Remetalling of stern tube bearings

I posted earlier about the centrifugal remetalling machine we commissioned in our workshop this year. Last week we had a total of three large stern tube bearings which had to be reconditioned.

First the old white metal (babbit) is being molten out of the steel bearing tube. The most important part of any remetalling job is the preparation of the surface of the bearing shell or tube. The surface has to be absolutely clean and oil free, in order to ensure an adequate bonding between the steel of the tube and the white metal.

After cleaning the tube is being put in an electric oven for the night at about 400 degrees C. This removes any traces of oil from the surface. The next step is the tinning pot, where the tube surface is covered with a thin layer of white metal. This step is crucial for an even bonding. Finally the tube is put in the remetalling machine, where the main layer of white metal is applied.

Now the bonding between steel and white metal has to be checked. We use an ultrasound measuring device, which can detect any ‘gaps’ between the steel tube surface and the white metal layer. In order to provide a smooth surface for the ultrasound probe, the inside of the stern tube bearing is machined close to the nominal diameter on a horizontal boring machine.

stern-tube.jpg

When everything is found in good order, the bearing is finished to nominal size. At present we can handle stern tube bearings up to a length of 2.2 meters.

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About Stranded Mariner

Marine Engineer and passionate sailor and cruiser, working in the marine business in China.
This entry was posted in Marine Engineering, Maritime & Navy, Ship Repair. Bookmark the permalink.

6 Responses to Remetalling of stern tube bearings

  1. Joseph CAROSIN says:

    Bonjour,
    thanks for this information, I am preparing an exam of marien engineer.
    One the subjet to be known concern “stern tube oil leakaege”l and mainly the maximum autorised oil that can escape from the seals. Marpol is not accurate on this, I’ve read something like 30 to 60 litres / running mile. Any information from your side would be appreciate. Thanks and regards.
    J. Carosin

    • Hi Joseph,

      I must admit that I don’t have that information right now, but will try if I can find something. But to be honest 30 to 60 liters per running mile seems to be VERY high.
      Best regards,
      Andreas

  2. elena d. singco says:

    Sir:
    I would like to know what white metal suits best for a stern tube bearing?

  3. yustin says:

    Sir :
    Do you have pictures of white metal bearings?
    Best Regards, Yustin

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