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OMAE2023-101405 OFFLOADING OPERABILITY OF NEAR-SHORE FLNG WITH
SIDE-BY-SIDE MOORED LNG CARRIER IN SHALLOW WATER DEPTH
Conference Paper · June 2023
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Proceedings of the ASME 2023 42nd International
Conference on Ocean, Offshore and Arctic Engineering
OMAE2023
June 11-16, 2023, Melbourne, Australia
OMAE2023-101405
OFFLOADING OPERABILITY OF NEAR-SHORE FLNG WITH SIDE-BY-SIDE MOORED LNG
CARRIER IN SHALLOW WATER DEPTH
Mun Sung Kim, Jae Hwan Lim, Rae Hyoung Yuck and Hyun Joe Kim
Samsung Heavy Industries, Co. Ltd.
Korea Republic
and
Jae Kyung Heo
Det Norske Veritas
Korea Republic
the offloading operability is affected by the side-by-side mooring
arrangement.
ABSTRACT
Recently, the FLNG projects have been developed for the LNG
production near shore field with shallow water depth. In this
field, FLNG is permanently moored by jetty system or special
structures such as Yoke mooring for the liquefaction of feed gas
by pipeline in land side. Like FLNGs which operated in deep
water, ship-to-ship (STS) offloading operation is considered in
near shore FLNG for the transfer of LNG cargo to shuttle LNG
carrier through marine loading arm (MLA) with side-by-side
(SBS) mooring arrangement.
However, unlike FLNGs which operated in deep water depth,
near shore FLNG has relatively short length due to the use of
electric and accommodation from the land side. Also, the
environmental conditions are quite differing in near shore as well
as finite water depth. This meaning that the need of the special
consideration of near shore FLNG for side-by-side (SBS)
mooring arrangement.
In this paper, a numerical motion analysis for the side-by-side
moored FLNG and LNG carrier in near shore field is carried out
in frequency-domain and time-domain. In order to assess the
offloading operability of near shore FLNG during operation,
dynamic loads acting on the mooring lines and fenders as well as
relative motion are calculated for several SBS mooring
arrangements.
Throughout the study, it is found that the important of numerical
accuracy of hydrodynamic analysis in shallow water depth and
environmental conditions such as wind, wave and current. Also,
KEYWORDS
Near Shore (NS) FLNG; Side-by-side (SBS) mooring; Ship to
ship (STS) offloading operability; Two-body motion.
1. INTRODUCTION
Until now, a natural gas supply chain has comprised of
production, possibly from an offshore platform with a subsea
pipeline to land, and an on-shore LNG process plant including
an LNG export terminal. This conventional gas supply chain
requires large scale investment over a long-term development
period.
Also, offshore gas production capacities will increase by
approximately 26% during 2017 ~ 2031, according to
classification society outlook model by DNV. Offshore LNG
production using floating LNG (FLNG) concept is promising
due to its capability to solve increasing challenges faced by onshore projects as a result of local demographic constraints and
increasing environmental and safety regulations [7].
The availability of new production solutions such as FLNG, will
also assist in making the case for continued new development of
offshore gas resources over the forecasting period up to 2050.
The future for FLNG now appears to be small-scale
developments [14] or near shore FLNG due to economic benefit,
however, rather than the large-scale FLNG projects [7].
Many of the technologies used on the FLNG facility have been
used successfully on-shore, but some have been extended or
1
© 2023 by ASME
modified in order for the processes such as liquefaction and
offloading to occur at open sea. The expertise accumulated by
shipbuilding companies on shipbuilding and offshore plants such
as FPSOs and FSRUs, are helping to make it possible to move
LNG production facilities from on-shore to offshore [6].
Also, near shore installation of a jetty- or special structuremoored FLNG may give advantages such as reduced cost,
shorter development time, reduced land use and reduced project
risk compared to traditional onshore LNG plant construction.
Near shore FLNG can be simplified and more standardized, thus
saving cost.
The purpose of this paper is to presents a numerical investigation
on the STS (ship-to-ship) offloading operability for the side-byside moored FLNG and shuttle LNG carrier in near shore field.
