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Presentation of the OLF/NSA Davit-Launched Lifeboats Project
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Transcript of Presentation of the OLF/NSA Davit-Launched Lifeboats Project
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OLF/NSA Davit-Launched Lifeboat Project (DLLBP)Summary by Project Manager Ole Gabrielsen
Contents
• Brief historical overview
• Findings and conclusions for four phases:• Lowering
• Water entry (landing)
• Release of wire falls
• Sail-away
• Test run of lifeboat engines
• Raft HAZID
• Main conclusions
28.10.2011
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Brief historical overview of DLLBP• Initiated in December 2009, completed in Juni 2011.
• Scope of work defined based on findings from NSA Lifesaving Appliances Project (LAP) and previous work for davit-launched lifeboats.
• Funded by Norwegian Shipowners’ Association and The Norwegian Oil Industry Association (OLF).
• Organized in six work packages:• WP 1 – Release systems
• WP 2 – Lowering, landing and sail-away
• WP 3 – Forces on occupants
• WP 4 – Third-party verification of WP 2
• WP 5 – Raft HAZID, test run of lifeboat engines and evacuation methodology
• WP 6 – Hull capacity
• Work performed by consultancy companies reporting to project manager.
• Project managed by an Owners’ Group with representatives from oil companies and drilling rig companies with davit-launched lifeboats.
• The overall goal of the project was to provide guidance/advice to use of existing davit-launched lifeboats such that these, as far as reasonably possible, can continue to satisfy the intentions laid down in the regulations.
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Lowering Phase (1/2)
• A considerable amount of simulations performed in wind spectres with gust winds
• Key parameters:• Loaded and empty boat
• Three lowering heights(22, 50 og 80 m)
• Three lowering speeds(0.5, 0.9 og 1.5 m/s)
• Three wind speeds(Beaufort 10, 11 og 12)
• Three wind directions(beam wind, bow quartering and near to head wind)
• Example of plots on the right
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Lowering Phase (2/2)
• A lowering speed of around 1.0 m/s appears to be a sound compromise between acceleration levels and release window requirements (time from water entry until the wave moves downwards).
• Lifeboat lowering from great heights (more than 50 m) in strong wind may lead to large pendulum motions.
• The project recommends implementation of ‘pull & go’ loweringlåring, if not already implemented by the owners.
• ‘Pull & go’ launching of lifeboats is in line with NORSOK R-002, but in conflict with requirements from IMO through SOLAS/LSA-code.
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Water Entry – Forces on Occupants (1/3)
• Work based on acceleration pulses generated for :• 3 boats
• 2 lowering speeds (0.9 m/s og 1.5 m/s)
• 5 wave directions (0, 45, 90 (beam sea), 135, 180 (head sea) degrees)
• 7 wave conditions (8.5, 11.7, 14.7, 16.0, 17.0, 17.8 and 20.3 m regular waves corresponding to rough waves in 100-year storms)
• 6 seats per boat
• Injury evaluation according to levels established by the Free-fall Lifeboat Project (Human Load Level)
• Selected simulations compared to laboratory tests.
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Below lower limit Between lower and upper limit Above upper limit
Water Entry – Forces on Occupants (2/3)
• There is a minor risk of injury to lifeboat occupants during water entry, even in waves representing extreme conditions.
• The largest risk occurs in beam sea conditions, mainly related to high loads on head and neck.
Boat 1 Boat 2 Boat 3
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Water Entry – Forces on Occupants (3/3)
• Another study investigated the effect of various parameters such as posture, belt arrangement and use of cushions. Proposals for improvement have been established.
• An assessment of the interaction between occupants sitting next to each other, opposite each other and back-to-back did not reveal any critical effects, but highlighted the possibility of collision between occupant if 2-point belt systems are used.
• A third study looking at the effect of body sizes concluded that the overall conclusions for forces on occupants are valid also for smaller and bigger occupants.
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Water Entry – Hull Capacity (1/3)
• The slamming methodology developed by the FFLBP was adjusted and applied to davit-launched lifeboats.
• Main steps in method:• Selection of design loads and load factors
• Establish skin model of lifeboat with indicator panels
• CFD analyses giving pressure on indicator panels
• Preparation of structural model of lifeboat
• Load mapping onto structural model
• Evaluation of stress and deflection
• The hull slamming capacity of two davit-launched lifeboats have been evaluated.
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Water Entry – Hull Capacity (2/3)
• The analyses show that the lifeboats have sufficient capacity for head sea and bow quartering sea. Requirements may be required for beam sea, stern quartering sea and following sea.
• Further work is required to determine specific reinforcements to each type of boat.
