Abstract

Stena Line of Gothenburg, Sweden, came to oresundsvarvet with a basic design of a new type of diving support vessel and supply vessel that had no comparison with existing vessels. The requirements where:

  • An advanced saturation diving system integrated with the vessels design.

  • A dieselelectric machinery.

  • Performance when diving as for a semisubmersible vessel.

The paper describes how the requirements were met and the different systems incorporated in the vessel.

Introduction

On Friday, June lath, 1978, the Managing Director of Oresundsvarvet (the Oresund Shipyard) in Landskrona, Sweden, received a phone call from their counterpart of the Stena Line in Gothenburg. The director of the Stena Line proposed a meeting for the discussion of design and construction of the most sophisticated offshore vessel that had ever been built. The first vessel was deliveredJanuary 4th, 1980.

As project Manager, I have had the privilege of participating in and following up the work on MSV Stena Constructor and her three sister ships. My remarks here today are based on the experience generated by this. project.

Vessel Design Requirements

Stena Line presented us with a list of basicrequirements that had to be met by the new diving support and supply ships:

  • Motion at sea had to be as smooth as possible, in order to facilitate diving operations in the North Sea and other water

  • The ships had to have advanced steering and manoeuvring characteristics and a high capability for maintaining position.

  • Fuel consumption had. to be slow.

  • The work deck had-to be large.

  • Cargo capacity had to be high.

  • The ships had to be equipped with firefighting systems and had to be able to accommodate up to two hundred survivors in case of drilling platform accidents or other disasters.

  • Finally, each vessel had to be built at a fraction of the ~ost of a semi-submersible, which is a relatively large ship, although performance-in general had to be equal to that of a semi-submersible.

Hull Design

Together with the owners we assigned the Swedish Maritime Research Centre the task of carrying out the theoretical calculations regarding the 'movements of the ships in heavy weather. These data were then used as a base for calculation of main dimensions.

The wave spectra from the North Sea showed that. A .length of around 100 m would be sufficient to give easy movements. For a vessel of this kind, economy when running at full speed ahead is not ofvital importance. This vessel is designed for keeping her position in open sea during rough weather conditions. Therefore tank testing started with sea keeping performance.

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