All Seatrax offshore cranes are based on the well proven kingpost concept. This basic design consists of a stationary or fixed kingpost and a revolving superstructure, which fits over and revolves around the stationary post. The boom, machinery house, operator's cabin, hoist and slewing machinery are all fitted to the revolving superstructure.
With Seatrax's design, the overturning moment is resolved by means of two vertically-spaced radial bearing assemblies. Each carries an equal and opposite horizontal (radial) load. All vertical loads (self weight of crane plus lifted load) are carried into the stationary kingpost by means of a concentric thrust bearing.
One way to visualize this concept is to consider a simple ball point pen with a cap. Imagine the pen is the kingpost and the cap is the revolving superstructure. The cap cannot detach from the pen because of the application of an overturning moment and a vertical load. The bearings provide only a means of support for rotating the cap about the body of the pen.
This analogy translates into the patented mounting concept. With this design, the structural and bearing functions are distinctly separate. A bearing failure cannot result in separation of the superstructure from the stationary kingpost. The kingpost mounts to the platform pedestal by welding.
An exclusive feature of the Seatrax design is the patented non-metallic upper and lower bearing assemblies. These bearings will last several thousand hours with minimum maintenance before replacement is necessary.
For more information, review our technical paper on our kingpost design or call 713-896-6500.