Propulsion Trends in LNG Carriers
Propulsion Trends in LNG Carriers Two-stroke Engines
MAN Diesel
Contents
Introduction.................................................................................................. 5 Market Development..................................................................................... 6 Definition and types of liquefied gas......................................................... 6 Types of LNG carriers and their containment systems............................... 6 Size of the LNG carriers........................................................................... 7 Ship classes............................................................................................ 7 LNG carrier market.................................................................................. 8 Average Ship Particulars as a Function of Ship Size..................................... 11 Average hull design factor, Fdes . ............................................................ 11 Average design ship speed.................................................................... 12 Propulsion Power Demand as a Function of Ship Size.................................. 14 Average LNG carriers............................................................................. 14 Propulsion Power Demand of Average LNG Carriers as a Function of Ship Speed................................................... 16 Summary.................................................................................................... 18 References................................................................................................. 18
MAN B&W Diesel Propulsion Trends in LNG Carriers
3
Propulsion Trends in LNG Carriers
Introduction
taken into operation in 1964 (scrapped
Natural gas is a “clean” fuel compared
in 1998), the steam turbine has almost
to diesel and heavy fuel oil and, togeth-
exclusively been used as the main
er with an increasing environmental re-
propulsion engine. The reason is the
sponsibility, there is a rising demand for
simplicity of utilising the boil-off gas
natural gas worldwide.
in steam boilers to produce steam for the steam turbines, even though the
Where it is not possible to transport
conventional steam propulsion system
natural gas by means of pipelines, the
has a low efficiency of about 28% com-
LNG (Liquid Natural Gas) carriers have
pared to the approx. 50% valid for the
to take over the transportation because
conventional two-stroke diesel propul-
natural gas in liquid form at atmospheric
sion system.
pressure only takes up 1/600 of the natural gas volume. LNG is a clear liquid with a density of about 450
kg/m3,
Because of the relatively high price of
i.e.
natural gas today, it may be an eco-
45% of the density of water [1]. Howev-
nomical advantage to utilise the expen-
er, the liquid form at atmospheric pres-
sive boil-off gas in a dual fuel (heavy
sure can only be maintained by boil-off
fuel and compressed natural gas) diesel
of some of the gas.
engine for main propulsion, as there will be no need for forced boil-off. A posm3
The first LNG carrier was the 150
sibility is also to reliquefy the expensive
forerunner Suehiro Maru No. 8 from
boil-off gas by means of a reliquefac-
1962 (scrapped 1983) with a four-stroke
tion plant, and then use an ordinary
diesel engine as prime mover.
heavy fuel oil driven diesel engine for main propulsion. In both cases, fuel
However, since the second LNG carrier, the 27,400
m3
Methane Princess, was
savings are obtained compared to the standard steam turbine system.
MAN B&W Diesel Propulsion Trends in LNG Carriers
5
Market Development
Only LNG carriers will be discussed in
in 1969, and in some few cases of the
Definition and types of liquefied gas
this paper.
structural prismatic design. The spheri-
A liquefied gas has a gaseous form at
cal tanks and tanks of the structural
normal ambient temperature and pres-
Types of LNG carriers and their con-
prismatic design are self-supporting
sure, but is liquefied by pressurisation
tainment systems
and are tied to the main hull structure.
or refrigeration, or by a combination of
The gas tankers are constructed ac-
both.
cording to the double-hull concept,
The tanks with the membrane wall sys-
including the bottom areas as a protec-
tem are rectangular and fully integrated
tion against ship grounding incidents.
into the hull and rely on the strength of
Most liquefied gases are hydrocarbons and flammable in nature. The main
the ship’s hull. The membrane system
groups of gas cargoes are LNG (Lique-
Furthermore, the gas must be carried
is based on a very thin primary steel
fied Natural Gas), LPG (Liquefied Pet-
according to the so-called “cargo con-
barrier (0.7-1.5 mm membrane of stain-
rol Gas) and a variety of petrochemical
tainment system” principle, i.e. the car-
less steel alloy) supported through the
gases.
go tanks are installed separately in the
insulation [2]. Such tanks, therefore, are
ship’s holds, and are not a part of the
not self-supporting, but only a relatively
ship’s structure.
small amount of steel has to be cooled.
whereas LPG contains the heavier gas
The gas tanks (fully refrigerated at at-
Today, membrane tanks are mostly
types butane and/or propane. LPG is
mospheric pressure) used today in LNG
being ordered because of its relatively
for example used as a bottled cooking
carriers (see Fig. 1) [2] are normally of
higher utilisation of the hull volume for
gas.
the spherical (Moss) type, introduced in
the cargo capacity, i.e. for the same
1971, and membrane type, introduced
cargo capacity, the ship dimensions
LNG contains mostly methane naturally occurring in association with oil fields,
LPG may be carried in either the pressurised or refrigerated form (butane
Examples the Membrane Membraneand andthe theSpherical Spherical(Moss) (Moss)types types Exampleson onequal equalsized sizedLNG LNGcarriers carriers based based on the
−5ºC and propane −42ºC), but in few cases also in the semi-pressurised form. LNG is always carried/transported cold at atmospheric pressure, i.e. in its liquefied form at its boiling point of as low
3 138,000 m 3 LNG carrier of the membrane type
LNG carrier carrier ofof thethe membrane type type 138,000 138,000 m3mLNG membrane
as −163ºC. As previously mentioned, in its liquid form, natural gas reduces its volume by 600 times and has a density of approx. 450 kg/m3. The LNG is always being refrigerated by means of its boil-off gas and, therefore, the LNG tanks will normally not be completely emptied because some of the LNG still has to cool down the tanks.
carrier of spherical (Moss) type type 138,000 m LNGcarrier 138,000 m3 LNG ofthe the spherical (Moss) 3 3
138,000 m LNG carrier of the spherical (Moss) type
All liquefied gases carried in bulk must
Fig. 1: Examples of equal-sized LNG carriers based on the membrane and the spherical (Moss) types
be carried on a gas carrier in accord-
shown in the same scale
ance with the Gas Code rules of IMO (International Maritime Organisation).
6
Propulsion Trends in LNG Carriers
are smaller than for a similar spherical
on the two, and almost only used, main
capacity, of course, corresponds to
(Moss) type LNG carrier, as also illus-
groups of LNG carriers:
a certain deadweight tonnage, which
trated in Fig. 1, showing the ships in
normally, when referring to the design
the same scale. However, the boil-off
1. Spherical (Moss) containment system
draught, is of the magnitude of 0.47-
gas amount is higher for the membrane
2. Membrane containment system
0.52 times the corresponding size in
tank type compared to that of the spherical tank type.
m3, and when referring to the scantling Size of the LNG carriers
(max.) draught is of the magnitude of
The deadweight of a ship is the carry-
0.52-0.58.
The membrane systems have been
ing capacity in metric tons (1,000 kg)
greatly improved since the introduction
including the weight of bunkers and
Ship classes
in 1969, and especially over the last
other supplies necessary for the ship’s
As mentioned earlier, there is a split up
decade, they have, after the improve-
propulsion. The maximum possible
in LNG carriers, but this is based on
ments, proved their suitability for LNG
deadweight tonnage of a tanker, for ex-
the differences in the construction of
carriers.
ample, will normally be used as the size
the cargo containment system, as for
About 55% of the existing fleet in serv-
of the tanker.
example the spherical (Moss) and the
ice (31 July 2007) consists of the mem-
membrane containment systems.
brane type, whereas about 80% of the
The size of an LNG carrier is, however,
LNG carriers on order today (31 July
normally not based on its deadweight
Depending on the ship size and par-
2007), in numbers, are based on the
tonnage, but on its obtainable volumet-
ticulars, the three main groups of mer-
membrane types [3], see Fig. 2.
ric capacity of liquid natural gas in m3.
chant ships, tankers, bulk carriers and
The main ship particulars of LNG car-
Depending on the density of the LNG
main groups or classes, like handymax,
riers analysed in this paper are based
and the ship size, the volumetric LNG
panamax, etc.
