Lifting Rules Example - DNV.pdf

DNV Marine Operations’ Rules
for Subsea Lifting
New Simplified Method for Prediction of Hydrodynamic Forces
Tormod Bøe
DNV Marine Operations
2nd December 2008

DNV Marine Operations' Rules for Subsea Lifting Slide 2
2 December 2008
Content
„ Brief overview of relevant DNV publications
„ DNV Rules for Marine Operations, 1996,
Pt.2 Ch.5 Lifting – Capacity Checks
„ New Simplified Method for calculation of
hydrodynamic forces
„ CFD Analyses – Test Cases

2 December 2008
Relevant DNV Publications
Lifting- and subsea operations :
DNV-OS-E402
Offshore Standard for Diving
Systems January 2004
(Amendments October 2008)
DNV Rules for Planning and Execution of
Marine Operations – 1996
’Special planned, non-routine operations of
limited durations, at sea. Marine operations are
normally related to temporary phases as e.g.
load transfer, transportation and installation.’
DNV Standard for Certification
No.2.22 Lifting Appliances
October 2008
DNV Standard for Certification
No. 2.7-1 Offshore Containers
April 2006
Special planned non-routine operations Routine operations

2 December 2008
Relevant DNV Publications - Other
„ DNV-RP-C205 Environmental Conditions
and Environmental Loads April 2007
(replacing Classification Notes No 30.5)
„ DNV-RP-H101 Risk Management in Marine
and Subsea Operations, January 2003
„ DNV-RP-H102 Marine Operations during
Removal of Offshore Installations, April
2004
„ Standard for Certification No. 2.7-3
Portable Offshore Units, June 2006
(a new revision is planned which will include subsea
units)

2 December 2008
Relevant DNV Publications - Purchase
DNV publications can be purchased at:
http://webshop.dnv.com/global/
„ The new DNV-RP-H103 (December draft version) will be
made available together with the presentation material
from this Subsea Lifting Operations seminar.
„ DNV accept use of the December draft version until
the official release is issued in April 2009.

2 December 2008
Content
„ Brief overview of relevant DNV
publications
Lifting – Capacity Checks
hydrodynamic forces

2 December 2008
Capacity Checks - DNV 1996 Rules
Rules for Planning and Execution of Marine Operations, 1996
Part 1 - General
Pt.1 Ch.1 - Warranty Surveys
Pt.1 Ch.2 - Planning of
Operations
Pt.1 Ch.3 - Design Loads
Pt.1 Ch.4 - Structural Design
Part 2 - Operation Specific Requirements
Pt.2 Ch.1 - Load Transfer Operations
Pt.2 Ch.2 - Towing
Pt.2 Ch.3 - Special Sea Transports
Pt.2 Ch.4 - Offshore Installation
Pt.2 Ch.5 - Lifting
Pt.2 Ch.6 - Sub Sea Operations
Pt.2 Ch.7 - Transit and Positioning
of Mobile Offshore Units

2 December 2008
Capacity Checks - DNV 1996 Rules
Part 2 Chapter 5
„ Dynamic loads, lift in air
„ Crane capacity
„ Rigging capacity,
(slings, shackles, etc.)
„ Structural steel capacity
(lifted object, lifting points,
spreader bars, etc.)
Part 2 Chapter 6
„ Dynamic loads, subsea lifts
(capacity checks as in Chapter 5 applying dynamic loads from Chapter 6)

2 December 2008
Capacity Checks – DAF for Lift in Air
„ Dynamic loads are accounted for by
using a Dynamic Amplification Factor
(DAF).
„ DAF in air may be caused by e.g.
variation in hoisting speeds or motions
of crane vessel and lifted 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 !
Table 2.1 Pt.2 Ch.5 Sec.2.2.4.4

2 December 2008
Capacity Checks - Crane Capacity
The dynamic hook load, DHL, is
given by:
DHL = DAF*(W+Wrig) + F(SPL)
ref. Pt.2 Ch.5 Sec.2.4.2.1
„ 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.

