COMMENTS SUMMARY

No 1/12
May 2012
Gas as a fuel for non-gas ships – cause for concern?
By Alan N. Campion CEng CMarEng FIMarEST FHEA
ABSTRACT
This paper relates to the current drive to use LNG as the main fuel for propulsion and
auxiliary machinery on non-gas ships – a move that has obvious benefits in both
environmental and economic terms. The author examines whether there might be some
serious cause for concern if this is carried out without proper management and control, given
the vast differences between conventional fuels and LNG. It is based on a lecture delivered at
Warsash Maritime Academy to a meeting of the Joint Southern Branch of RINA-IMarEST
on 12 January 2012.
The views expressed in this paper are those of the author, and do not necessarily represent
the views of either the IMarEST or Warsash Maritime Academy.
CONTENTS
Conclusion .................................................................................................................... 2
History ........................................................................................................................... 2
Benefit to the Environment? ....................................................................................... 2
Landmarks.................................................................................................................... 3
Regulation – gas ships.................................................................................................. 5
Safety Record and LNG Shipping Incidents ............................................................. 6
Keeping it Cool ............................................................................................................. 7
Propulsion Systems ...................................................................................................... 7
Dual fuel boiler + steam turbine................................................................................. 7
Dual Fuel Medium Speed Diesel Electric .................................................................. 8
Slow Speed Diesel plus Reliquefaction and Dual Fuel Operation ............................. 8
HP Gas Supply ........................................................................................................... 9
Methane Slip? ........................................................................................................... 10
Recent Developments ................................................................................................. 11
LNG Expands ........................................................................................................... 11
Questions..................................................................................................................... 11
LNG and CNG............................................................................................................ 12
CNG and Temperature ............................................................................................. 12
Joule – Thomson Effect ............................................................................................. 12
Release of Compressed Fuel Gas .............................................................................. 13
Comparing Fuels ........................................................................................................ 14
-1–
Regulation ................................................................................................................... 14
LNG Cargo: LNG Bunkers ....................................................................................... 15
Training? .................................................................................................................... 15
Training – Gas Ships ................................................................................................ 15
Draft IGF .................................................................................................................. 15
Specialised Training ................................................................................................. 15
Training Delivery ..................................................................................................... 16
Training: Draft IGF .................................................................................................. 16
Training – Seafarers Only? ...................................................................................... 16
Assessment ............................................................................................................... 16
Training: Summary .................................................................................................. 17
Outcomes? .................................................................................................................. 17
Conclusion: Prevention is Better Than Cure ............................................................ 17
Bibliography: .............................................................................................................. 18
CONCLUSION
Never one to be conventional, I am going to start with a conclusion.
Not mine I hasten to add – this is part of the conclusion to the 1997 Presidential address to
the IMarE (as it was at the time). The address was entitled “The development of Liquefied
Natural Gas Carriers – a Marine Engineering Success” and was given by the then president,
the late David Cusdin:
“The ships have earned themselves an excellent safety record and it is of the utmost
importance that it is kept that way. Much of the improvement in the performance of
the ships has been as a result of the work of the seagoing and ex-seagoing marine
engineers who have been and are working on all aspects of the many gas projects.
The LNG shipping business is, I believe, a success story for marine engineering and
the seafarer.” (Cusdin 1997)
I intend to explore whether or not the same conclusion might be drawn 25 years later in 2022
regarding the use of gas as fuel in non-gas ships, bearing in mind that 2022 is now only 10
years away.
HISTORY
To be fair to those with limited knowledge of LNG
and its transport by sea I will start with a brief history
and overview of LNG, LNG ships, and the
development of the different modes of propulsion
before examining LNG as a fuel for propulsion of nongas ships.
Fig 1: Methane Pioneer (1959)
Benefit to the Environment?
Much is said about the environmental benefit of using LNG as a marine fuel; Table 1
summarises the main ones, based on a vessel with a nominal daily consumption of 100t HFO.
Due to LNG having a heating value (or calorific value) about 28% higher than HFO the fuel
consumption could be reduced by as much as 22% per day. That said, over twice the volume
of LNG will be required due to the low density of the liquid – typically below 0.44.
-2–
Table 1: Environmental Benefit
Each tonne of LNG burnt will produce 0.4t
less CO2 than each tonne of HFO; the
overall result of the reduced consumption
and reduced CO2 resulting from combustion
is a decrease in CO2 emissions of up to 31%.
LNG contains no sulphur, so there can be no
sulphur oxides produced; also particulate emissions due to ash etc. are negligible when using
LNG as fuel. NOx emissions are also reduced, and no sludge is produced through fuel oil
treatment.
LNG may contain between 65% and 99.5% methane, the remainder being a mixture of
ethane, propane, butane and nitrogen, in differing proportions depending on source and the
production process. It is normally carried at a little over atmospheric pressure and 1m³ of
liquid methane will expand to form about 630m³ of gas.
Methane is a colourless, odourless, hydrocarbon with 1 carbon and 4 hydrogen atoms, the
lightest compound in the paraffin (alkane) series. It has a boiling point at atmospheric
pressure of –163°C where the liquid density is 423kg/m³. At this temperature most normal
shipbuilding materials will become brittle, and may crack. The actual boiling point and
density of an LNG cargo will vary with the constituents. The temperature is maintained by
allowing the cargo to boil, and removing vapour from the tank to maintain the pressure just
above atmospheric. This vapour is commonly burned in the ship’s boilers instead of fuel oil,
and originally any not required for the ship’s use was vented to atmosphere. Since that time
methane has been identified as the second most abundant greenhouse gas after CO2 – 1t
methane having the same environmental effect as about 21t CO2. When burnt, however, each
tonne of methane only produces 2.75t CO2, so venting is avoided wherever possible. The
different options for burning the boil off gas will be examined later.