A two-body motion analysis in shallow water depth has been
carried out by a three-dimensional hydrodynamic analysis
program. In order to estimate the accurate offloading operability,
the numerical dynamic simulation is performed in both
frequency- and time-domain considering wind, current and
waves in near shore field.
Various environmental conditions and two mooring
configurations are considered to investigate their effects on the
offloading operability of FLNG at near shore.
2. “NEAR SHORE FLNG” CONCEPT AND DESIGN
BASIS
The concept is named NS FLNG for near shore FLNG with
pipeline feed gas and conventional LNG carrier for STS
offloading operation. This concept is developing its own
conceptual design for FLNG taking into account the large
experience capitalized by SHI on all biddings and project
executions for Liquefied Natural Gas Carriers (LNGCs),
Floating Storage and Regasification Unit (FSRUs) and FLNGSs
during last 25 years.
NS FLNG is a standalone vessel moored to a jetty or special
mooring structures and is designed for 2.5~3.5 MTPA of LNG
production capacity. NS FLNG to be located in the North
America or East/South Asia with the following considerations:
•
•
•
Treated LNG gas will be supplied through an
on-shore pipeline.
The development consists of two (2) liquefaction
trains each with 2.5~3.5 MTPA LNG capacity.
No condensate production is considered
The NS FLNG shall receive the feed gas from on-shore
processing facility. The on-shore facility will receive natural gas
from pipeline then conditioned to provide treated gas to the
FLNG.
In order to limit the system on board, except fuel gas and power
generation system, utility systems will be located on-shore and
supplied to the NS FLNG. It is believed that locating these
systems on-shore will provide cost effective design of NS FLNG
and can be shared with the on-shore facility. Therefore, some
facilities like living quarters, gas treatment or utilities can be
installed on-shore, not on NS FLNG.
The NS FLNG is designed for 25 years of operation. The
expected availability of NS FLNG is over 96% from RAM
analysis. The NS FLNG will be designed to produce in the range
of 2.5 to 3.5 MTPA of LNG with a nitrogen liquefaction cycle or
SMR (Single Mixed Refrigerant). The comparison between the
NS FLNG and standard FLNGs is shown in Figure 1. It is shown
that the level of complexity of the NS FLNG is much less than
that of other FLNGs at open sea.
FIGURE 1: Comparison between NS FLNG and Standard
FLNGs
The hull dimensions and LNG tank capacity were defined
considering the compatibility between the NS FLNG and shuttle
LNG carrier, which has a 180,000m3 LNG storage capacity. The
principal particulars of NS FLNG and LNGC are given in Table
1.
Table 1 Principal Particulars
Ship type
NS FLNG
Lbp (m).
286.0
Breadth (m)
62.0
Depth (m)
32.0
LNGC
290.0
47.0
26.2
The NS FLNG is designed for locations with benign sea
conditions, such as North America or East/South Asia. Main
assumed environmental extreme data is summarized in the Table
2.
Table 2 Main Environmental Extreme Data
1-yr
Items
RP
1 hour wind speed (m/s)
16.9
Significant wave height [m]
1.0
Peak wave period [s]
4.0
Surface current speed [m/s]
0.34
2
100-yr
RP
24.7
1.3
5.0
0.48
© 2023 by ASME
The mooring system is needed to keep the location of NS FLNG
exposed to environmental conditions (wave, wind, current)
during a given return period. NS FLNG is located at port or shore
with side-by-side mooring and marine loading arms (MLA) for
STS LNG offloading and feed gas and utilities will be supplied
from on-shore.
Generally, for side by side offloading using marine loading arms,
mooring of LNGC to FLNG is typically achieved by mooring the
LNGC alongside the FLNG with floating pneumatic fenders
protecting the steel hulls from direct contact. SBS mooring lines
will be deployed from the LNGC to the FLNG mooring deck.
Typically, several mooring lines will be deployed. Each mooring
line will have a single mooring fairlead on the FLNG leading to
a quick release hook (QRH). Some form of mooring load
monitoring system will be provided, if possible. With a proper
and reliable mooring between NS FLNG and the LNGC,
offloading using marine loading arms is chosen as the most
workable method.
