Testing of Segment Specimens and Full Scale Pipes for the Assessment of Fracture During Reeling Installation

This Paper describes the testing of Segment Specimens and Full Scale Pipes carried out at DNV within the Joint Industry Project “Fracture Control for Installation Methods Introducing Cyclic Plastic Strain – Development of Guidelines for Reeling of Pipelines”. The JIP was a cooperation between DNV, TWI and Sintef. A total of 24 full thickness Segment Specimens, with cracks/notches introduced in the Base Metal, Fusion Line Root and Fusion Line Cap, were tested. The specimens were loaded both monotonically and cyclically, simulating reeling installation. Two Full Scale Pipes were subjected to a bending loading program simulating a reeling installation. Each pipe contained three test welds and cracks/notches were introduced both at the 6 o’clock and the 12 o’clock positions, i.e. six cracks/notches in each pipe. In one pipe the cracks/notches were introduced in the Weld Metal and in the other in the Fusion Line from the Cap side. After the loading program all the cracks/notches were broken open and the stable crack growth were measured and compared to predictions based on fracture mechanics principals (essentially following BS 7910-1999). A method for adjusting the analysis procedure, in order to obtain good agreement between the predictions and the experimental observations, is suggested. The JIP also included Materials Testing and FEM Analyses. A Guideline Document was developed which is currently being used by the project participants and it is the intention to issue a DNV Recommended Practice in support of the DNV Offshore Standard OS-F101 “Submarine Pipeline Systems – 2000” based on the experience gained and feed back received from the participants. The Guideline document is described in another paper (OMAE2004-51061) at the conference.