The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Siobhan Austen - One of the best experts on this subject based on the ideXlab platform.
-
Alternative Lifeboat Slipway Bearing Materials
2010Co-Authors: Ben Thomas, Mark Hadfield, Siobhan AustenAbstract:The Royal National Lifeboat Institution has provided marine search and rescue cover along the UK and Irish coast since 1771. This is accomplished using a variety of Lifeboats and lifeboat stations depending on local conditions. In regions where there is a large tidal range, or where there is no nearby natural harbour it is necessary to use an inclined slipway station to launch Lifeboats. This consists of an inclined slipway, usually at a gradient of 1 in 5-6, with a large boathouse holding the lifeboat under cover at the top. The lifeboat is released from the boathouse and proceeds under its own weight along the slipway into the sea. Recovery is performed by manoeuvring the lifeboat keel onto the slipway keelway where a winch line is attached and the lifeboat hauled back into the boathouse at the top of the slipway. Advances in lifeboat technology has seen the size and mass of slipway Lifeboats increase over the years culminating in the new 35+ tonne Tamar class (introduced 2005) and this has presented considerable engineering challenges to the safe and consistent operation of lifeboat slipway stations. Previous slipway launch practice had involved using a greased steel channel, along which the lifeboat keel slides, however with increasing lifeboat mass this has become unsuitable with problems of high friction along the slipway and concerns regarding the environmental impacts of the grease repeatedly being washed into the sea surrounding the base of the slipway. This research focuses on the search for suitable alternative slipway linings and lubricants culminating in the recommendation of a new jute/phenolic resin composite lining material to be used with a novel freshwater or seawater lubrication system, and with the development of techniques to reduce panel wear and to establish consistent panel monitoring and replacement criteria with the aim of reducing the environmental, material and economic costs associated with reliable lifeboat slipway operation.
-
Wear and Friction Modeling on Lifeboat Launch Systems
Tribology Transactions, 2010Co-Authors: Ben Thomas, Mark Hadfield, Siobhan AustenAbstract:The Royal National Lifeboat Institution (RNLI) provides search and rescue cover along the UK and RoI coast using a variety of Lifeboats and launch techniques. In locations where there is no natural harbor it is necessary to use a slipway to launch the lifeboat into the sea. Lifeboat slipway stations consist of an initial section where the boat is held on rollers followed by an inclined keelway lined with low-friction composite materials; the lifeboat is released from the top of the slipway and proceeds under its own weight into the water. The lifeboat is later recovered using a winch line. It is common to manually apply grease to the composite slipway lining before each launch and recovery in order to ensure sufficiently low friction for successful operation. With the introduction of the Tamar-class lifeboat it is necessary to upgrade existing boathouses and standardize slipway operational procedures to ensure consistent operation. The higher contact pressures associated with the new lifeboat have led to ...
-
Wear And Friction Modelling On Lifeboat LaunchSlipway Panels
WIT transactions on engineering sciences, 2010Co-Authors: Ben Thomas, Mark Hadfield, Siobhan AustenAbstract:The Royal National Lifeboat Institution provides search and rescue cover along the United Kingdom and Republic of Ireland coast using a variety of Lifeboats and launch techniques. In locations where there is no natural harbour it is necessary to use an inclined slipway to launch the lifeboat into the sea. Slipway stations consist of an initial section where the boat is held on rollers followed by an inclined keelway lined with low friction composite materials, the lifeboat is released from the top of the slipway and proceeds under its own weight into the water. The lifeboat is subsequently recovered to the top of the slipway using a winch line. With the introduction of the new, larger ‘Tamar’ class lifeboat it is necessary to upgrade existing boathouses and standardise slipway operational procedures to ensure consistent operation. The higher contact pressures and launch velocities associated with the new lifeboat have led to issues of high friction and wear on the low friction composite linings and a number of methods have been adopted to mitigate this effect. This paper presents a methodology for assessing slipway lining performance so that friction and wear conditions along the slipway can be monitored to ensure consistent operation. A multidisciplinary approach using tribometer testing in conjunction with finite element analysis and real world slipway condition surveys is adopted to extend the scope of investigation to incorporate common real world effects such as panel misalignments. Various lubricants are assessed for their suitability with regard to friction and wear performance in addition to sustainability considerations using the methodology, and modifications to the design of slipway panels, guidelines for lifeboat operation procedures and suitable panel installation tolerances are developed. Finally, new slipway condition monitoring procedures are proposed www.witpress.com, ISSN 1743-3533 (on-line) WIT Transactions on Engineering Sciences, Vol 66, © 2010 WIT Press Tribology and Design 209 doi:10.2495/TD100181 incorporating slipway panel failure and replacement criteria and recovery winch based condition monitoring.