LNG vapour is flammable when mixed with air in the ratio 5-15% v/v, and requires around
0.3mJ ignition energy to start a flammable mixture burning. This is a little less than would be
experienced due to a static discharge from a hotel room door after walking on a nylon carpet,
but, to put it in perspective, it represents 17× the energy required to ignite the hydrogen given
off during battery charging (flammable range 4-76% v/v). Acetylene requires about the same
ignition energy as hydrogen and has a flammable range 2 – 100%.
LANDMARKS
Transport of LNG of on river barges in the US to the cattle markets in Chicago for use as a
cooling medium was initially proposed in 1915, but the first seaborne cargo of LNG was
carried from Lake Charles, La, to Canvey Island UK in 1959 by the converted cargo ship
Methane Pioneer which had conventional diesel propulsion (Nordberg 2000bhp); the
pressure in the vertical cylindrical cargo tanks was controlled by venting vapour. Six further
trips followed the initial trial.
Building on the experience gained from this the Methane
Princess and Methane Progress were delivered to British Gas in
1964 to carry LNG from Arzew (in Algeria), also to Canvey
Island, on a 15 year contract. These 26 500m3 ships were finally
-3–
Fig 2: Methane Princess
scrapped in 1986 and 1997 respectively – a considerably longer life than the original 15 year
contract indicated. They were fitted with Conch prismatic tanks and 12 500shp steam turbine
propulsion; they were the first to use boil-off gas from the tanks as fuel, on-board
reliquefaction being regarded at that time as uneconomic.
Simultaneously with the development of Methane Princess and Methane Progress French
companies were developing a range of cargo systems for carrying LNG from Algeria to
France; three of these were trialled in 1962 in Beauvais, a converted liberty ship. Following
these trials the Jules Verne was built, and delivered in 1965; a similar size to the Methane
Princess and Methane Progress, she was built to a Gaz de France design with seven 9%
Nickel steel cylindrical tanks using PVC and Perlite insulation, and propulsion power was
developed by a Parsons 15 000shp steam turbine plant. Re-named Cinderella in 2004 she
was finally scrapped in 2008 – a 43 year commercial lifespan.
The next significant step was the delivery in 1969/70 of the 71 500m3 Polar Alaska and
Arctic Tokyo for trade between Alaska and Japan. Still trading over 40 years later as the SCF
Tokyo and SCF Alaska, they feature the Gaz Transport Invar and Perlite NO82 containment
system, and steam turbine propulsion.
Hard on the heels of the Alaska-Japan project came the building, between 1972 and 1975, of
seven 75 000m3 near sister ships in France for the Brunei-Japan trade. Due to the location of
the loading terminal the ships were fitted with the means to load via a platform at the stern,
with a linked ship-shore shut-down and emergency release system; something now common
in virtually all LNG terminal operations. Five of these ships had the stainless steel and balsa
wood Technigaz Mk1 containment system; two had the Gaz Transport NO82 system. All
were Stal-Laval steam turbine propulsion, 20 800shp, and five are still trading some 40 years
later.
The next noteworthy development, in 1973, was the 87 000m3 Norman Lady, the first vessel
to feature the Moss type spherical tanks, closely followed in 1975 by the Hilli – also with
Moss type tanks, however Hilli was the first LNG ship to have a capacity of over 100 000m3.
Before long the ‘standard’ size for an LNG ship was in the range 135 000m3 to 145 000m3;
only a few smaller vessels being built.
In 1993 the 89 880m³ Arctic Sun and Polar Eagle entered service on the Alaska to Japan
route. These vessels had IHI type B self-supporting aluminium tanks – the only ones to see
service in the LNG trade – and 21 000shp steam propulsion. They are still trading as Arctic
Spirit and Polar Spirit.
The next major step, in 2002, was in fact two steps taken concurrently, so arguably this
constituted a leap; the Gaz de France energY featured not only the new GTT CS1 cargo
containment system, but was also the first to feature a Dual Fuel Diesel Electric (DFDE)
system that supplied all the ship electrical power including 26 000hp for propulsion; the boiloff gas was now being disposed of in more efficient medium speed diesel engines rather than
the thermally inefficient boiler/turbine arrangement. The CS1 containment system never
caught on, though large numbers of DFDE vessels have been built since.
