Offshore gas pipeline operators are presented with many obstacles when developing or maintaining an integrity management program, especially when it comes to inline inspection (ILI). Challenges including multi-diameter pipeline setup, extreme wall thickness, ID restrictions, no liquid medium, etc., can prevent standard stand-alone technologies, such as MFL and UT, from fulfilling all inspection requirements. As a primary threat to these pipelines is internal corrosion, and because the dimensions of the corrosion anomalies play a distinct role for the depth sizing, a reliable and accurate monitoring solution is necessary. Therefore, ROSEN has developed the RoCorr IEC Service.
RoCorr IEC Service
The RoCorr IEC service, which utilizes Eddy Current (EC) technology, measures the dimensions of the corrosion anomalies more precisely compared to standard technologies, and can also better distinguish between adjacent anomalies, which is important for sizing models. The high-resolution caliper tool design supports the EC sensors that are guided smoothly through the pipeline. Thanks to the use of two sensor planes, 100% coverage is ensured in one run. The sensors are essentially contactless and require no coupling to the wall. Moreover, because the metal-loss features are measured in absolute terms, the tool functions properly regardless of wall-thickness levels. Additional abilities of the IEC service include:
- Detection of pits with minimum diameters of 10 mm and minimum depths of 1.0 mm
- High-accuracy sizing (i.e. +/- 1.3mm) of internal shallow defects with a maximum depth of 10 mm
- Capable of up to 80% ID passage
- Capable to cope with pipeline diameters between 6” and 56” and multi-diameter pipelines
RoCorr IEC Service Combined with MFL Technology
The RoCorr IEC service can be combined with MFL technology, as well as any other desired sensor technology, in order to fulfil the needs of any offshore gas pipeline inspection.
In the combination with MFL technology, the IEC technology supplements the relative wall-loss measurements of the MFL sensors by supporting defect identification and depth sizing, thanks to its higher spatial resolution. If general thinning has taken place in the pipeline, the caliper component of IEC reveals a general impression of the thinning, whereas the MFL component measures the smaller indications within the general thinning area.
By combining the two complimentary technologies, the service is capable of delivering optimum inspection results for the majority of anomalies that can be expected in a pipeline, including the absolute measurement and depth sizing of metal-loss defects, improved distinction of individual pits in dense clusters, and the determination of wall thickness and general thinning.
Over the past decade, IEC technology has been applied to more than 15,000 km (10,000 miles) of pipeline. The experience gathered over time has aided our experts in the further optimization of this technology, allowing for:
- Qualitative discrimination between different materials within a pipeline, enabling operators to monitor the condition of internal coatings.
- Clear identification and discrimination of ferromagnetic debris from corrosion signals.
- Assessment of pipelines with corrosion resistant alloys (CRA), i.e. identification of defects within the stainless steel layer which is not possible when using stand-alone MFL technology.
Further benefits of the RoCorr IEC Service include:
- High accuracy in the absolute measurement of internal corrosion in both liquid and gas pipelines
- Applicable in pipelines with high wall thickness
- Suitable for pipelines with ID restrictions
- Dataset collected also includes pipe geometry information, allowing for dent strain/stress calculations
- Detection of general pipe wall thinning
- Inspection of pipelines with CRA cladding or internal flow coatings