Hingston, D.L., Vickers-Interek Ltd. UK.

Introduction

Vickers-Intertek Limited was formed in May 1976 in order to promote the demonstration and marketing of applications of the Neutrabaric method of working underwater in a one-atmosphere water-filled environment. Intertek are the inventors of the Neutrabaric system, which has now been patented in several other countries and Vickers were one of the first companies to develop the use of manned submersibles with lock-out capability. In January 1977, Vickers-Intertek launched a multisponsor project to design and build a prototype subsea wellhead chamber which would demonstrate an important application of the Neutrabaric system. The sponsors included American, Norwegian and British Oil Companies who made a significant contribution to the project through a Technical Advisory Committee which supervised the design, construction and trials ensuring that the prototype was designed to incorporate the latest developments in subsea technology and tested to meet all current and future oilfield requirements. Trials of the prototype were successfully completed in September 1978. The unit was installed first in 80 ft and then in 400 ft of water at a site near Kyle-of-Lochalsh off the West Coast of Scotland and was hydrostatically tested to 700 ft for Lloyds Certification. A diverless installation was demonstrated using hydraulic handling tools operated remotely from the surface. The unit was accessed on several occasions at each depth by men working at one atmosphere pressure from a manned submersible. A number of typical installation and maintenance tasks(and some unscheduled tasks) were demonstrated and the unit was recovered to the surface using the same diverless handling techniques.

DESIGN PHILOSOPHY

The fundamental philosophy behind the system is that standard oilfield equipment and standard techniques are used such as would apply to a wet-exposed tree subsea completion.

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