A further giant leap took place in 2007 with the entry into service of the first Q-Flex vessel
Al Ruwais, with a capacity of 210 000m3, propulsion by highly efficient twin slow-speed
diesels developing a total of 50 000hp, and with on-board LNG reliquefaction capability. Al
Ruwais was followed in 2008 by the similar in concept, but much larger, Q-Max vessel
Mozah boasting 60 000hp total from twin slow speed diesels. As of August 2011 there were
30 Q-flex vessels in operation, and 14 Q-Max with more to come.
These landmarks in the development of LNG ships are tabulated below:
-4–
Year
Ship(s)
Size
(M³)
Power
(PS)
1959
Methane Pioneer
5000
2030
1964
Methane Princess & Methane Progress
26 450
12 673
1965
Jules Verne (Cinderella)
25 500
15 200
1969/70
Polar Alaska & Arctic Tokyo (now SCF Alaska & SCF
Tokyo)
71 500
20 280
1972
Gadinia & 6 ‘sisters’
75 000
21 090
1973
Norman Lady
87 600
30 000
1975
Hilli
126 227
40 000
1993
Arctic Sun & Polar Eagle (now Arctic Spirit & Polar
Spirit)
87 500
21 300
2002
Gaz de France energY
74 100
26 000
2007
Al Ruwais
210 000
50 000
2008
Mozah
266 000
60 000
Table 2: LNG Ship Development
REGULATION - GAS SHIPS
Gas ships in general – and LNG ships in particular – have an exceptional safety record, and
this is not just by chance. In October 1976 a Code for Existing Ships Carrying Liquefied
Gases in Bulk, plus a Code for the Construction & Equipment of Ships Carrying Liquefied
Gases in Bulk for ships built after that date came into effect; they were originally published
by what was then IMCO – the body that later became the IMO; these are known respectively
as the EGC and GCC codes. Compliance with these was voluntary, but operators of LNG
ships at that time tended to comply.
In 1986 the GCC was superseded by the International Code for
the Construction and Equipment of Ships Carrying Liquefied
Gases in Bulk, commonly referred to as the IGC Code as
otherwise it is a bit of a mouthful! This was published as volume
III of the 1983 amendments to SOLAS; and the link to SOLAS
now made it mandatory for ships in international trade to comply.
In 1993 the code was updated and the second edition published.
Currently under review, the next edition of the IGC Code is
expected to be ratified by 2014.
The IGC code has been developed through the use of advanced
hazard and risk analysis techniques rather than representing
retrospective controls implemented following incident or disaster,
Fig 3: IGC Code
and includes, for example, a requirement to site cargo containment
-5–
a minimum distance from the ships side; all cargo pipes must be in the open above the
weather deck and enter the tank from the top. The accommodation may not be situated above
the cargo area, and there are strict controls over many other matters, but all are based on the
degree of hazard posed by the cargo.
In conjunction with this there are comprehensive minimum requirements for training of
personnel operating gas ships, particularly management level Officers; these are detailed in
STCW, and the IMO publish Model courses for guidance. There is also a lot of guidance
regarding best practice that has been collated from the industry promulgated by independent
organisations such as the International Chamber of Shipping (ICS) and SIGTTO, the Society
of International Gas Tanker & Terminal Operators, who have also produced a suggested
competency standard for officers on LNG ships that exceeds the minimum requirement set
out in STCW; training to this enhanced standard is required by many charterers.
SAFETY RECORD AND LNG SHIPPING INCIDENTS
The combined result of all this is an enviable safety record for LNG shipping: as of the 45
years LNG service to December 2009, LNG ships had carried in excess of 59 000 cargoes
across over 150 million nautical miles without loss of life or vessel due to a cargo related
incident. Despite this record, the public perception is that LNG ships are extremely
dangerous.
It would be wrong, however, to say that there have been no incidents whatsoever!
Over the same 45 year period referred to above there have been 41 reported incidents
involving LNG ships including 8 collisions; 4 of these involving contact with other vessels, 2
were jetty contact incidents, plus one where an LNG ship alongside was hit by a ‘passing’
vessel and one where a submarine tried to extend its periscope through the ship.
There have been 4 cargo-related fires – two of which
were vent mast fires where venting vapour was ignited
by lightning, one insulation fire during building, and
one fire due to vapour ignition during disconnection.
In total there have been 13 liquid releases, most of
these extremely minor, some resulting in small cracks
to strength parts of the vessel, or significant cracking to
non-strength parts; others have caused no structural
damage
at all. During this period there have also been
Fig 4: El Paso Paul Kayser
5 grounding incidents, none of which led to any cargo
release – and this includes the1975-built El Paso Paul Kayser, shown here in dry-dock after
she had grounded at 17kts fully loaded near Gibraltar in 1979. Even here there was no cargo
release, although the containment system suffered some damage; in fact the cargo was
successfully transferred to a sister ship using the Paul Kayser’s own pumps before preparing
for docking, and the Paul Kayser continued trading for another 10 years until she was
scrapped in 1985.
I am not of the opinion that these statistics indicate that LNG ships are intrinsically safe; the
record is due to the high standards of regulation and training extant in the industry, and the
engineering excellence that has prevailed over many years.
It is worth considering that during same period there were over 100 major oil tanker incidents
that resulted in 700 fatalities and the spillage of over 1m tonnes of oil.
-6–
KEEPING IT COOL
Keeping any low pressure gas cargo cold is quite simple: the tanks are heavily insulated to
limit heat ingress, and to compensate for the small quantity of heat energy that does
inevitably pass through the insulation the cargo is allowed to boil; by extracting cargo vapour
the added energy is removed, thus keeping the cargo tank thermodynamic energy level
constant, and hence the pressure and temperature stable. With LPG cargoes the gas that is
removed is re-liquefied and returned to the tanks; with LNG cargoes (until recently, that is)
the easiest way of utilising the boil-off gas was as fuel in the ship’s boilers, hence the use of
steam turbine propulsion. Part of the rationale permitting the use of LNG vapour as fuel in
this way is that, if heated to above –100°C, LNG vapour becomes lighter than air, making
any potential leak into the engine room easier to trap, detect, and extract.