container vessels, are split into different
Distribution in containment systems of LNG fleet Number of LNG carriers in % 80
70
Existing LNG fleet 239 ships - 31 July 2007
LNG carriers on order 136 ships - 31 July 2007
80%
Ref.: LNG World Shipping Journal September/October 2007
60 55% 50 42%
109
40
30
132 100
20
17%
10
0
23 3% 7 Others
3% 4 Moss
Membrane Containment system
Others
Moss
Membrane Containment system
Fig. 2: Distribution in containment systems on LNG fleet
MAN B&W Diesel
Propulsion Trends in LNG Carriers
7
However, for LNG carriers, there is no
LNG carrier classes
Dimensions
Ship size - LNG capacity
such similar general split-up into different groups or classes based on the di-
up to 90,000 m3
Small B: LOA:
up to 40 m up to 250 m
B: LOA:
41 - 49 m 270 - 298 m
Large Conventional
Tdes: B: LOA:
up to 12.0 m 43 - 46 m 285 - 295 m
150,000 - 180,000 m3
Q-flex
Tdes: B: LOA:
up to 12.0 m approx. 50 m approx. 315 m
200,000 - 220,000 m3
Q-max
Tdes: B: LOA:
up to 12.0 m 53 - 55 m approx. 345 m
more than 260,000 m3
mensions alone. The reason is that ever since 1962, LNG carriers have normally been designed for specific purposes/ routes and LNG terminals (with the resulting limitations to the ship dimensions) in large series of the same size. Thus, the most common size of LNG carriers delivered or on order is between 120,000-180,000 m3, and often referred to as Conventional. The demand for lower LNG transportation costs is most effectively met by increasing the LNG capacity of the LNG carriers. Thus, the LNG carriers to and
120,000 - 149,999 m3
Small Conventional
Examples of special LNG carrier sub-classes: Med-max (Mediterranean maximum size) about 75,000 m3 Atlantic-max (Atlantic sea maximum size) about 165,000 m 3
from Qatar ordered over the last few years are of the large sizes of approx.
Fig. 3: LNG carrier classes
210,000 m3 and 265,000 m3, and referred to as Q-flex and Q-max, respectively. Thus, the LNG carrier classes often
Number of LNG carriers in % 90
LNG carrier fleet 31 July 2007 - 239 ships Ref.: Lloyd’s Register - Fairplay’s “PC-Register”
used today can therefore be referred to as listed in Table I and Fig. 3. Besides the main classes described for LNG carriers, special sub-classes are
83% 80 70 60
often used to describe the specialty of the ship in question, as for example the Med-max and Atlantic-max, see Fig. 3. LNG carrier market
50 198
40 30
Small:
Up to 90,000 m3
20
Small Conventional:
120,000-149,999 m 3
10
Large Conventional:
150,000-180,000 m3
0
Q-flex:
200,000-220,000 m3
Q-max:
More than 260,000 m3
15% 36 Small
Small Conventional
2% 5 Large Conventional
0% Q-flex
Fig. 4a: Distribution of existing LNG carriers in service (number of ships) Table I: Main LNG classes
8
Propulsion Trends in LNG Carriers
0% Q-max Classes
Distribution of LNG carriers on order (number of ships)
The first LNG carrier with a capacity of 150 m3 was introduced in 1962, and the second one of 27,400 m3 in 1964,
LNG carriers on order 31 July 2007 - 136 ships
Number of LNG carriers in %
Ref.: Lloyd’s Register - Fairplay’s “PC-Register”
40 37%
and since the mid 1970s the maximum and commonly used LNG carrier size has been approx. 125,000-140,000 m3 for 30 years.
35 30 26%
25
However, recently there has been a dramatic increase in the size of the LNG carriers ordered, with 266,000
m3
23%
20
50
15
36
(Q-max) as the largest one (31 July 2007), but LNG carriers as large as 300,000 m3 are now on the project stage. The reason for this is that the larger the LNG carrier, the lower the transportation costs.
31
10
9% 5%
5
12
7
0
Small
This increase in ship size will also in-
Small Conventional
Large Conventional
Q-flex
volve design modifications of new LNG plants and terminals. Today, the maxi-
Q-max Classes
Fig. 4b: Distribution of LNG carriers on order (number of ships)
mum loaded ship draught in service is still approx. 12 m, because of the limitations of the existing harbour facilities. Distribution of LNG carriers today
Number of LNG carriers delivered 60
As of 31 July 2007, the number of LNG
50
carriers on order is 136, correspond-
40
ing to about 57% of the existing fleet in
30
service (239), see Fig. 2.
20
classes of the existing LNG carriers in
Q-max Q-flex Large Conventional Small Conventional Small
10 0
19 90 19 91 19 92 19 93 19 94 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10
Fig. 4a shows the split-up in LNG
LNG carrier fleet 31 July 2007 Ref.: Lloyd’s Register - Fairplay’s “PC-Register”
service. As can be seen, the current
Year of delivery
fleet is dominated by relatively small ships of the ‘‘Small’’ and ‘‘Small Con-
Fig. 4c: Year of delivery of LNG carriers
ventional’’ classes. Only 2% of the LNG carrier fleet is larger than 150,000 m3 (Large Conventional).
creased greatly during this period.
Fig. 4c shows, as indicated in Fig. 4b, that large LNG carriers like the “Large
LNG carriers on order
At the same time, the contracting of
Conventional” and Q-flex and Q-max
However, according to Fig. 4b, which
“Small” ships has come to a complete
will enter operation in the coming years.
shows the LNG carriers on order as of
standstill. On the other hand, some
31 July 2007, the distribution of the fleet
“Small Conventional” LNG carriers have
Fig. 4d, which shows the average ship
on LNG classes will change drastically.
been ordered as well, probably be-
size of the ships delivered, also con-
Thus, the number of large LNG carriers
cause of the application for a specific
firms that the average LNG size to be
ordered over the last three years has in-
trade/route.
delivered will be larger in the future.
MAN B&W Diesel
Propulsion Trends in LNG Carriers
9
LNG carrier fleet 31 July 2007 Ref.: Lloyd’s Register - Fairplay’s “PC-Register”
Average size of ship, LNG capacity m3 200,000
175,000
150,000 Average of the 2007 fleet
125,000
100,000
19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10
97 98 19
96
19
19
94 95 19
93
19
19
91 92 19
19
19
90
75,000 Year of delivery
Fig. 4d: Average size of LNG carriers delivered
Distribution of Propulsion Systems of LNG Fleet on order
However, because many small LNG carriers have also been ordered, the average LNG size may not be as high
Number of LNG carriers on order, in %
as expected.
50
Until now, very few LNG carriers have
40
LNG carriers on order 136 ships - 31 July 2007 Ref.: LNG World Shipping Journal September/October 2007 40%
been scrapped.
33% 30
26%
Distribution of propulsion systems on LNG carriers
20
55 45
Of the ships on order as of 31 July 2007, 33% are with two-stroke diesel
35
10
engines and reliquefaction, 26% with diesel electric propulsion and 40% with steam turbine propulsion [3], see Fig. 5a. Fig. 5b shows the distribution of the propulsion systems chosen in the LNG fleet delivered or on order as of 31 July 2007, and shown as a function of year of delivery. This curve also confirms the emerging shift from steam turbine to diesel.
10 Propulsion Trends in LNG Carriers
0
1% 1 Steam turbine
Two-stroke diesel and reliquefaction
Dieselelectric
Fig. 5a: Distribution of propulsion systems of LNG fleet on order
Others
Number of ships per year
Average Ship Particulars as a Function of Ship Size
LNG carrier fleet Delivered or on order 31 July 2007
On the basis of LNG carriers built or
60
contracted in the period 1997-2007, as
Two-stroke diesel 50
Diesel-Electric
reported in the Lloyd’s Register – Fair-
Steam turbine
play’s “PC-Register”, we have estimated the average ship particulars of the
40
different sizes of LNG carriers based on the spherical (Moss) and the membrane
30
containment systems, respectively.
20
However, as only very few LNG carriers of some ship sizes have been built in this period, for these ship types, it has
10
also been necessary to look back to the 0
time before 1997. 1965
1970
1975
1980
1985
1990
1995
2000 2005 2010 Year of delivery
Average hull design factor, Fdes Based on the above statistical mate-
Fig. 5b: Distribution of propulsion systems of LNG fleet in year of delivery Average Hull Design Factor of LNG Carriers (Membrane Type)
rial, the average design relationship between the ship particulars of the LNG carriers can, as an indication, be ex-
Average hull design factor, Fdes 1.5
pressed by means of the average hull
1.4
design factor, Fdes, see below and Fig. 6:
1.3 1.2 1.1
Fdes = LPP x B x Dscant/Q
1.0 0.9 0.8 0.7
Main ship particulars
where
0.6
Lpp B Dscant Q Fdes
LPP: length between perpendiculars (m)
0.5 0.4 0.3 0.2
: Length between perpendiculars (m) : Breadth (m) : Scantling draught (m) : LNG capacity (m3) : Average hull design factor
0.1 0
B:
0
50,000
100,000
150,000
ship breadth
Dscant: scantling draught (max.)
