Anti Flooding Tool: How to Reduce Consequences of a Wet Buckle During Lay

Trunk lines are laid in continuously increasing water depth. The risk of a wet buckle, with the consequent flooding of the line, asks for remedial actions that require, among others, dewatering of the line within a limited timeframe, typically few weeks. The availability of a set of air compressors ready for such quick intervention during all the time of the lay is extremely demanding in terms of costs and required facilities. To minimize the risks of flooding of trunk line in case of a wet buckle and to avoid the need to set up the air temporary compression station at the land facilities, Saipem started a R&D project to develop a proprietary Anti Flooding Tool (AFT). The primary objectives for the development of the tool were: to run inside the pipe during the entire lay, always remaining behind the first Buckle Arrestor after Touch-Down Point; to automatically plug the pipe in case of an accidental flooding event. The tool development had also to consider the need to monitor and control the tool from the laying vessel without any physical connections with it and to work out a method to recover and install the AFT from the lay vessel in both S and J Lays. Due to the specific operational requirements of this tool, a dedicated simulation program has been developed to evaluate the behaviour of the AFT when running in the pipe. The paper describes the AFT, its working principle and its operability at field. A short description of validation tests done during the development is also presented. At present the tool is finalized for the South Stream project and it is expected to go in operations at beginning of December 2014. The AFT concept is patent pending.