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Renewal of the foundation flange with a diameter of 17m onboard of crane ship ORION I has been done in close cooperation with COSCO Qidong, LIEBHERR Rostock, and DEME OFFSHORE in 2021.

After contact between DEME Offshore and OSM Belgium, OSM worked intensively with Cosco Qidong and Liebherr Rostock for on-site machining of the new flange.

The urgency was high and the time frame extremely short.

The scope was divided into 5 main tasks:

  1. Preparation of the circumferential welding edge bevel

  2. Machining of 2 vertical welding grooves

  3. Machining of the top surface of the flange in 2 stages: rough and then fine milling

  4. Drilling/line boring of the 216 x 126mm holes

  5. Machining of the bottom surface of the flange

One of the main issues in the entire scope was the fact that the main supply transformer for the crane was situated at the turning point in the center of the crane pedestal, extending above the flange, and could not be removed. Consequently, a spider-like milling machine could not be used in this special situation. Our challenging task was to study and propose a new machining method for machining the top and bottom surfaces of the flange.

Transformer in the middle of the flange
Transformer in the middle of the flange - Protruding the top of the flange
Circular milling machine
Spider-like milling machine - normal way of top and bottom flange machining

An innovative machining method developed in-house was used for this special application. A state-of-the-art milling machine was designed and manufactured in our company's workshop.

This innovative machining method has several advantages, such as:

  • No heavy rotating support beam to sustain the cutting tools;

  • No difficult machine alignment procedure and no need for daily follow-up;

  • Once the hull structure with the crane foundation is complete, the survey and machining works can begin;

  • Displacements in the hull due to the movement of the large onboard weight transfer do not affect the accuracy of machining

  • Machining of the flange with several identical machines operating at the same time;

  • From the moment the position of the raw flange is surveyed, the machining operations are started and continued until they are completed, without any fear of interruption or delay due to the transfer of big weights and the finishing works of the vessel.

The very small and stringent machining tolerances of this massive flange were a huge challenge and tested the OSM team to the limit.

On top of these challenging conditions, in order to minimize the downtime of the vessel, the scope had to be performed with the ship moored at various locations, where machining activities continued during the mobilizations of the vessel between the different locations. This created difficult logistical moments, where the changeable weather conditions may not be underestimated.

Thanks to this new and advanced technique, downtime was kept to a minimum while strict tolerances were met with the approval of all parties involved.

If you wish to receive more details regarding this project, feel free to contact us.


OSM machined the crane pedestal in 2021 and is proud to see the crane operational.


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