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Case Studies / Application Notes

• River Crossings
Teletest technology was used to inspect and assess the integrity of the aerial river crossings for a 203mm (8”) condensate line in New Zealand. These regions were ideal for guided wave inspection due to the areas having limited access for conventional NDT localized inspection. Guided wave provided a 100% volumetric coverage of the pipe wall very efficiently. The widest of the aerial crossings inspected was 65m (213 ft) in length, after which the line entered a buried section.

• Corrosion Under Insulation (CUI)
The Teletest Focus+ system is a guided wave NDT instrument developed for screening pipe-work for areas of metal loss damage. In the present case, the system was used in Argentina on two cryogenic jetty lines at 203mm (8”) and 76mm (3”) diameters. The inspection proved to be very successful with 100% of both lines being inspected over a 2-week period. Each jetty line was approximately 2km (1.2 mile) in length including several expansion loops and pipe bridges.

• Large Finned Tubes
Teletest technology was recently called to inspect large finned tubes in the Middle East. These tubes are subject to severe corrosion and are notoriously difficult to inspect due to the fins preventing direct access for conventional NDT probes. Moreover, internal tools are typically expensive and impractical to use. Thanks to the Multimode™ capability of the Focus+ system, it was possible to mitigate the adverse effect of radial fins along the tube length and successfully detect a defect approximately 3,5m (11,5 ft) away from the sensors.

• Desert Road Crossing Inspection
In this case study, a 305mm (12”) condensate line was buried at a depth of between 1m (3,3 ft) and 2m (6,6 ft). In the buried section, the pipeline changed schedule and was also FBE coated. Teletest’s 5-ring torsional system was put to contribution since it was specifically developed for these types of pipelines with high attenuation. The Teletest system detected areas of metal loss and the client excavated this region. Extensive external corrosion was found around a girth weld and in the region adjacent to it. The road crossing was subsequently decommissioned and production flow rerouted via an alternate crossing.

• Nuclear Boiler Spines
During a routine Teletest guided wave inspection for a UK-based nuclear client, a significant change in response was found on a boiler spine at an area of known high risk. The unique penetration capabilities of the Teletest 5-ring torsional modules allow a full inspection length of the entire 21m (69 ft) spines to be achieved from the only accessible location at the top of the spine.

• Drill Risers
Inspection of pipes using the Focus+ LRUT system from Teletest is commonplace. Drill risers are clearly similar in geometry to pipes, but with added complexity on their external surfaces such as clamps and other attachments. Therefore, Teletest has developed a special array system, which takes advantage of the availability of access to the internal surface of the cylinder. The laboratory experiment shown very promising results, with a very low noise level from 0 to 8m (26 ft) in particular.

• Top-side Inspection of Caissons
Teletest was called to trial the Focus+ guided wave system to inspect caissons on an offshore installation. Access to these caissons is difficult, and the system has the ability to inspect the whole length of the caisson from the top-side, making it one of most efficient NDT screening tool one can imagine for this application. From the results it was possible to see the end of the caisson at 65m (213 ft). This indicated that the caisson was in reasonable condition. There was found to be an increased area of corrosion at approximately 34m (112 ft) from the datum that corresponds with the splash-zone.

• Storage Sphere Legs
There is a general concern about the long-term integrity of the legs supporting storage spheres worldwide. In addition, there are access problems that often make it difficult to inspect sphere legs by conventional NDE techniques. Teletest technology provides an efficient way to rapidly screen the legs for corrosion, as long as access to the leg can be obtained for a sufficient length for the transducer ring to be mounted. The full 6m (20ft) height of the 254mm (10”) and 355mm (14”) diameter legs was inspected in one test.

• Buried Line inspection
In this case study, Teletest technology was used to inspect and assess the integrity of an un-piggable buried section of the 610mm (24”) Yatagun pipeline which extends from gas fields in the Andaman Sea through Myanmar and into Thailand. The line was buried at depths between 3m (10 ft) to 5m (16 ft) and the pipe was coated with Tri-laminate coating made up from FBE (fusion bonded epoxy), adhesive, and an outer later of HDPE (high density polyethylene). Even with the presence of such coating, it was possible to achieve 90%+ coverage utilizing the 5-ring torsional tool from Teletest. At some locations, scans of up to 75m (246 ft) were diagnosed.

• Extra Large Diameter Pipeline Inspection
Teletest developed and demonstrated the capability of its system to inspect and assess the integrity of an un-piggable elevated section of a 1372mm (54”) natural gas flare line at a refinery in the Middle East. The main advantage was to avoid having to erect extensive (and expensive) scaffolding, typically required by conventional NDT methods. However, the challenge facing Teletest was the large diameter of the pipe. Historically, the system had only been applied to pipelines of less than 1220mm (48”) in diameter. For pipelines above that size, it has been demonstrated that three Teletest collars need to be linked together. The standard test schedule was modified to remove some of the higher frequency tests, in order to reduce the capacitive load.

Other case studies and technical briefs:
• LRUT Inspection of Bitumen lines
• Sprinkler pipe system inspection