-
Experimental wear modelling of lifeboat slipway launches
Tribology International, 2009Co-Authors: Ben Thomas, Mark Hadfield, Siobhan AustenAbstract:It is necessary to use an inclined slipway to launch Lifeboats in locations where there is no natural harbour. Slipway stations consist of an initial roller section followed by an inclined keelway, the lifeboat is released from the top of the slipway and proceeds under its own weight into the water. Contact is between the lifeboat keel and a lined, greased keelway and this determines the friction along the slipway. This paper describes a bench test methodology to investigate this contact. The selection of a modified TE57 reciprocating tribometer and design of a modified pin on plate arrangement is discussed. A test schedule for both the original nickel/chromium coated steel lining and the new low friction jute fibre/phenolic resin composite lining is developed to accurately reflect real world conditions including environmental contamination such as seawater or wind-blown sand. Environmentally conscious lubricants including water and bio-greases are investigated and compared for their effects in reducing slipway panel friction and wear. Experimental data are collected to establish wear mechanisms, wear volumes and friction characteristics for a range of lubricants and environmental contaminants for the two most common lifeboat keelway lining materials. Implications of this research for future lifeboat slipway design are discussed.
-
Wear observations applied to lifeboat slipway launches
Wear, 2009Co-Authors: Ben Thomas, Mark Hadfield, Siobhan AustenAbstract:Abstract It is necessary to use an inclined slipway to launch a large lifeboat in locations where there is no natural harbour or where there is a large tidal range. Slipway stations consist of an initial section where the boat is held on rollers followed by an inclined Keelway of nickel/chromium coated steel, the lifeboat is released from the top of the slipway and proceeds under its own weight into the water. The lifeboat is subsequently recovered to the top of the slipway using a winch line. With the introduction of the new, larger Tamar class lifeboat existing boathouses are being upgraded and existing low friction coated steel slipway lining materials replaced with a low friction jute fibre/phenolic resin composite, which is designed to operate with unlubricated conditions. This has led to problems of high wear on slipway panels, particularly where the lifeboat mounts the slipway for recovery. This paper describes a method for assessing slipway lining materials and lubricants. The selection of an appropriate test machine, the TE92 rotary tribometer, and design of a modified ring on disc arrangement is described. An experimental methodology is developed using programmed running intervals to simulate dwell effects. Experimental data is thus presented to establish slipway panel wear rates for a range of lubricants and contact pressures. Results and implications of this research for future lifeboat slipway design are discussed.
Thomas Michel Sauder - One of the best experts on this subject based on the ideXlab platform.
-
Integrity Assessment of a Free-Fall Lifeboat Launched From a FPSO
Volume 3: Structures Safety and Reliability, 2015Co-Authors: Guomin Ji, Thomas Michel Sauder, Sébastien Fouques, Nabila Berchiche, Svein-arne ReinholdtsenAbstract:The paper addresses the structural integrity assessment of lifeboat launched from floating production, storage and offloading (FPSO) vessels. The study is based on long-term drop lifeboat simulations accounting for more than 50 years of hindcast data of metocean conditions and corresponding FPSO motions. Selection of the load cases and strength analyses with high computational time is a challenge. The load cases analyzed are those corresponding to the 99th percentile of long term distribution of indicators for large slamming loads (CARXZ) or large submergence (Imaxsub). For six selected cases, the time-varying pressure distribution on the lifeboat hull during and after water impact is calculated by CFD simulations using StarCCM+. The finite element model (FEM) of the composite structure of the lifeboat is modelled by ABAQUS. Quasi-static finite element (FE) analyses are performed for the selected load cases. The structural integrity is assessed by the maximum stress and Tsai-Wu failure measure.In the present study, the load and resistance factors are combined and applied to the response. A sensitivity study is performed to investigate the non-linear load/response effects when the load factor is applied to the load. In addition, dynamic analysis is performed with the time-varying pressure distribution for selected case and the dynamic effect is investigated.Copyright © 2015 by ASME
-
Reliable and efficient injury assessment for free-fall lifeboat occupants during water entry: Correlation study between lifeboat acceleration indicators and simulated human injury responses
Volume 4B: Structures Safety and Reliability, 2014Co-Authors: J. Uittenbogaard, Svein-arne Reinholdtsen, Sébastien Fouques, Thomas Michel SauderAbstract:The evacuation of personnel from an offshore installation in severe weather conditions is generally ensured by free-fall Lifeboats. During the water entry phase of the launch, the lifeboat may be subject to large acceleration loads that may cause harmful acceleration-induced loads on the occupants. The present/common methodology for assessing the occupant safety of free-fall Lifeboats uses one single characteristic launch to perform injury risk analysis for a given free-fall lifeboat launch condition that includes e.g. weather conditions, lifeboat and host installation loading conditions. This paper describes an alternative methodology to fully assess the risk of injury for lifeboat occupants during water entry by introducing a correlation model between acceleration load indicators and injury responses. The results are presented in terms of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.
