This paper deals with the problem of buckle propagation and arrest in pipe-in-pipe systems. A recent experimental study illustrated that if the geometric integrity of the carrier pipe is compromised, local collapse can result. In a pressure controlled environment such as that encountered in the sea, collapse will propagate dynamically usually collapsing both pipes. A new buckle arrestor consisting of a ring placed inside the annulus between the two pipes has been proposed. A methodology for designing such rings has been developed based on quasi-static buckle propagation and arrest experiments. Here we evaluate experimentally the adequacy of this design methodology under the more realistic case of dynamic buckle propagation. This is achieved by initiating collapse in a constant pressure environment similar to that encountered on the sea floor. The study involves first establishing the effect of the presence of the inner pipe on the velocity of buckles initiated at various external pressures ranging between the propagation pressure of the two-pipe system and the collapse pressure of the carrier pipe. Subsequently, the arresting efficiency of several internal ring buckle arrestors designed by the quasi-static criteria developed is established for buckles travelling at high velocities. Details of the experimental procedures used are presented along with the experimental results and discussion of their implications in practice.