Recent advances have meant that options other than boilers are available for the disposal of
boil-off gas; however even including new-buildings yet to be delivered, almost 70% of LNG
vessels utilise steam based propulsion.
PROPULSION SYSTEMS
For many years, it seemed that, so long as there were LNG ships in service, there would
always be a home for the dyed-in-the-wool steam engineer. Boilers raising steam for
propulsion and power generation were the obvious way of disposing of the gas; despite the
low efficiency of the boiler/steam turbine system – about 29% – this was offset by the low
heavy fuel oil consumption (possibly as low as zero), and the need to dispose of the boil-off
gas safely.
Dual fuel boiler + steam turbine
So, here we have the classic LNG vessel fuel gas supply system ... the BOG is taken from the
tanks by a small, single stage high speed centrifugal
compressor referred to as the Low Duty or Gas
Burning compressor delivering low pressure gas to the
boiler burners via a heater that raises the temperature to
between 25°C and 45°C. As the machinery spaces are
to be maintained safe from the entry of gas – gas safe
in other words – the safety barrier between the gashazardous and gas safe areas is extended to the boiler,
and a gas master valve, shown in green, acts as an
Fig 5: Steam plant with gas
automated safety shut off device (see Fig 4). Before
burning
and after each gas burning session the pipeline between this gas master valve and the boiler is
purged with nitrogen, and gas burning can only be initiated on a register already burning fuel.
If the gas master valve should close in response to a safety trip, fuel oil burning will be
automatically reinstated. If more gas is required than can be provided by the naturally
occurring boil-off, liquid is pumped from the tanks through a vaporizer and the extra gas that
is created added to the boiler supply.
It therefore seemed, for many years, that this system would ensure that LNG ships would
always provide a potential berth for the steam engineer. However, this was not to be!
-7–
Dual Fuel Medium Speed Diesel Electric
In or around the year 2000, engine manufacturers developed what was marketed as a ‘new’
system for gas ship propulsion; dual fuel medium speed engines driving alternators in a
diesel electric propulsion and power generation system (DFDE) achieving a propulsion
efficiency of 43% rather than the 29% achieved when
using steam turbine plant. Actually this was nothing
really new – dual fuel medium speed diesels have been
in use in the on- and off- shore petroleum industries for
many years, utilising, for example, well-head gases for
fuel. Equally, diesel electric propulsion systems had
been in use for many years
on cruise and container
vessels – all it really
Fig 6: DFDE Schematic
needed was the vision to
put the two together.
As large quantities of effectively free electricity were now
available it was suggested that some of the excess power might
be used for partial reliquefaction and this paved the way for the
next development, Slow Speed 2 Stroke Diesel propulsion with
full reliquefaction of the cargo boil-off gas.
In the dual fuel medium speed engine the fuel gas is injected
into the air stream at each cylinder inlet, compressed along with Fig 7: Gas injection to a
the air charge, and ignited by a pilot injection of fuel oil – either medium speed engine
HFO or MDO. Compared with the boiler system this requires a
slightly higher fuel gas pressure – in the region of 4 – 6 bar(g). As this pressure cannot be
achieved with a single stage centrifugal compressor two stage centrifugal compression is
generally fitted, sometimes with pre-cooling.
Slow Speed Diesel plus Reliquefaction and Dual Fuel Operation
It was calculated that, especially with the new generation larger LNG vessels – the so-called
Q-Flex & Q-Max types developed for the Qatar project – delivering the full cargo as loaded
by fitting reliquefaction and conventional slow speed diesel engine propulsion with
efficiency around 50%, would more than offset the cost of running the reliquefaction plant.
The ships were therefore built with twin slow speed diesel main engines and medium speed
generator engines all running on HFO, plus a reliquefaction plant that featured two stage
compression for the gas process – so about 4 – 6bar(g) again – and a nitrogen gas charged
reverse Brayton cycle cooling system.
This was fine, and several ships were delivered, until increasing fuel prices upset the balance,
so that the value of the extra cargo delivered no longer outweighed the fuel cost; this resulted
in a drive to operate the slow speed two stroke engines on dual fuel, which was not a new
concept; in fact David Cusdin referred to it in his 1997 presidential address, and the
manufacturers already had experience with land-based plant. The ships delivered with two
stroke diesel propulsion and reliquefaction plant are now scheduled for conversion to dual
fuel operation, and I understand that any remaining new-buildings will be delivered with this
option.
One of the major concerns here, however, is the gas supply to the engine: because of the way
a two stroke engine operates taking the fuel gas in with the combustion air is not an option
-8–
and direct injection to the cylinder is required. To get the appropriate quantity of gas into the
cylinder in the required time at the correct part of the cycle a higher pressure is required than
for boiler, DFDE or reliquefaction systems: the figure generally quoted at present by many
sources is 150-265bar, but I have also seen reference to pressures as high as 360bar.
HP Gas Supply
There are two main options for producing gas at these high pressures.
The first is to take LNG vapour from storage, and compress it – which requires a large
compressor, probably 6-cylinder, 5-stage. If there is insufficient vapour supply from natural
boil-off then a vaporiser would be used to augment the supply. Removing just the vapour will
also lead to a slow change in the constituents of the liquid & hence its characteristics, and the
characteristics of the associated vapour – a process known as weathering.
The second alternative would be to compress the liquid by using a multi-stage HP pump, and
then to vaporize the high pressure liquid.
