OSV Rules Singapore

August 2009

Class Rules and Complementary CFD Simulations for Offshore Service Vessels (OSVs)

Helge Rathje, Thomas E. Schellin, and Jan Kaufmann

August 2009 OSV Rules No. 2

Class Notation: Offshore Service Vessel - OSV

Statutory Rules: Resolutions, Guidelines, Codes, etc.

Design and Construction IMO A.469 (XII)

Transport of Hazardous Liquid Substances IMO A.673 (16)

Dynamic Positioning IMO MSC/Circ.645

Safe Practice for Carriage of Cargoes and Persons IMO A.863 (20)

Prevention of Collisions at Sea COLREGs (1972)

Practical Constraints

Guard rails

Double bottom and stern tubes

Bridge visibility

Navigational lights


Additional Class Notations

Oil recovery and transportation_____________________________________________

Special Purpose Ship

Oil Recovery______________

SPS

Standby and rescueStandby

Fire fightingFire Fighter

Well stimulationWS

Anchor handlingAH

Carrying hazardous and noxious liquid substancesHNLS

Offshore Service VesselOSV


Offshore Service Vessel - General

Hull Arrangement and Strength

Cargo Handling Arrangement

Intact Stability

Subdivision and Damage Stability

Superstructures and Deckhouses

Windows and Side Scuttles

Equipment


Hull Arrangement and Strength

Special requirements for fenders, frames, shell plating, and side longitudinals

Cargo deck plating minimum thickness of 8 mm

strengthened deck in areas of heavy cargo units (drilling rig anchors)

wooden sheathings should cover the deck

Stow racks, steel cradles, or steel or wooden dunnage to uniformly distribute cargo weight in deck structures

Freeing ports to ensure drainage of water trapped in pipe deck cargoes and in

recesses at aft end of forecastle


Cargo Handling Arrangement

Special requirements

ships that occasionally handle, store, and transport recovered oil from a spill

ships intended for transportation of liquids with flash point below 60C Cargo pumps

remote shut down devices

segregation between cargo piping systems by means of spectacle flanges, spool pieces, etc.

Cargo tanks for dry cement or mud

to be separated from engine room and accommodation spaces by steel bulkheads and decks

Tanks for hazardous and noxious liquid cargo

quantities of cargo are limited (800 m or 40% of ship deadweight)

separated from other spaces by cofferdams


Intact Stability Stability manual

to assess the ships stability in different service conditions

Loading conditions

ship fully loaded departure and arrival

ship in ballast departure and arrival

ship in worst anticipated operating condition

ship while towing

Assumptions for calculating loading conditions

cargo tanks are full as well as empty

account for deck cargo and water ballast

account for free surface effects of partially filled tanks

Stability requirements for towing

maximum righting lever > 50% of heeling lever caused by pull of towing line

account for effects of anti-rolling tanks


Subdivision and Damage Stability

Damage stability manual

limiting VCG and GM values

permissible range of static stability of operation

Assumptions for calculating loading conditions

damage anywhere along the ships length between transverse watertight bulkheads

vertical and transverse extent of damage

account for progressive flooding caused by tunnels, ducts, pipes, etc.

account for permeability of damaged compartments

Damage stability criteria

account sinkage, trim, and heel caused by progressive flooding through openings

heel angle from asymmetric flooding < 15 or 17 if the deck does not immerge stability must be sufficient during intermediate and final stages of flooding


Windows and Side Scuttles

Windows

2nd tier and higher above freeboard deck in aft deck end bulkhead and in deckhouse sides

3rd tier and higher above freeboard deck in forward bulkheads of deckhouse

Deadlights and storm covers on windows

at deckhouse sides in 2nd and 3rd tier and at aft end bulkheads

wooden sheathings should cover the deck

on windows in wheelhouse front

Side scuttles

to comply with ISO Standard 1751

Arrangement of windows and side scuttles


Equipment

Towing arrangement to satisfy requirements for anchor handling tug/supply vessels

Steering gear capable of changing rudder angle from 35 to 30 on the opposite side in 28 s

Exhaust outlets to be located as high as practical above deck

to be fitted with spark arresters

Anchoring equipment

increase diameter and length of chain cables above minimum class requirements

Chain locker arranged as gas-safe spaces

hull penetrations for chain cables to be arranged outside gas-dangerous spaces


HNLS Vessel for Carrying Hazardous and Noxious Substances

Products that may be carried

hazardous and noxious liquids listed in table of permitted cargoes for chemical ships

noxious liquids that would be permitted for carriage on chemical ships (flash point < 60C)

Cargo area

includes cargo tanks, cargo pump rooms, hold spaces, cofferdams, ballast or void spaces surrounding integral tanks, and deck areas

