A running joint industrial project (JIP) aims to validate an acceptance criterion for avoidance of hydrogen embrittlement of subsea dissimilar joints. Acoustic emission (AE) is being used to monitor full-scale testing.
There is a need for inspection and condition monitoring of subsea pipelines in petrochemical and electrical applications. Corrosive environments and pressures experienced in these pipelines, particularly for ageing plants, can lead to creep, fatigue and corrosion type defects. Safety is of paramount importance and recent failures have demonstrated the importance of the formation of defects in these structures.
The JIP aims to provide the following benefits to industry:
- a validated recommendation for materials and welding procedure specifications resistant to hydrogen embrittlement
- a validated qualification method giving confidence in materials selection and welding procedure for through-life performance
- avoidance of further costly and, potentially, environmentally damaging dissimilar joint failures
- establish confidence in performance limits for existing joint designs and material combinations, minimising risk of future failures.
- Small-scale testing following qualification procedure
- Large-scale testing (tensile)
- Simpler small-scale testing
- Monitoring of AE activity during full-scale tensile test.
Acoustic emission monitoring
Acoustic emission monitoring can be carried out while a constant load is applied. Acoustic emission is generated when stress waves are produced by sudden stress redistribution within the material, caused by changes in the internal structure (crack initiation, growth, opening and closure). Part of this energy is released in the form of ultrasonic waves that propagate through the structure and are captured by the AE sensors.
Acoustic emission uses different signal parameters to evaluate the potential crack characteristics and location, including AE counts, peak levels and energies. By means of a rigorous analysis, these parameters can be correlated with defect formation and growth. This technique is currently an effective way of detecting fatigue and fracture behaviours of materials, making it ideal for pipeline monitoring. Most of the sources of AE are damage-related; thus, the detection and monitoring of these emissions are commonly used to predict material failure.
If you would like to know more about this type of project, please visit our Joint Industry Projects page.
If you would like further information about acoustic emission please contact our Integrity Management team.
For any further information on resistance of subsea dissimilar joints to hydrogen embrittlement please contact our Metallurgy team.