Teletest® inspection of road crossings on the North Slope

Teletest® transducer ring installed on 24" pipe in Alaska

After a brief but successful trial in the autumn of 1998, Teletest® surveys have been carried out for Phillips Petroleum and BP at their facilities at Prudhoe Bay and Kuparuk on the North Slope of Alaska during 8-week campaigns in the summers of 1999 and 2000. Some 300 road crossings (pipes in culverts) have been examined. The particular concern is external corrosion at junctions between the shop-applied insulation and the 'weld packs' (insulation installed on site at the weld positions). Pipe diameters cover sizes from 6" to 42", and the road crossings range in span up to 45 metres.

ARCO found Teletest® very successful in this application, although the pipes are insulated with sound-attenuating polyurethane foam and the required inspection range was very demanding. Of particular importance to ARCO is Teletest®'s ability to clearly 'see' the girth welds as they provide excellent markers: if present, external corrosion at weld packs is usually located about ½ metre to either side of the weld. Other Teletest® features that are attractive to ARCO include the system's ability to detect internal as well as external corrosion, the quantitative indication of the severity of corrosion provided by the system, and the ability to positively identify real corrosion features apart from mode-converted 'ghost' echoes. Phillips envisage continuing use of Teletest® in the summer of 2001 and in subsequent years.

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