Advancements in Remotely Operated Vehicle (ROV) technology during the last few years have proven their capabilities and economic advantages in performing installation and maintenance tasks, pipeline surveys and general Inspections associated with subsea oil production In proceeding further in fully integrating ROV's Into offshore hydrocarbon production, a joint development program, funded by the OSO, Mobil North Sea Ltd, Slingsby Engineering Ltd, Technical Software Consultants Ltd and Camera Alive Subsea Offshore Ltd, was initiated to develop equipment to completely replace divers in performing Non-Destructive Testing (NDT) of structural members and nodes In steel jacket platforms This paper describes the design and test results of a manipulator and its associated supervisory control system specifically developed for the performance of NDT

The design objectives were to develop a manipulator which could perform all functions required to Inspect welds using state-of-the-art subsea NDT equipment, including Magnetic Particle, Visual, Eddy Current, AC-FM, Flooded Member Detectors In addition the design objectives Included the development of a manipulator supervisory feedback control system capable of moving the NDT end effectors along any conceivable nodal weld trajectories within the specified performance envelopes for the device


When one considers the age, the fabrication methods and the environment under which they operate, it is not surprising that many of the platforms used for offshore hydrocarbon production in the North Sea (and elsewhere in the world) contain fatigue cracks in their structural members It is because of this loss in structural integrity that the classification societies imposed inspection requirements for welded joints in these platforms It is also not surprising, that the offshore oil industry, which has made a concerted effort during the past decade to eliminate divers from subsea operations, should turn to Remotely Operated Vehicles (ROVs) and telerobotics to perform these platform weld inspections This paper discusses the "ARM Project" which is one of several ongoing projects with the objectives of performing subsea visual and non-destructive testing (NDT) inspections utilizing ROVs

The project, which was initiated in the autumn of 1990, is jointly handed by the Offshore Supplies Office (OSO) of the Department of Trade and Industry, Slingsby Engineering Limited, Technical Software Consultants Limited, Camera Alive Subsea Offshore Limited and Mobil North Sea Limited The basic objective of this program was to design, manufacture and test a manipulator and associated vision and control system software that could perform all functions required for the inspection of welds using state-of-the-art NDT equipment, including Magnetic Particle, Visual, Eddy Current, AC-FM and Flooded Member Detectors Further objectives were to develop means of deploying cleaning systems capable of preparing the surfaces to be inspected to the degree necessary for the particular NDT device and to develop an effective means of holding the ROV in position on the structure while the Inspection is being performed Follow on phases in the project will include the design and manufacture of a modular NDT tooling skid which can be used in conjunction with ROVs of opportunity and at sea testing of the equipment

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