Launchpad, November - December 2005
For a full list of proposed, active and closed projects see here
Factors influencing the sour corrosion fatigue behaviour of C-Mn steel catenary riser welds
To be launched: Quarter 1, 2006
Cost per sponsor: £40 000, two payments
Project Leader: Richard Pargeter
Carbon manganese steel is generally the most economic material for the construction of steel catenary risers and offers other advantages such as ease of inspection. However, in sour service environments, the fatigue resistance of welds is significantly degraded in comparison with air, and it becomes necessary to utilise an environmental reduction factor to account for the expected reduction in endurance. Environmental parameters such as temperature, pH and partial pressure of H2S are expected to exert a degree of influence on corrosion fatigue behaviour and it therefore becomes important to ensure that laboratory test conditions are as representative as possible of the actual service environment. Mechanical parameters such as stress ratio and waveform, and material parameters such as welding process and consumable chemistry may also be important. A test programme is proposed to explore the effect that these and other variables have on corrosion fatigue performance.
Factors affecting the sour fatigue performance of girth welded clad and corrosion resistant alloy pipe
To be launched: Quarter 1, 2006
Cost per sponsor: £45 000, two payments
Project Leader: Richard Pargeter
In sour service environments the corrosion fatigue performance of carbon manganese steel welds is significantly degraded in comparison with performance in air. In circumstances where this reduction in endurance is not acceptable, the use of clad or corrosion resistant alloy pipe may provide a suitable alternative. As only limited data are available on the corrosion fatigue performance of these materials, a test programme is proposed to determine both endurance and fatigue crack propagation data in simulated sour environments.
'Safe stainless LNG' - safe specification requirements for the avoidance of fracture in austenitic stainless steel welds in pressurised components operating at low temperature.
To be launched: March 2006
Cost per sponsor: £30 000, two payments
Project leader: Henryk Pisarski
Recent work conducted by TWI has indicated that ferrite number (FN) alone is a poor guide to the toughness of stainless steel weld metal (such as 308L) used to fabricate pressurised LNG components. It is proposed that remote measurement of FN, coupled with measurement of composition, using analytical methods requiring small samples (eg chippings from the weld cap), could provide a powerful means of identifying welds that compromise integrity in order to avoid fracture during low temperature operation. The proposed project is aimed at delivering: a near non-destructive method of weld assessment in the field; rational Charpy toughness requirements related to fitness for service; a better understanding of the relationship between weld metal composition, FN content and toughness. In addition, practical guidance will be provided on how to determine FN and composition and how these can be controlled.
