One of the two original LNG ships that carried
LNG from Cook Inlet to Japan
Unlike today, back in 1969, natural gas from Cook Inlet was
plentiful. It was that year when Phillips Petroleum and Marathon
Oil began shipping natural gas from Cook Inlet to the Tokyo Power
Company in Negishi, Japan. Right next to what is now the Agrium
anhydrous ammonia plant in Nikiski, Phillips Petroleum Company
had a plant which processed liquefied natural gas or methane
from a production platform in Cook Inlet and readied it for export
to Japan. The methane was shipped on two identical liquefied
natural gas carriers called the POLAR ALASKA and the ARCTIC TOKYO.
The liquefied natural gas or methane has a boiling point around
258 degrees below zero Fahrenheit. The LNG was carried at this
extremely super cold temperature. The tanks in the POLAR ALASKA
and ARCTIC TOKYO were specially designed pressure vessels just
for this purpose. The tanks on these LNG ships were of the membrane
design. The primary barrier was made of Invar, a 36% nickel-steel
alloy. The Invar sheets were only 0.7 millimeters in thickness.
The name Invar was a shortening of the word "invariable."
The nickel-steel alloy had a very low coefficient of thermal
expansion. As the tanks were cooled down there was hardly any
change in size at all. They were essentially "invariable"
in size due to expansion or contraction of the metal from temperature
changes. They could not stand alone under their own weight. They
were backed up by balsa wood boxes filled with perlite in the
barrier spaces surrounding them. It was very much like carrying
the cargo in a huge fragile balloon. LNG tankers, in those days
were all powered with boilers and steam turbines. The reason
for this is that part of the LNG cargo boils off during the voyage
between the loading and discharge ports. As the gas boils off
it absorbs its latent heat of vaporization from the surrounding
liquid gas. This keeps the remaining liquid cool. The gas boil
off is piped into the engine room of the LNG ship and burned
in the boilers so the ship actually consumes a portion of her
own cargo as fuel.Nowadays, the very newest LNG tankers are being
built with diesel propulsion with engines specially designed
to burn the LNG as fuel.
Detail of cargo tank internal construction. Note the lack
of internal structures. |
ARCTIC TOKYO and POLAR ALASKA under construction in Sweden. |
Midship section showing the relationship between thecargo
and ballast tanks, insulation and primary barriers making
up the cargo space. |
The sheer size of these ships was staggering. Both of them had
gross tonnages of over 44,000 measurement tons. Their deadweight
carrying capacity was listed as 36,896 tons. They were just short
of 800 feet long. Their Stal-Laval steam turbines could provide
20,000 shaft horsepower. The ships made about a twenty one day
round trip carrying natural gas from Cook Inlet to Japan.
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| ARCTIC TOKYO at her berth at the Phillips LNG
facility in Nikiski . . . |
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| Scene from the Cargo Control Room on the POLAR
ALASKA showing pump control panel |
One of the original gas ships at her moorings in Nikiski . .
. LNG storage tanks in the foreground . . .
The POLAR ALASKA and the ARCTIC TOKYO carried
thousands of tons of liquefied natural gas between Alaska and
Japan safely from the early 1970's until 1993 when they were
replaced by two brand new bigger ships called POLAR EAGLE and
ARCTIC SUN. The two new ships were built at the Ishikawajima
Harima Industries yard in Japan and once again are on the cutting
edge of technology. Instead of using the thin Invar membrane
design, the new ships have four prismatic cargo tanks constructed
of heavy aluminum plate. The tanks are supported in the ship's
hull on a matrix of laminated wooden blocks which allow for expansion
and contraction. More than eleven inches of polyurethane insulation
is formed around the tanks to keep them cool. Each ship carries
87,500 metric tons of methane.
POLAR EAGLE arriving in Nikiski on her maiden voyage in June
1993 . . .
New gas ship arriving in Kachemak Bay |
On deck POLAR EAGLE |
View of engine room of new gas ship from upper fidley |
Propeller shaft of new gas ship enters stern tube . . . |
ARCTIC SUN lifeboat . . . |
Inside pilothouse POLAR EAGLE . . . |
New gas ship hull arrangement showing prismatic cargo tanks
showing supporting wooden blocks, ballast tanks |
ARCTIC SUN in Kachemak Bay |
POLAR EAGLE AT SEA . . .
The POLAR EAGLE and ARCTIC SUN operated on the run between Nikiski,
Alaska, and Negishi, Japan, from 1993 to the present day. On
14 December 2007, the ARCTIC SUN was renamed ARCTIC SPIRIT.
On 11 January 2008, the POLAR EAGLE was renamed POLAR SPIRIT.
When the ships were renamed they were reflagged from Liberia
to the Bahamas.
POLAR SPIRIT traverses Unimak Pass January 29, 2008, tracked
by AIS signal by the Marine Exchange . . .
Postscript: The old gas ship POLAR ALASKA is now named
the SCF POLAR and is trading between Arzew, Algeria and Fos,
France. The old gas ship ARCTIC TOKYO is now named SCF ARCTIC
and as of mid January 2008 had passed south through the Suez
Canal and was enroute to Ras Laffan, Qatar, to load LNG for a
Mediterranean destination. What is absolutely remarkable is that
these two ships, built in the late 1960s, are still going strong
after more than 37 years of service. It is a testament to the
skill and determination of the crews who manned them for all
these years and the original designers and builders who put together
these marvelous ships almost 40 years ago.
LNG Ship Photos provided courtesy of Phillips Petroleum
Company and Marathon Oil Company . . . |