At first glance there seems little to choose between these two alternatives – until one
considers both the total work that must be done on the gas, and how this is achieved.
In option 1, vapour compression, assuming the starting position is just above atmospheric
pressure, there would need to be several stages of compression – typically 5 – with
intercooling, to achieve the final result. The total work required to be done on the gas by the
compressor would be of the order of 540kJ per kg gas passing through. If the vaporizer were
required the latent heat energy input to turn liquid to vapour would be 645kJ/kg; a total heat
+ compression energy requirement of 1185kJ/kg.
On the other hand, if we were to use liquid compression + vaporizing, based on the same
starting pressure, the energy added to the liquefied gas during pumping is around 100kJ per
kg, leaving 655 to be added in the vaporizer – total energy requirement 755 kJ/kg.
Fig 8: Comparing Compression and Pumping
-9–
The major difference between these alternatives?
In the compressor-based system energy addition is mainly by way of mechanical means; the
liquid compression + vaporizing option adds most of the energy by using static heat
exchange equipment. The vaporizer requirement for both systems would be about the same,
utilising heat energy from the steam produced by the waste heat recovery system which can
therefore be ignored. The major difference would be in the power requirement for the
compressor, being over 5 × greater when compared with the pump – not to mention
maintenance considerations.
Methane Slip?
You may have heard the expression ‘Methane Slip’; if not you probably will before long!
This refers to unburned fuel gas that might be released to atmosphere with the exhaust as part
of the combustion process. In a well managed boiler installation or a direct injection two
stroke slow speed diesel engine plant this will be zero. However the four stroke medium
speed engine where gas intake is with the combustion air, may present a problem due to the
scavenging overlap that is a normal part of the cycle.
It is the part of the cycle highlighted in red – where
the intake air is used to expel the remaining exhaust
gas – that is the main concern. Because methane has
21× the Global Warming Potential of CO2; methane
slip is often quoted in arguments against LNG fuel in
general, although it only affects the 4S engines;
engine designers are making huge reductions to the
amount of gas expelled in this way, although in some
older engines it is possible that methane slip could
negate the environmental advantage of the reduction
in CO2 emissions achieved. Methane slip is highest at
low loads.
Fig 9: Four Stroke Cycle
Propulsion Summary
To summarise the different propulsion options:
There are four options available for propulsion of LNG vessels: dual fuel steam or medium
speed diesel power plant, or slow speed diesel plant with reliquefaction; these all feature low
or moderate gas supply pressures. Then there is slow speed dual fuel operation with a
significantly higher gas supply pressure.
Regarding propulsion efficiency, either form of diesel plant has significant energy savings
compared with steam, although methane slip may reduce the environmental advantage of the
medium speed diesel solution, especially where conversion from conventional fuel is
concerned.
Regarding the steam option, not only is it inefficient, but there is a great deal of difficulty in
recruiting engineers with appropriate qualifications and experience. The technology,
however, exists to use LNG as a fuel source for virtually any type of merchant vessel
whether using slow speed or medium speed diesels for propulsion.
- 10 –
RECENT DEVELOPMENTS
So far I have related everything to ships designed and operated within the strictures of the
IGC code, and STCW training requirements. However, recent environmental and economic
pressures have resulted in a massive interest in LNG as fuel outside this carefully managed
and regulated situation. It should be mentioned here that some vessels are already running
with LNG as fuel – on coastal routes where international legislation is not necessarily a
major influence.
LNG Expands
When LNG is turned from liquid to vapour the volumetric expansion will be anywhere
between 600 and 630 times, and since 2009 interest in the use of LNG as fuel for propulsion
outside LNG ships has expanded in much the same way, and some interesting proposals have
resulted, some of which, it must be said, show a lack of basic understanding of how the cargo
is used as fuel in existing LNG carriers.
Concept designs have included the prospect of fitting the LNG
fuel tanks immediately below the accommodation – which I
would suggest is a proposal that can only be based in
economics, rather than being on risk and hazard analysis of
safety considerations.
Much continues to be written about LNG for propulsion in the
maritime press, with reference to, and quotes from, engine
manufacturers, ship operators, ship builders, and Classification
Societies, along with a great deal of comment relating to
emission control areas and the need to reduce SOx, NOx and
Fig 10: LNG fuelled
CO2 – all more easily achieved when using LNG as fuel.
Container Vessel Concept
Even LPG (which is heavier than air) has been mooted as a possible fuel, and more and more
publicity was given to the potential for the new, ‘green’ ships with concept designs, and
reports of orders being negotiated and placed for new-buildings and conversions.
The one aspect that seemed to cause little concern, only meriting a passing mention (if indeed
any mention at all) was the matter of training for the crew operating the vessel. But it is not
cargo, is it? It is only bunkers. Not the same, surely?
In fact it appears that having the bunkering infrastructure in place has now become the major
talking point, so that LNG is readily available as fuel; it therefore seems that the concept of
utilising LNG as fuel is now accepted to the point where it is not really even newsworthy –
only the logistical problems in achieving that end create headlines.
QUESTIONS
To my mind this, now inevitable, expansion of the use of LNG fuel to non-gas ships – where
the IGC code and STCW requirements regarding carriage of gas as cargo do not apply –
raises several questions. The first, and most obvious to me, is this: – is any training in
operations with this ‘new’ bunker fuel necessary? If so, why? If it is required, then to what
level should it be given?
