Teletest® long range UT inspection of road crossings in Alaska
| Teletest transducer ring installed on 24in pipe in Alaska |
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After a brief but successful trial in the autumn of 1998, annual Teletest surveys have been carried out for ARCO, Phillips Petroleum and BP at their facilities at Prudhoe Bay and Kuparuk on the North Slope of Alaska.
Some 400 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 inch, 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 500mm to either side of the weld.
Other attractive features 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.