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Initial indications are that fine metal debris that collected in the lube oil filter caused the system to shut down, but the cause is not known, the Times reported.
tomahawk6 said:I hope tthey dont have to replace the engine,
Occam said:Perhaps some stoker types can confirm, but my understanding is that if they had to stop in the water due to metal debris in the lube oil pumps, then the problem isn't the engines. She has two gas turbines, and two diesels - any one of which should be able to independently drive the ship. Would I be correct in assuming the problem would be in the main gearbox or CRPP systems if they had shut down all propulsion?
tomahawk6 said:Good to know that filings doesnt mean a bad engine.I wonder if this will cause the maintainers to look at this issue across the fleet to see if this was an isolated instance or not ?
Oldgateboatdriver said:The Freedom class ships don't have variable pitch propellers nor "shafts", in fact they don't have screws but four water-jets for propulsion, each engine driving one water jet, so there is no "main" gearbox either but four separate ones that gear each engine to the impellers of its own water-jet.
I agree with Chief Stoker, though: Any metal filings in the LO system on a commissioning ship is cause for concern (alarm?).
As to why she got completely disabled when she has four separate engines and waters-jets (thus four separate gearboxes), it also depends on the design of the LO cooling system and the concept of operation in use. While she has four engines (and from here on I am speculating, so don't quote me on this), she may have only two LO cooling heat exchangers and the system is set up so either can be used singly to cool everything, switched from one to the other for redundancy or "isolated" and then half the systems run on one and the other half runs on the other. This is all fine if your concern is cooling the oil only. If you lose cooling, likely as a failure of the water pumps or blockage of the water intake, you switch to the other one and it usually resolves the problem.
The problem with such set up is that, if you run everything on one and you get lube oil contamination instead, then you quickly spread the contamination to the whole system being lubricated. Now, on a brand new ship, I would definitely not expect such contamination to occur: The ship has been run at full speed trials and passed, after which the lube oil was (or at least should have been) tested of any problems, and before even running the engines the first time, the whole lube oil system had (or again should have been) flushed and tested. So running everything on one cooler (heat exchanger) was a very very low risk matter. 10 to 15 years from now, perhaps, it would be wise to run on two separate coolers for half the systems each, as I suspect you would do in action also.
Chief Stoker said:The ship has two cruise diesels and two gas turbines in a CODAG arrangement. Most likely the port and stbd main combining gearbox that input into two separate gearboxes, that in turn feed the four water jets. There are two shaft lines involved with this and not separate gearboxes for each individual water jet. It appears that the port combining gearbox had the problem, they locked out that side and continued on the stbd and on two water jets.