Manned Submarines And Remotely Operated Equipment As Construction Tools For Advanced Offshore Projects
Authors: Silvestri Antonio , Oliveri Vincenzo 
Published: October 2008

The trend of the offshore industry towards even deeper waters and increasingly advanced projects has gradually suggested to reconsider the extent of direct human intervention. Manned submarines and remotely operated apparatuses are preferable whenever they can sistematically and operationally take the place of men.

The manufacturing industry. of such specialised equipment, advanced as it is, faces the challenge within its own natural terms of reference, assigning priority to general capabilities of underwater manoeuvrability and versatility (surveying and visual inspections, micro-operational tasks).

The approach followed by an advanced pipelaying contractor is different as it takes into consideration the best available equipment with a view of integrating it with its offshore pipelaying spread.

On complex proj ects, the need to produce timely speciaL equipment for use on occasional obvious areas, normally impervious to traditional techniques based on direct human actions, makes it important to foresee and plan each construction stage in function of the possible requirements for remotely operated equipment and manned submarine, for normal as well as for emergency interventions.

A typical case history can be made for SAIPEM wet buckle repair system: it is of the essence to difficuIt pipelaying jobs to ensure reliable and quick repair methods while laying, more so in very deep water beyond divers reach: SAIPEM's wet buckle repair system was successfully tested in 1976 in 560 metres of water (see OTC paper 2910 - 1977).

It required only minor submarine interventions to position and to activate the system which could be profitably employed also in shallow waters comparingfavourably in terms of reliability and safety with conventional repair techniques requiring interventions with divers.

Increased use of manned submarine within the construction spread started with SAIPEM in 1974 in the North Sea (Forties Field: shaped charges were played bya Viker'ssubmarine on the pipe to open three holes needed for dewatering of the line with a pig, without any damage to the line) and in the Mediterranean (Messina crossing trials - see OTC paper 1974).

A brief description is given of the subsequent developments, culminating in the recent SAIPEM Ragno Due multipurpose vessel for deep water intervention.

There are now realistic prospects of an emergingrole for remotely operated underwater equipment and submarines to serve as contractor's tools conceptually and operationally integrated within advanced lay vessel spreads and as independent systems for maintenance and repair of submarine lines and offshore structures.

Important progresses are expected from future manned submarines and remotely operated underwater equipment specifically developed as integrated components of advanced offshore construction spreads.

Integration Of Surface And Underwater Activities On Advanced Pipelaying Projects

Nowadays pipelaying technology has to cope with ever more challenging offshore projects and the high accuracy and quality required by these new advanced tasks, added to the necessity of reducing the production costs, demand increasing technical skill from the field personnel and sophistication from the lay vessel and supporting craft.