Offshore Lifting for Subsea Equipment

8/10/2019 Offshore Lifting for Subsea Equipment

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Offshore Lifting for Subsea Equipment

Muhammad

Naval Architect

Braemar Technical Services Offshore

BREAEMAR

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16th September 2014



Content

• General Light lift

Heavy lift

Lifting Capacity Checks

• Rule/Code (DNV-RP-H103) Lifting Through Wave Zone

Deepwater Lowering Operation

Landing on Seabed and Retrieval

• Practice in Offshore Industries

16 September 2014 Offshore Lifting for Subsea Equipment 2

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General

• Equipment : Crane, Crane Vessel, Transport Vessel, Lifted Object

• Main consideration:

Clearence :• Between lifted object and crane boom

• Between crane boom and any other object/structure

• Between the lifted object and any other object/structure

• Between the underside of the lifted object and grillage or seafastening • Bottom of crane vessel and the seabed (at shallow water)


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General

• Light Lift

• Heavy Lift

• Lift off the Object


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General

• Light Lift

Crane Tip Motion

• Crane boom assumed to be stiff, therefore crane tip motion canbe determined from wave induced rigid body motion.

• Surge, sway & heave = RAO of the vessel in 6 DOF (at COG)

• Response amplitude ( ct ), velocity (V ct ), eigenperiod (T 0r )

o Analytical solution

o Equation are available at DNV-RP-H103 Chapter 9.


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General

• Light Lift

Hydrodynamic Interaction

For the case of:A. The presence of other fixed or floating structure in the

vicinity of the vessel Recalculate RAO of the vessel:

B. Lifting from or to transport vessel/barge recalculate RAO

for both vessel (coupled 12 DOF)


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General


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• Heavy Lift

– Equipment: Semi-submersible Crane Vessel (SSCV) & computer

controlled ballast system

– Lift-off operation for bow-mounted crane:• Pre-trimmed to stern up

• Pre-hoist operation:

– transferrinig 80% of the load from the barge to the SSCV

– The barge and SSCV oscilate together as a almost rigid system

in vertical direction

– Ballast operation to reverse the trim

– Load is lifted 4-5 m within 90 second 5 cm/s



General


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• Heavy Lift

Motion analysis

• 12 DOF ( 6 DOF from SSCV + 6 DOF from the barge)• After lift-off : 18 DOF (6DOF extra from the object)

– Lifted object + SSCV + Barge coupled each other

– Horizontal motion of lifted object critical

• Time domain analysis



General


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• Heavy Lift

Motion analysis- Coupled Dynamic Motioin

• Neglect rotation motion of lifted object

12 DOF become 9 DOF

• Mass matrix, spring matrix and response motion analysis refer

to part 9.3.3



General


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• Lift off The Object

Side-by-side position: relative motion between the crane hook and

the barge

Feasibility of lift-off operation:

• The hoisting speed of the crane (depends on the weight of the object to be

lifted, a lower limit is usually taken to be in the order of 0.1 m/s).

• The combined motion characteristics of the barge and the crane vessel.

• The weather condition, combined with the orientation of the two vessels.

Probability of barge hitting lifted object : analytical solution.

available at part 9.5.2



Content


Heavy lift



Deepwater Lowering Operation

Landing on Seabed and Retrieval



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• Reference : (DNV Rules for Marine Operation 1996, Pt. 2 Ch. 5)

Dynamic loads, lift in air

Crane Capacity Rigging capacity (slings, shackles, etc.)

Structural steel capacity(lifted object, lifting points, spreader bars, etc.)


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• Dynamic loads (DAF) for Lift in Air

DAF in air may be caused by e.g. variation in

hoisting speeds or motions of crane vessel andlifted object.

The given table is applicable for offshore lift in air

in minor sea states, typically Hs <2-2.5m.

DAF must be estimated separately for lifts in air at

higher seastates and for subsea lifts !


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• Dynamic loads (DAF) for Lift in Air


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• Crane Capacity

DHL = DAF*(W+Wrig) + F(SPL)

– W is the weight of the structure, including a weight inaccuracy factor

– The DHL should be checked against available crane capacity.

– The crane capacity decrease when the lifting radius increase.


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• Rigging capacity (slings, shackles, etc.)

Sling Load• The maximum dynamic sling load, Fsling:

Fsling = DHL∙SKL∙kCoG∙DW / sin φ

Where:

SKL = Skew load factor → extra loading caused by equipment and

fabrication tolerances.

kCoG = CoG factor → inaccuracies in estimated position of centre ofgravity.

DW = vertical weight distribution → e.g. DWA = (8/15)∙(7/13) in sling

A.

φ = sling angle from the horizontal plane.


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• Rigging capacity (slings, shackles, etc.)

– The sling capacity ”Minimum breaking load”, MBL, is checked by:

The safety factor is minimum sf ≥ 3.0.