Assuming training is to take place what about assessment – or is knowledge transfer just to
be assumed to take place? Who should supply the training – the employer? The equipment
manufacturer? A training establishment?
- 11 –
Is it only the shipboard personnel that will need training? What about others involved in the
overall operation of shipping – charterers, agents, and so on?
I would like to briefly explore various aspects of these questions, based in both the
technology concerned, and current draft proposals soon to go before IMO, and offer some
possible answers. But first, a few more facts about the use LNG as a fuel in the ways already
discussed, and as proposed for non-gas ships.
LNG AND CNG
LNG = Liquefied Natural Gas – that is natural gas that has been cooled sufficiently to
become liquid. It is therefore below the critical temperature of –84°C, and for low pressure
storage is more likely to be below –160°C. At these very low temperatures, of course, most
engineering and shipbuilding materials become brittle. Above the critical temperature the
product becomes natural gas – just as you get from the distribution system to your home if
you have mains gas. If it is not liquid, it is not LNG!
When it is compressed, it becomes compressed natural gas, or CNG, allowing a greater mass
to be stored in the same volume, although the scantlings of the containment will need to be
significantly heavier. When natural gas is stored in this compressed state, even at ambient
temperature, the potential for low temperatures and brittle fracture is not removed, however.
CNG and Temperature
Some reports have suggested that natural gas for ship propulsion could be stored as CNG at
pressures up to 275bar; this is also the pressure generally quoted for the supply of fuel gas to
a slow speed diesel engine on full load, although higher pressures have also been proposed.
Depending on the vessels trading area this CNG could be at 37°C, 25°C or even 0°C. How
can this cause concern regarding low temperature?
Even when not doing work in the process, most gases exhibit a fall in temperature when
expanded; this phenomenon is referred to as the Joule-Thomson or sometimes Joule-Kelvin
effect.
If CNG is expanded from 275bar it does not matter whether it is to 6bar, or to atmospheric
pressure, the effect will be virtually the same.
Joule – Thomson Effect
The Joule Thomson effect relates to the temperature change in a fluid when it undergoes
isenthalpic expansion – ie expansion with no change in enthalpy, the thermodynamic energy
level; in other words without performing work. This temperature change may be positive or
negative, and at low pressures the change is often negligible and the effect is best illustrated
by use of a Mollier Diagram.
On the next page is the Mollier diagram for methane – the major constituent of natural gas.
Included are lines that indicate constant pressures of 1bar(a) (ie atmospheric pressure,
7bar(a), and 275bar. Also shown are the lines of constant temperature for +37, +25, ±0, -50, 75 and -100°C.
If CNG at 275bar(a) is expanded from +37°C to atmospheric pressure, the temperature will
fall to around -50°C – cold enough to cause physical harm to unprotected personnel, and,
assuming sufficient mass, to cool steel to the point where brittle fracture is possible.
From the same pressure and +25°C the temperature would fall to below -75°C with an even
greater likelihood of embrittlement or personnel injury, and from 0°C to below -100°C –
where the gas is now not just cold, but heavier than air.
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Fig 11: Cooling effect of expansion
Compare this with expansion from 6 bar(g) to atmospheric pressure, where there is very little
temperature change at all – only a few degrees.
Release of compressed fuel gas
There are many incidents that could cause release of fuel gas into the machinery space –
potentially resulting in gas contamination of a space nominally safe from such an event.
Although any limited release due to pipe fracture, flange gasket failure etc. should be
contained within the negative pressure ventilated protective double-wall pipe system or
trunk-way, other causes of failure are possible. For example injudicious movement of large
engine spares (pistons, liners for example) could carry away the pipe system completely, as
could support system failure due to fatigue resulting from vibration.
Whatever the cause, if we consider 20m of 150mm pipe containing CNG at 275bar suffering
a catastrophic failure so that the contained gas was released to atmosphere it would create, at
ambient temperature, a gas cloud of about 100m3 – the initial temperature would be much
less of course, probably about –50°C – but it would rapidly warm. This 100 m3 of gas when
mixed with air could create up to 2000m3 of flammable mixture at the LFL of 5% by
volume. Not only is this a large cloud of flammable vapour, but such an event would also
rapidly displace a lot of air, reducing the oxygen available to support life, not to mention the
possible effect on a running internal combustion engine. Whilst the likelihood of this type of
event might be low, the consequence would be extremely high, so this is something I believe
worth including in risk assessment procedures!
Conventional diesel engine design ensures that rupture of a high pressure fuel pipe results in
release of a minimal quantity of flammable material; one that is liquid and significantly more
difficult to ignite than gas.
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Comparing fuels
Having looked at some of the possible hazards of LNG as a fuel, I would like to summarise
what I see as the main differences between the main fuel types – distillate, residual and
natural gas.
Table 3: Fuel comparison
Apart from cryogenic LNG at –160°C, most fuels will be stored at or above ambient
temperature; similarly service temperatures will vary for all these fuels between ambient and
+140°C depending on the machinery design requirement. The limited vapour resulting from
use and storage of conventional fuels is heavier than air; natural gas vapour below –100°C is
also heavier than air, but above this temperature the vapour becomes lighter than air. The
flashpoint of conventional fuels for marine use is regulated by SOLAS, and must be greater
than +60°C unless for engines in lifeboats, emergency generators etc, when flashpoints down
to +43°C may be permitted. The flashpoint of LNG is significantly lower at –221°C,
although the auto-ignition temperature is high at 535°C – 595°C.