2 December 2008
Capacity Checks - Sling Loads
The maximum dynamic sling load, Fsling,
can be calculated by:
Fsling = DHL·SKL·kCoG·DW / sin φ
ref. Pt.2 Ch.5 Sec.2.4.2.3-6
where:
„ SKL = Skew load factor → extra loading
caused by equipment and fabrication tolerances.
„ kCoG = CoG factor → inaccuracies in estimated
position of centre of gravity.
„ DW = vertical weight distribution → e.g.
DWA = (8/15)·(7/13) in sling A.
„ φ = sling angle from the horizontal plane.
Example :

2 December 2008
Capacity Checks - Slings and Shackles
The sling capacity ”Minimum breaking load”,
MBL, is checked by:
The safety factor is minimum γsf ≥ 3.0.
(Pt.2 Ch.5 Sec.3.1.2)
sf
sling
sling
γ
MBL
F <
”Safe working load”, SWL, and ” MBL, of the
shackle are checked by :
a) Fsling < SWL· DAF
and b) Fsling < MBL / 3.3
Both criteria shall be fulfilled (Pt.2 Ch.5 Sec.3.2.1.2)

2 December 2008
Capacity Checks – Structural Steel
Other lifting equipment:
A consequence factor of γC = 1.3
should be applied on lifting yokes,
spreader bars, plateshackles, etc.
Lifting points:
The load factor γf = 1.3, is increased by a
consequence factor, γC = 1.3, so that total
design faktor, γdesign , becomes:
γdesign = γc· γf = 1.3 · 1.3 = 1.7
The design load acting on the lift point becomes:
Fdesign = γdesign· Fsling = 1.7· Fsling
Structural strength of Lifted Object:
The following consequence factors
should be applied :
A lateral load of
minimum 3% of the
design load shall be
included. This load
acts in the shackle
bow !
(ref. Pt.2.Ch.5 Sec.2.4.3.4)
Table 4.1 Pt.2 Ch.5 Sec.4.1.2

2 December 2008
Content
publications
hydrodynamic forces

2 December 2008
New Simplified Method - DNV-RP-H103
„ A new Recommended Practice; ”DNV-RP-
H103 Modelling and Analysis of Marine
Operations” will be issued.
„ A new Simplified Method for calculating
hydrodynamic forces on objects lifted
through wave zone is included in chapter 4.
„ This new Simplified Method will supersede
the calculation guidelines in DNV Rules for
Marine Operations, 1996, Pt.2 Ch.6.
„ The DNV 1996 Rules will be replaced by a
set of New Offshore Standards on Marine
Operations.

2 December 2008
New Simplified Method - Assumptions
The Simplified Method is based upon the
following main assumptions:
„ 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
The intention of the Simplified Method is to
give simple conservative estimates of the
forces acting on the object.

2 December 2008
New Simplified Method - Assumptions

2 December 2008
New Simplified Method – Crane Tip Motions
„ The Simplified Method is unapplicable if the crane tip
oscillation period or the wave period is close to the
resonance period, Tn , of the hoisting system
K
A
M
Tn
33
2
+
= π
„ 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
„ If the vessel heading is not fixed,
vessel response should be
analysed for wave directions at
least ±15° off the applied vessel
heading

2 December 2008
New Simplified Method – Wave Periods
There are two alternative approaches:
13
9
.
8 ≤
≤
⋅ z
T
g
Hs
A lower limit of Hmax=1.8·Hs=λ/7 with
wavelength λ=g·Tz
2
/2π is here used.
Alt-1) Wave periods are included:
Analyses should cover the following zero-
crossing wave period range:
g
H
z
T
S
⋅
≥ 6
.
10
A lower limit of Hmax=1.8·Hs=λ/10 with wavelength
λ=g·Tz
2
/2π is here used.
Alt-2) Wave periods are disregarded:
Operation procedures should in this case reflect that the calculations are only valid for
waves longer than:

2 December 2008
New Simplified Method – Wave Kinematics
Alt-1) Wave periods are included:
The wave amplitude, wave particle
velocity and acceleration can be taken as:
„
„
„
S
a H
⋅
= 9
.
0
ζ
g
T
z
a
w
z
d
e
T
v
2
2
4
2
π
π
ζ
−
⋅
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
⋅
=
g
T
z
a
w
z
d
e
T
a
2
2
4
2
2
π
π
ζ
−
⋅
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
⋅
=
s
H
d
35
.
0
v e
s
H
g
30
.
0
w
−
⋅
= π
s
H
d
35
.
0
a e
g
10
.
0
w
−
⋅
= π
Alt-2) Wave periods are disregarded:
The wave particle velocity and acceleration can
be taken as:
„ d : distance from water plane to CoG of
submerged part of object
„
„

2 December 2008
New Simplified Method – Hydrodynamic Forces
Slamming impact force
Slamming forces are short-term impulse
forces that acts when the structure hits the
water surface.
AS is the relevant slamming area on the
exposed structure part. Cs is slamming coeff.
The slamming velocity, vs, is :
2
2
w
ct
c
s v
v
v
v +
+
=
„ vc = lowering speed
„ vct = vertical crane tip velocity
„ vw = vertical water particle velocity
at water surface
g
V
F ⋅
⋅
= δ
ρ
ρ
Varying buoyancy force
Varying buoyancy, Fρ , is the change in
buoyancy due to the water surface elevation.
δV is the change in volume of displaced
water from still water surface to wave
crest or wave trough.
2
2
~
ct
a
w
A
V η
ζ
δ +
⋅
=
g
V
F ⋅
⋅
= δ
ρ
ρ
„ ζa = wave amplitude
„ ηct = crane tip motion amplitude
„ Ãw = mean water line area in the
wave surface zone

2 December 2008
New Simplified Method – Hydrodynamic Forces
Drag force
Drag forces are flow resistance on
submerged part of the structure. The drag
forces are related to relative velocity between
object and water particles.
The drag coefficient, CD, in oscillatory flow for
complex subsea structures may typically be
CD ≥ 2.5.
Relative velocity are found by :
2
2
w
ct
c
r v
v
v
v +
+
=
„ vc = lowering/hoisting speed
„ vct = vertical crane tip velocity
„ vw = vertical water particle velocity
at water depth , d
„ Ap = horizontal projected area
Mass force
“Mass force” is here a combination of inertia
force, Froude-Kriloff force and diffraction
force.
Crane tip acceleration and water particle
acceleration are assumed statistically
independent.
( )
[ ] ( )
[ ]2
33
2
33 w
ct
M a
A
V
a
A
M
F ⋅
+
+
⋅
+
= ρ
„ M = mass of object in air
„ A33 = heave added mass of object
„ act = vertical crane tip acceleration
„ V = volume of displaced water relative to
the still water level
„ aw = vertical water particle acceleration
at water depth, d

2 December 2008
New Simplified Method – Hydrodynamic Force
The hydrodynamic force is a time dependent function of slamming impact
force, varying buoyancy, hydrodynamic mass forces and drag forces. In the
Simplified Method the forces may be combined as follows:
2
2
slam
hyd )
F
F
(
)
F
F
(
F M
D ρ
−
+
+
=
„ The structure may be divided into
main items and surfaces contributing
to the hydrodynamic force
„ Water particle velocity and
acceleration are related to the
vertical centre of gravity for each
main item. Mass and drag forces
contributions are then summarized :
∑
=
i
i
M
M F
F ∑
=
i
i
D
D F
F
FMi and FDi are the individual
force contributions from each
main item

2 December 2008
New Simplified Method – Load Cases Example
Load Case 1
Still water level beneath top of ventilated buckets
„ Slamming impact force, Fslam, acts on top of
buckets.
„ Varying buoyancy force, Fρ , drag force, FD
and mass force, FM are negligible.
The static and hydrodynamic force should be calculated for different stages. Relevant
load cases for deployment of a protection structure could be:
Load Case 2
Still water level above top of buckets
„ Slamming impact force, Fslam, is zero
„ Varying buoyancy, Fρ , drag force, FD and
mass force, FM, are calculated. Velocity and
acceleration are related to CoG of submerged
part of structure.

