LIFTING EQUIPMENT DESIGN
OPC designed a bespoke pin extraction and handling system for DEME’s Neptune jack-up vessel, for fabrication by Marine Repair B.V.
The equipment was developed to remove and handle jacking pins weighing approximately 710 kg each. The design needed to support the pin throughout extraction, retain it once withdrawn and provide a means of moving it clear of the jacking assembly.
Extraction and Handling Arrangement
The solution combined a pin-receiving frame with a separate lifting boom attached to the vessel’s bulkhead through bolted interfaces.
A hollow hydraulic jack withdrew the pin progressively into the frame. Once fully extracted, the pin could be secured within the frame and the combined assembly supported by a chain block on the lifting boom.
The boom incorporated a hinged pedestal and a slewing arrangement, allowing the captured pin to be repositioned after removal. The equipment and operating sequence were developed together, accounting for assembly aboard the vessel and the transfer of the load between the fixed supports and lifting equipment.
Structural Design and Verification
OPC designed the frame, boom, pedestal and bolted connections using readily available steel sections, with attention to keeping component weights manageable during installation.
Finite element analysis assessed the lifting boom and receiving frame in their different support conditions. These included the frame attached to the bulkhead and the frame suspended with the extracted pin. Hand calculations checked the bolted connections.
The assessment covered operational and overload-test conditions, including allowances for dynamic effects and side loading, using design criteria drawn from DNV-ST-N001.
Fabrication and Operational Documentation
The engineering package included:
- General arrangement and detailed fabrication drawings.
- Component details and plate-cutting files.
- Structural design report, finite element analysis and connection calculations.
- An illustrated installation and operation manual covering equipment assembly, pin extraction, securing and handling.
The pin puller was subsequently used successfully aboard the vessel to remove the jacking pins. The project brought equipment design, structural verification and the working method together in a purpose-built solution for a specific maintenance task.