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Water Entry – Hull Capacity (3/3)
• Video from CFD-simulationCFD = Computational Fluid Dynamics
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Release Phase (1/4) - Summary• Survey of release systems
• Existing systems in use
• Novel systems under development
• Gap analysis vs. NORSOK R-002
• Development of new release systems is required to fulfil all requirements of NORSOK R-002 (Preliminary edition April 2010).
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Release Phase (2/4) - Summary• Simulation parameters
• 2 lifeboats
• 2 lowering heights (28 m and 80 m)
• 3 lowering speeds (0.5 m/s, 0.9 m/s and 1.5 m/s)
• 5 weather directions (0, 45, 90 (beam sea), 135, 180 (head sea) deg)
• 6 sea states (7.5, 10, 13, 15, 18 and 20 m – regular waves corresponding to rough waves in a 100-year sea state)
• 10 landing positions in each wave
• It is important to release the lifeboat from the wire falls as soon as it is waterborne (on the first wave) to prevent re-entry. Rapid release is vital to avoid detrimental loads on occupants and on the lifeboat itself.
• Time to release (time from the boat is in contact with the water until the wire falls are released) should be less than 3 seconds. For a time to release of 3 seconds there is a very small risk of severe re-entry loads.
• The risk of severe re-entry loads is eliminated for a time to release of 1 second.
• The importance of rapid release should be communicated to lifeboat crews and training centres so that the crew may practice rapid releases.
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Release Phase (3/4) - Results
Lowering speed: 0.9 m/s
97 %
71 %
22 %
0 %
10 %
20 %
30 %
40 %
50 %
60 %
70 %
80 %
90 %
100 %
0 10 20 30 40Time from water contact to release (s)
Perc
enta
ge o
f no
n-ex
ceed
ence
(%
)
Time to release = 1.0 sTime to release = 3.0 sTime to release = 5.0 s
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Release Phase (4/4) – Full-scale Tests
• Full-scale tests have been performed for several release systems. The newest systems have results from 1 to 1.5 seconds.
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Sail-away Phase (1/3)
• A study of the sailing phase concludes that the setback for davit-launched lifeboats in head sea and bow quartering sea is considerable even at moderate sea states (Beaufort force 7).
• The setback is influenced by engine size and delay or no delay in engagement of propulsion.
• For beam sea, following sea and stern quartering sea the setback is small.
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Sail-away Phase (2/3)
• Setback in head sea
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Sail-away Phase (3/3)
• Setback in bow quartering sea
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Overview of numerical simulations
Phase(s) Scope/objective Number of simulations
Låring/fri-gjøring
Effect of delayed release and lowering speed on peak accelerations at water entry, wire forces and CAR index
3 600
Study of pendulum effects; effect of lowering speed and weight
9 900
Water entry
Establish peak accelerations (acceleration pulses) 3 500 (giving 21 000 acceleration pulses)
Evaluation hull capacities 20 CFD analyses
40 structural analyses
G-force parameter study: belt systems, postures, cushions
156
Interaction between occupants with 2-point belt systems
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Boat-specific analyses of G-forces during water entry 1 260
Injury potential in extreme re-entry loads 55
Study of correlation between numerical simulations of dummy models and human models
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Sail-away Simulation of setback and propulsion in various sea states
12 600
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Procedure for Test Run of Lifeboat Engines
• A separate study evaluating the procedure for test run of lifeboat engines concluded that idle-running should not exceed 3 minutes to avoid soothing that may impair the engines maximum output.
• The optimal test interval is every second week (in contrast to SOLAS which prescribes once a week).
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HAZID of Raft Systems
• The HAZID report highlights that the owners should, in cooperation with equipment suppliers, evaluate amount and type of training to ensure high probability of correct use.
• The importance of correct training was called for by the employee representatives who participated in the HAZID.
• The HAZID revealed a number of uncertainties which should be evaluated by the owners.
• It is the responsibility of the owners to evaluate the findings of the raft HAZID and to initiate any minigating measures.
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Main Conclusions
Lowering • A loweing speed of around 1.0 m/s is recommended.
• Pull & go principle should be implemented.
Water Entry • There is a small risk of injury for occupants during water entry.
• Hull reinforcement should be evaluated.
Release • Development of novel release systems is required to fulfil all requirements of NORSOK R-002 (April 2010 edition).
• Detrimental re-entry loads (on occupants and boat) in the release phase can be avoided by ensuring rapid release of wire falls.
Sail-away • The setback in head sea and bow quartering sea can be considerable.
• The setback may be reduced by optimazing the bollard pull and launching procedure.
Other • The findings from the project should be implemented in training programs for lifeboat crew.
• The owners should address the findings of the raft HAZID.
• Idle-running should not exceed 3 minutes to avoid soothing that may reduce the engine’s maximum output. The optimum test interval is every second week.
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