-
influence of wave induced skid motions on the launch of free fall skid Lifeboats from floating hosts experimental and numerical investigations
ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014Co-Authors: Neil Luxcey, Svein-arne Reinholdtsen, Sébastien Fouques, Thomas Michel Sauder, Wojciech Kauczynski, Geir HovlandAbstract:The evacuation of personnel from offshore installations in severe weather conditions is generally ensured by free-fall Lifeboats. Their performance can be assessed by means of numerical simulations to estimate accelerations loads on occupants, structural loads on the lifeboat hull, as well as forward speed after water-exit. These parameters strongly depend on the water entry conditions of the lifeboat, which in turn are very sensitive to the previous phases of the launch that starts on the skid. On floating production, storage and offloading (FPSO) vessels in the Norwegian Sea, Lifeboats are often installed on skids at the bow so that waves may induce large skid motions with typical extreme vertical amplitude of fifteen to twenty meters in a 100-year storm condition. Moreover, wave-induced motions may also cause trim and list of the skid, which initiates more complex six degrees-of-freedom trajectories during free-fall. In such conditions, a proper modelling of the lifeboat trajectory on the moving skid is necessary in order to assess the performance of the lifeboat with numerical simulations.This paper investigates the effects of the wave-induced skid motion on the launch of free-fall Lifeboats from floating hosts. The first part of the paper describes the six-degrees-of-freedom numerical skid model used in MARINTEK’s lifeboat launch simulator VARUNA. The second part presents two model test campaigns aimed at validating the numerical skid model. The model test results are compared to those obtained from the numerical simulations. Finally, the importance of the skid motion on the lifeboat trajectory is discussed.Copyright © 2014 by ASME
-
effect of wind loads on the performance of free fall Lifeboats
ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014Co-Authors: Thomas Michel Sauder, Sébastien Fouques, Eloise Croonenborghs, Nabila Berchiche, Svein-arne ReinholdtsenAbstract:The paper presents a model describing the launch of free-fall Lifeboats from offshore structures in strong environmental wind.Six-degrees-of-freedom numerical simulations of the lifeboat launch are performed using the free-fall lifeboat simulator VARUNA with a complete set of wind coefficients for the lifeboat. Those wind coefficients are obtained by CFD simulations validated against wind tunnel tests. The lifeboat launch simulations are then verified against time-domain CFD simulations of the whole launch in air until water entry.It is shown by means of numerical simulations that wind-induced loads on the lifeboat have a strong influence on its kinematics until water entry, and subsequently on the acceleration loads experienced by the occupants, on the structural loads on the lifeboat, and on its forward speed after water exit.It is concluded that the effect of wind-induced loads on the lifeboat performances should in general be investigated when establishing the operational limits for a given offshore installation.Copyright © 2014 by ASME
-
human injury probability during water entry of free fall Lifeboats operational criteria based on long term simulations using hindcast data
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE OMAE2014-24074 4B, 2014Co-Authors: Sébastien Fouques, Svein-arne Reinholdtsen, Thomas Michel Sauder, J. UittenbogaardAbstract:The paper addresses the safety of occupants in free-fall Lifeboats launched from turret-moored floating production, storage and offloading (FPSO) vessels. It presents a methodology for assessing operational limits with respect to acceleration-induced loads experienced by the passengers during water entry. The probability of being injured is estimated by means of numerical simulations for several seat rows and in various sea states described in terms of significant wave height and mean wind velocity. Those results are therefore practical for on-site decisions regarding the use of the free-fall Lifeboats. The numerical simulations performed to estimate the 6-degrees of freedom (6-DOF) water entry accelerations