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Part 1 continued.
The engines behaved themselves until Northern Star was homeward bound, between Tahiti and Panama. It was a case of deja vu.
The starboard thrust bearing failed again, but this time the job only took 12 hours, and as soon as it was completed and the engine running again, the port engine was stopped and the thrust pads removed before total failure occurred. This proved to be the key in determining the real cause of the troubles. Another 12 hours frantic work followed, during which I became a snowman for the fourth time, and we were back on our trusty two half engines. I totted up the running hours from the Engine Room log, and found that the time from new to the first failures was almost identical to that between the Sydney rebuild and the second round failures. Hardly a coincidence. And so we finally returned to Southampton, 10 days late. Probably the most troublesome maiden voyage by a major passenger liner since Titanic!
We were lucky that the ship never actually stopped at sea, and the ship’s Engineers can be proud of isolating a main engine turbine four times in a single voyage. It is fairly certain that this had never happened before, and with the few remaining steam ships left at sea today, it is certainly a record that will never be equalled.
While the ship had been making its way home at 16 knots, the salvaged thrust pads were flown home and subjected to exhaustive tests and investigations. The primary cause of the failures was finally tracked down, and proved to be a chemical reaction that deposited a hard carbonised iron coating onto the thrust disc. This scored the machined steel face of the disc, which was an integral part of the turbine rotor. Eventually the soft white metal of the pads was ground away, allowing the turbine shaft to move forward by the thickness of the missing white metal. Builder’s dirt in the oil system was also thought to be a contributing factor. Certainly, a lot of rubbish was removed from the oil filters in the early days. I did not learn some of these detailed reasons until two years or so later when I received a copy of the paper that George Jackson presented to The Institute of Marine Engineers (now IMarEST) in Mark Lane. Surprisingly, no previous ship had been built and run with the combination of the particular steel for the turbine rotor and white metal for the thrust pads, together with the grade of oil to lubricate the turbine bearings and gearing. All three elements were widely used in many naval and merchant ship applications, but never together in combination.
The cure proved to be very straightforward. Before setting off on V2, the original “Extreme Pressure” grade oil, which was usually only used on high powered naval ships, was removed, the system cleaned and flushed and refilled by a fresh charge of straight mineral oil, without the EP additives. Parsons did extensive work to the rotors and blading, restoring them to near new condition.
I seem to remember that the grade of white metal was also changed. Certainly the pads themselves were new, and where supported by a hydraulic self aligning arrangement, and every pad incorporated a thermocouple, to continually monitor and record operating temperatures.
For the next 3 voyages at least, the Thrust Bearings were opened up regularly for inspection.
As far as I know, no other problems with the Thrust Bearings were experienced for the remainder of Northern Star’s short but eventful life.
Dick Goodey
6th January 2012
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