Fdes = Lpp x B x Dscant/Q 200,000
250,000 300,000 m3 Size of ship, LNG capacity
Q:
(m) (m)
LNG capacity (max.) of ship (m3)
Based on the above design factor Fdes, Fig. 6: Average hull design factor of LNG carriers (membrane type)
any missing particular can approximately be found as: LPP
= Fdes x Q/(B x Dscant)
m
B
= Fdes x Q/(LPP x Dscant)
m
Dscant = Fdes x Q/(LPP x B) Q
= LPP x B x Dscant/Fdes
m m3
MAN B&W Diesel Propulsion Trends in LNG Carriers 11
In Figs. 7, 8 and 9, the first three ship
Length between perpendiculars m 400
particulars are shown as a function of Large Conventional
Q-max
Q-flex
Small Conventional
the ship size in LNG capacity (Q). The main groups of LNG carrier classes are also shown.
300 Small
ane
br Mem
ss)
Mo
al (
ric phe
The ship particulars of the Moss type
S
ships are only shown up to about
200
150,000 m3 as being the largest one built of this containment type. 100
Average design ship speed 0
In Fig. 10, the average ship speed Vdes, 0
50,000
100,000
150,000
200,000
250,000 300,000 m3 Size of ship, LNG capacity
used for design of the propulsion system and valid for the design draught of the ship, is shown as a function of the
Fig. 7: Average length between perpendiculars of LNG carriers (membrane and Moss types)
ship size. The design draught is normally from 5% to 10% lower than the scantling draught (max. draught) used for calculations of the hull strength.
Breadth m 60
Large Conventional
Q-max
Q-flex
Small Conventional
50 Small
rica
he Sp
40
ss)
o l (M
the higher the ship speed, and today the average design ship speed is about 20
ane mbr
knots for ships larger than 150,000 m3.
Me
30
20
10
0
0
50,000
100,000
150,000
200,000
250,000 300,000 m3 Size of ship, LNG capacity
Fig. 8: Average ship breadth (beam) of LNG carriers (membrane and Moss types)
12 Propulsion Trends in LNG Carriers
The larger the LNG capacity of the ships,
Design draught m 14
Large Conventional
Q-flex
Q-max
Small Conventional
13 12 11
Small
10
ca eri
h
9
Sp
8
s)
os
l (M
7
e
ran
mb
Me
6 5 4 3 2 1 0
0
50,000
100,000
150,000
200,000
250,000 300,000 m3 Size of ship, LNG capacity
Fig. 9: Average design draught of LNG carriers (membrane and Moss types)
Average design ship speed knots 22
Large Conventional
Q-flex
Q-max
Small Conventional
20
18
Small
16
14
12
10
0
50,000
100,000
150,000
200,000
250,000 300,000 m3 Size of ship, LNG capacity
Fig. 10: Average design ship speed of LNG carriers
MAN B&W Diesel Propulsion Trends in LNG Carriers 13
Propulsion Power Demand as a Function of Ship Size
Furthermore, the size of the propel-
Average LNG carriers
as up to approx. 76% of the design
In such a case, a twin-skeg/twin-screw
Based on the average ship particulars
draught, because the ships are nor-
solution will be an attractive alternative
and ship speeds already described for
mally sailing with a big draught also in
to the standard single-screw solution,
LNG carriers built or contracted in the
ballast conditions (low density cargo).
as a potential reduction of the propul-
ratios being relatively high (above 4.0).
ler diameter is assumed to be as high
period of 1997-2007, we have made a
sion power up to 9% is possible.
power prediction calculation (Holtrop &
The average ship particulars of these
Therefore, the large LNG carriers, besides
Mennen’s Method) for such LNG car-
LNG carriers are shown in the tables
the single-screw version, see Fig. 12,
riers in various sizes from 19,000 m3
in Fig. 11, and Figs 12 and 13 valid
have also been calculated for the twin-
to 265,000
m 3.
However, as the mem-
for LNG capacity 19,000-138,000
m3
skeg/twin-screw solution, see Fig. 13.
brane type LNG carrier seems to be-
and 150,000-265,000 m3, respectively.
come the dominating type in the future,
On this basis, and valid for the design
The twin-skeg/twin main engine LNG
cf. Fig. 2, a power prediction has only been
draught and design ship speed, we
carrier would also meet the safety de-
made for LNG carriers of this type.
have calculated the specified engine
mands of the future to install at least
MCR power needed for propulsion.
double propulsion drives enhancing the
For all cases, we have assumed a sea
redundancy of the prime movers.
margin of 15% and an engine margin
The maximum design draught for the
of 10%, i.e. a service rating of 90%
large LNG carriers in service is limited
In fact, the Q-flex and Q-max ships
SMCR, including 15% sea margin.
to about 12.0 m because of harbour facili-
have only been made/ordered in the
ties. This results in beam/design draught
twin-skeg/twin-screw version.
Membrane Type Single-Screw
Small
Small (Med-max)
Small Conventional
Ship size, LNG capacity
m3
19,000
75,000
138,000
Scantling draught Length overall Length between pp Breadth Design draught Sea margin Engine margin
m m m m m % %
7.1 130.0 124.0 25.6 6.5 15 10
10.6 220.0 210.0 35.0 9.7 15 10
12.0 276.0 263.0 43.4 11.3 15 10
Average design ship speed SMCR power Main engine options
Knots kW 1. 2. 3. 4.
15.0 5,300 5S40ME-B9 5S42MC7 7S35ME-B9
17.5 14,200 6S60ME-C8 7S60ME-C7 5L70ME-C7 5S65ME-C8
19.5 28,000 7K80ME-C9 6K90ME-C9 8K80ME-C6 6K90ME9
Average design ship speed - 0.5 kn SMCR power Main engine options
Knots kW 1. 2. 3. 4.
14.5 4,600 5S40ME-B9 5S42MC7 6S35ME-B9
17.0 12,800 6S60ME-C7 5L70ME-C7 5S65ME-C8
19.0 25,500 6K80ME-C9 6K90ME-C6 8L70ME-C8 8S70ME-C8
Average design ship speed + 0.5 kn SMCR power Main engine options
Knots KW 1. 2. 3. 4.
15.5 6,150 6S40ME-B9 6S42MC7 8S35ME-B9
18.0 15,900 7S60ME-C7 5L70ME-C8 6L70ME-C7 6S65ME-C8
20.0 30,800 7K80ME-C9 6K90ME-C9 7K90ME-C6 6K90ME9
Fig. 11: Ship particulars and propulsion SMCR power demand (membrane type), LNG capacity 19,000-138,000 m3, single-screw
14 Propulsion Trends in LNG Carriers
Membrane Type Single-Screw 3
Large Conventional
Q-flex
Q-max 265,000
Ship size, LNG capacity
m
150,000
210,000
Scantling draught Length overall Length between pp Breadth Design draught Sea margin Engine margin
m m m m m % %
12.3 288.0 275.0 44.2 11.6 15 10
12.7 315.0 303.0 50.0 12.0 15 10
12.7 345.0 332.0 54.0 12.0 15 10
Average design ship speed SMCR power Main engine options
Knots kW
20.0 31,400
20.0 39,300
20.0 45,200
1. 2. 3. 4.
6K90ME9
7K90ME9 7K98ME7
8K90ME9 8K98ME6 8K98ME7
Average design ship speed - 0.5 kn SMCR power Main engine options
Knots kW 1. 2. 3. 4.
19.5 28,500 6K90ME9
19.5 35,700 7K90ME9 6K98ME7
19.5 41,100 8K90ME9 7K98ME7 8K98ME6
Average design ship speed + 0.5 kn SMCR power Main engine options
Knots kW 1. 2. 3. 4.
20.5 34,300 6K90ME9
20.5 43,200 8K90ME9 7K98ME7
20.5 49,600 9K90ME9 9K98ME6 9K98ME7
The SMCR power results are also shown in the tables in Figs. 11-13 ‘‘Ship Particulars and Propulsion SMCR Power Demand’’ together with the selected main engine options of the MAN B&W two-stroke engine types. The similar results valid for +/- 0.5 knots compared to the average design ship speed are also shown.