2 December 2008
Load Case 3
Still water level beneath roof cover.
„ Slamming impact force, Fslam, acts on the roof
cover.
„ Varying buoyancy, Fρ , drag force, FD and mass
force, FM are calculated on the rest of the
structure. Drag- and mass forces acts mainly on
the buckets and is related to a depth, d, down to
CoG of submerged part of the structure.
Load Case 4
Still water level above roof cover.
„ Slamming impact force, Fslam, and varying
buoyancy, Fρ, is zero.
„ Drag force, FD and mass force, FM are calculated
individually. The total mass and drag force is the
sum of the individual load components, e.g. :
FD= FDroof + FDlegs+ FDbuckets applying correct CoGs

2 December 2008

2 December 2008
New Simplified Method – Static Weight
„ In addition, the weight inaccuracy factor should be applied

2 December 2008
New Simplified Method - DAF
Capacity Checks
The capacities of crane, lifting equipment and
lifted object are checked as for lift in air. The
following relation should be applied:
where
Mg : weight of object in air [N]
Ftotal : is the characteristic total force on the
(partly or fully) submerged object. Taken as the
largest of;
Ftotal = Fstatic-max + Fhyd or
Ftotal = Fstatic-max + Fsnap
„ Fstatic-max is the maximum static
weight of the submerged object
including flooding and weight
inaccuracy factor
„ Fhyd is the hydrodynamic force
„ Fsnap is the snap load (normally
to be avoided)
Mg
F
DAF total
=

2 December 2008
New Simplified Method – Slack Slings
The Slack Sling Criterion.
„ Snap forces shall as far as possible
be avoided. Weather crietria should
be adjusted to ensure this.
„ The following criterion should be
fulfilled in order to ensure that snap
loads are avoided:
min
static
hyd F
9
.
0
F −
⋅
≤
„ Fstatic-min = weight before flooding,
including a weight reduction implied
by the weight inaccuracy factor.

2 December 2008
New Simplified Method – Added Mass
Hydrodynamic added mass for flat plates
b
a
4
76
.
0
A 2
33 ⋅
⋅
⋅
⋅
=
π
ρ
Example:
Flat plate where
length, b, above
breadth, a, is
b/a = 2.0 :

2 December 2008
Added Mass Increase due to Body Height
The following simplified approximation of the
added mass in heave for a three-dimensional
body with vertical sides may be applied :
o
33
2
2
33 A
)
1
(
2
1
1
A ⋅
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
+
−
+
≈
λ
λ
p
p
A
h
A
+
=
λ
Added Mass Increase due to Body Height
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
0 0.5 1 1.5 2 2.5
ln [ 1+ (h/sqrt(A)) ]
A33/A33o
1+SQRT((1-lambda^2)/(2*(1+lambda^2)))
and
where
„ A33o = added mass for a flat plate with a
shape equal to the horizontal projected
area of the object
„ h = height of the object
„ Ap = horizontal projected area of the object

2 December 2008
Added Mass from Partly Enclosed Volume
A volume of water partly
enlosed within large plated
surfaces will also contribute
to the added mass, e.g.:
„ The volume of water
inside suction anchors
or foundation buckets.
„ The volume of water
between large plated
mudmat surfaces and
roof structures.

2 December 2008
Added Mass Reduction due to Perforation
.
Effect of perforation on added mass
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50
Perforation
Added
Mass
Reduction
Factor
e^-P/28
BucketKC0.1-H4D-NiMo
BucketKC0.5-H0.5D-NiMo
PLET-KC1-4
Roof-A0.5-2.5+
Hatch20-KCp0.5-1.8
Hatch18-KCp0.3-0.8
BucketKC0.1
BucketKC0.6
BucketKC1.2
RoofKCp0.1-0.27
RoofKCp0.1-0.37
DNV-Curve
Mudmat CFD
0
.
1
A
A
S
33
33
=
[ ]
34
/
)
5
p
(
cos
3
.
0
7
.
0
A
A
S
33
33
−
+
= π
28
p
10
S
33
33
e
A
A
−
=
if p< 5
if 5 < p < 34
if 34 < p < 50
Recommended reduction:
A33S = added mass for a non-
perforated structure.
„ No reduction applied in added mass when perforation is small. A significant drop in the
added mass for larger perforation rates. Reduction factor applicable for p<50.

