The quest for new oil and gas fields has taken the oil companies Into areas of great depths and hostile environments To make the exploitation of these findings possible, there is a need for new and advanced technology.

The distance between the surface support and the diver is increasing This adds to the technical difficulties and drastically lessens the margins for the diver life support systems This calls for new philosophies in many of the problem areas and perhaps totally new concepts for their solution.

Attempts to obtain increased surface independence have led to the development of so-called flying bells. These are diving bells free from guide wires and equipped with thrusters in order to give horizontal manoeuvrability. In the near future we will also meet the large autonomous submarine ‘Saga’, a mix between the old concept of a stationary habitat and a lock-out submersible as it occurred in the early 1970s

This chapter intends to describe the pros and cons of these systems and to compare them with the conventional diver transportation systems. This will not be done by a precise statistical method, but rather by analysis of a systematically collected interview material We shall try to show the potential of this kind of analysis and hopefully be able to continue to make similar studies of offshore diving.

SYSTEM DESCRIPTION

For the comparative analysis of the different transportation systems, a system outline, a performance table and a theoretical bell-run efficiency diagram have been prepared.

System Outline

The outline is roughly divided into structure, main supply systems and diver worn components From the beginning our intention was to compare system components of different diver support systems to establish their influence on the total efficiency of the system We found no such differences of any significance, although some system components, mutual to all systems, proved to be in need of improvement (Fig.1)

(Fig. 1 is available in full paper)

Performance Table

A number of system characteristics have been listed The information is mostly gathered from commercial brochures (Fig 2)

Note the following

MDU Emergency tame This is most likely 24 hours as defined in classification Rules

FB and MDU Turnaround time It is not likely that the FB closes one bell-run and starts the next within one hour A more credible estimate is two hours That figure is a rough estimate based on the turnaround time for the SDC and the launch to lock-out time for the MDU

Flying bell Launch to lock-out No information is given concerning this operation It is, however, very likely that the time for the operation will be close to that of the MDU

MDUand DL0 Costs The costs are estimated from old information and the need for a special support vessel (Fig. 2 is available in full paper)

Theoretical Bell-Run Efficiency

Figure 3 shows the theoretical ability to keep a diver at the worksite The necessary ineffective bell-run time is estimated from interview material In practice, the influence from various systems of different technical maturity will cause further delays in turnaround time

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