Side-by-side offloading has several processes; approach/
berthing, offloading, depart. Among the processes, offloading
process takes more time to transfer the gas by using marine
loading arm in the side-by-side mooring arrangement [14]. The
limitations of offloading process are mooring line tension, fender
force and loading arms envelop from relative motion between
NS FLNG and LNGC.
3. TWO-BODY MOTION ANALYSIS
To describe the motion responses between two floating structures
in waves, we consider three sets of right-handed orthogonal
(Cartesian) coordinate systems as shown in Figure 2.
O-XYZ is the space fixed coordinate system. O A-XAYAZA and
OB-XBYBZB are the oscillatory coordinate systems fixed with
respect to ship A and ship B, respectively. The O-XY plane
coincides with the undisturbed free-surface, the X-axis in the
direction of the body’s forward and the Z-axis vertically upward.
The oscillatory coordinate systems OA-XAYAZA and OB-XBYBZB
are used to describe the floating body motion in six degrees of
freedom (6-DOF) with complex amplitudes j (j=1,2,…,12).
v
ZA
YA
3
2
> 6
5
v
2
e ( M ij
 Aij )  i e Bij  C ij ] j  Fi for i=1,2,.,12 (1)
j 1
where, Mij is the generalized mass matrix for the ship A and ship
B, Cij is the restoring force matrix for ship A and ship B,
respectively, j is the complex amplitude of the response motion
in each of the six degree of freedom for each body, and Fi is the
complex amplitude of the wave exciting force for ship A and ship
B.
In the present two-body motion analysis, two combinations are
considered for FLNG and LNG carrier loading conditions;
•
•
Loading combination #1: FLNG ballast, LNGC
fully loaded,
Loading combination #2: FLNG fully loaded,
LNGC ballast.
Table 3 and Figure 3 show the selected loading conditions and
mooring arrangement as design cases of NS FLNG and LNG
carrier for side-by-side moored analysis. The calculation
positions of relative motion are selected at the manifold on LNG
carrier portside.
Table 3 Loading conditions
Ship type
NS FLNG
Loading cond.
Full load/Ballast
Draft (m)
13.6/12.3
Disp. (MT)
238468.5/214825.6
KG (m)
21.86/20.28
LCG (m)
142.99/142.99
LNGC
Ballast/Full load
9.2/11.5
96520.6/124205.6
12.59/17.15
140.71/139.26
XA
1
4
X
XB
7
ZB
O
P
12
 [
Z
OA Y
GA

FIGURE 2: Definition of Co-ordinate Systems for two floating
structures [11]
3.1 Numerical modeling
Under the assumption that the responses are linear and harmonic,
the twelve coupled linear differential equations of motion for two
floating bodies can be written in the following form;
8
11
v
9
YB
>
v
10
12
OB
GB
1
2
3
4
5
6
: Surge for ship A
: Sway for ship A
: Heave for ship A
: Roll for ship A
: Pitch for ship A
: Yaw for ship A
7 : Surge for ship B
8 : Sway for ship B
9 : Heave for ship B
10 : Roll for ship B
11 : Pitch for ship B
12 : Yaw for ship B
FIGURE 3: Panel Arrangement of Near shore FLNG and sideby-side positioned LNG carrier (Distance: 4.5 m) [5]
3.2 Roll damping
The roll damping coefficients applied to the NS FLNG and
LNGC in SBS connection would be different from those in the
single body operation. In extreme condition, the roll damping is
3
© 2023 by ASME
increasing and thus combination of linear and quadratic roll
damping is quite popular. However, SBS offloading is generally
made in relatively milder environment, and thus it is valid to use
the linear damping only including shallow water depth effect.
The roll damping coefficients are determined from the database
of reference FLNG projects, and the numerical roll damping
curves (critical) from time-domain analysis [20] are shown in
Figure 4.
can be adjusted for specific environment condition after wave
basin model test is carried out. Instead, the present study uses the
constant damping intensity as like below;
𝜀 = 0.02~0.03
Figure 5 shows the panel models applied to numerical
computation. Since WADAM adopts the linear theory, only the
underwater part of surfaces is given to computation.
