Measuring of the slewing bearing

Measuring of the slewing bearing

Nowadays I revise my old article and I remember my experiences on board commercial or offshore vessels as hydraulic troubleshooter

Measuring of the slewing bearing with balls

The measurements has to be taken when the ship have as little list/trim as possible.

Not any load or cargo handling equipment (e.g. grab) should be on the crane hook.

I remember once I attended to a ship for inspections of deck cranes. Among others I had measuring of the slewing bearing. It was the first time when I was doing the test.

I knew the procedure from the maker manual and I also got all the needed information from some experience colleagues. I was  trained and prepared.

But I was using a Vernier Caliper instead of dial indicator and the result was wrong. With the dial indicator the measurement is more accurately.

On the cranes bottom plate two reference point need to be marked. The reference points have to be used for the future measuring. The marked surfaces should be on the front and rear bottom plate of the crane.

It is important to use about the same position for all further measurements to be able to compare the measurements.

The dial indicator should be positioned between the rotating and non rotating bearing races and crane jib must be raised maximum up and maximum down.

Measurements shall be taken on four positions of the slewing bearing. With the jib pointing: forward, starboard, aft, port side.

Set the indicator at zero then raise the crane jib at maximum up and record the value. The indicator of dial indicator should return to zero when the crane jib is lowered back to its original position.

Above I presented one method that I am familiar with, but out there are others method of slewing gear ring measuring like: rotation method or tilt method.

That’s why before doing the test you should become familiar with the crane and Maker recommendations should be checked.

Procedure of deck crane rocking test
  • For accurate measurements use dial indicator.
  • Marked 2 reference points on the front and rear bottom plate of the crane.
  • Attach dial indicator between rotating and nonrotating bearing races.
  • Jib raised maximum up and maximum down – luffing out and luffing in. 
  • Measure slewing bearing in 4 points.

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