in the Lifeboats are based on more than 50 years of hindcast metocean data. These consist of sea state parameters provided every third hour and including the significant wave height, the peak period and the direction of both wind-sea and swell as well as the direction and mean velocity of the wind. In a first step, the motion of the FPSO is computed for the whole time period covered by hindcast metocean data, using a state-of-the art numerical model validated against experimental data. The model includes nonlinear excitation forces, a dynamic positioning system with a realistic heading control strategy, mooring line forces as well as turret-hull coupling. The obtained FPSO motion is then used in Monte Carlo simulations of lifeboat launches performed for selected time windows in the original metocean hindcast database corresponding to selected intervals of the significant wave height and mean wind velocity. In addition to the 6-DOF skid motion, the lifeboat launch simulations account for the effects of wind and waves diffracted by the FPSO hull. Finally, a probabilistic model describing the joint-distribution of several injury types and water entry acceleration parameters computed through the launch simulations is used to evaluate the injury probability. The results are presented in term of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.
Sébastien Fouques - One of the best experts on this subject based on the ideXlab platform.
-
Integrity Assessment of a Free-Fall Lifeboat Launched From a FPSO
Volume 3: Structures Safety and Reliability, 2015Co-Authors: Guomin Ji, Thomas Michel Sauder, Sébastien Fouques, Nabila Berchiche, Svein-arne ReinholdtsenAbstract:The paper addresses the structural integrity assessment of lifeboat launched from floating production, storage and offloading (FPSO) vessels. The study is based on long-term drop lifeboat simulations accounting for more than 50 years of hindcast data of metocean conditions and corresponding FPSO motions. Selection of the load cases and strength analyses with high computational time is a challenge. The load cases analyzed are those corresponding to the 99th percentile of long term distribution of indicators for large slamming loads (CARXZ) or large submergence (Imaxsub). For six selected cases, the time-varying pressure distribution on the lifeboat hull during and after water impact is calculated by CFD simulations using StarCCM+. The finite element model (FEM) of the composite structure of the lifeboat is modelled by ABAQUS. Quasi-static finite element (FE) analyses are performed for the selected load cases. The structural integrity is assessed by the maximum stress and Tsai-Wu failure measure.In the present study, the load and resistance factors are combined and applied to the response. A sensitivity study is performed to investigate the non-linear load/response effects when the load factor is applied to the load. In addition, dynamic analysis is performed with the time-varying pressure distribution for selected case and the dynamic effect is investigated.Copyright © 2015 by ASME
-
Reliable and efficient injury assessment for free-fall lifeboat occupants during water entry: Correlation study between lifeboat acceleration indicators and simulated human injury responses
Volume 4B: Structures Safety and Reliability, 2014Co-Authors: J. Uittenbogaard, Svein-arne Reinholdtsen, Sébastien Fouques, Thomas Michel SauderAbstract:The evacuation of personnel from an offshore installation in severe weather conditions is generally ensured by free-fall Lifeboats. During the water entry phase of the launch, the lifeboat may be subject to large acceleration loads that may cause harmful acceleration-induced loads on the occupants. The present/common methodology for assessing the occupant safety of free-fall Lifeboats uses one single characteristic launch to perform injury risk analysis for a given free-fall lifeboat launch condition that includes e.g. weather conditions, lifeboat and host installation loading conditions. This paper describes an alternative methodology to fully assess the risk of injury for lifeboat occupants during water entry by introducing a correlation model between acceleration load indicators and injury responses. The results are presented in terms of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.