(a) FLNG in ballast, LNGC in full load condition,
(b) FLNG in full load, LNGC in ballast condition
FIGURE 5: Panel model used in frequency-domain analysis
(WADAM)
FIGURE 4: Roll damping curve for full load condition
(Infinite water depth vs finite water depth: 50m)
The viscous roll damping is subsequently added to the potential
damping in the hydrodynamic analysis in Eq. (1). Actual roll
damping would be confirmed from the wave basin model test
during next design stage.
3.3 Free-surface damping in the gap
The flow between NS FLNG and LNG carrier is quite
complicated, and thus the numerical computation assuming
linear theory has limitation to calculate the flow appropriately.
Therefore, free-surface (lid technique) is widely applied to
suppress the violent flow inside gap [1]. The intensity of
damping in free-surface is highly dependent on the wave
elevation and floating body’s motion. Therefore, an accurate
calibration is possible after the ocean basin model test is carried
out.
WADAM [19] applies the damping in free-surface by modifying
the free surface boundary condition, as like below:
𝜕𝜙
𝜕𝑧
=
𝜔2
𝑔
(1 − 2𝑖𝜀 − 𝜀 2 )𝜙
(2)
where,
𝜙: velocity potential of free surface flow,
𝜔: wave circular frequency,
𝑔: gravity constant,
𝜀: damping intensity.
The damping intensity, ε is used to damp out the flow, as well as
to keep the dispersion relation. Therefore, the damping intensity
A three-dimensional motion analysis program, WADAM [19] is
used for the computation of motion response such as
hydrodynamic coefficients, 6-degree of freedom motions and
mean drift forces. WADAM is based on WAMIT developed by
MIT (Massachusetts Institute of Technology), and it can solve
the radiation/diffraction problem in frequency-domain.
The FLNG will normally operate upright with no permanent
trim. Therefore, the design operating condition for offloading
operation is 1 year-RP in North America as shown in Table 2.
3.4 Frequency-domain results for Two-Body motion
The motion RAOs are calculated when NS FLNG and LNG
carrier are arranged in side-by-side. However, no coupling effect
is modeled when hydrodynamic coefficients are calculated from
WADAM.
Figure 6, 7 and 8 show the longitudinal, transverse and vertical
relative motion RAO at head sea ±90o separated angle,
respectively.
The large relative motions between two floating bodies occur
around low frequency regions and coupled resonance frequency
regions. The hydrodynamic interaction effect between two
floating bodies comes from the scattering and reflection of
incident and radiation waves and resonance of trapped waves due
to the presence of neighboring bodies [8], [9], [10], [11], [12],
[13, [15], [21].
The relative motion varies as the wave-heading angle varies from
90o to 270o. The vertical relative motion does not appear in low
and high frequency region because NS FLNG and LNGC
motions have the same phase in that frequency region.
Unlike the vertical relative motion, the horizontal motions occur
in low frequency region due to the shallow water depth effect.
Also, the relative motions occur if NS FLNG and LNGC motions
are out of phase and in phase with different motion amplitude.
4
© 2023 by ASME
The heading angles in which the longitudinal relative motions
are significant in head and bow quartering sea, especially when
LNGC is on weather side (β=135o). The transverse relative
motion was found in head seas due to hydrodynamic interaction
[12]. The highest vertical relative motion occurs in beam sea
(β=90o) where the LNGC is on weather side.
The relative motion response is obtained by calculation of short
term analysis. The basis of calculation is given in Table 4.
FIGURE 6: Longitudinal Relative motion RAOs at loading
arm and manifold (FLNG: full load, LNGC: ballast)
Table 4 Basis of calculation
Item
Return periods
Statistical method
Spectrum
Gamma
Spreading function
Heading profile
Probability of
response level
Connected (Side-by-side)
1yr RP (operating condition)
Short term
JONSWAP
1.0
Long crest
Omni-direction
3 Hours. Max.
(MPM)
The relative motions between NS FLNG and LNGC in North
America field are estimated by using the calculated the relative
motion RAOs. The JONSWAP spectrum is used to analyze the
relative motion responses of FLNG in the operating conditions.