All above ME engines can also be delivered in ME-GI version (gas injected)
Fig. 12: Ship particulars and propulsion SMCR power demand (membrane type), LNG capacity 150,000-265,000 m3, single-screw
Membrane Type Twin-Screw
Large Conventional
Q-flex
Q-max 265,000
Ship size, LNG capacity
m3
150,000
210,000
Scantling draught Length overall Length between pp Breadth Design draught Sea margin Engine margin
m m m m m % %
12.3 288.0 275.0 44.2 11.6 15 10
12.7 315.0 303.0 50.0 12.0 15 10
12.7 345.0 332.0 54.0 12.0 15 10
Knots
20.0 2x14,900 2x5S70ME-C7 2x6S65ME-C8
20.0 2x18,300 2x6S70ME-C7 2x7S65ME-C8
20.0 2x20,800 2x7S70ME-C7 2x8S65ME-C8
Knots kW 1. 2. 3. 4.
19.5 2x13,600 2x5S70ME-C7 2x5S65ME-C8
19.5 2x16,700 2x6S70ME-C7 2x6S65ME-C8
19.5 2x19,000 2x6S70ME-C8 2x7S65ME-C8
Average design ship speed + 0.5 kn Knots kW SMCR power Main engine options 1. 2. 3. 4.
20.5 2x16,300 2x5S70ME-C8 2x6S70ME-C7 2x6S65ME-C8
20.5 2x20,100 2x7S70ME-C7 2x7S65ME-C8
20.5 2x22,800 2x7S70ME-C8 2x8S65ME-C8
Average design ship speed SMCR power Main engine options
kW 1. 2. 3. 4.
Average design ship speed - 0.5 kn SMCR power Main engine options
All above ME engines can also be delivered in ME-GI version (gas injected)
Fig. 13: Ship particulars and propulsion SMCR power demand (membrane type), LNG capacity 150,000-265,000 m3, twin-skeg and twin-screw
MAN B&W Diesel Propulsion Trends in LNG Carriers 15
Propulsion Power Demand of Average LNG Carriers as a Function of Ship Speed
It is possible to derate the engine, i.e.
When the required ship speed is
MCR power needed for a given main
changed, the required SMCR power
engine is too high for a required ship
will change too, as mentioned above,
speed. This would also result in a lower
and other main engine options could
specific fuel consumption of the engine.
use an SMCR power lower than the nominal MCR power, if the nominal
be selected. This trend – with the average ship particulars and average ship
Therefore, in some cases it could be of
speed as the basis – is shown in detail
particular advantage, considering the
in Figs. 14 and 15 for single-screw ves-
high fuel price today, to select a higher
sels, and in Fig. 16 for large twin-skeg/
mark number than needed and derate
twin-screw vessels.
the engine.
SMCR power kW
Including: 15% sea margin 10% engine margin
40,000
Small Conventional 7K90ME9/ME-C9
21.0 kn 20.5 kn 20.0 kn
30,000
7K80ME-C9
19.5 kn
7L70ME-C8
20,000
6L70ME-C8 7S60ME-C8 5L70ME-C7 6S60ME-C8
16.5 kn
7S40ME-B9 6S40ME-B9 5S40ME-B9 5S35ME-B9
6K80ME-C6
18.0 kn 17.5 kn
6S65ME-C8
5S65ME-C8
16.0 kn
14.5 kn 14.0 kn
0
15.0 kn
50,000
15.5 kn
100,000
150,000 m3 Size of ship, LNG capacity
Fig. 14: Propulsion SMCR power demand of an average LNG carrier (membrane type), Small and Small Conventional – single-screw
16 Propulsion Trends in LNG Carriers
6K80ME-C9 8S70ME-C8
18.5 kn 7S70ME-C8
gn
si de ge era eed v A sp ip sh
17.0 kn
5S60ME-C7
10,000
19.0 kn
8L70ME-C8
Small
0
8K80ME-C9 6K90ME9/ME-C9
SMCR power kW 70,000
Q-max
Including: 15% sea margin 10% engine margin
Q-flex
Large Conventional
60,000
10K98ME7 21.0 kn
9K90ME9
50,000
20.5 kn
esign
7K90ME9
ge d Avera
peed
19.5 kn
ship s
19.0 kn
6K90ME9 7K80ME-C9
30,000
8K98ME7
20.0 kn
8K90ME9 40,000
9K98ME7
7K98ME7 7K98ME6 6K98ME6
5K90ME9 8S70ME-C8 7S70ME-C8
20,000
10,000
0
All above engines can also be delivered in ME-GI version (gas injected) 100,000
150,000
250,000
200,000
300,000 m3 Size of ship, LNG capacity
Propulsion SMCR Power Demand of an Average LNG Carrier (Membrane Type) Large Conventional, Q-flex and Q-max - Twin Screw Fig.15: Propulsion SMCR power demand of an average LNG carrier (membrane type), Large Conventional, Q-flex and Q-max – single-screw
Total SMCR power kW 60,000
Including: 15% sea margin 10% engine margin
Q-max Large
50,000
Q-flex
21.0 kn
Conventional
40,000
2 x 6S70ME-C8 2 x 6S70ME-C7
esign
ge d Avera
2 x 6S65ME-C8 2 x 5S70ME-C8 2 x 5S70ME-C7 2 x 5S65ME-C8
30,000
20.5 kn
peed
ship s
2 x 8S70ME-C8 2 x 8S70ME-C7
20.0 kn
2 x 8S65ME-C8 2 x 7S70ME-C8 2 x 7S70ME-C7
19.5 kn
2 x 7S65ME-C8
19.0 kn
20,000
10,000 All above engines can also be delivered in ME-GI version (gas injected)
0 100,000
150,000
200,000
250,000
300,000 m3 Size of ship, LNG capacity
Fig. 16: Propulsion SMCR power demand of an average LNG carrier (membrane type), Large Conventional, Q-flex and Q-max – twin-skeg and twin-screw
MAN B&W Diesel Propulsion Trends in LNG Carriers 17
Summary
The LNG carrier market is an increas-
References
Safety and reliability of LNG carriers
ingly important and attractive transport
[1] Introduction to LNG Center for
have always been important demands
segment which, due to the increasing
Energy Economics
to the design of this type of ship, as can
global demand to “clean” fuel, is ex-
The University of Texas at Austin
also be seen from the stringent stand-
pected to become of even greater im-
January 2007
ards given by IMO and several coun-
portance in the future. Thus, the CO2
tries. Thus, the most widely used LNG
emission by burning LNG is about 23%
[2] Liquefied Gas Handling Principles
containment systems – the Moss and
lower than for heavy fuel oil.
on Ships and in Terminals
the membrane – have been applied for
McGuire and White Witherby &
many years because of their reliability.
As described, MAN B&W engines are
Company Limited, London
Today, the membrane type LNG carrier
able to meet the engine power needs
Third Edition 2000
seems to take over the major market
of any size in the modern LNG carrier
share because of its better utilisation of
fleet.
the ship’s hull volume.
[3] LNG World Shipping Journal
September/October 2007
It should be noted that today the alterFor many years the steam turbines
native Compressed Natural Gas (CNG)
[4] LNG Carriers
have almost exclusively been used as
transportation form has potential to
ME-GI Engine with High Pressure
prime movers for LNG carriers, even
match the LNG transportation form for
Gas Supply System
though its efficiency is much lower than
shorter routes. Is now being investi-
MAN Diesel A/S, Copenhagen,
e.g. directly coupled two-stroke diesel
gated, but has so far not yet been ma-
Denmark, January 2007
engines. The reason is the simplicity of
terialised in a ship, even though there
utilising the boil-off gas in steam boilers
are some projects with CNG carriers.
[5] The Trans Ocean Gas
to produce steam for steam turbines.
CNG’s gas density is about 2/3 of LNG
CNG Transportation
[5]. The advantage of CNG is that, in
Technical & Business
However, with the introduction of the
contrast to LNG, CNG does not need
Development Plan
reliquefaction plant and/or gas-driven
any costly processing plants to offload
Trans Ocean Gas Inc.
diesel engines some few years ago, it is
the gas. The tanks have to be of the cy-
April 2004
today also possible to install high-effi-
lindrical pressure types or of the coselle
ciency diesel engines as prime movers,
type, i.e. of the coil/carousel type. Also
and thereby cut the fuel costs [4].
for this ship type, the MAN B&W twostroke diesel engines are feasible.