-
influence of wave induced skid motions on the launch of free fall skid Lifeboats from floating hosts experimental and numerical investigations
ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014Co-Authors: Neil Luxcey, Svein-arne Reinholdtsen, Sébastien Fouques, Thomas Michel Sauder, Wojciech Kauczynski, Geir HovlandAbstract:The evacuation of personnel from offshore installations in severe weather conditions is generally ensured by free-fall Lifeboats. Their performance can be assessed by means of numerical simulations to estimate accelerations loads on occupants, structural loads on the lifeboat hull, as well as forward speed after water-exit. These parameters strongly depend on the water entry conditions of the lifeboat, which in turn are very sensitive to the previous phases of the launch that starts on the skid. On floating production, storage and offloading (FPSO) vessels in the Norwegian Sea, Lifeboats are often installed on skids at the bow so that waves may induce large skid motions with typical extreme vertical amplitude of fifteen to twenty meters in a 100-year storm condition. Moreover, wave-induced motions may also cause trim and list of the skid, which initiates more complex six degrees-of-freedom trajectories during free-fall. In such conditions, a proper modelling of the lifeboat trajectory on the moving skid is necessary in order to assess the performance of the lifeboat with numerical simulations.This paper investigates the effects of the wave-induced skid motion on the launch of free-fall Lifeboats from floating hosts. The first part of the paper describes the six-degrees-of-freedom numerical skid model used in MARINTEK’s lifeboat launch simulator VARUNA. The second part presents two model test campaigns aimed at validating the numerical skid model. The model test results are compared to those obtained from the numerical simulations. Finally, the importance of the skid motion on the lifeboat trajectory is discussed.Copyright © 2014 by ASME
-
effect of wind loads on the performance of free fall Lifeboats
ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014Co-Authors: Thomas Michel Sauder, Sébastien Fouques, Eloise Croonenborghs, Nabila Berchiche, Svein-arne ReinholdtsenAbstract:The paper presents a model describing the launch of free-fall Lifeboats from offshore structures in strong environmental wind.Six-degrees-of-freedom numerical simulations of the lifeboat launch are performed using the free-fall lifeboat simulator VARUNA with a complete set of wind coefficients for the lifeboat. Those wind coefficients are obtained by CFD simulations validated against wind tunnel tests. The lifeboat launch simulations are then verified against time-domain CFD simulations of the whole launch in air until water entry.It is shown by means of numerical simulations that wind-induced loads on the lifeboat have a strong influence on its kinematics until water entry, and subsequently on the acceleration loads experienced by the occupants, on the structural loads on the lifeboat, and on its forward speed after water exit.It is concluded that the effect of wind-induced loads on the lifeboat performances should in general be investigated when establishing the operational limits for a given offshore installation.Copyright © 2014 by ASME
-
human injury probability during water entry of free fall Lifeboats operational criteria based on long term simulations using hindcast data
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE OMAE2014-24074 4B, 2014Co-Authors: Sébastien Fouques, Svein-arne Reinholdtsen, Thomas Michel Sauder, J. UittenbogaardAbstract:The paper addresses the safety of occupants in free-fall Lifeboats launched from turret-moored floating production, storage and offloading (FPSO) vessels. It presents a methodology for assessing operational limits with respect to acceleration-induced loads experienced by the passengers during water entry. The probability of being injured is estimated by means of numerical simulations for several seat rows and in various sea states described in terms of significant wave height and mean wind velocity. Those results are therefore practical for on-site decisions regarding the use of the free-fall Lifeboats. The numerical simulations performed to estimate the 6-degrees of freedom (6-DOF) water entry accelerations in the Lifeboats are based on more than 50 years of hindcast metocean data. These consist of sea state parameters provided every third hour and including the significant wave height, the peak period and the direction of both wind-sea and swell as well as the direction and mean velocity of the wind. In a first step, the motion of the FPSO is computed for the whole time period covered by hindcast metocean data, using a state-of-the art numerical model validated against experimental data. The model includes nonlinear excitation forces, a dynamic positioning system with a realistic heading control strategy, mooring line forces as well as turret-hull coupling. The obtained FPSO motion is then used in Monte Carlo simulations of lifeboat launches performed for selected time windows in the original metocean hindcast database corresponding to selected intervals of the significant wave height and mean wind velocity. In addition to the 6-DOF skid motion, the lifeboat launch simulations account for the effects of wind and waves diffracted by the FPSO hull. Finally, a probabilistic model describing the joint-distribution of several injury types and water entry acceleration parameters computed through the launch simulations is used to evaluate the injury probability. The results are presented in term of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.
