The Coast Guard is monitoring repairs aboard the liquid natural gas carrier Excel in Homer, Alaska, Friday.
Coast Guard Sector Anchorage issued an order for the vessel to remain anchored in Kachemak Bay near Homer after the 908-foot, Belgium-flagged vessel experienced a loss of propulsion due to a failed engineering gasket while inbound to Cook Inlet Monday.
The Excel was examined by Coast Guard inspectors from Marine Safety Detachment Homer, Tuesday, who conducted a Port State Control annual exam and verified the engineering gasket was replaced.
While preparing to get underway Wednesday, the vessel experienced an automated engineering casualty and canceled its voyage until a Bureau Veritas (BV) classification surveyor could arrive and verify the engineering casualty was fully resolved. After arriving aboard the vessel, the class surveyor directed the vessel’s crew to test the automated engineering system and deduced that the casualty was a product of a faulty engine order telegraph; a device used on ships for the pilot on the bridge to order engineers in the engine room to power the vessel at a certain desired speed. Coast Guard Sector Anchorage issued another order for the vessel to remain in Kachemak Bay.
Friday, the vessel was allowed to continue sailing to her destination at the ConocoPhilips LNG plant in Nikiski after additional safety measures were implemented. As part of the safety measures, the tug Stellar Wind escorted the vessel from Kachemack Bay to Nikiski and a second tug, the Glacier Wind, stood by in Nikiski to assist with docking operations.
The Excel completed her voyage and safely moored at the ConocoPhilips pier in Nikiski at approximately noon Friday where it remains until permanent repairs are verified by the class surveyor and Coast Guard inspectors.
“Ensuring safe navigation in Western Alaska, particularly in Cook Inlet, is one of my highest priorities,” said Capt. Paul Mehler III. “Our crews worked closely with the Southwest Alaska Pilots Association, the class surveyor and towing vessel industry to coordinate a safe and secure transit of the Excel from Kachemak Bay to Nikiski. The weather was also in our favor with clear skies, light winds, and steady ebb tide during the transit in Cook Inlet.”
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Shipping Cook Inlet Liquefied Natural Gas - The Tankers
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. |
Inside membrane cargo tank of POLAR ALASKA or ARCTIC TOKYO . . .
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 . . .
LNG Ship Photos provided courtesy of Phillips Petroleum Company and Marathon Oil Company . . .
February 2011 Update: Employees at the Liquefied Natural Gas (LNG) Plant in Nikiski were notified in early February 2011 that the plant would be shutting down later in the spring. The closure will be a mothballing process so the facility could be used again in the future if LNG demand is warranted.
The plant received needed export license extensions last year, but was not able to get a satisfactory price for its LNG. Conoco Phillips has been producing LNG to ship to Japan from Nikiski for the last 40 years. A Marathon Oil spokesman said the business case does not support continuing exports at this time.
The company will continue to produce natural gas from the Beluga and Tyonek fields to fulfill other natural gas contracts in Alaska, but there is some likelihood that production will be diminished. There were thirty plus employees at the LNG plant and thirty plus employees on the Tyonek gas platform in Cook Inlet whose jobs will be lost. The ARCTIC SPIRIT and POLAR SPIRIT will no longer operate between Nikiski and Japan and the ship's owners will need to find employment for the ships on other routes.
November 2012 Update: In a reversal of what was reported in February 2011, the Conoco Phillips LNG Plant in Nikiski resumed shipping LNG to Japan in April 2012 utilizing the 1978 built Marshall Islands flagged 95,084 gross ton LNG GEMINI. At least five shipments took place between April and October 2012. LNG GEMINI was built in 1978 in Quincy, Massachusetts.
Source: http://www.mxak.org