2 December 2008
New Simplified Method – Example Case
Example: Submerged Foundation Bucket
kg
21867
0
.
2
3
4
2
A 3
o
33 =
⋅
⋅
⋅
⋅
= π
π
ρ
( )
s
33
2
2
2
s
33
o
33
2
2
'
s
33
2
2
3
o
33
A
8
4
0
.
2
4
.
0
100
P
61546
25
.
3
75
.
1
29496
A
29496
A
78
.
0
1
2
78
.
0
1
1
A
78
.
0
0
.
2
1
0
.
2
21867
0
.
2
3
4
2
A
of
reduction
No
:
n
Perforatio
kg
:
volume
inside
Incl.
kg
:
increase
Height
:
factor
Height
kg
:
plate
Flat
⇒
<
=
⋅
⋅
⋅
=
=
⋅
⋅
⋅
+
=
=
⋅
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
+
⋅
−
+
=
=
⋅
+
⋅
=
=
⋅
⋅
⋅
⋅
=
π
π
ρ
π
π
π
λ
π
π
ρ
„ Added mass for a thin circular disc:
„ Added mass increase due to body height:
( ) kg
33803
A
50
.
0
1
2
50
.
0
1
1
A
50
.
0
0
.
2
5
.
3
0
.
2
o
33
2
2
'
s
33
2
2
=
⋅
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
+
⋅
−
+
=
⇒
=
⋅
+
⋅
=
π
π
λ
„ Added mass including partly enclosed volume:
kg
65854
25
.
3
75
.
1
33803
A 2
s
33 =
⋅
⋅
⋅
+
= ρ
π
„ Added mass reduction due to perforation:
s
33
2
2
A
4
0
.
2
4
.
0
100
P of
reduction
No
SMALL ⇒
≈
=
⋅
⋅
⋅
=
π
π
Bucket Dimensions:
„ Height = 3.5m
„ Diameter = 4.0m
„ Plate thickness = 0.25m
„ Ventilation hole diameter = 0.8m

2 December 2008
New Simplified Method – Example Case
Example: Submerged Foundation Bucket
( ) N
5
2
2
2
r
P
D
D 10
37
.
0
48
.
1
25
.
0
0
.
2
96
.
0
0
.
2
5
.
0
v
A
C
5
.
0
F ⋅
=
+
⋅
⋅
⋅
⋅
=
⋅
⋅
⋅
⋅
= π
ρ
ρ
( )
[ ] ( )
[ ] ( ) N
5
2
w
33
2
ct
33
M 10
33
.
1
69
.
1
65854
13031
a
A
V
a
A
M
F ⋅
=
⋅
+
=
⋅
+
+
⋅
+
= ρ
2
m/s
and
m/s 69
.
1
v
5
.
5
2
a
48
.
1
e
5
.
5
2
75
.
1
v w
w
81
.
9
5
.
5
)
25
.
1
1
(
4
w
2
2
=
⋅
⎟
⎠
⎞
⎜
⎝
⎛
=
=
⋅
⎟
⎠
⎞
⎜
⎝
⎛
⋅
= ⋅
+
⋅
− π
π
π
Regular Wave Data:
„ Wave Height, Hmax = 3.5m
„ Wave Period, Tz = 5.5s
„ Water particle velocity and acceleration:
„ Drag force:
„ Mass force:
„ Hydrodynamic force:
1.0m
1.25m
CoG
Other Data
„ Buoyancy, ρV = 13031kg
„ Negligible crane tip motions
„ Lowering speed = 0.25m/s
( ) ( ) ( ) ( ) N
5
2
5
2
5
2
M
2
slam
D
hyd 10
4
.
1
10
33
.
1
10
37
.
0
F
F
F
F
F ⋅
=
⋅
+
⋅
=
−
+
+
= ρ

