It has long been experienced that Launching of lifeboat from rigs and Positioning of offshore supply vessel (OSV) near rigs are very critical and vulnerable operations as regards to the safety. In present days, sophisticated & expensive Dynamic Positioning (DP) Systems are used in order to avoid the collision of OSVs with rigs. However, it is observed that despite the provision of such sophisticated means, accidents are still occurring. Loss of control during positioning of OSVs can lead to severe accident (e.g. collision of OSV Samudra Shakti with Mumbai High North (MHN) platform in 2005). To avoid such accidents, considerable gap needs to be maintained between the OSV and the rig position. Also launching of lifeboat is known to be another safety critical operation. Particularly in rough weather, the landing of lifeboat requires to be at least 20 to 30m away from the platform. This is essential for preventing the lifeboat to drift under the platform and colliding with the structure & piping system there at. Lifeboat launching by davit lowering or freefall have got their own traditional problems as widely known in shipping industry. These are described in the paper “Safety of Lifeboat launching - Some Possible Improvements {P19J_AB27}” presented at Design for Safety Conference-2010 held in Italy. Considering both the issues as described above, it is evident that maintaining adequate distance from the rig is a crucial factor for improving safety of Life Boat launching and positioning of OSVs alongside the rigs. In order to achieve this, an additional structural part of the rig is proposed in this paper. This new structural entity is to be in the form of an inclined truss which will act as launching skid for the lifeboat. This arrangement will provide a guided slipway to enable landing of lifeboat at a considerable distance from the rig. Also this structure will be configured suitably to enable berthing & mooring of supply vessels alongside the rig. In this arrangement the DP system will be required for a short time only, at the initial stage of placing the vessel. After having the vessel positioned, she can be moored with the new proposed truss structure. Thus the dependency of DP System will reduce significantly to avoid collisions. So the authors believe that the proposed arrangement will improve the safety of offshore operation in a significant manner.
Dual-Interlocked-Storage-Cell-Based Double-Node-Upset Self-Recoverable Flip-Flop Design for Safety-Critical Applications