18 Propulsion Trends in LNG Carriers
MAN B&W Diesel Propulsion Trends in LNG Carriers 19
Copyright © MAN Diesel · Subject to modification in the interest of technical progress. · 5510-0035-01ppr Aug 2009 · Printed in Denmark
MAN Diesel Teglholmsgade 41, 2450 Copenhagen, Denmark Phone +45 33 85 11 00 Fax +45 33 85 10 30 [email protected] www.mandiesel.com
MAN Diesel
Contents
Introduction.................................................................................................. 5 Market Development..................................................................................... 6 Definition and types of liquefied gas......................................................... 6 Types of LNG carriers and their containment systems............................... 6 Size of the LNG carriers........................................................................... 7 Ship classes............................................................................................ 7 LNG carrier market.................................................................................. 8 Average Ship Particulars as a Function of Ship Size..................................... 11 Average hull design factor, Fdes . ............................................................ 11 Average design ship speed.................................................................... 12 Propulsion Power Demand as a Function of Ship Size.................................. 14 Average LNG carriers............................................................................. 14 Propulsion Power Demand of Average LNG Carriers as a Function of Ship Speed................................................... 16 Summary.................................................................................................... 18 References................................................................................................. 18
MAN B&W Diesel Propulsion Trends in LNG Carriers
3
Propulsion Trends in LNG Carriers
Introduction
taken into operation in 1964 (scrapped
Natural gas is a “clean” fuel compared
in 1998), the steam turbine has almost
to diesel and heavy fuel oil and, togeth-
exclusively been used as the main
er with an increasing environmental re-
propulsion engine. The reason is the
sponsibility, there is a rising demand for
simplicity of utilising the boil-off gas
natural gas worldwide.
in steam boilers to produce steam for the steam turbines, even though the
Where it is not possible to transport
conventional steam propulsion system
natural gas by means of pipelines, the
has a low efficiency of about 28% com-
LNG (Liquid Natural Gas) carriers have
pared to the approx. 50% valid for the
to take over the transportation because
conventional two-stroke diesel propul-
natural gas in liquid form at atmospheric
sion system.
pressure only takes up 1/600 of the natural gas volume. LNG is a clear liquid with a density of about 450
kg/m3,
Because of the relatively high price of
i.e.
natural gas today, it may be an eco-
45% of the density of water [1]. Howev-
nomical advantage to utilise the expen-
er, the liquid form at atmospheric pres-
sive boil-off gas in a dual fuel (heavy
sure can only be maintained by boil-off
fuel and compressed natural gas) diesel
of some of the gas.
engine for main propulsion, as there will be no need for forced boil-off. A posm3
The first LNG carrier was the 150
sibility is also to reliquefy the expensive
forerunner Suehiro Maru No. 8 from
boil-off gas by means of a reliquefac-
1962 (scrapped 1983) with a four-stroke
tion plant, and then use an ordinary
diesel engine as prime mover.
heavy fuel oil driven diesel engine for main propulsion. In both cases, fuel
However, since the second LNG carrier, the 27,400
m3
Methane Princess, was
savings are obtained compared to the standard steam turbine system.
MAN B&W Diesel Propulsion Trends in LNG Carriers
5
Market Development
Only LNG carriers will be discussed in
in 1969, and in some few cases of the
Definition and types of liquefied gas
this paper.
structural prismatic design. The spheri-
A liquefied gas has a gaseous form at
cal tanks and tanks of the structural
normal ambient temperature and pres-
Types of LNG carriers and their con-
prismatic design are self-supporting
sure, but is liquefied by pressurisation
tainment systems
and are tied to the main hull structure.
or refrigeration, or by a combination of
The gas tankers are constructed ac-
both.
cording to the double-hull concept,
The tanks with the membrane wall sys-
including the bottom areas as a protec-
tem are rectangular and fully integrated
tion against ship grounding incidents.
into the hull and rely on the strength of
Most liquefied gases are hydrocarbons and flammable in nature. The main
the ship’s hull. The membrane system
groups of gas cargoes are LNG (Lique-
Furthermore, the gas must be carried
is based on a very thin primary steel
fied Natural Gas), LPG (Liquefied Pet-
according to the so-called “cargo con-
barrier (0.7-1.5 mm membrane of stain-
rol Gas) and a variety of petrochemical
tainment system” principle, i.e. the car-
less steel alloy) supported through the
gases.
go tanks are installed separately in the
insulation [2]. Such tanks, therefore, are
ship’s holds, and are not a part of the
not self-supporting, but only a relatively
ship’s structure.
small amount of steel has to be cooled.
whereas LPG contains the heavier gas
The gas tanks (fully refrigerated at at-
Today, membrane tanks are mostly
types butane and/or propane. LPG is
mospheric pressure) used today in LNG
being ordered because of its relatively
for example used as a bottled cooking
carriers (see Fig. 1) [2] are normally of
higher utilisation of the hull volume for
gas.
the spherical (Moss) type, introduced in
the cargo capacity, i.e. for the same
1971, and membrane type, introduced
cargo capacity, the ship dimensions
LNG contains mostly methane naturally occurring in association with oil fields,
LPG may be carried in either the pressurised or refrigerated form (butane
Examples the Membrane Membraneand andthe theSpherical Spherical(Moss) (Moss)types types Exampleson onequal equalsized sizedLNG LNGcarriers carriers based based on the
−5ºC and propane −42ºC), but in few cases also in the semi-pressurised form. LNG is always carried/transported cold at atmospheric pressure, i.e. in its liquefied form at its boiling point of as low
3 138,000 m 3 LNG carrier of the membrane type
LNG carrier carrier ofof thethe membrane type type 138,000 138,000 m3mLNG membrane
as −163ºC. As previously mentioned, in its liquid form, natural gas reduces its volume by 600 times and has a density of approx. 450 kg/m3. The LNG is always being refrigerated by means of its boil-off gas and, therefore, the LNG tanks will normally not be completely emptied because some of the LNG still has to cool down the tanks.
carrier of spherical (Moss) type type 138,000 m LNGcarrier 138,000 m3 LNG ofthe the spherical (Moss) 3 3
138,000 m LNG carrier of the spherical (Moss) type
All liquefied gases carried in bulk must
Fig. 1: Examples of equal-sized LNG carriers based on the membrane and the spherical (Moss) types
be carried on a gas carrier in accord-
shown in the same scale
ance with the Gas Code rules of IMO (International Maritime Organisation).
6
Propulsion Trends in LNG Carriers
are smaller than for a similar spherical
on the two, and almost only used, main
capacity, of course, corresponds to
(Moss) type LNG carrier, as also illus-
groups of LNG carriers:
a certain deadweight tonnage, which
trated in Fig. 1, showing the ships in
normally, when referring to the design
the same scale. However, the boil-off
1. Spherical (Moss) containment system
draught, is of the magnitude of 0.47-
gas amount is higher for the membrane
2. Membrane containment system
0.52 times the corresponding size in
tank type compared to that of the spherical tank type.
m3, and when referring to the scantling Size of the LNG carriers
(max.) draught is of the magnitude of
The deadweight of a ship is the carry-
0.52-0.58.
The membrane systems have been
ing capacity in metric tons (1,000 kg)
greatly improved since the introduction
including the weight of bunkers and
Ship classes
in 1969, and especially over the last
other supplies necessary for the ship’s
As mentioned earlier, there is a split up
decade, they have, after the improve-
propulsion. The maximum possible
in LNG carriers, but this is based on
ments, proved their suitability for LNG
deadweight tonnage of a tanker, for ex-
the differences in the construction of
carriers.
ample, will normally be used as the size
the cargo containment system, as for
About 55% of the existing fleet in serv-
of the tanker.
example the spherical (Moss) and the
ice (31 July 2007) consists of the mem-
membrane containment systems.
brane type, whereas about 80% of the
The size of an LNG carrier is, however,
LNG carriers on order today (31 July
normally not based on its deadweight
Depending on the ship size and par-
2007), in numbers, are based on the
tonnage, but on its obtainable volumet-
ticulars, the three main groups of mer-
membrane types [3], see Fig. 2.
ric capacity of liquid natural gas in m3.
chant ships, tankers, bulk carriers and
The main ship particulars of LNG car-
Depending on the density of the LNG
main groups or classes, like handymax,
riers analysed in this paper are based
and the ship size, the volumetric LNG
panamax, etc.