– ”Safe working load”, SWL , and ” MBL , of the shackle are checked by :

Both criteria shall be fulfilled




• Structural steel capacity – The load factor f = 1.3, is increased by a consequence factor, C =

1.3, so that total design factor, design , becomes:

– The design load acting on the lift point becomes:

– A lateral load of minimum 3% of the design load shall be included. This

load acts in the shackle bow !


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• Structural steel capacity

Other lifting equipment:

A consequence factor of C = 1.3 should be applied on lifting yokes,

spreader bars, plateshackles, etc.

Structural strength of Lifted Object:


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• Summary


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Content


Heavy lift



Deepwater Lowering Operation Landing on Seabed and Retrieval



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Rule/Code

• DNV-RP-H103 (Modelling and analysis of Marine Operation)

Lifting through wave zone

Deepwater lowering operation Landing on seabed and retrieval


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Rule/Code

• Lifting through wave zone

Hydrodynamic forces General Method

Simplified Method

Stability of lifting operation

Snap forces

Moonpool operation


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Rule/Code

• Hydrodynamic Forces (General Method)

– General• Accurate prediction of design load during lowering/ retrieval

– Loads• Weight of object, Buoyancy force, Current force, viscous drag

force: analitical solution. Equation are available in part 3.2

• Inertia force due to moving object, Wave damping force, Waveexcitation force, Slamming force, vertical motion of lifted object:

numerical calculation in time domain


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Lifting Through Wave Zone (DNV-RP-H103)



Rule/Code

• Hydrodynamic Forces (General Method)

Calculation methods• Simplified Method

• Regular design wave approach

– Shallow water effects are neglected.

– Fhyd = Fρ + Fm + Fs + Fd [N]

where : Fρ = varying buoyancy force [N], Fm = hydrodynamic mass force

[N], Fs = slamming impact force [N], Fd = hydrodynamic drag force [N]

• Time domain analyses

– 3 hours simulation period for each load case.

– 30 minutes simulation for sensitivity analysis

– CFD analysis


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Rule/Code

• Hydrodynamic Forces (Simplified Method)

the Simplified Method is to give simple conservative

estimates of the forces acting on the object.

Main assumption:

• the horizontal extent of the lifted object is small compared to the wave

length

• the vertical motion of the object is equal the vertical crane tip motion

• vertical motion of object and water dominates → other motions can be

disregarded


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Rule/Code

• Simplified Method – Time Domain Analysis –


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Rule/Code

• Simplified Method – Crane Tip Motion –

– T crane tip Tn, Simplified method is unapplicable

– Heave, pitch and roll RAOs for the vessel should be combined with

crane tip position to find the vertical motion of the crane tip

– If operation reference period is within 30 minutes, the most probable

largest responses may be taken as 1.80 times the significant

responses.

– Unless the vessel heading is fixed, vessel response should be analysed

for wave directions at least ±15° off the applied vessel heading


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Rule/Code

• Simplified Method – Wave Period –

There are two alternative approaches:

1. Wave periods are included:

Analyses should cover the following zero-crossing wave period range:

A lower limit of Hmax =1.8∙Hs=λ/7 with wavelength λ=g∙Tz2/2π is here used.

2. Wave period are disregarded:Operation procedures should in this case reflect that the calculations are only

valid for waves longer than:

– A lower limit of Hmax =1.8∙Hs=λ/10 with wavelength λ=g∙Tz2/2π is here used.


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Rule/Code

• Simplified Method – Wave Kinematics –


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Rule/Code

• Simplified Method – Hydrodynamic Forces –


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Rule/Code



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Rule/Code

• Simplified Method – Added Mass –


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Rule/Code



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Rule/Code

• Simplified Method – Load Cases Example –


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Rule/Code

• Simplified Method – Static Weight –


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Rule/Code

• Simplified Method – DAF –


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Rule/Code

• Simplified Method – Slack Slings –


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Rule/Code

• Simplified Method – Summary –


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Rule/Code

• Simplified Method – Summary –

The simplified method assumes that:• Vertical motion of structure is equal to the crane tip motion.

• The horizontal extension of the structure is small.

• Only vertical motion is present.

