ROV WELD INSPECTION - THE NEXT STAGE

In 1993, Technical Software Consultants Ltd delivered a fully integrat ed ROV deployed weld inspection system using the Alternating Current F ield Measurement (ACFM) multi-element array technology for Norsk Shell to be used in the inspection of the Draugen offshore platform. This s ystem was produced so that it could operate with a range of work-class ROV and manipulator combinations. The system was subjected to intensi ve tank and open water trials. Probability of Detection and Accuracy o f Sizing trials were carried out and a 98% detection rate was achieved with only two Salse calls. In addition, sizing accuracy for length an d depth measurements was as good as that previously produced by diver application of the ACFM technique. The main objective for the system w as that it should be able to be applied by any work-class ROV/manipula tor combination. Since its production, the ACFM array and a standard A CFM probe has been used in trials and inspection work with an addition al three ROVs and inspection companies. It has been used with systems in Aberdeen and Norway using computer-aided telemanipulators (CATS) an d stereo imaging and offshore in the North Sea. Sonsub - Saipem used t he system with ATES (Advanced Telerobotic System) using a Schilling ma nipulator TV track meter and Perry Tritech ROW and Stolt Comex Seaway used both the array and a standard probe with the REMO system during t he Intercalibration of NDT (ICON) trials in Norway. Subsea Offshore ha ve used an array system with a Pioneer ROV and a Slingsby manipulator for jacket inspection in the North Sea. The rigid array is capable of detecting and sizing cracks at the node connections. Thus Technical So ftware Consultants Ltd have completed their objective of proving that the ACFM ROV system can be mobilised with a number of ROV/manipulator combinations. TSC have also developed an in-house computer program cap able of assessing the access and reach of most commonly used ROV and m anipulator combinations. This can provide valuable task planning infor mation on any ROV/manipulator limitations prior to the inspection prog ramme. Information which can then be used to optimise the inspection p rogramme.