Makoto Arai - One of the best experts on this subject based on the ideXlab platform.
-
Water Entry Simulation of Free-fall Lifeboat
Journal of the Society of Naval Architects of Japan, 2009Co-Authors: Makoto Arai, M. Reaz H. Khondoker, Yoshiyuki InoueAbstract:Free-fall Lifeboats provide significant advances in the maritime lifesaving systems. Much of the danger associated with conventional lifeboat systems can be eliminated by this new evacuation method if the boat is launched selecting suitable launching parameters. A primary consideration in the freefall lifeboat system is the acceleration field to which the occupants are subjected during water entry. The international regulation, therefore, requires that a lifeboat for free-fall launching shall be capable of ensuring protection against harmful accelerations when it is launched with its full complement of persons and equipment from at least the maximum designed height.When the lifeboat enters the water, the acceleration forces exerted upon the boat due to impact are very high. According to the basic study upon the human body response, tolerance level for acceleration is different for each axis of the human body. Therefore, the safe seats in a free-fall lifeboat are usually reclined relative to the axes of the lifeboat to reduce the effect of high accelerations. In this paper, the authors introduce a new and probably the simplest concept to evaluate the acceleration field of the free -fall lifeboat and apply it to the analysis of the safe seat orientation for the occupants. The results have been compared with those of the SRSS acceleration criteria and the dynamic response criteria, both of which are recommended by the IMO, and good agreement has been found.
-
new launching concept for free fall Lifeboats and validation by model experiments and numerical simulations
Journal of ship and ocean technology, 2002Co-Authors: Makoto AraiAbstract:A new concept for launching free-fall Lifeboats, proposed by Yokohama National University is described in this paper. It has been pointed out that, using the conventional single-skid free-fall system, the potential for dangerous lifeboat motions (in which the lifeboat moves backward or jerks on the surface after entering the water) increases with the fall height of the lifeboat. One of the principal causes of this undesirable motion is vertical rotation of the lifeboat during its restricted fall at the edge of the launching skid. Thus a new "double-skid"launching concept is proposed to effectively eliminate the rotation of the lifeboat at the skid end and to enable the lifeboat to move smoothly after entering the water. In order to evaluate the performance of the proposed method, a series of model experiments and numerical simulations is carried out in which two lifeboat models with overall lengths of 1 meter and 6 meters are used. The effects of design parameters such as skid angle and skid height are investigated, and an example of the implementation of this new system at the stern of a large merchant ship is illustrated.
-
a new launching concept for free fall Lifeboats
Major hazards offshore. Conference, 2000Co-Authors: Makoto AraiAbstract:Free-fall lifeboat is a newly developed evacuation system suitable for use in large merchant ships and offshore structures. Although its efficient launching performance, the motion of the boat after water entry can become a dangerous one if the launching conditions such as fall-height, launch-skid angle are not appropriate. In this paper, detailed studies on the boat motion and exerted acceleration on hull structure, by using a series of model experiments and a numerical method developed by our group, are described. Specific characteristics of the system become clear by those studies. The authors, thus, propose a new launching method that improves the motion of the free-fall lifeboat launched from the conventional skid. Remarkable improvement of the lifeboat motion after water entry is illustrated. Results of a large-scale model experiment with 6 m long GFRP lifeboat model will be shown to validate the behaviours of our proposed new launching method.
-
double skid method for launching free fall Lifeboats
Journal of the Society of Naval Architects of Japan, 1999Co-Authors: Makoto Arai, Kazushige Okazaki, Shinichi KamimuraAbstract:This paper describes a new concept for launching free-fall Lifeboats proposed by Yokohama National University. Using the conventional single-skid free-fall system, as the fall height of the lifeboat increases, the potential for increasing incidence of dangerous lifeboat motions, in which the lifeboat moves backward or stumbles on the surface after entering the water, has been pointed out. One of the principal causes of this undesirable motion is rotation of the lifeboat during its restricted fall at the edge of the launching skid. Thus a new “double- skid” launching concept is proposed to effectively eliminate the rotation of the lifeboat at the skid end and to enable the lifeboat to move smoothly after entering the water. In order to confirm the performance of the proposed method a series of numerical simulations and model experiments are carried out in which two lifeboat models with overall lengths of 1 meter and 6 meters are used. The effects of design parameters such as skid angle, skid height, etc., are investigated and an example of the implementation of this new system at the stern of a large merchant ship is illustrated.
