Paper: The Norwegian Lifeboat Project

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During a full scale test of a freefall lifeboat on a permanent production installation offshore Norway in June 2005, weaknesses in the superstructure was experienced. The lifeboat had been type …

During a full scale test of a freefall lifeboat on a permanent production installation offshore Norway in June 2005, weaknesses in the superstructure was experienced. The lifeboat had been type approved by Norwegian authorities, based on design and testing requirements in international codes. As a result of the discovery, The Norwegian Oil Industry Association - OLF, on behalf of its member companies, initiated a full investigation of all 16 freefall lifeboat types on the Norwegian Continental Shelf (NCS). During a four year programme of investigations, tests and analysis, several weaknesses have been disclosed. The outcome of the Norwegian Lifeboat project (LBP) has lead to proposed remedial actions for existing lifeboats and the development of a new standard for future freefall lifeboats. The project has been carried out in co-operation with unions, lifeboat manufacturers and authorities. It has been a unique life boat review project, and has reduced the risk of a potential evacuation situation offshore.
Rolf Skjæveland, M Sc. Per Otto Selnes, M. Sc.
Principal Engineer Safety Technology Manager Operations
Statoil

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  • 1. SPE 2010 - 127341 The Norwegian Lifeboat Project Rolf Skjæveland, M Sc. Per Otto Selnes, M. Sc. Principal Engineer Safety Technology Manager Operations Statoil OLF Abstract During a full scale test of a freefall lifeboat on a permanent production installation offshore Norway in June 2005, weaknesses in the superstructure was experienced. The lifeboat had been type approved by Norwegian authorities, based on design and testing requirements in international codes. As a result of the discovery, The Norwegian Oil Industry Association - OLF, on behalf of its member companies, initiated a full investigation of all 16 freefall lifeboat types on the Norwegian Continental Shelf (NCS). During a four year programme of investigations, tests and analysis, several weaknesses have been disclosed. The outcome of the Norwegian Lifeboat project (LBP) has lead to proposed remedial actions for existing lifeboats and the development of a new standard for future freefall lifeboats. The project has been carried out in co-operation with unions, lifeboat manufacturers and authorities. It has been a unique life boat review project, and has reduced the risk of a potential evacuation situation offshore. The result applies to design and operation of freefall lifeboats in offshore areas world wide. The reports resulting from the project can mainly be divided into three topical groups; strength of superstructure and hull, impact on the human body from acceleration forces, and positive headway immediately after water entry. As regards existing freefall lifeboats, it has been necessary to reinforce the superstructure of 140 lifeboats and to develop new seats with 5-point seat belts. In certain weather conditions it is recommended to take operational precautions when there is a risk of excessive acceleration forces or a risk that existing boats do not have sufficient positive headway. A new navigational tool has also been developed. The results of the studies and tests carried out have been documented in a number of reports, available on request. Additional project activities, not included in the initial scope, has been to study launching arrangements for evacuation means in general, as well as specific challenges for conventional launchable lifeboats. The main parts of the latter studies have been carried out within a project initiated by, and paid by, the Norwegian Ship owner Association. The results of the studies of the two additional areas, have been documented in separate reports. The main Norwegian offshore unions have made important contributions throughout the project The main project, as well as the part on launching arrangements, and additional studies on launchable lifeboats, has been financed by the oil & gas companies on the NCS.
  • 2. Introduction Offshore installation tests in close to calm water carried out in 2005 revealed an unacceptable structural degree of deflection of the roof in one of the 16 types of free-fall lifeboats. OLF Oljeindustriens Landsforening www.olf.no 10 Immediate remedial action was initiated by the OLF, including the study and documentation of the main performance factors for free-fall lifeboats in up to 100-year weather conditions. The findings revealed that the design and testing requirements to free fall lifeboats issued by UN’s International Maritime Organisation (IMO) are inadequate.
  • 3. Studies and tests A four year extensive programme of tests and analysis have been carried out by leading technical institutions in Norway and abroad, satisfying 100-year weather conditions. There were at the beginning of the project 212 freefall lifeboats on the NCS, representing 16 different types, produced by two manufacturers. The testing program included up to over 20.000 model tests of freefall lifeboats in a wave tank. Systematic tests to document pressure loads, acceleration loads, and forward speed have been performed in selected wave heights and wave headings. Calm-water model test results were compared to 250 full-scale drop tests. In addition, up to 1.500.000 simulations have been carried out. We have applied numerical models of the seat and restraint system with an automotive crash dummy as a replacement for a real 50th percentile human occupant. The reports can mainly be divided into three topical groups; positive headway, strength and accelerations.
  • 4. Strength Realistic tests have been carried out, and the 16 different freefall lifeboat types have been analysed and examined against a set of structural criteria, including suitable load cases and structural safety levels. It has been necessary to reinforce the superstructure of 140 lifeboats, representing 11 of the 16 types. The reinforcements required have been made by installing additional beams in order to strengthen the superstructure (canopy), and strengthening the frames of the access hatches and doors. For each boat type there is a report summarising the results from tests and Finite element (FE) analysis. OLF Oljeindustriens Landsforening www.olf.no 12
