Shall we play a game?

A place to exchanges questions and ideas of a technical / procedural nature. Go ahead, try to stomp us !
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Dieseldame
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Currently located: Nova Scotia / Caribbean

Shall we play a game?

Postby Dieseldame » Thu Jan 24, 2008 5:35 pm

Okay, this post is a request for you experienced types to share experiences in the form of a question for further discussion or research - a learning opportunity if you will. So, what kind of mysteries and mistakes have you run across the might serve as a learning experience for others??

DD

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ArkSeaJumper
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Currently located: Ireland

Postby ArkSeaJumper » Fri Jan 25, 2008 1:02 am

Good Plan
I will start it off with the oddest one I’ve had in the last few years.

We just purchased a vessel, 10 year old small bulk carrier.
After the purchase drydock, the vessel was sent for the first cargo. After sailing from the load port, I noticed a very loud ‘squeak’ around the tail shaft. (slowspeed, fixed pitch),
The squeak was there throughout the speed range of the engine.
It was not there (I swear guv) when the ship was in ballast.

We did all the usual tests, and then some more unusual ones. No big problems showed up.
I recorded the noise on a little Dictaphone, and played it down a phone to a propeller repair expert. He instantly identified the noise as ‘A Singing Propeller’

On the trailing edge of the blade, if it is blunt, a vibration can be setup, that is why all modern blades have this edge ground to a taper. I.e. knife shape.

To fix the problem, we had to tip the ship and grind the trailing edge of the blades.

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JK
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Joined: Tue Sep 04, 2007 2:29 am
Currently located: East Coast, Canada

Postby JK » Fri Jan 25, 2008 7:04 am

Ah, the singing tip. We had a singing props that supposedly had ati-singing edges. When we sent a diver down, the edge was ground on the wrong side of the blades.

We had a severely vibrating engine.
The crew swore up and down it was getting worse, to the point it was felt in the Captain/Chief Engineers cabins. We checked everything, dampers, fuel timing, it was to the point that we were starting to think the rubber blocks under the engine bedplate were starting to fail allowing more vibration.
After all of this work we had a Chief return back to the ship after 8 years away and he started looking around the engine. He noticed some minor deformations in the gussets and tanktop, that had been overlooked and he theorized that the forward edge of the engine seat could have been slightly depressed. (Think of an engine on a raft). He put a hydraulic jack in under the seat and just pumped it up enough to make contact and the vibration stopped. It appears that the location of the engine and the ship structure were transmitting the vibration up 5 decks to the point everyone was expecting the engine to disintegrate.

Om another ship we had a knocking coupling. It only did it on certain low RPMs though. At the end of it, everyone assumed that the locking plate was off inside the coupling and knocking. With the ship due for dock, it was left.
When the coupling was split, it was found the locking plate was still bolted in place, however the holes had elongated, allowing the plate to rock as the shaft tuned- the source of our knock.

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The Dieselduck
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Currently located: Nanaimo, British Columbia, Canada (West Coast of Canada)

Nasty tricks

Postby The Dieselduck » Mon Feb 04, 2008 10:06 pm

There more than a few trip and tricks that can be done on a ship...

I was told of a particular dirty trick to watch for. The boat was being transferred to some other, cheaper crew. That decision did not sit well with the engineer that ran it. So instead of filling the lube oil tanks with oil, they filled them with water then poured lube oil down the sounding tube. When the new crew did their soundings, the oil was a nice colour and level... but in reality it was water they transferred into the engine sumps.

Come to think of it, perhaps thats what happened to the Northern Adventure. mmmmmm.
Martin Leduc
Certified Marine Engineer and Webmaster
Martin's Marine Engineering Page
http://www.dieselduck.net


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