-
effects of hull shape and launching conditions on the behaviors of free fall Lifeboats after water entry
Journal of the Society of Naval Architects of Japan, 1999Co-Authors: Makoto Arai, Shinichi Kamimura, Katsuhiro Harano, Yutaka HashizumeAbstract:In the research and development of free-fall lifeboat systems, emphasis has been mainly on the performance confirmation tests using full-scale prototype boats. On the other hand, fundamental studies that illustrate the behaviors of free-fall Lifeboats during water approach and entry have not been sufficiently carried out. The purpose of this paper is to show the effectiveness of a numerical simulation method in evaluating quantitatively the effects of hull shape and launching conditions on the behaviors of free-fall Lifeboats. Two lifeboat models having different hull shape, weight distribution, moment of inertia, etc., are utilized in a series of model experiments. Computed results such as boat motion and impact acceleration on the hull are compared with measured ones, and the comparison confirms the validity of our numerical method. The marked effect of guide rail length on boat motion and acceleration are also illustrated. In the case of a boat with an extreme transom stern, it is found that an impulsive force is exerted on the stern during the run of the boat below the water surface. A sharp bow, shown herein, is effective for smooth evacuation motion.
Svein-arne Reinholdtsen - One of the best experts on this subject based on the ideXlab platform.
-
Integrity Assessment of a Free-Fall Lifeboat Launched From a FPSO
Volume 3: Structures Safety and Reliability, 2015Co-Authors: Guomin Ji, Thomas Michel Sauder, Sébastien Fouques, Nabila Berchiche, Svein-arne ReinholdtsenAbstract:The paper addresses the structural integrity assessment of lifeboat launched from floating production, storage and offloading (FPSO) vessels. The study is based on long-term drop lifeboat simulations accounting for more than 50 years of hindcast data of metocean conditions and corresponding FPSO motions. Selection of the load cases and strength analyses with high computational time is a challenge. The load cases analyzed are those corresponding to the 99th percentile of long term distribution of indicators for large slamming loads (CARXZ) or large submergence (Imaxsub). For six selected cases, the time-varying pressure distribution on the lifeboat hull during and after water impact is calculated by CFD simulations using StarCCM+. The finite element model (FEM) of the composite structure of the lifeboat is modelled by ABAQUS. Quasi-static finite element (FE) analyses are performed for the selected load cases. The structural integrity is assessed by the maximum stress and Tsai-Wu failure measure.In the present study, the load and resistance factors are combined and applied to the response. A sensitivity study is performed to investigate the non-linear load/response effects when the load factor is applied to the load. In addition, dynamic analysis is performed with the time-varying pressure distribution for selected case and the dynamic effect is investigated.Copyright © 2015 by ASME
-
Reliable and efficient injury assessment for free-fall lifeboat occupants during water entry: Correlation study between lifeboat acceleration indicators and simulated human injury responses
Volume 4B: Structures Safety and Reliability, 2014Co-Authors: J. Uittenbogaard, Svein-arne Reinholdtsen, Sébastien Fouques, Thomas Michel SauderAbstract:The evacuation of personnel from an offshore installation in severe weather conditions is generally ensured by free-fall Lifeboats. During the water entry phase of the launch, the lifeboat may be subject to large acceleration loads that may cause harmful acceleration-induced loads on the occupants. The present/common methodology for assessing the occupant safety of free-fall Lifeboats uses one single characteristic launch to perform injury risk analysis for a given free-fall lifeboat launch condition that includes e.g. weather conditions, lifeboat and host installation loading conditions. This paper describes an alternative methodology to fully assess the risk of injury for lifeboat occupants during water entry by introducing a correlation model between acceleration load indicators and injury responses. The results are presented in terms of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.