Cargo segregation

by means of a cofferdam, void space, cargo pump room, empty tank, or fuel oil tank

separate pumping and piping systems, separate venting system

cargo not to be carried in fore or aft peak tanks

Cargo tanks

to be constructed according to rules for gas ships or chemical ships

to have vapor detection and alarm systems, gaging and level detection systems, emergency shutdown systems, decontamination showers, and protective safety equipment

Accommodations, machinery spaces, and control stations

not to be located within the cargo area

entrances, air inlets, openings, service and machinery spaces should not face the cargo area


AH Anchor Handler

Structural configuration clear deck

winches to deploy and recover anchors

stern roller

chain lockers under the main winch

shark jaws, towing pins, heavy duty bollards

reinforced shell plating

Working deck deck area protected by wooden sheathing

Equipment foundations to be reinforced for deck equipment, such as winches and stern rollers


WS Well Stimulation Vessel Arrangement

tanks and pumps not to be located within accommodation areas

tanks for acid and liquid nitrogen to be located at least 760 mm from ships sides and bottom

tanks and piping systems for well stimulation to be separated from machinery

acid spill protection is to be provided

emergency shutdown systems

Ventilation independent ventilation systems for spaces housing installations for acid

enclosed spaces containing tanks, piping, pumps, etc. to have entrances from open deck through air locks with independent mechanical ventilation

Liquid nitrogen system, acid system in accordance with special requirements

Personal protection decontamination showers

personal protective equipment


Fire Fighter

Service notation category 1 for early stage fire fighting and rescue

category 2 for continuous fire fighting of large fires from a safe distance

category 3 larger water pumping capacity and more comprehensive fire fighting equipment

Maneuverability side thrusters and sufficiently powerful propulsion for fire fighting operations

power management system to avoid overloads

Protection against external heat radiation water spraying system

hull and superstructure to be constructed of steel

Water and foam monitors number and characteristics to be in accordance with service notation


Standby Vessel

Rescue zone clearly marked rescue zone of at least 8 m length on each side

ships sides to be clear of obstructions (no fenders)

satisfactory lighting along rescue zone

deck area free of pipes valves, hatches, etc.

searchlights on each side of the ship

power assisted scrambling net on each side of the ship

Survivors accommodation treatment room for casualties

Safety equipment at least 1 fast rescue craft

SOLAS approved life buoys

immersion suit for each crew member

lifejackets for crew and survivors


Oil Recovery Vessel

Arrangement suitable working deck

storage tanks for recovered oil

adequate visibility from maneuvering station

pumping and piping for transfer and discharge of recovered oil

Fire protection exterior boundaries of superstructures to be insulated to A-60 standard

insulation to A-0 standard is acceptable if water spray system is installed

Tanks cofferdams separate tanks for recovered oil from accommodations and engine room

Hazardous areas zone 0 interior spaces

zone 1 cargo pump room, enclosed spaces with flanges and/or valves, etc.

zone 2 cofferdams and spaces adjacent to tanks for recovered oil


Complementary Computations

1. OSV in head seas Design pressures on bow and superstructure

Regular waves:

6.5 m height

7.5 s period

Twin propellers, 500 kN thrust each

2. OSV in following seas Dynamic stability - capsizing

Natural seaway:

4.0 m sig. wave height

7.5 s mean period

Zero speed running of an anchor

Port side of stern rail - open


RANS Solver COMET

Nonlinear RANSE computations

Finite amplitude (high) waves

Finite volume method

Interface-capturing technique

Volume of fluid (VOF) method

3D effects, no explicit free surface

Two-phase flow formulation, free surface flows

Overturning (breaking) waves

Flow separation, vortex formation

Air trapping

Disturbed waves

Viscous effects

Fully geometric modeling of body

Principal particulars of OSV

11 000 tDisplacement

6.5 mDraft

22 mMolded breadth

100 mLength bet. pp

Numerical grid on surface of OSV


Wave-Induced Loads on Bow of OSVPressure [kPa] at bow

Pressure distribution

OSV in head seas

Max. computed pressure = 118 kPa

Rule design pressure = 105 kPa


Capsizing of OSV

Zero forward speed

Following waves, H = 4.0 m

6 DoF motions

Grid morphing technique

Computed pitch Computed roll Computed yaw


Mesh DeformationGrid morphing technique mesh adoption to rigid body motions,

enabling computation of large rotational motions


Capsizing of OSV in Following Waves

Elapsed time = 200 s Elapsed time = 600 s

Elapsed time = 700 s Elapsed time = 800 s Elapsed time = 900 s

Series of screen shots


Thank you for your attention

OSV Rules Singapore

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