Applications for Olver Lockout Submersibles

ABSTRACT This paper will describe recent industrial applications of diver lockout submersibles operating in the North Sea. Types of tasks which can be accomplished more efficiently and economically with diver lockout submersibles will be identified. Innovative solutions to problems presented by lockout submersibles will be discussed, as well as specific oil field applications of diver lockout capabilities and comparisons of diver lock out capabilities with other types of underwater work. INTRODUCTION The technique of divers exiting and reentering the confines of submarines while submerged is not new. In fact, it has been used in varying forms by the armed forces since World War II. From these generally clandestine type operations has evolved the diver lockout from submersibles as exists within the offshore oil industry. HISTORY This process of evolution has not been one of joint development, but more one of converging the paths of two individual services set up to supply the ever increasing demands of an industry under pressure to satisfy energy needs of modern civilization. These demands have caused the search for oil and gas to expand from land to the sea bed of the continental shelf, which in turn produced the requirement for the underwater worker. Initially, while in shallow water, the scope of operation of these underwater workers/divers was satisfactory, but as exploration, construction, and the supporting maintenance moved further a field and into deeper water, so the diving technique had to change. Now the diver needed a bell or chamber from which to dive and larger support systems, such as deck decompression chambers, on the surface to maintain him. The handling of the bell from the surface and the ability to position that bell in the close vicinity of the job required a platform of considerable size that could be positioned accurately and held in that position irrespective of the natural elements. This was achieved by either heavy mooring or dynamic mooring systems, which on the one hand is a time consuming process with ever present danger of anchors dragging and causing damage to subsea equipment, or on the other hand a very sophisticated and expensive system which is generally installed in the larger type of vessel. While the demands on the diver were increasing depth-wise and his range of operation from the surface base reduced, so the submersible was developing to cope with the demands for survey and inspection work over on an every increasing area. The "shirt sleeve" environment of the submersible provided the ability for survey and inspection of as much as 8 or 9 km of pipeline per day, where in many cases, a diver would be hard pressed to cover as much as 1.5 km per day. Also with the use of manipulators certain simple engineering tasks could be performed by the occupants of those submersibles.