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Stability and Flooding

This presentation provides an overview of stability criteria, intact and damage stability, and the impact of flooding progression on vessel safety. It discusses the importance of monitoring stability for vessel certification and addressing flooding risks. The case study of the Alaska Ranger highlights the consequences of astern travel and rudder loss on stability and flooding progression. Insights into the propulsion system, including causes of astern travel and system modifications, are also discussed.

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Stability and Flooding

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  1. Stability and Flooding Eric Stolzenberg

  2. Presentation Overview • Stability • Flooding progression • Impact of physical rudder loss • Effects of astern travel

  3. Vessel Configuration Fishing Vessel Alaska Ranger OSV Ranger Wheelhouse Fo’c’sle Deck Trawl Deck Factory Deck Ramp Freezers Processing Area Machinery Spaces Hold Rudder

  4. Stability • Stability criteria • Intact stability: capsizing • Damage stability: flooding • Stability requirements • Necessary for vessel certification • Incorporate stability criteria

  5. Vessel Intact Stability • Owner monitored stability • Not required • Intact stability through T&S booklet • Damage stability not monitored or required • Postaccident Coast Guard MSC review • Stability test confirmed • T&S booklet met requirements • Intact stability met requirements

  6. Intact Stability Margin • Large stability margin prior to sinking • Downflooding points located aft • Engineroom intake vents • Aft trim conditions at deeper drafts quickly reduced the margin

  7. Flooding Progression

  8. Flooding Progression — Profile Aft Fish Bin (Freezer)

  9. Flooding Progression — Plan Watertight Bulkheads Watertight Bulkhead

  10. Flooding Rate Verification Coast Guard scenarios Estimate 5 minutes to flood rudder room Estimate 50 minutes for water to reach switchboard Electrical switchboard Will short if flooded Vessel loses electrical power Loss of rudder flooding rate roughly corresponds to event timeline

  11. Rudder Lock Nut Thrust Bearing Rudder Stock Hull Starboard Rudder Upper Rudder Assembly

  12. Vessel Traveling Astern • Exacerbated flooding • Increased rate • Decreased distance to downflooding points • Increased pressure on hatches and doors • Prevented crew from entering liferafts

  13. Stability and Flooding Summary • Vessel had adequate intact stability • Most likely encountered rudder loss • Would not have sunk if flooding contained to rudder room • Sank from uncontrolled progressive flooding • Astern travel accelerated flooding

  14. Propulsion System Eric Stolzenberg

  15. Presentation Overview • Causes of astern travel • Propulsion system overview • Propulsion system modification • Means to stop travel

  16. CPP System Overview

  17. Propulsion System Layout Gear Propulsion Shaft Port main engine Propeller Hydraulic pumps Main Switchboard Propeller Stbd main engine Propulsion Shaft Gear

  18. Spindle Torque Forces Spindle Axis Centrifugal Force Net Spindle Torque Hydrodynamic Lift ASTERN Hub Rotation Rolls-Royce

  19. CPP Hub Rolls-Royce

  20. CPP System Modifications Port Engine Stbd Engine Main Switchboard Port CPP Hydraulic Pumps Stbd CPP Hydraulic Pumps

  21. Consequences of Modifications Stbd Propeller Port Propeller

  22. Astern Travel Summary • Causes • CPP pump modifications affected system redundancy • Astern travel resulted from electrical power loss • Engines were still turning propeller shafts • Stopping astern travel • No means to control blade pitch • Crew could have secured engines to stop shaft

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