The maximum relative motions at the connected loading arm
position of offloading system between FLNG and LNGC are
shown in Figure 9. The relative motion responses become
noticeably small when the LNGC is on leeside due to sheltering
effect of FLNG. The initial horizontal and vertical relative
motion criteria of Marine Loading Arm (MLA) from the
reference FLNG are 2.5m and 2.0m, respectively.
FIGURE 7: Transverse Relative motion RAOs at loading arm
and manifold (FLNG: full load, LNGC: ballast)
FIGURE 9: Relative motion responses at loading arm and
manifold in North America (1-yr RP), wind sea only
FIGURE 8: Vertical Relative motion RAOs at loading arm and
manifold (FLNG: full load, LNGC: ballast)
The maximum longitudinal relative motion is smaller than the
design criteria in the all heading waves. The maximum
transverse and vertical relative motions are also smaller than the
design criteria in the all heading waves including the beam sea
(β=90o and 270o) in which LNG carrier is on weather side.
5
© 2023 by ASME
Unlike the FLNG operated in deep water depth, the relative
motion of FLNG in near shore is not high, therefore the timedomain analysis should be required to check the impact of wind
and current environmental loads as well as wave loads. The
maximum limiting criteria for the loading arms are based on the
relative motions between FLNG and LNGC at the manifold
position. The following limits are applied initially:
Table 6 Specification of Side-by-side mooring system [3], [16]
SBS
mooring
Table 5 Operability criteria for Marine Loading Arm (MLA)
Item
Max.
m
±2.5
Surge (x-direction)
relative
m
±2.5
Sway (y-direction)
motion at
m
±2.0
Heave (z-direction)
manifold
Mooring
lines
Fender
These criteria of MLA would be changed after the summation of
other LNG carriers.
4. SIDE-BY-SIDE MOORING AND OFFLOADING
ANALYSIS
Generally, side-by-side mooring lines and floating pneumatic
fenders are used for the offloading operation of side-by-side
moored FLNGs. In this paper, 16 mooring lines and 4 fenders are
applied for the side-by-side mooring system. The FLNG is also
moored by a strut mooring system which consists of 4 identical
truss structure. Strut mooring effect is included in the analysis
simply.
Side-by-side mooring analysis is carried out using SIMO/ SIMA
developed by MARINTEK [17], [18]. SIMO/SIMA is a program
for time-domain simulation of motions and station-keeping
behavior of floating vessels and suspended loads.
4.1 Configuration of SBS mooring system
The side-by-side mooring configuration is shown in figure 10,
with 16 mooring lines and 4 fenders. The line and fender
characteristics are tabulated in Table 6. Each breast line
represents 12 lines, and each spring line represents 4 lines. The
mooring lines are assumed to have a bi-linear stiffness. The
fender is a typical pneumatic floating fender, with 4.5 m diameter
and 9.0 m length. The safety factor of 1.8 (55%) and 2.5 (40%)
is applied to calculate maximum allowable load, following the
OCIMF guideline [16]. The lines and fenders are numbered from
bow to stern.
Type
Max.
Breaking
Load
(MBL),
kN
Safety
Factor
(S.F.)
Max.
allow.
loads,
kN
Steel wire
(42mm
Dia.)
1,344
(137 ton)
1.8
739.2
2,011
(205 ton)
2.5
804.4
5,749
(60%
deflection)
2.0
2,874
Nylon tail
(88mm
Dia., 22m
length)
Floating
Pneumatic
(4.5m x
9.0m)
4.2 Environmental loads
Wave, wind and current loads are considered in side-by-side
mooring analysis. The results of two-body motion analysis are
applied as a wave loads effect.
Wind and current load including shielding effects are used for
the SBS mooring analysis. The environmental coefficients are
computed using model test results of reference FLNG project as
shown in Figure 11 and 12.
Wind and current load is computed as following equations.