The main non-fire issue with conventional fuels is, of course, pollution – not a problem with
natural gas as it will vaporise and disperse quickly. However the large liquid-to-vapour
expansion ratio (1:630) will rapidly result in a large gas cloud with the potential to displace
air resulting in asphyxia, and anywhere from low to extremely low temperatures. This
indicates that there will be significant differences when handling, storing and caring for these
‘new age bunkers’.
REGULATION
I have already mentioned regulation regarding the construction and equipment of ships
carrying liquefied gases in bulk, and the training requirements for the officers and crew.
Does the fact that natural gas, in whatever form, is being used as bunkers make any
difference?
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LNG Cargo: LNG Bunkers
If we were to compare the potential risks of LNG as bunkers, or as cargo, we would, of
course, find no difference at all: it is the same product, merely different quantity and purpose.
However, none of the regulations that apply to gas ships are applicable; they are specific to
gas carried as cargo.
At present the only training ‘requirement’ other than individual flag state regulations is in the
Draft Code on Safety for Gas Fuelled Ships – or Draft IGF Code as it is currently known. A
lot of work by a number of people has been put into this document to get to the present
position, though there still remains much to be done.
TRAINING?
The Training requirement that may (or may not) end up in the finalised IGF is a matter that is
still under discussion at IMO and by the BLG correspondence group to which I am a recent
recruit.
It is fairly obvious that, given the huge differences between handling HFO and MDO bunkers
with >60°C flashpoint and handling LNG as fuel that some form of adequate training is
essential, always remembering that formal training regarding operations with oil fuel bunkers
and the relevant regulations is included in both deck and engineer officer certification to
augment the experiential learning that occurs naturally during on-board service: neither form
of training is available for gas as fuel at present.
Training – Gas Ships
For service in gas ships STCW 95 requires advanced training leading to the issue of a tanker
endorsement for all personnel who have ‘... immediate responsibility for loading, discharging
and care in transit or handling of cargo ...’ (IMO, 1993); however it is not uncommon to find
on LNG ships that many more than just the specified officers (Master, C/E/O, ChOff, 2/E/O,
Cargo Eng. for example) have completed this training.
For issue of a Tanker Endorsement (Liquefied Gas) it is necessary that those concerned
receive training in handling all the gases covered by the IGC code, and there are over 30 at
present. Training for those on non-gas ships using gas as fuel will obviously not need to
cover all of these, but I see no reason for it to be less detailed in respect of those gases that
are proposed for use as fuel.
Draft IGF
So, what does the draft IGF code say? When I first read it the proposal was that:
„... crew members with direct responsibility for the operation of gas-related equipment on
board should receive special training. The company should document that the personnel
have acquired the necessary knowledge, and that this knowledge is maintained at all times.‟
(IMO, 2009)
The code then outlines the training requirements: firstly for all members of the operational
crew, who should receive ‘basic safety training’, which was designated ‘Category A’.
Specialised Training
Following category ‘A’ training comes categories B and C training – for deck and engineer
officers respectively. What constituted this training would be decided by the Master and
Company, who would arrange the training level: „ based on an evaluation of the concerned
crew member‟s job instructions/area of responsibility on board.‟ (IMO, 2009)
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With all due respect I would question the competence of, for example, a container ship
operating company, in consultation with its Masters, to reach a realistic and informed
decision without specialised training themselves – which receives no mention. If retained,
this wording could also potentially lead to different training being required when an officer
moved from one ship to another, even in the same fleet, depending on the individual Master!
A less than satisfactory solution, and very ship specific rather than generic.
Training Delivery
There is also the matter of the delivery of the training; training leading to issue of a Tanker
Endorsement must be carried out in accordance with the requirements of STCW which
includes recommendations on the qualifications and experience of instructors; this type of
training must be approved by the flag state issuing the seafarers qualifications, so in the UK
this is the MCA.
The draft IGF suggested that training should be carried out by: ‘suppliers of equipment’ or
‘other specialists with in-depth knowledge of the gas in question and the technical gas
systems that are in use on board‟ (IMO, 2009)
This would presuppose repeat training every time a new or different system was encountered,
and equipment suppliers with competent training departments. There is no mention of
assessment.
Training: Draft IGF
So, to summarise, the draft IGF left training requirements to the Company and the Master;
one having budgetary constraints as a major influence, the other with little enough time
already. With the best intentions in the world, neither is likely to possess the requisite
experience to make an informed judgement, so I would venture to suggest that a global
solution is required, not a ship-specific one such as the current proposal. Many equipment
suppliers admit that their training package, should it exist, is concentrated totally on their
own equipment rather than the entirety of an installation, and this may not necessarily
include generic safety training for the product handled.
There is no clearly defined requirement as to breadth or depth of training, nor an identified
requirement for assessment.
Training – Seafarers Only?
As well as training seafarers I believe that there is also a good argument for mandatory
training for operating company superintendents and procurement staff, agents, port personnel
and so on to ensure that errors that may be costly in terms of injury to personnel or damage to
assets can be avoided. I would argue that if a vessel designed to operate on LPG fuel at a
minimum temperature of –42°C was supplied with LNG at –160°C the results could be
somewhat more catastrophic than loading 460cSt fuel into a ship designed to run on 180cSt,
or to ISO specification RMK380 rather than RMG380. This will become especially
important as different containment systems having different limitations are developed.