-
influence of wave induced skid motions on the launch of free fall skid Lifeboats from floating hosts experimental and numerical investigations
ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014Co-Authors: Neil Luxcey, Svein-arne Reinholdtsen, Sébastien Fouques, Thomas Michel Sauder, Wojciech Kauczynski, Geir HovlandAbstract:The evacuation of personnel from offshore installations in severe weather conditions is generally ensured by free-fall Lifeboats. Their performance can be assessed by means of numerical simulations to estimate accelerations loads on occupants, structural loads on the lifeboat hull, as well as forward speed after water-exit. These parameters strongly depend on the water entry conditions of the lifeboat, which in turn are very sensitive to the previous phases of the launch that starts on the skid. On floating production, storage and offloading (FPSO) vessels in the Norwegian Sea, Lifeboats are often installed on skids at the bow so that waves may induce large skid motions with typical extreme vertical amplitude of fifteen to twenty meters in a 100-year storm condition. Moreover, wave-induced motions may also cause trim and list of the skid, which initiates more complex six degrees-of-freedom trajectories during free-fall. In such conditions, a proper modelling of the lifeboat trajectory on the moving skid is necessary in order to assess the performance of the lifeboat with numerical simulations.This paper investigates the effects of the wave-induced skid motion on the launch of free-fall Lifeboats from floating hosts. The first part of the paper describes the six-degrees-of-freedom numerical skid model used in MARINTEK’s lifeboat launch simulator VARUNA. The second part presents two model test campaigns aimed at validating the numerical skid model. The model test results are compared to those obtained from the numerical simulations. Finally, the importance of the skid motion on the lifeboat trajectory is discussed.Copyright © 2014 by ASME
-
effect of wind loads on the performance of free fall Lifeboats
ASME 2014 33rd International Conference on Ocean Offshore and Arctic Engineering, 2014Co-Authors: Thomas Michel Sauder, Sébastien Fouques, Eloise Croonenborghs, Nabila Berchiche, Svein-arne ReinholdtsenAbstract:The paper presents a model describing the launch of free-fall Lifeboats from offshore structures in strong environmental wind.Six-degrees-of-freedom numerical simulations of the lifeboat launch are performed using the free-fall lifeboat simulator VARUNA with a complete set of wind coefficients for the lifeboat. Those wind coefficients are obtained by CFD simulations validated against wind tunnel tests. The lifeboat launch simulations are then verified against time-domain CFD simulations of the whole launch in air until water entry.It is shown by means of numerical simulations that wind-induced loads on the lifeboat have a strong influence on its kinematics until water entry, and subsequently on the acceleration loads experienced by the occupants, on the structural loads on the lifeboat, and on its forward speed after water exit.It is concluded that the effect of wind-induced loads on the lifeboat performances should in general be investigated when establishing the operational limits for a given offshore installation.Copyright © 2014 by ASME
-
human injury probability during water entry of free fall Lifeboats operational criteria based on long term simulations using hindcast data
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE OMAE2014-24074 4B, 2014Co-Authors: Sébastien Fouques, Svein-arne Reinholdtsen, Thomas Michel Sauder, J. UittenbogaardAbstract:The paper addresses the safety of occupants in free-fall Lifeboats launched from turret-moored floating production, storage and offloading (FPSO) vessels. It presents a methodology for assessing operational limits with respect to acceleration-induced loads experienced by the passengers during water entry. The probability of being injured is estimated by means of numerical simulations for several seat rows and in various sea states described in terms of significant wave height and mean wind velocity. Those results are therefore practical for on-site decisions regarding the use of the free-fall Lifeboats. The numerical simulations performed to estimate the 6-degrees of freedom (6-DOF) water entry accelerations in the Lifeboats are based on more than 50 years of hindcast metocean data. These consist of sea state parameters provided every third hour and including the significant wave height, the peak period and the direction of both wind-sea and swell as well as the direction and mean velocity of the wind. In a first step, the motion of the FPSO is computed for the whole time period covered by hindcast metocean data, using a state-of-the art numerical model validated against experimental data. The model includes nonlinear excitation forces, a dynamic positioning system with a realistic heading control strategy, mooring line forces as well as turret-hull coupling. The obtained FPSO motion is then used in Monte Carlo simulations of lifeboat launches performed for selected time windows in the original metocean hindcast database corresponding to selected intervals of the significant wave height and mean wind velocity. In addition to the 6-DOF skid motion, the lifeboat launch simulations account for the effects of wind and waves diffracted by the FPSO hull. Finally, a probabilistic model describing the joint-distribution of several injury types and water entry acceleration parameters computed through the launch simulations is used to evaluate the injury probability. The results are presented in term of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.
