Balance

A place to exchanges questions and ideas of a technical / procedural nature. Go ahead, try to stomp us !
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ArkSeaJumper
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Balance

Postby ArkSeaJumper » Fri Feb 29, 2008 6:03 am

A little story for you.
A new dredger was being built with two little CAT engines, 1500kw, gearbox to shaft at the aft of each engine and a large alternator coupled to the fwd end.
The engine is on resilient / rubber mountings.

All parts were aligned, and signed of by all interested parties.
The engine was prepared for trials.

When the engine was run there was heavy vibration, mainly at the forward end.

It turned out, the piping system on the engine holds most of the 1,5 tonnes of water at the fwd end of the engine, this changed the alignment, dropping the fwd end and lifting the aft end.
The CW system was only filled just before the trials.

I would have assumed, for the sake of alignment, the fluids in an engine were fairly evenly balanced, apparently not.

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JK
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Postby JK » Fri Feb 29, 2008 7:32 am

Sorry, I laughed :oops:
Sounds like something that would happen to me.

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ArkSeaJumper
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Joined: Fri Sep 07, 2007 8:02 am
Currently located: Ireland

Postby ArkSeaJumper » Fri Feb 29, 2008 8:04 am

Dont mind, not my ship.

The service engineer was to be on mine, but he was a little busy.

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D Winsor
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Postby D Winsor » Wed Mar 05, 2008 3:06 pm

It sounds as if the free end drive may have been aligned to the engine with no allowance for thermal expansion and growth. This will cause vibration and potential bearing failure in either the engine or driven equipment. If the alignment is correct it may be necessary, to reduce the vibration in the Cat, to redesign or even remove the free end torsional damper to compensate for the added weight of the drive coupled to the crank.

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JK
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Postby JK » Thu Mar 06, 2008 11:44 am

We had some gearbox bearings fail. After a group of grown-up engineers stood around for an hour drawing circles in the air figuring out rotations we decided on engine alignment.
When we looked at the existing alignement, it was discovered that the previous job had gotten the growth of the engine correct only they had moved it the wrong way. They must have drawn their circles facing aft :D


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