Assessment
I have mentioned assessment several times, and you may ask – why? Most education and
training professionals agree that any teaching and learning experience requires assessment in
order to support the learning, demonstrate that learning has taken place and inform the
development of the process leading to the learning experience. Here are some comments by
teaching and learning experts:
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 „... assessment is an integral component of the teaching and learning system’ and
„...to be effective assessment should be valid, reliable and fair‟ (Wakeford, 2003)
 Assessment should „... require an active demonstration of the knowledge in question‟
(Biggs, 2003)
 „Assessment can and should support student learning in a number of ways’
(MacDonald, 2008)
Put simply, without assessment how can we be certain that the teaching is effective and that
learning has occurred?
Training: Summary
I was concerned when I first read the IGF Code proposals regarding training as I questioned
whether or not they had definition, transparency, or were robust enough to promote safe
operation. I also felt that there was little evidence of accountability or comparability between
suppliers – in other words the proposal as it stood was unacceptable.
The final decision on this is yet to be taken; one current suggestion is that the IGF code is not
the rightful place for training requirements, rather that these should be in STCW, which I
believe is a fair comment. However, if that idea was to be carried, it could well be at least
another two years before any regulation is in place following adoption of the IGF code, and a
lot could happen in the interim period.
OUTCOMES?
Remembering that LNG is viewed by many outside the industry as highly dangerous my fear
is that, without training backed up by adequate and robust regulation and direction, there
will, inevitably, be an incident resulting in loss of life or assets that could easily elicit a
disproportionate political response leading to imposition of unworkable requirements that
totally disregard the standards current in LNG ships. This could even compromise the
existing safety record of LNG ships if decisions are taken by those who are uninformed,
badly informed or have purely political gain as motive. An example of this relates to the
steering gear regulations for tankers that followed the Amoco Cadiz grounding in 1978:
despite the official flag-state enquiry identifying the main cause of the steering gear failure
that led to the incident as incorrect procedures regarding the bolting of hydraulic flanges,
regulations were established for redundancy, alarms and auto-change-over for tanker steering
gears.
The first vessel I sailed on that fully complied with the new regulations had such a complex
system that it was easy for a bridge watch-keeper who failed to follow the motor change-over
procedure exactly to end up with no operational steering at all until the duty engineer had
been called to reset and restart the system; a somewhat disconcerting experience when
transiting the Dover Strait.
CONCLUSION: PREVENTION IS BETTER THAN CURE
I believe that all maritime industry professionals have a responsibility to ensure that all of
those who may be involved in the operation of non-gas ships using gas as fuel in the future
receive appropriate, assessed, training; the regulation governing this should will need to start
in the IGF code, and should be based on the current proven training required for service on
gas ships, but restricted to the products concerned.
David Cusdin was posthumously awarded the Merchant Navy medal in 2011, partly for
services to marine engineering and partly for his charity work; if economic grounds are
allowed to outweigh technical safety in the design, development, and operation of future gas- 17 –
fuelled merchant ships, then when we reflect, in 10 years time, on the use of gas as fuel in
non-gas ships I consider it doubtful that we will be echoing his words regarding a Marine
Engineering success story, which will be a sad reflection on the way the technical
management of ship operations and safety has been eclipsed by relatively uninformed
economics.
BIBLIOGRAPHY
Biggs, J. (2003) Teaching for quality learning at university, Open University Press,
Maidenhead
Campion, A. (2011) Fuel gas on non-gas ships, In: Proceedings of Gastech 2011,
Amsterdam, March 2011
Cusdin, D.R. (1997) The development of liquefied natural gas carriers – a marine
engineering success, London, IMarEST
IMarEST: MER & Shipping World & Shipbuilder, various editions
IMO (1993) International code for the construction and equipment of ships carrying
liquefied gases in bulk, Second Edition, London, IMO
IMO (1996) International standards for training certification & watchkeeping for seafarers
1978 as amended 1995, London, IMO
IMO (2009) MSC.285(86) including draft code on safety for gas fuelled ships, London, IMO
MacDonald (2008) Blended learning and online tutoring, Gower, Aldershot
McGuire and White (1986) Liquefied gas handling principles on ships and in terminals,
London, SIGTTO/Witherby
Nautilus International, Telegraph volume 44, edition 11, December 2011
Riviera Maritime Media LNG world shipping, Various editions
Tradewinds shipping news, various editions, including lngunlimited.com
Vaudalon, A. (2000) Liquefied gases marine transportation & storage, London, Witherby
Wakeford, R. (2003) In: A handbook for teaching & learning in higher education (Eds: Fry,
H., Ketteridge, S., Marshall, S.,) RoutledgeFalmer, London
Woodward J. & Pitblado R. (2010) LNG risk based safety, Hoboken, Wiley/ AIChE
www.coltoncompany.com
www.dnv.com
www.imo.org
www.lloydslist.com
www.SIGTTO.org
www.wartsila.com
About the Author
Alan Campion joined Warsash Maritime Academy as a Senior Lecturer in 2004 where his
specialist area is safe and efficient cargo management on gas tankers. This followed 35 years
working deep sea as a Marine Engineer, starting out as an apprentice on passenger ships
before an early move into tankers – initially crude oil and products, but later (and for a total
of over 25 years) on to gas ships, both LNG and LPG, much of the time as Chief Engineer
Officer. As well as ‘normal’ work onboard, he has also spent time in various company
offices involved with docking specifications and new-building projects as well as work on
early ISM initiatives.
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