TWI designed and built a unique custom rig capable of testing full-scale pipe welds in an internal sour environment, to support its Industrial Members in the oil and gas sector.
Steel catenary risers are commonly used within deepwater oil and gas developments, and fatigue performance is often a critical factor in their overall design. Resonance fatigue testing of full-scale girth welds has become standard industry practice to demonstrate adequate performance.
However, these tests alone take no account of aggressive service environments such as sour production fluids. In these instances qualification testing is usually a two-stage process involving full-scale resonance fatigue testing to demonstrate the required performance in air, and small-scale (strip) fatigue testing (in air and in the sour environment) to determine a fatigue life reduction factor that is then applied to the base design curve. This approach accounts for geometry effects (ie the difference between strip and full-scale testing) and environmental effects individually, and has been adopted on many projects. However, the validity of the approach had not been demonstrated, so TWI launched a JIP with that aim.