March 1977 - Maritime Reporter and Engineering News

Mitsubishi Delivers World's First Internally Insulated LPG Carrier

After years of research on internal insulation systems for LPG carriers under license from Shell Research, Ltd., and fully utilizing the company's experience in the construction of independent tank-type LPG carriers, Mitsubishi Heavy Industries, Ltd. of Japan completed the world's first internally insulated LPG carrier, the Pioneer Louise.

The Pioneer Louise is a large refrigerated-type LPG carrier built at MHI's Yokohama Shipyard & Engine Works for Goldcup Shipping Inc. of Liberia. A pioneer vessel in the field of internal insulation systems for LPG carriers, it is the first of MHI's 77,500-cubic-meter standard LPG carriers adopting this cargo stowage system. The ship is operated by The Sanko Steamship Co., Ltd., under charter to Shell Senpaku, K.K., for transport of low-temperature liquefied propane, butane or their mixture, from the Arabian Gulf to Japan.

The company is now fitting out two sisterships.

The vessel is a flush decker having a through deck, with the engine room, accommodations and bridge located aft. Watertight bulkheads segment the hull into forepeak void, fore deep tank, five cargo holds, engine room and aft peak tank. The cargo hold has a double-hull structure. The double bottom and topside compartments around the cargo tanks are used as water-ballast tanks.

On the upper deck above the cargo holds is a deckhouse for the cargo machinery, such as the reliquefier; cargo piping, including two each of liquid and gas crossovers, and cargo-tank domes for connecting the piping and wiring to the tanks.

The interior of the cargo tanks is insulated with polyurethane foam insulation, sprayed directly onto the flush interior surfaces of the cargo holds. Originally conceived by Shell Research, Ltd., this system was developed by MHI under Shell's license for practical application.

The tanks are prismatic and have octagonal cross-sections for sufficient stability and strength of the hull. In the bow and stem, the tank shapes are tapered to match the hull form.

For effective application of insulating material, it is desirable to keep the tank interior as free of protruding objects as possible.

For this reason, the cargo pumps and other fixtures to be installed within the tanks are fitted on a truss structure which consists of cargo loading and discharge pipes and is suspended from the tank dome.

The cargo-handling systems were designed for handling and transporting two different kinds of cargo simultaneously. The standard loading and unloading rates are 5,500 cubic meters per hour. Each cargo tank is equipped with two electric submerged main cargo pumps and an auxiliary pump of the same type.

During cargo loading, displaced gas and vaporized gas generated by effects of external heat on the tanks are transferred ashore by means of five sets of reliquefaction compressors and/or a shore gas compressor. These gases may be reliquefied when the shore plant is not ready to receive them.

While at sea, cargo vapor generated by effects of external heat on the tanks or by liquid motion, is reliquefied and returned to the tanks by the reliquefaction plant.

The reliquefaction plant has sufficient capacity to maintain the pressure and temperature of the cargo on the same level as at the time of loading.

It is of vital importance for safe operation of LPG carriers that centralized surveillance be maintained on the physical state of the cargo, operating conditions of the cargo handling gear and related machinery, ship's trim, etc., at the time of cargo handling as well as during navigation.

The cargo control room is arranged in the aft deckhouse and is equipped with cargo-tank pressure and temperature indicators, flammable gas detector for various compartments, alarm devices and performance indicators for cargo handling machinery, cargo and ballast-tank level gauges, draft indicators, etc. Each cargo tank is provided with pilotoperated safety valves which, should the tank pressure become excessive, release cargo vapor by means of vent risers at a safe height.

In addition to the usual fire extinguishing devices, the vessel also is equipped with carbondioxide total-fiooding-type fire extinguishers in the reliquefaction compressor room.

The propulsion plant consists of one set each of Mitsubishi MAN 12V 52/55 and 14V 52/55 diesel engines (maximum output —26,000 hp) with reduction gear, combined with a KaMeWa controllable- pitch propeller and a 1,800-kw main generator driven by a main engine.

The machinery plant qualifies for Nippon Kaiji Kyokai's "MO" notation. The main engines are remotely controlled from an airconditioned engine control room, and the c-p propeller is controlled from the wheelhouse.

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