container vessels, are split into different
Distribution in containment systems of LNG fleet Number of LNG carriers in % 80
70
Existing LNG fleet 239 ships - 31 July 2007
LNG carriers on order 136 ships - 31 July 2007
80%
Ref.: LNG World Shipping Journal September/October 2007
60 55% 50 42%
109
40
30
132 100
20
17%
10
0
23 3% 7 Others
3% 4 Moss
Membrane Containment system
Others
Moss
Membrane Containment system
Fig. 2: Distribution in containment systems on LNG fleet
MAN B&W Diesel
Propulsion Trends in LNG Carriers
7
However, for LNG carriers, there is no
LNG carrier classes
Dimensions
Ship size - LNG capacity
such similar general split-up into different groups or classes based on the di-
up to 90,000 m3
Small B: LOA:
up to 40 m up to 250 m
B: LOA:
41 - 49 m 270 - 298 m
Large Conventional
Tdes: B: LOA:
up to 12.0 m 43 - 46 m 285 - 295 m
150,000 - 180,000 m3
Q-flex
Tdes: B: LOA:
up to 12.0 m approx. 50 m approx. 315 m
200,000 - 220,000 m3
Q-max
Tdes: B: LOA:
up to 12.0 m 53 - 55 m approx. 345 m
more than 260,000 m3
mensions alone. The reason is that ever since 1962, LNG carriers have normally been designed for specific purposes/ routes and LNG terminals (with the resulting limitations to the ship dimensions) in large series of the same size. Thus, the most common size of LNG carriers delivered or on order is between 120,000-180,000 m3, and often referred to as Conventional. The demand for lower LNG transportation costs is most effectively met by increasing the LNG capacity of the LNG carriers. Thus, the LNG carriers to and
120,000 - 149,999 m3
Small Conventional
Examples of special LNG carrier sub-classes: Med-max (Mediterranean maximum size) about 75,000 m3 Atlantic-max (Atlantic sea maximum size) about 165,000 m 3
from Qatar ordered over the last few years are of the large sizes of approx.
Fig. 3: LNG carrier classes
210,000 m3 and 265,000 m3, and referred to as Q-flex and Q-max, respectively. Thus, the LNG carrier classes often
Number of LNG carriers in % 90
LNG carrier fleet 31 July 2007 - 239 ships Ref.: Lloyd’s Register - Fairplay’s “PC-Register”
used today can therefore be referred to as listed in Table I and Fig. 3. Besides the main classes described for LNG carriers, special sub-classes are
83% 80 70 60
often used to describe the specialty of the ship in question, as for example the Med-max and Atlantic-max, see Fig. 3. LNG carrier market
50 198
40 30
Small:
Up to 90,000 m3
20
Small Conventional:
120,000-149,999 m 3
10
Large Conventional:
150,000-180,000 m3
0
Q-flex:
200,000-220,000 m3
Q-max:
More than 260,000 m3
15% 36 Small
Small Conventional
2% 5 Large Conventional
0% Q-flex
Fig. 4a: Distribution of existing LNG carriers in service (number of ships) Table I: Main LNG classes
8
Propulsion Trends in LNG Carriers
0% Q-max Classes
Distribution of LNG carriers on order (number of ships)
The first LNG carrier with a capacity of 150 m3 was introduced in 1962, and the second one of 27,400 m3 in 1964,
LNG carriers on order 31 July 2007 - 136 ships
Number of LNG carriers in %
Ref.: Lloyd’s Register - Fairplay’s “PC-Register”
40 37%
and since the mid 1970s the maximum and commonly used LNG carrier size has been approx. 125,000-140,000 m3 for 30 years.
35 30 26%
25
However, recently there has been a dramatic increase in the size of the LNG carriers ordered, with 266,000
m3
23%
20
50
15
36
(Q-max) as the largest one (31 July 2007), but LNG carriers as large as 300,000 m3 are now on the project stage. The reason for this is that the larger the LNG carrier, the lower the transportation costs.
31
10
9% 5%
5
12
7
0
Small
This increase in ship size will also in-
Small Conventional
Large Conventional
Q-flex
volve design modifications of new LNG plants and terminals. Today, the maxi-
Q-max Classes
Fig. 4b: Distribution of LNG carriers on order (number of ships)
mum loaded ship draught in service is still approx. 12 m, because of the limitations of the existing harbour facilities. Distribution of LNG carriers today
Number of LNG carriers delivered 60
As of 31 July 2007, the number of LNG
50
carriers on order is 136, correspond-
40
ing to about 57% of the existing fleet in
30
service (239), see Fig. 2.
20
classes of the existing LNG carriers in
Q-max Q-flex Large Conventional Small Conventional Small
10 0
19 90 19 91 19 92 19 93 19 94 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10
Fig. 4a shows the split-up in LNG
LNG carrier fleet 31 July 2007 Ref.: Lloyd’s Register - Fairplay’s “PC-Register”
service. As can be seen, the current
Year of delivery
fleet is dominated by relatively small ships of the ‘‘Small’’ and ‘‘Small Con-
Fig. 4c: Year of delivery of LNG carriers
ventional’’ classes. Only 2% of the LNG carrier fleet is larger than 150,000 m3 (Large Conventional).
creased greatly during this period.
Fig. 4c shows, as indicated in Fig. 4b, that large LNG carriers like the “Large
LNG carriers on order
At the same time, the contracting of
Conventional” and Q-flex and Q-max
However, according to Fig. 4b, which
“Small” ships has come to a complete
will enter operation in the coming years.
shows the LNG carriers on order as of
standstill. On the other hand, some
31 July 2007, the distribution of the fleet
“Small Conventional” LNG carriers have
Fig. 4d, which shows the average ship
on LNG classes will change drastically.
been ordered as well, probably be-
size of the ships delivered, also con-
Thus, the number of large LNG carriers
cause of the application for a specific
firms that the average LNG size to be
ordered over the last three years has in-
trade/route.
delivered will be larger in the future.
MAN B&W Diesel
Propulsion Trends in LNG Carriers
9
LNG carrier fleet 31 July 2007 Ref.: Lloyd’s Register - Fairplay’s “PC-Register”
Average size of ship, LNG capacity m3 200,000
175,000
150,000 Average of the 2007 fleet
125,000
100,000
19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10
97 98 19
96
19
19
94 95 19
93
19
19
91 92 19
19
19
90
75,000 Year of delivery
Fig. 4d: Average size of LNG carriers delivered
Distribution of Propulsion Systems of LNG Fleet on order
However, because many small LNG carriers have also been ordered, the average LNG size may not be as high
Number of LNG carriers on order, in %
as expected.
50
Until now, very few LNG carriers have
40
LNG carriers on order 136 ships - 31 July 2007 Ref.: LNG World Shipping Journal September/October 2007 40%
been scrapped.
33% 30
26%
Distribution of propulsion systems on LNG carriers
20
55 45
Of the ships on order as of 31 July 2007, 33% are with two-stroke diesel
35
10
engines and reliquefaction, 26% with diesel electric propulsion and 40% with steam turbine propulsion [3], see Fig. 5a. Fig. 5b shows the distribution of the propulsion systems chosen in the LNG fleet delivered or on order as of 31 July 2007, and shown as a function of year of delivery. This curve also confirms the emerging shift from steam turbine to diesel.
10 Propulsion Trends in LNG Carriers
0
1% 1 Steam turbine
Two-stroke diesel and reliquefaction
Dieselelectric
Fig. 5a: Distribution of propulsion systems of LNG fleet on order
Others
Number of ships per year
Average Ship Particulars as a Function of Ship Size
LNG carrier fleet Delivered or on order 31 July 2007
On the basis of LNG carriers built or
60
contracted in the period 1997-2007, as
Two-stroke diesel 50
Diesel-Electric
reported in the Lloyd’s Register – Fair-
Steam turbine
play’s “PC-Register”, we have estimated the average ship particulars of the
40
different sizes of LNG carriers based on the spherical (Moss) and the membrane
30
containment systems, respectively.
20
However, as only very few LNG carriers of some ship sizes have been built in this period, for these ship types, it has
10
also been necessary to look back to the 0
time before 1997. 1965
1970
1975
1980
1985
1990
1995
2000 2005 2010 Year of delivery
Average hull design factor, Fdes Based on the above statistical mate-
Fig. 5b: Distribution of propulsion systems of LNG fleet in year of delivery Average Hull Design Factor of LNG Carriers (Membrane Type)
rial, the average design relationship between the ship particulars of the LNG carriers can, as an indication, be ex-
Average hull design factor, Fdes 1.5
pressed by means of the average hull
1.4
design factor, Fdes, see below and Fig. 6:
1.3 1.2 1.1
Fdes = LPP x B x Dscant/Q
1.0 0.9 0.8 0.7
Main ship particulars
where
0.6
Lpp B Dscant Q Fdes
LPP: length between perpendiculars (m)
0.5 0.4 0.3 0.2
: Length between perpendiculars (m) : Breadth (m) : Scantling draught (m) : LNG capacity (m3) : Average hull design factor
0.1 0
B:
0
50,000
100,000
150,000
ship breadth
Dscant: scantling draught (max.)