  • 5. Accelerations Although free-fall boats have been used in thousands of full-scale training drops and are currently installed on platforms, only limited technical studies have been published investigating their free-fall impact. The majority of these studies have focused on the hydrodynamic impact performance of the boat in an effort to understand variations such as centre of gravity (CG), mass distribution, environmental effects (waves) and hull design. All studies used boat acceleration as the primary response characteristic as measured at various locations throughout the boat. A handful of studies have considered the impact response of the occupants, but were often limited to global acceleration based injury criteria using signals obtained from the boat. Only one study could be found investigating the impact response of a hybrid dummy during free- fall impacts, which was focused on its ability to predict occupant injury potential. In the LBP, the safety level for life boat occupants have been evaluated up to a 100-year weather condition using a numerical model of the seat and restraint system with a automotive crash dummy as a replacement for a real 50th percentile human occupant. The overall purpose of this sub-project within the LBP was to provide a comprehensive assessment of occupant injury risk during drop conditions of currently installed freefall lifeboats, in an effort to improve occupant safety. The entire research scope has included injury biomechanics, occupant assessment criteria, boat hydrodynamics, full-scale testing, model-scale testing, numerical modelling, sensitivity analysis and optimization, and sled testing. The project has consulted experts on consequences on human beings from car crash testing, but it has been necessary to develop specific acceptance injury criteria and limits. A number of important findings explained why the existing international criteria are inadequate when requiring final prototype testing in calm water only. The impact on the human body from high accelerations varies not only with drop height, but more importantly with wave height and direction, and also the loading (weight) of the boat. Furthermore it was found that persons seated in seats at the extreme ends of a boat are generally subject to higher impact than if seated in the middle.
  • 6. Positive headway Forward distance / speed immediately after water entry, thrust and steering capacity have been evaluated up to a 100-year weather condition. As for acceleration tests, a learning from this part of the project is that weather conditions plays an important role, and in this case, particularly wind and wave direction. It is also crucial that the life boat propeller is being started as quickly as possible. The forward distance reports present boat particulars, model test results, short description of correlation and extrapolation methods, the selection of simulation tracks and final results showing lifeboat capability to obtain distance away from launch position. Final results are given as contour plots for four sea states representing the Norwegian Sea typical 100-year condition (Hs=15.7m), 10-year condition (Hs=13.7m), 1-year weather condition (Hs=11.4m) and Hs=8.0m including constant wind velocities. Results are given for two launch directions (head seas and bow oblique seas) and two values of time for start propeller after water entry (5s and 10s). Example – Lifeboat location vs installation structure Lifeboat closest to the + structure Engine starts 10 sec. after water impact Column Column 11
  • 7. New navigation assistance system developed. The LBP funded the development of a new, simple and robust navigational aid, making it easier for the lifeboat pilots to steer the lifeboat away from the installation in conditions of poor visibility.
  • 8. Hull CFD analyses are being carried out to determine the pressure loads on the lifeboat hull during slamming. The slamming phase starts when the boat enters the water, and is characterized by large pressure loads on the hull. The first tests have disclosed some possible weaknesses the hull, and installation specific tests will have to be carried out. Such specific tests had not started at the time of writing this paper. Reports The results of the tests and the analysis have been described in a number of reports which can mainly be divided into three topical groups; positive headway, strength and accelerations. See Appendix CONCLUSION The work carried out during the Norwegian Lifeboat Project has made it possible to reduce the risk of accidents should evacuation to sea from an offshore installation become necessary. Acknowledgements The authors want to thank the project leaders from ConocoPhillips and Statoil and the Statoil based project organisation, the consulting firms Fedem, Marintek and TNO for their contributions during the project described in this paper. Funding, management, working method and organisation The LBP was funded by the lifeboat owners and managed by OLF, and has been carried out over a period of 4.5 years. The cost, including reinforcement of lifeboat superstructure, external contract cost, project management and the contribution by company and external representatives in the various work groups has been some NOK 400 millions. The technical project organisation was provided by Statoil and ConocoPhillips. The lifeboat owners BP, ConocoPhillips, ExxonMobil, Gassco, Marathon, Shell, Statoil and Talisman, formed a steering committee, and in addition there was a reference committee with representatives from the main offshore unions IndustryEnergy, SAFE, Lederne and the marine officers, from the lifeboat producers Umoe Schat Harding and Norsafe, as well as observers from the Norwegian Petroleum Safety Authority and the Norwegian Maritime Directorate. Nomenclature CFD - Computational Fluid Dynamics CG - Centre of gravity FE - Finite element Hs – Significant wave height IMO - UN’s International Maritime Organisation LBP – The Norwegian Lifeboat Project NOK – Norwegian kroner OLF - Norwegian Oil Industry Association PSA – The Norwegian Petroleum Safety Authority TNO - Netherlands Organisation for Applied Scientific Research Building and Construction UN – United Nations
  • 9. Appendix – Reports Positive headway Forward distance / speed immediately after water entry, thrust and steering capacity are evaluated up to a 100-year weather condition. Strength Lifeboats are examined against the newly developed set of structural criteria and reinforced when necessary. For each boat type there is a report summarising the results from tests and FE analysis. Accelerations The safety level for life boat occupants are evaluated up to a 100-year weather condition using a numerical model of the seat and restraint system with a automotive crash dummy as a replacement for a real 50th percentile human occupant. Miscellaneous In the interest of promoting safety and further research and development some documents are available for free downloads. A full list of the reports can be accessed at www.olf.no/ lifeboatreports/. For information about price and other provisions, please contact StatoilHydro ASA,NO-4035 Stavanger, Norway. Attn.: Rolf Skjaeveland rolsk@statoilhydro.com