1 - The Different Phases of a Subsea Lift From an Offshore Construction Vessel - KTF 2009

SUBSEA LIFTING OPERATIONS

The different phases of a subsea lift from an offshore construction vessel 02/12/09 – Vidar Kupen

2Subsea Lifting Operations 2009

Preparations for offshore lifting- Structures, installation vessel and project specific requirements

- Engineering tools

- Available equipment / tools on vessel

Lifting offshore - Different phases of subsea lift- Seafastening

- Lift-off from deck

- Slewing / overboarding

- Through the splash zone

- Landing phase

- Recovery to deck

Summary

Contents


Preparations for offshore liftingInstallation vessel, structures and project specific requirements

Engineering toolsAvailable equipment / tools on vessel


Installation vessel - Skandi Arctic

Main DimensionsLength overall: 156.9 m

Breadth: 27.0 m

Depth to 1st deck: 12.0 m

Draft (design): 6.5 m

Draft (scantling): 8.5 m

Cranes400 Te box boom crane NOV

58 Te knuckle boom crane


Structures - ManifoldMain dimensions L x B x H, 20.3 x 15.0 x 6.1 m

Weight 175 Te

Supported on circular mudmats

Large area roof hatches

Manifold at Skandi Arctic deck


Main dimensions 9 off spools.

L and Z-shaped, pipe dimension 4”, 6” and 10”

Heavy terminations: Termination heads (2.5 Te) and SPEMs (5.0 Te)

Typical termination head

Typical SPEM

Structures - Spools

Spools at load-out quay


Presence of drill rigWhen overboarding and landing spools

Operations inside 500m zone, no welding allowed

Positioning systems relative to drill rig when landing

Risk of reduced visibility when cementing wells

Landing inside existing structures, ROV to observe closely to avoid clash

Project specific requirements





Engineering toolsIAF – Incident Analysis and Feedback:Database with records of incidents in recent projects (2002 onwards).

Consulted when starting new projects, in risk assessment, HAZOP etc.

“To avoid repeating costly mistakes, and to understand the reason for these mistakes. Its objective is to improve the quality of our work “


Engineering toolsAutocad useful tool for:- Deck layouts, 3D models for complicated spool layouts

- Installation sketches

- Clearance to ship side / crane

- Lift radius vs crane capacity and hook height

Clash check & verification of hook height

Spool

Deck layout


Engineering tools

Deck layout

Simulation of Marine Operations, SIMO:Installation analyses:

- Splash zone (slack slings, crane capacity)

- Crane tip motion (landing criteria)

Input:

- Vessel description

- Describe installed object (weight, buoyancy, CoG, slamming, drag, added mass)

- Environmental data

SIMO – Analysed submergence levels


Engineering toolsSimulation of Marine Operations, SIMO:Output:

- Sling tension (time history or statistical)

- Crane tip motion (position, velocity & acceleration)

http://www.sintef.no/Home/Marine/MARINTEK/Software-developed-at-MARINTEK/SIMO/

SIMVIS – Visualisation of SIMO analysisStatistical representation of results


Engineering toolsShip Manoeuvring Simulator Centre, SMSC: Simulation of lift using crane drivers from Skandi Arctic. Tool helpful for:

- Planning deck layout, positioning of bumpers, tagging towers and check for clashes

- Simulate operations. Videos used for familiarisation meetings, HAZOPs etc.

- Training for crane drivershttp://www.smsc.no/

SMSC – Skandi Arctic lifting spools SMSC – Control room “bridge”


Engineering toolsShip Manoeuvring Simulator Centre, SMSC:





Available equipment / tools on vesselEquipment available for controlling the load:Lift-off: Endless rope taglines (riggers)

In air: Tagging towers with winches +

Crane tugger winches

Landing: Guidewire winches + Clumpweight

Tagging Towers

Crane tugger winchesGuidewire winches


Different phases of offshore liftToolbox talkSeafastening

Lift riggingLift-off from deck

Slewing / OverboardingSplash zone

LandingRecovery


Toolbox talkOperational personnel gathered to discuss:Installation procedure / work plan

Lift plan & rigging specifications drawing

Deck layout

Contingency operations

Experiences from load-out





LandingRecovery


Seafastening / Mudmat interface:Curved steel plate to establish contact between mudmats and seafastening beams.

To be shimmed towards mudmat.

- Confirm seafastening design is acceptable

- No welding to mudmat / manifold

Seafastening - Manifold


Spools at different elevations: Bumpers integrated in supports for spool ends, SPEM and termination head.