1
𝐹𝑤𝑖 = 𝜌𝑤 𝐶𝑤𝑖 𝑉𝑤2 𝐴𝑤
for i = x, y, xy
(3)
𝜌 𝐶 𝑉 2𝐿 𝑇
2 𝑐 𝑐𝑖 𝑐 𝐵𝑃
for i = x, y, xy
(4)
𝐹𝑐𝑖 =
2
1
where,
F : Wind and current force/moment
ρ : Air and water densities
C : Wind and current load coefficient
A : Transversal and longitudinal projected area of above water
level
T : Mean draft of vessel
V : Wind and current velocity
FIGURE 11: Wind loads coefficients in SBS configuration
FIGURE 10: Configuration of side-by-side mooring system
6
© 2023 by ASME
(Cond. 7)
(Cond. 8)
FIGURE 13: Environmental conditions for SBS offloading
FIGURE 12: Current loads coefficients in SBS configuration
In order to safe STS offloading operation, the dynamic loads
acting on the mooring system have to be smaller than the
maximum allowable loads in Table 6.
Also, for the safe loading arm operation, the operational envelop
is one of key factors to ensure offloading operation. In this paper,
the STS offloading operability for two mooring configurations
are estimated using results of the mooring analysis.
4.3 Calculation conditions
For estimation of the STS offloading operability, various
environmental conditions are defined as tabulated in Table 7.
Environmental directions are shown in Figure 13.
Table 7 Environmental conditions for SBS offloading
Cond.
No.
Wave
Hs
(m)
Tp
(s)
1
2
1.0 4.5
3
4
5
6
0.7 4.0
7
8
*) from Shore
Wind
Dir.
(deg.)
27.5
10.0
360.0*)
342.5*)
140.0
157.5
175.0
207.5*)
Vw
(m/s)
16.9
13.5
Current
Dir.
(deg.)
27.5
10.0
360.0
342.5
140.0
157.5
175.0
207.5
Vc
(m/s)
0.34
0.34
The environments are modeled as follows:
- Wind-sea: JONSWAP spectrum (  : 1.0)
- Wind: NPD wind spectrum
- Current: constant velocity
Two (2) side-by-side mooring configurations are considered for
FLNG at near shore due to relatively short hull length as shown
in Figure 14. The case 1 configuration is the initial arrangement
with longer extended deck at bow area. The other configuration
has short extended deck and different angle of the bow and breast
lines from the case 1 to reduce the longer extended deck. The
number of bow line and horizontal angle of the breast lines
against x-axis is decreased. The configuration of the spring lines
and fenders is not modified, but the pretension of mooring lines
is slightly difference between two cases.
The time domain simulation is made for 3 hours in real scale,
with additional 30 minutes to stabilize the simulation. Therefore,
total simulation time is 3.5 hours, and data for 3 hours from end
of simulation is used for post-process. Total 5 simulations with
different random seeds are computed for each environmental
conditions.
Dir.
(deg.)
5.0
344.5
185.0
162.5
5.0
344.5
185.0
162.5
(Case 1 configuration)
(Cond. 1)
(Cond. 2)
(Cond. 3)
(Cond. 4)
(Cond. 5)
(Cond. 6)
(Case 2 configuration)
FIGURE 14: Configuration for offloading operability analysis
7
© 2023 by ASME
The maximum of design values is obtained by summation of
mean of each simulation maximum and standard deviation with
factor 1.8 [2].
Maximum load = Tm + aⅹTs
(5)
where,
Tm: Mean of each simulation maximum
a: factor (1.8)
Ts: Standard deviation of each simulation maximum
4.5 Time-domain results for SBS offloading operability
Figure 15 shows the results of the mooring lines tension for two
cases. Generally, the mooring line tension responses of Case 1
are lower than those of Case 2 because of 16 mooring lines with
longer extended deck.
The maximum fender force and relative motion results for case
2 in time domain are shown in Figure 16 and 17, respectively.
As we can see, the maximum line tension and fender force of
case 2 are smaller than allowable limit in Table 6 even it has 15
mooring lines and small extended deck.