Fdes = Lpp x B x Dscant/Q 200,000
250,000 300,000 m3 Size of ship, LNG capacity
Q:
(m) (m)
LNG capacity (max.) of ship (m3)
Based on the above design factor Fdes, Fig. 6: Average hull design factor of LNG carriers (membrane type)
any missing particular can approximately be found as: LPP
= Fdes x Q/(B x Dscant)
m
B
= Fdes x Q/(LPP x Dscant)
m
Dscant = Fdes x Q/(LPP x B) Q
= LPP x B x Dscant/Fdes
m m3
MAN B&W Diesel Propulsion Trends in LNG Carriers 11
In Figs. 7, 8 and 9, the first three ship
Length between perpendiculars m 400
particulars are shown as a function of Large Conventional
Q-max
Q-flex
Small Conventional
the ship size in LNG capacity (Q). The main groups of LNG carrier classes are also shown.
300 Small
ane
br Mem
ss)
Mo
al (
ric phe
The ship particulars of the Moss type
S
ships are only shown up to about
200
150,000 m3 as being the largest one built of this containment type. 100
Average design ship speed 0
In Fig. 10, the average ship speed Vdes, 0
50,000
100,000
150,000
200,000
250,000 300,000 m3 Size of ship, LNG capacity
used for design of the propulsion system and valid for the design draught of the ship, is shown as a function of the
Fig. 7: Average length between perpendiculars of LNG carriers (membrane and Moss types)
ship size. The design draught is normally from 5% to 10% lower than the scantling draught (max. draught) used for calculations of the hull strength.
Breadth m 60
Large Conventional
Q-max
Q-flex
Small Conventional
50 Small
rica
he Sp
40
ss)
o l (M
the higher the ship speed, and today the average design ship speed is about 20
ane mbr
knots for ships larger than 150,000 m3.
Me
30
20
10
0
0
50,000
100,000
150,000
200,000
250,000 300,000 m3 Size of ship, LNG capacity
Fig. 8: Average ship breadth (beam) of LNG carriers (membrane and Moss types)
12 Propulsion Trends in LNG Carriers
The larger the LNG capacity of the ships,
Design draught m 14
Large Conventional
Q-flex
Q-max
Small Conventional
13 12 11
Small
10
ca eri
h
9
Sp
8
s)
os
l (M
7
e
ran
mb
Me
6 5 4 3 2 1 0
0
50,000
100,000
150,000
200,000
250,000 300,000 m3 Size of ship, LNG capacity
Fig. 9: Average design draught of LNG carriers (membrane and Moss types)
Average design ship speed knots 22
Large Conventional
Q-flex
Q-max
Small Conventional
20
18
Small
16
14
12
10
0
50,000
100,000
150,000
200,000
250,000 300,000 m3 Size of ship, LNG capacity
Fig. 10: Average design ship speed of LNG carriers
MAN B&W Diesel Propulsion Trends in LNG Carriers 13
Propulsion Power Demand as a Function of Ship Size
Furthermore, the size of the propel-
Average LNG carriers
as up to approx. 76% of the design
In such a case, a twin-skeg/twin-screw
Based on the average ship particulars
draught, because the ships are nor-
solution will be an attractive alternative
and ship speeds already described for
mally sailing with a big draught also in
to the standard single-screw solution,
LNG carriers built or contracted in the
ballast conditions (low density cargo).
as a potential reduction of the propul-
ratios being relatively high (above 4.0).
ler diameter is assumed to be as high
period of 1997-2007, we have made a
sion power up to 9% is possible.
power prediction calculation (Holtrop &
The average ship particulars of these
Therefore, the large LNG carriers, besides
Mennen’s Method) for such LNG car-
LNG carriers are shown in the tables
the single-screw version, see Fig. 12,
riers in various sizes from 19,000 m3
in Fig. 11, and Figs 12 and 13 valid
have also been calculated for the twin-
to 265,000
m 3.
However, as the mem-
for LNG capacity 19,000-138,000
m3
skeg/twin-screw solution, see Fig. 13.
brane type LNG carrier seems to be-
and 150,000-265,000 m3, respectively.
come the dominating type in the future,
On this basis, and valid for the design
The twin-skeg/twin main engine LNG
cf. Fig. 2, a power prediction has only been
draught and design ship speed, we
carrier would also meet the safety de-
made for LNG carriers of this type.
have calculated the specified engine
mands of the future to install at least
MCR power needed for propulsion.
double propulsion drives enhancing the
For all cases, we have assumed a sea
redundancy of the prime movers.
margin of 15% and an engine margin
The maximum design draught for the
of 10%, i.e. a service rating of 90%
large LNG carriers in service is limited
In fact, the Q-flex and Q-max ships
SMCR, including 15% sea margin.
to about 12.0 m because of harbour facili-
have only been made/ordered in the
ties. This results in beam/design draught
twin-skeg/twin-screw version.
Membrane Type Single-Screw
Small
Small (Med-max)
Small Conventional
Ship size, LNG capacity
m3
19,000
75,000
138,000
Scantling draught Length overall Length between pp Breadth Design draught Sea margin Engine margin
m m m m m % %
7.1 130.0 124.0 25.6 6.5 15 10
10.6 220.0 210.0 35.0 9.7 15 10
12.0 276.0 263.0 43.4 11.3 15 10
Average design ship speed SMCR power Main engine options
Knots kW 1. 2. 3. 4.
15.0 5,300 5S40ME-B9 5S42MC7 7S35ME-B9
17.5 14,200 6S60ME-C8 7S60ME-C7 5L70ME-C7 5S65ME-C8
19.5 28,000 7K80ME-C9 6K90ME-C9 8K80ME-C6 6K90ME9
Average design ship speed - 0.5 kn SMCR power Main engine options
Knots kW 1. 2. 3. 4.
14.5 4,600 5S40ME-B9 5S42MC7 6S35ME-B9
17.0 12,800 6S60ME-C7 5L70ME-C7 5S65ME-C8
19.0 25,500 6K80ME-C9 6K90ME-C6 8L70ME-C8 8S70ME-C8
Average design ship speed + 0.5 kn SMCR power Main engine options
Knots KW 1. 2. 3. 4.
15.5 6,150 6S40ME-B9 6S42MC7 8S35ME-B9
18.0 15,900 7S60ME-C7 5L70ME-C8 6L70ME-C7 6S65ME-C8
20.0 30,800 7K80ME-C9 6K90ME-C9 7K90ME-C6 6K90ME9
Fig. 11: Ship particulars and propulsion SMCR power demand (membrane type), LNG capacity 19,000-138,000 m3, single-screw
14 Propulsion Trends in LNG Carriers
Membrane Type Single-Screw 3
Large Conventional
Q-flex
Q-max 265,000
Ship size, LNG capacity
m
150,000
210,000
Scantling draught Length overall Length between pp Breadth Design draught Sea margin Engine margin
m m m m m % %
12.3 288.0 275.0 44.2 11.6 15 10
12.7 315.0 303.0 50.0 12.0 15 10
12.7 345.0 332.0 54.0 12.0 15 10
Average design ship speed SMCR power Main engine options
Knots kW
20.0 31,400
20.0 39,300
20.0 45,200
1. 2. 3. 4.
6K90ME9
7K90ME9 7K98ME7
8K90ME9 8K98ME6 8K98ME7
Average design ship speed - 0.5 kn SMCR power Main engine options
Knots kW 1. 2. 3. 4.
19.5 28,500 6K90ME9
19.5 35,700 7K90ME9 6K98ME7
19.5 41,100 8K90ME9 7K98ME7 8K98ME6
Average design ship speed + 0.5 kn SMCR power Main engine options
Knots kW 1. 2. 3. 4.
20.5 34,300 6K90ME9
20.5 43,200 8K90ME9 7K98ME7
20.5 49,600 9K90ME9 9K98ME6 9K98ME7
The SMCR power results are also shown in the tables in Figs. 11-13 ‘‘Ship Particulars and Propulsion SMCR Power Demand’’ together with the selected main engine options of the MAN B&W two-stroke engine types. The similar results valid for +/- 0.5 knots compared to the average design ship speed are also shown.
