The riser system for BG International's Neptune platform was under construction at Barmac's Ardersier yard. The risers are assembled in bundles before insertion into caissons. The caisson tops are sealed with lids, each riser having an anchor flange which sits in a recess in the lid. Once sealed in the caissons, direct access to the risers will no longer be possible. It was suggested that an ideal application for Teletest® would be to inspect the risers in their pristine state, so that a fingerprint could be obtained, against which their condition in service could be compared and any degradation due to corrosion detected. The opportunity was taken to carry out some exploratory tests whilst the riser assemblies were still in the yard. It was found that transmission of ultrasound past the anchor flanges was possible and that the sprayed aluminium coating had no adverse effect on propagation. The pipe ends, 63m away, were readily detected and the possibility of detecting 9% metal loss flaws in the splash zone, 18-20m from the transducers was demonstrated. BG International are now considering whether to perform a baseline survey of all accessible offshore risers after final installation and at periodic intervals thereafter.
This work was carried out by TWI's wholly owned subsidiary, Plant Integrity Ltd (P i). P i's client was BP who were managing the project on behalf of BG International.
