Modules Towed To Site For Construction Of Offshore Plants

With the rapid increase in the need for large plants in nonindustrialized areas, major Japanese shipbuilders have each developed unique methods to build large plants utilizing their engineering and shipbuilding techniques, such as barge-mounted plants. Some of them have already exported bargemounted plants for production of pulp and mortar, as well as for desalination.

A method described below is a "Module Plant System" which was developed by Mitsubishi Heavy Industries, Ltd. The plant constructed under this system is the offshore natural gas liquids facilities for Qatar General Petroleum Corporation, and final shipment was recently completed.

Mitsubishi-developed Module Plant System is, in a word, an efficient prefabrication method for plant construction. It has the following features: (1) Specially developed system and equipment for transportation and erection; (2) Easily transportable, and completely assembled modules of high quality, and (3) Simplified, no piling foundation. MHI has all the fundamental techniques required for this system, which have been acquired through long experience as one of the leading shipbuilders, heavy machinery manufacturers and plant engineering contractors. Major steps of the Module Plant System are divided into the following six stages: (1) Engineering, (2) Procurement and/or fabrication of equipment and materials, (3) Module fabrication, (4) Loading and ocean transport, (5) Unloading and inland transport, and (6) Civil engineering and installation work.

Of the above-mentioned major steps, the module fabrication is carried out under the following process: Equipment and materials are delivered to and stocked at the module fabrication factory under a firm schedule and careful material control.

Fabrication of modules is made under the same production control as in well-equipped factories. A factory with ample stock yard and facilities for module fabrication, as well as loading on oceangoing vessels, is considered to be most suitable.

The Module Plant System has the following advantages as compared to conventional methods: (1) High quality, (2) Lower cost, (3) Faster delivery, (4) Less work at site, and (5) Less effects from local conditions. As the main stages of the construction process are carried out under the same production control as applied in the factories, and because on-site work is minimized, it is possible to eliminate unfavorable local factors which may seriously affect work flow at site.

Moreover, making the most of these advantages, the system makes it possible to undertake construction of any type of plant based on a total integrated contract.

The LNG facility for Qatar General Petroleum Corporation is to separate gas from oil during offshore drilling and transport it to shore by a process developed by Mitsubishi. The LNG facility will be installed in waters with a depth of 35 meters, about 85 kilometers offshore east of Doha, along the coast facing the Persian Gulf. Installation of the entire facility is scheduled to be completed by July 1979.

Composition of the facility: At present, there are three oil wells in operation in the sea area. For these three oil wells, three stations will be erected, each comprising a compressor (compression unit) platform, a glycol dehydrator/power generator platform, and a living quarters platform (for the operators) . The platforms will be connected by bridges.

Weight of platforms and modules: Compressor platform — three units, each 4,000 tons. Each unit consists of three modules, which are put together at the site. Glycol dehydrator/power generator platform—three units, each 1,100 tons. Each unit consists of one module. Living quarters platform—three units, each 1,100 tons. Each unit consists of module.

As described above, one station includes five modules and weighs a total of 6,200 tons. The three stations weigh 18,600 tons in total. In addition, a riser-deck with a weight of 100 tons will be added. This means that there will be in all, 16 modules.

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