Depth limitations on hyperbaric manned operations on the one side and the Increasing water depth in oil field exploration and development on the other, create an increasing demand for diverless, remotely operated technologies and systems guaranteeing the production and supply of primary energy (01.1 and gas) from deep sea resources [1]
Strong efforts are made world-wide to develop and supply diverless systems to be applicable and safely operated In water depths beyond manned operational levels Systems must be available and applicable for installation activities as well as for repair procedures Some major oil producing companies have taken up the challenge of the development of high sophisticated remotely operated technologies to be prepared for the future and to meet the upcoming demand in deep water oil field exploration and development
Operation of pipelines on the sea bed would not be possible without on-site installation, repair and exchange procedures Welding procedures carried out m hyperbaric dry environments are the most favoured procedures to perform such tasks since in this way the achieved mechanical properties comply with the applicable code requirements Dry hyperbaric welding operations could be classified in two distinct groups according to the working depth manned operations (down to approximately 400 msw) and diverless operations (at all working depths even beyond 500msw)
Repair operations at water depths greater than 500 m (the present limit for ambient pressure diving) can only be carried out by fully automatic systems, part of a diverless underwater working station. The two different diverless underwater repair methods generally considered for deep water repair are mechanical connectors and hyperbaric welding The latter is shall generally considered as the best known repair method The growing potential of hyperbaric welding associated with the recent developments in robotics for underwater work suggested a possible solution for a diverless repair station.
This work presents a conceptual description of the main element of a diverless repair station - the underwater habitat - consisting basically of robots and manipulators to prepare the pipe and to weld the spool piece. Also described are the man subsystems of such a Station, its working procedures and the R&D requirements to realize the whole system
A fully automatic robotic underwater working cell represent one of the best alternatives for a diverless repair Station Considering the task in question robots present some distinct advantages over other mechanised systems (e.g orbital systems) such as
handling more than one tool (1 e. welding torch, machining tools, grinding devices, NDT equipment, etc.),
operating Instruments and control panels (input/output user friendly interfaces),
welding other than circumferential joints
capability of carrying out tasks in response other than the joint area
The accelerated development of the robot technology in the mid eighties encouraged the GKSS-Forschungszentrum Geesthacht GmbH to set up a major research project to implement the use of robots in underwater work particularly for hyperbaric welding The initial objective of this research programme was to modify and test an industrial robot for hyperbaric dry work down to 120 bar [2]