All above ME engines can also be delivered in ME-GI version (gas injected)
Fig. 12: Ship particulars and propulsion SMCR power demand (membrane type), LNG capacity 150,000-265,000 m3, single-screw
Membrane Type Twin-Screw
Large Conventional
Q-flex
Q-max 265,000
Ship size, LNG capacity
m3
150,000
210,000
Scantling draught Length overall Length between pp Breadth Design draught Sea margin Engine margin
m m m m m % %
12.3 288.0 275.0 44.2 11.6 15 10
12.7 315.0 303.0 50.0 12.0 15 10
12.7 345.0 332.0 54.0 12.0 15 10
Knots
20.0 2x14,900 2x5S70ME-C7 2x6S65ME-C8
20.0 2x18,300 2x6S70ME-C7 2x7S65ME-C8
20.0 2x20,800 2x7S70ME-C7 2x8S65ME-C8
Knots kW 1. 2. 3. 4.
19.5 2x13,600 2x5S70ME-C7 2x5S65ME-C8
19.5 2x16,700 2x6S70ME-C7 2x6S65ME-C8
19.5 2x19,000 2x6S70ME-C8 2x7S65ME-C8
Average design ship speed + 0.5 kn Knots kW SMCR power Main engine options 1. 2. 3. 4.
20.5 2x16,300 2x5S70ME-C8 2x6S70ME-C7 2x6S65ME-C8
20.5 2x20,100 2x7S70ME-C7 2x7S65ME-C8
20.5 2x22,800 2x7S70ME-C8 2x8S65ME-C8
Average design ship speed SMCR power Main engine options
kW 1. 2. 3. 4.
Average design ship speed - 0.5 kn SMCR power Main engine options
All above ME engines can also be delivered in ME-GI version (gas injected)
Fig. 13: Ship particulars and propulsion SMCR power demand (membrane type), LNG capacity 150,000-265,000 m3, twin-skeg and twin-screw
MAN B&W Diesel Propulsion Trends in LNG Carriers 15
Propulsion Power Demand of Average LNG Carriers as a Function of Ship Speed
It is possible to derate the engine, i.e.
When the required ship speed is
MCR power needed for a given main
changed, the required SMCR power
engine is too high for a required ship
will change too, as mentioned above,
speed. This would also result in a lower
and other main engine options could
specific fuel consumption of the engine.
use an SMCR power lower than the nominal MCR power, if the nominal
be selected. This trend – with the average ship particulars and average ship
Therefore, in some cases it could be of
speed as the basis – is shown in detail
particular advantage, considering the
in Figs. 14 and 15 for single-screw ves-
high fuel price today, to select a higher
sels, and in Fig. 16 for large twin-skeg/
mark number than needed and derate
twin-screw vessels.
the engine.
SMCR power kW
Including: 15% sea margin 10% engine margin
40,000
Small Conventional 7K90ME9/ME-C9
21.0 kn 20.5 kn 20.0 kn
30,000
7K80ME-C9
19.5 kn
7L70ME-C8
20,000
6L70ME-C8 7S60ME-C8 5L70ME-C7 6S60ME-C8
16.5 kn
7S40ME-B9 6S40ME-B9 5S40ME-B9 5S35ME-B9
6K80ME-C6
18.0 kn 17.5 kn
6S65ME-C8
5S65ME-C8
16.0 kn
14.5 kn 14.0 kn
0
15.0 kn
50,000
15.5 kn
100,000
150,000 m3 Size of ship, LNG capacity
Fig. 14: Propulsion SMCR power demand of an average LNG carrier (membrane type), Small and Small Conventional – single-screw
16 Propulsion Trends in LNG Carriers
6K80ME-C9 8S70ME-C8
18.5 kn 7S70ME-C8
gn
si de ge era eed v A sp ip sh
17.0 kn
5S60ME-C7
10,000
19.0 kn
8L70ME-C8
Small
0
8K80ME-C9 6K90ME9/ME-C9
SMCR power kW 70,000
Q-max
Including: 15% sea margin 10% engine margin
Q-flex
Large Conventional
60,000
10K98ME7 21.0 kn
9K90ME9
50,000
20.5 kn
esign
7K90ME9
ge d Avera
peed
19.5 kn
ship s
19.0 kn
6K90ME9 7K80ME-C9
30,000
8K98ME7
20.0 kn
8K90ME9 40,000
9K98ME7
7K98ME7 7K98ME6 6K98ME6
5K90ME9 8S70ME-C8 7S70ME-C8
20,000
10,000
0
All above engines can also be delivered in ME-GI version (gas injected) 100,000
150,000
250,000
200,000
300,000 m3 Size of ship, LNG capacity
Propulsion SMCR Power Demand of an Average LNG Carrier (Membrane Type) Large Conventional, Q-flex and Q-max - Twin Screw Fig.15: Propulsion SMCR power demand of an average LNG carrier (membrane type), Large Conventional, Q-flex and Q-max – single-screw
Total SMCR power kW 60,000
Including: 15% sea margin 10% engine margin
Q-max Large
50,000
Q-flex
21.0 kn
Conventional
40,000
2 x 6S70ME-C8 2 x 6S70ME-C7
esign
ge d Avera
2 x 6S65ME-C8 2 x 5S70ME-C8 2 x 5S70ME-C7 2 x 5S65ME-C8
30,000
20.5 kn
peed
ship s
2 x 8S70ME-C8 2 x 8S70ME-C7
20.0 kn
2 x 8S65ME-C8 2 x 7S70ME-C8 2 x 7S70ME-C7
19.5 kn
2 x 7S65ME-C8
19.0 kn
20,000
10,000 All above engines can also be delivered in ME-GI version (gas injected)
0 100,000
150,000
200,000
250,000
300,000 m3 Size of ship, LNG capacity
Fig. 16: Propulsion SMCR power demand of an average LNG carrier (membrane type), Large Conventional, Q-flex and Q-max – twin-skeg and twin-screw
MAN B&W Diesel Propulsion Trends in LNG Carriers 17
Summary
The LNG carrier market is an increas-
References
Safety and reliability of LNG carriers
ingly important and attractive transport
[1] Introduction to LNG Center for
have always been important demands
segment which, due to the increasing
Energy Economics
to the design of this type of ship, as can
global demand to “clean” fuel, is ex-
The University of Texas at Austin
also be seen from the stringent stand-
pected to become of even greater im-
January 2007
ards given by IMO and several coun-
portance in the future. Thus, the CO2
tries. Thus, the most widely used LNG
emission by burning LNG is about 23%
[2] Liquefied Gas Handling Principles
containment systems – the Moss and
lower than for heavy fuel oil.
on Ships and in Terminals
the membrane – have been applied for
McGuire and White Witherby &
many years because of their reliability.
As described, MAN B&W engines are
Company Limited, London
Today, the membrane type LNG carrier
able to meet the engine power needs
Third Edition 2000
seems to take over the major market
of any size in the modern LNG carrier
share because of its better utilisation of
fleet.
the ship’s hull volume.
[3] LNG World Shipping Journal
September/October 2007
It should be noted that today the alterFor many years the steam turbines
native Compressed Natural Gas (CNG)
[4] LNG Carriers
have almost exclusively been used as
transportation form has potential to
ME-GI Engine with High Pressure
prime movers for LNG carriers, even
match the LNG transportation form for
Gas Supply System
though its efficiency is much lower than
shorter routes. Is now being investi-
MAN Diesel A/S, Copenhagen,
e.g. directly coupled two-stroke diesel
gated, but has so far not yet been ma-
Denmark, January 2007
engines. The reason is the simplicity of
terialised in a ship, even though there
utilising the boil-off gas in steam boilers
are some projects with CNG carriers.
[5] The Trans Ocean Gas
to produce steam for steam turbines.
CNG’s gas density is about 2/3 of LNG
CNG Transportation
[5]. The advantage of CNG is that, in
Technical & Business
However, with the introduction of the
contrast to LNG, CNG does not need
Development Plan
reliquefaction plant and/or gas-driven
any costly processing plants to offload
Trans Ocean Gas Inc.
diesel engines some few years ago, it is
the gas. The tanks have to be of the cy-
April 2004
today also possible to install high-effi-
lindrical pressure types or of the coselle
ciency diesel engines as prime movers,
type, i.e. of the coil/carousel type. Also
and thereby cut the fuel costs [4].
for this ship type, the MAN B&W twostroke diesel engines are feasible.
18 Propulsion Trends in LNG Carriers
MAN B&W Diesel Propulsion Trends in LNG Carriers 19
Copyright © MAN Diesel · Subject to modification in the interest of technical progress. · 5510-0035-01ppr Aug 2009 · Printed in Denmark
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