2 December 2008
Content
publications
hydrodynamic forces

2 December 2008
CFD Analyses – Test Cases
„ Computational Fluid Dynamics
(CFD) is a numerical method for
computing fluid flows based on
the Navier Stokes equations.
„ The CFD-program COMFLOW is
able to study complex free
surface problems applying the
Volume of Fluid method.
„ The fluid domain consists of a
cartesian grid where the fluid
cells are defined either as
boundary cells, empty cells,
surface cells or fluid cells.
„ Pressure forces are calculated
as the integral of the pressure
along the boundary of an object.
„ Motion responses are not
included, but the object can be
given a prescribed motion.
Structure
Fluid
domain
Inflow boundary,
Airy or Stokes
5th wave
Numerical
beach at
aft end

2 December 2008
CFD Analyses – Protection Structure
CFD analysis:
Regular Stokes 5th
wave: H=3.5m T=5.5s
Domain 95x30x37m
4.4 million fluid cells
Minimum grid size
0.18m near object,
stretched elsewhere
8.5x8.5m solid roof
and 10x10xØ1.0m top
frame
Ø1.0m legs, height 8m
and hollow
3.5xØ4.0m buckets at
x,y=±8.5m
ventilation holes
Ø0.8m
Wall thickness 0.25m
half model
60s simulation time
computer time 6weeks

2 December 2008
Highest upwards
hydrodynamic force
when bucket is fully
submerged occurs
at time t=21s where
the object is located
in a wave trough.
Fhyd ≈ 1.1·105N
Buoyancy, ρVg

2 December 2008
Half wave length
is ~23.5m and
the distance
between buckets
are 17m.
Hence, there is a
large phase
difference
between the
hydrodynamic
forces on forward
and aft bucket.

2 December 2008
ComFlow results
show very high
slamming loads
on bucket top
and the solid roof
structure.
These values are
most likely too
high as
compressibility
and formation/
collapse of air
cushions are not
included in the
simulation.
Slamming load
on aft bucket
Slamming load
on roof structure

2 December 2008
CFD Analyses – Spool Piece
CFD analysis:
Regular Stokes 5th
wave: H=3.5m
T=5.5s
The wave length is
~equal spool length
Domain
130x30x31m
2.2 million fluid cells
Minimum grid size
0.25m near object,
stretched elsewhere
50m long closed
pipe with diameter
Ø1.0m
Two simulations;
1) half submerged
2) 2m below surface
22s simulation time
computer time 13-
18hrs

2 December 2008
CFD Analyses – Spool Piece Half Submerged
N
N 5
5
2
m
vertical
5
2
2
w
add
m 10
4
.
1
10
6
.
0
81
.
9
25
4
0
.
1
F
Vg
F
10
6
.
0
2
5
.
3
5
.
5
2
2
25
4
0
.
1
0
.
2
a
)
m
V
(
F ⋅
=
⋅
−
⋅
⋅
⋅
⋅
=
+
=
⇒
⋅
−
=
⋅
⎟
⎠
⎞
⎜
⎝
⎛
⋅
⋅
⋅
⋅
⋅
⋅
−
≈
⋅
+
= π
ρ
ρ
π
π
π
ρ
ρ
The wave length is equal
the spool piece length
Vertical force on aft half at time t=5s :
Half of the spool piece is
always out of the water.
The total force on each
half vary between zero
and buoyancy+Fhyd

2 December 2008
CFD Analyses – Spool Piece 2m Submerged
Total vertical force
Vertical force,
fwd half
Vertical force,
aft half
N
5
2
2
w
add
m 10
45
.
0
2
5
.
3
5
.
5
2
77
.
0
2
25
4
0
.
1
1025
0
.
2
a
)
m
V
(
F ⋅
=
⋅
⎟
⎠
⎞
⎜
⎝
⎛
⋅
⋅
⋅
⋅
⋅
⋅
≈
⋅
+
=
π
π
π
ρ
Brief approximation of mass force:
Dynamic force amplitude (mainly mass forces)
≈ 0.55·105 kN

2 December 2008
And then – One Final Comment:
When planning
Marine Operations,
remember to take
into account ....

2 December 2008
Easy Handling ..

2 December 2008
.. and Survey Access !!

2 December 2008

Lifting Rules Example - DNV.pdf

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