Experimental LNG Carrier Will Evaluate Two Tank Systems Under Operating Conditions

An experimental LNG carrier was recently launched at the Taguma Shipyard of Naikai Shipbuilding & Engineering Co., Ltd., one of Hitachi Zosen's affiliated companies. This 1,000 cubic meter LNG ship is one of the steps being taken by Hitachi Zosen to solve shipbuilding and design problems prior to entering into the construction of large LNG carriers. This Japanese firm established in 1970 an LNG Carrier Development Project to conduct 'research based on its previous experience in building LPG carriers.

The purposes given by Hitachi Zosen for this project are: 1. To confirm the greater safety of the Hitachi Zosen system (a prismatic, independent tank) and the Chicago Bridge & Iron system (a spherical, independent tank).

2. To solve problems regarding construction methods.

3. To obtain an accurate measure of building efficiency per unit of time.

4. To make sure by the trialrun construction that the construction of actual LNG carriers can be performed smoothly.

The testing program will include : 1. Detailed tests will be conducted on land on the strength of the tank and the tank-supporting structure in a static state before installation, since there are many restrictions on the methods of measuring and testing on board ship.

2. After the tanks have been installed in the ship and while at the dock, relations (between the hull and the tank will be checked by rolling and pitching the carrier on a calm sea surface.

3. Based on the above test data, tests will 'be performed at sea to check the relations between the hull and the tanks and the surface effects of liquids in the tanks.

4. After cooling the tanks with liquid nitrogen until the working temperature is reached, the insulation, cooling conditions and the deformation of the tanks and the hull will be checked.

5. After the ship has sailed as an ethylene carrier, long-term tests will be conducted to determine the actual sailing conditions under which the LNG carrier must operate.

This will enable the compilation of the necessary statistical data.

This experimental ship has a length between perpendiculars of 196 feet 10 inches, a beam of 42 feet inches, a depth of 21 feet 4 inches and a 'draft of 13 feet Sx/2 inches. It is propelled by a single diesel engine developing 1,300 bhp.

As can be noted from the accompanying sketches of the ship, two tank systems are being tested. The prismatic tank with insulation were constructed by the Innoshima Shipyard of Hitachi Zosen. The CBI-type spherical tank and related parts were built at the Kanagawa Shipyard of Hitachi Zosen.

The Hitachi Zosen system was developed through the Hitachi Zosen's unique technology in the fields of LNG carriers based on its previous experience and joint research and development by Hitachi Zosen and Exxon International Company. The main features of this system are: Self-supporting, prismatic, independent tank of nine percent nickel steel; welding of nine percent nickel steel 'by using a new filler metal, "HZ-OL," developed for automatic welding by Hitachi Zosen; a double thermalinsulation system, and specially treated plywood with a simple and rational structure for the secondary barrier.

The spherical, independent tank was made of aluminum and is based on the system developed by Chicago Bridge & Iron Company. The main features of this system are: Self-supporting, spherical, independent tanks of aluminum that can be manufactured outside of the hull.

Maritime Reporter Magazine, page 24,  Feb 1974

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