The relative motion responses are increased due to static and low
frequency environmental load from wind and current because the
small wave height and short wave period. In all cases, the
maximum relative motion responses are smaller than the criteria.
This meaning that MLA can be operated without any restriction
in North America field (1-yr RP).
(Case 1: 16 mooring lines)
FIGURE 16: Maximum Fender forces in operation condition
(Case 2)
FIGURE 17: Maximum Relative motions in operation
condition (Case 2)
Generally, the relative motion, fender force and mooring line
tension responses of environmental condition 1 are higher than
other conditions because of larger relative heading angle
between FLNG and wind sea wave.
Base on the numerical results, it is known that the mooring
system configuration is a key factor for the offloading
operability.
The side by side mooring arrangement may be determined by
modification of mooring fitting location to improve the
offloading operability in detail design stage.
Also, the wave basin model test results would be required to
validate the numerical calculation results in the next design
stage.
5. CONCLUSION
In this paper, the two-body motion and mooring analysis both
frequency- and time-domain for side-by-side moored FLNG and
LNG carrier have been performed in order to estimate the STS
offloading operability at near shore field with shallow water
depth. Through the presented study, it can be concluded as
follows:
(Case 2: 15 mooring lines)
FIGURE 15: Maximum SBS mooring line tensions in
operation condition
Unlike FLNG which operated in deep water, the designed FLNG
will operated in near shore with shallow water depth. For the
side-by-side mooring analysis for FLNG and LNG carrier, the
special considerations are required such as roll damping, gap
wave as well as sloped sea-bed effects.
8
© 2023 by ASME
The environmental conditions are quite differing in near shore.
The relative motion and mooring tensions are increased due to
static and low frequency environmental load from wind and
current in spite of small wave height and short wave period in
near shore field.
Waves”, Journal of Ship and Ocean Technology, Vol. 6, No. 3,
pp 13-25.
[12] Kim, M.S. and Ha, M.K. (2003). “Relative Motions between
LNG-FPSO and Side-by-Side positioned LNG carrier in
Waves”, Proceedings of 13th International Offshore and Polar
Engineering Conference (ISOPE), Hawaii, USA.
Near shore FLNG has relatively short hull length due to the use
of electric module and accommodation from onshore side, there
are need some extended mooring deck on bow and stern area of
FLNG. To reduce the length of extended deck, the side-by-side
mooring configuration is a key factor for the STS offloading
operability. The operability is considerably affected by the
arrangement of lines and fenders. In order to enhance the
offloading operability, the optimization of mooring arrangement
is required in the next design stage.
[13] Kim, M.S. (2017), “Study on Relative Motion and reduction
method for FLNG”, Ph.D Thesis(written in Korean), Pusan
National University
[14] Kim, M.S. et al (2017), “Offloading operability of Small
Scale AG FLNG with Side-by-Side moored Small Scale LNG
Carrier in Offshore West Africa”, Proc. 36th OMAE,
Trondheim, Norway
[15] Kim, M.S. et al (2018), “Wave induced coupled Motions
and Structure loads between Offshore Floating Structures in
Waves”, Brodogradnja/Shipbuilding, Vol. 69(3), pp. 149-173.
http://dx.doi.org/10.21278/brod69309
[16] Oil Companies International Marine Forum, OCIMF.
“Mooring Equipment Guidelines (MEG4)”, 4th Edition.
[17] SIMA, User Manual, DNV
[18] SIMO, User Manual, DNV
[19] WADAM, User Manual, DNV
[20] WASIM, User Manual, DNV
[21] Yuck, R.H., Park, M.K., Choi, H.S. (2007). “Estimation of
Current Loads on Side-by-Side Moored Two Vessels”,
Proceedings of 17th International Offshore and Polar
Engineering Conference (ISOPE), Lisbon, Portugal.
For the validation of numerical simulation of FLNG in near shore
field with shallow water depth effect, the wave basin model test
results would be required in detail design stage.
Acknowledgments
The authors would like to thank to Samsung Heavy Industries
and DNV for supporting to publish this paper.
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