perhaps had a top end failure in that individual power unit, causing damage to the piston and or connecting rod. Maybe a valve dropped, damaging the injector causing overfuel into that unit, or the injector itself fed too much fuel into the unit causing a detonation damaging the running gear. I am just brainstorming here.

Scary pictures, nobody likes to see this, kinda ruins your day. What else did you find on that power unit? What does the cylinder head look like? Maybe the injection pump has had some kind of failure - the drive, or timing slipped, broken shaft or the likes.
Martin Leduc
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http://www.dieselduck.net

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The Dieselduck
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Re: Diesel engine overspeed

Postby The Dieselduck » Mon Sep 17, 2012 6:22 am

Come to think of it. Maybe the "overspeed" might be a bit of a "red herring".

It's not unheard of for the bolted on counter weights to fail, I know of a very similar incident - similarly doing some pretty nasty damage. Have a look at the those two failed bolts closely on the counterweight you mentioned, see if you can determine the failure point.

The story I know of, goes like this. The engine, an MTU 2000, threw a counter weight not long after rebuild - which then proceeded to destroy itself. The engine had a complete overhaul as per specs. The contractor, a OEM authorized shop, failed to replace the counterweight bolts as required, which apparently have a very precise working life of 30,000 hrs.

Maybe your failure is the counterweight bolts, as suggested by the comment that you found them broken. In the case of dramatic failures like this, it's not uncommon for the alarm system to register / record multiple alarms, the first not necessarily being the cause of all your problems.

When was the last major overhaul, and what was done regarding the counterweights - whats required?
Martin Leduc
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http://www.dieselduck.net

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JK
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Re: Diesel engine overspeed

Postby JK » Mon Sep 17, 2012 6:26 am

Is it a MAK engine?
The counterweight bolts broke when the overspeed caused so much centrifugal force that they were overloaded to failure. If the counterweight is not keyed on, then it is only the bolts that are keeping it on. If you look at the bolt fractures you will be able to see where the failure started.
If you do some reverse engineering you will be able to tell what the engine speed was at the material failure.

Or as Martin has posted, the counterweight bolts not changed at the hours or replaced with blackmarket parts will also lead to failure.

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The Dieselduck
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Re: Diesel engine overspeed

Postby The Dieselduck » Mon Sep 17, 2012 4:36 pm

the exhaust manifold has HND casted in. According to Wikipedia, its a Chinese engine manufacturer under license from Deutz and MAN - http://en.wikipedia.org/wiki/Henan_diesel_engine
Martin Leduc
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JK
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Re: Diesel engine overspeed

Postby JK » Fri Sep 21, 2012 2:09 am

a chinese Deutz. Mind boggling in the implications....

Pengze
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Re: Diesel engine overspeed

Postby Pengze » Mon Oct 08, 2012 11:16 pm

The consequences of engine overspeeding
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Pengze
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Re: Diesel engine overspeed

Postby Pengze » Mon Oct 08, 2012 11:33 pm

Dear Gents,
First & foremost, Dieselduck is very sharp, the HND is in fact HENAN diesel engine, the so-called Chinese Deutz (by JK).
All the cylinder heads were found in good order.
Have not check the pistons & lubrication yet.
The speed controller is found in good condition.
The fuel pump has not yet been investigated.
The analysis results of the broken bolts have not come in yet.
Intend to check the overspeed controller card for any defects.

I am wondering if there was a oil lubrication failure but then no alarm indication about the lube oil pressure and temperature. As reported visually on the gauges ,all were found to be normal.

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JK
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Re: Diesel engine overspeed

Postby JK » Tue Oct 09, 2012 2:02 am

Also, if you wiped bearings in the overspeed, you should check the piston heads for babbit in the LO cooling. The babbit will deposit there.


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