The technology for automatic umbilical handling has existed for many years. It has been widely used for the tether management of remotely operated vehicles (ROV's), and with the composite umbilicals and tension winches of saturation systems.
There are many other uses in industry, but these systems do not have the difficulties which present themselves in applications underwater. In the air diving range there have been no significant advances in the method I of umbilical handling, which is a chore for both the diver and the tender.
The use of the mini-bell or TUP (transfer under pressure) as it has become known, and the use of two divers In the water, prompted the question "how can the umbilical be automatically handled to assist the diver and lessen the chore of racking
This paper describes the problems that were encountered and the features that were included to promote both safety and efficiency
The challenge was to provide the diver with an automatically managed umbilical, which has a better drag profile, is flexible, less prone to fouling, while providing safely the services the diver requires for his life support. As well as the factors of design, product reliability and maintainability must also be considered. Weight and space are also a major problem particularly as it has to fit an existing diving system. The safety aspects of both the design and its operation were carefully thought through and a schedule of tests and trials were devised Once the main problems had been identified a more detailed design could be drawn up. Each component part of the system is dealt with in turn
The main constraint in the design of this item are space and weight.
a) Space
Where should the umbilical stored? The original concept was to mount the umbiliwheels horizontally below the bell stage. Calculations showed that there was insufficient clearance for these to be fitted in this position and still allow the bell to be moved, nor was their sufficient access for maintenance The alternative was therefore to fit one wheel on either side of the bell In this area problems were encountered with the position of the bell guide wires and the onboard air supplies. The available space would only allow for a single wrap umbilical rather than the 2 or 3 wrap as was first envisaged. With this as a deciding factor umbilical length and diameter must be thoroughly investigated
b) Weight
The all up weight of the diving bell was already close to the maximum, which left little room for heavy spooling gear, hydraulics and umblliwheel side plates A number of materials were considered, the favoured one being alloy for both lightness and rigidity This was however far too heavy and had to be discarded at a very early stage Plastics, fibreglass, and marine ply were considered and experimented with. To produce the side plates of 1760nim diameter and maintain rigidity without the use of alloy was a major problem.