Flexible supports for spool piping

Cargo strops

Seafastening - Spools


Spreader frame resting 4.0m above deck level: Bumpers integrated in supports.

Guiding spreader frame into position offshore.

Cargo strops for easy release and to re-establish seafastening

Seafastening - Spreader Frame





LandingRecovery


Lift rigging, spool to spreader frameSafe connection from deck level: Spreader frame resting in supports, no personnel under suspended loads.

Pre-rigged slings on spools and spreader frame

ROV shackles for subsea release. ROV hooks not used due to potential of release during installation.


Lift rigging, spreader frame to tuggersSafe connection from deck level: Spreader frame resting in supports, no personnel under suspended loads.

ROV hooks for subsea release and connection during recovery

Crane tuggers

Tagging towers


Lift rigging, spreader frame to crane hookSafe connection from deck level: Spreader frame resting in supports, no personnel under suspended loads.

Lift slings inside spreader frame, hook lowered to deck level





LandingRecovery


Lift-off from deckManifold: Crane tuggers – not to be used

Tagging tower winches – not installed

Control rotation of structure using endless rope taglines

Position crane hook above manifold lift-off location, recorded during mobilisation

Contingency – increase crane radius during overboarding to avoid clash with vessel in

case manifold start spinning.


Lift-off from deckSpreader frame:Crane tugger bridle tensioned to control spreader frame

Lift against bumpers

Control spreader frame using crane tuggers and tagging towers

Position spreader frame above spool lift-off location, recorded during mobilisation


Lift-off from deckSpool: Crane tugger bridle and tagging towers to control spreader frame

Endless rope taglines at spool ends (termination head and SPEM)

Limit movements to avoid clashing with supports & structures on deck





LandingRecovery


Slewing / Overboarding

Clash check & verification of hook heightDeck layout

Manifold Installation, 175 Te No crane tuggers

No tagging towers

Taglines to control lift-off

Ballasting system prepared

Where? NOT above other subsea infrastructure


Slewing / OverboardingSpool Installations58 Te spreader frame + approx 20 Te spool

2 off crane tuggers

3 off tagging towers

Taglines to control lift-off


Slewing / Overboarding





LandingRecovery


Splash zoneSlack slings or challenging crane capacity?Large crane radius and hydrodynamic loads -> Crane capacity

Buoyancy, drag, added mass & slamming -> Slack slings

Entrapped air, collapse of structural members


Splash zoneDisconnect winch wiresLeave structure at -15m to allow water to flood structural members

Crane tugger wires and tagging towers are disconnected at -40m using ROV hooks.





LandingRecovery


Landing - SpoolsPrepare landing area Open hatches for access

Install guideposts

Install guiding arrangement Establish guidewires

Apply correct tension in guidewires

Landing Land spool in supports

Continue lowering spreader frame

Release rigging


Landing - ManifoldEstablish guiding arrangement Seabed indicators

Clumpweight to keep stable heading

Transponders and Gyro verify position heading

Digiquartz and Bullseye to verify after landing





LandingRecovery


RecoveryIn general recovery of installation aids Slings with excessive movements (all secured, shackles?)

Clumpweight, ROV basket, guideposts (loose items)

Spreader bar or spreader frame (control)

Contingency: Recovery of installed structure / spool

Deck layout & preparations

Crane capacity for recovery

Seafastening of recovered structure


Recovery – Spreader FrameMeans to control spreader frame:ROV connect crane tugger winches and tagging tower winches at -15m depth.

Increase crane radius and tension up crane tugger bridle as spreader frame comes to surface

Ensure slow water exit, the spreader frame will be emptied for water.


Landing in supports / disconnection of lift rigging Spreader frame resting against bumpers

Land spreader frame in supports

Seafasten spreader frame using cargo strops

Disconnect spool lift rigging

Recovery – Spreader Frame


RecoveryDeck layout and preparationsDepending on the structure to be recovered and equipment available, prepare:

Bumpers

Grillage

Winch philosophy – avoid entanglement

Ballasting operations

Know all load details, footprint, weight, submerged weight, enclosed fluids

Assume loose items, stones / sand, entrapped water


Summary


SummaryImportant aspects when planning and executing offshore lifts: Deck layout, slewing path

Winches for controlling loads in air

Crane capacity curves, also for recovery (alarm settings)

Communication with offshore personnel

Learn from mobilisation (crane settings, ballasting requirements, load handling)

HSE – Plan to avoid working at height and under suspended loads

Plan for contingencies!


Documents

1 - The Different Phases of a Subsea Lift From an Offshore Construction Vessel - KTF 2009