More accurate calculations can be performed

applying:• Regular design wave approach (Ch. 3.4.2)

• Time domain analyses

• CFD analyses


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Rule/Code

• Lifting through wave zone

Hydrodynamic forces General Method

Simplified Method

Stability of lifting operation

Snap forces

Moonpool operation


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Rule/Code

• Stability of Lifting Operation

Partly air-filled objects

• lifting of objects where the buoyancy is distributed differently

• If no other forces, object will rotate untill CB is above CG

• Lift wire must be above CF to avoid tilting

• Sling length adjustment required for horizontal landing on seabed


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Rule/Code

• Stability of Lifting Operation

Effects of free water surface inside the object

• GB must be large enough to give :

up-righting moment > overturning moment (by water inside the

object)


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Rule/Code

• Snap Force

• Moonpool Operation


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Rule/Code



Deepwater lowering operation Landing on seabed and retrieval


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Rule/Code

• Deepwater Lowering Operation

Main consideration:

Stretched length of cable

Horizontal offset

Dynamics motion of lifted object

Methods for controlling vertical motion of lifted object

Static Forces

Dynamic Forces Heave Compensation


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Rule/Code


Static Forces

• Stretched length of a cable

• Horizontal offset due to current

• Vertical displacement

• Vertical cable stiffness

• Horizontal stiffness

• Cable payout – quasi-static loads


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Rule/Code


Dynamic Forces

• Dynamic drag forces

• Application

• Natural frequencies, straight vertical cable

• Eigen periods

• Longitudinal pressure waves

• Response of lifted object in a straight vertical cable exposed toforced vertical oscillations

• Slack cable conditions

• Horizontal motion response of lifted object in a straight vertical

cable


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Rule/Code

• Deepwater Lowering Operation• DNV-RP-H103 chapter 5 contains a simplified method for establishing

dynamic loads and limiting weather criteria during deepwater lifting

operations.


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Rule/Code



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Rule/Code



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/C



Rule/Code



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R l /C d



Rule/Code



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R l /C d BREAEMAR



Rule/Code



Deepwater lowering operation

Landing on seabed and retrieval


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R l /C d BREAEMAR



Rule/Code

• Landing On Seabed and Retrieval• Main consideration:

– Foundation failure shouldn’t take place

– Damage does not occur to acceleration sensitive equipment

• Landing on Seabed

– Landing impact problem definition

– Physical parameters and effects to be considered

– Iterative analysis procedure

– Simplified method for foundations without skirts

– Simplified method for foundations with skirts on soft soil

– Application of safety factors

– Calculation of skirt penetration resistance

• Installation by Suction and Levelling

• Retrieval Foundation


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C t t BREAEMAR



Content


Heavy lift



Deepwater Lowering Operation Landing on Seabed and Retrieval



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P ti i I d t i BREAEMAR



Practice in Industries

• Case Studies:

Technip – Manifold and Spool Installation

Chevron Makassar – Franklin Offshore – Suction Pile Installation


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• Technip - Manifold and Spool Installation -


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Preparation for Offshore Lifting

Structures : - Manifold 175 Te

- Spools (OD 4”, 6”, & 10”) Installation vessel : - Skandi Arctic (LOA 156.9 m)

- 400 Te box boom crane NOV

- 58 Te knuckle boom crane

Specific requirements : Presence of drill rig

Engineering tools : - Incident Analysis and Feedback (IAF)

- AutoCad- Simulation of Marine Operation (SIMO)

Installation analyses : - Splash Zone (slack sling, crane capacity),

- Crane tip motion for landing criteria

(position, velocity & acceleration)

- Ship Maneuvering Simulator Centre (SMSC)





• Technip - Manifold and Spool Installation -


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Equipment on

vessel

: For controlling the load:

- Lift-off : Endless rope taglines (riggers)

- In air : Tagging towers with winches + Crane tugger winches

- Landing : Guidewire winches + Clumpweight





• Technip - Manifold and Spool Installation –

Lifting offshore - Different phases of subsea lift

• Toolbox talk

• Seafastening

• Lift-off from deck

• Slewing / overboarding

• Through the splash zone

• Landing phase

• Recovery to deck


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Lifting offshore - Different phases of subsea lift

• Toolbox talk

– Installation procedure / work plan

– Lift plan & rigging specifications drawing

– Deck layout

– Contingency operations

– Experiences from load-out


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Important 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

• Contingencies plan


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Practice in Industries BREAEMAR




• Chevron Makassar – Franklin Offshore

Suction Pile Installation


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Structures : Suction pile (to be installed)

Installation vessel : - Bourdon Oceanteam 104 (LOA 136.6 m)

- 250 MT at 10m radius (at 1.3 DAF). Located at portside

- 90 MT at 13m radius (at 1.6 DAF). Located at stern








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Vessel Description








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Major Equipment & Material List







Procedures:

• Site arrival

– DP and USBL preparation

– Pre-check and preparation activities

– As-found survey

• Pre-deployment preparation• Suction pile over-boarding

• Suction pile selft-penetration

• Suction pile


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Contingencies Plan:

• Vessel breakdown

• Equipment breakdown

• Suction pile positioning and penetration


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Several issues not covered in DNV-RP-H103:

• Overpressure for retrieval (lower bound – upper bound)

• Refusal on penetration

• Expected Self penetration


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When planning Marine Operations,

remember to take into account ....


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Easy handling...


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... And survey access!!

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Offshore Lifting for Subsea Equipment

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