The qualification of high temperature flexible risers was a critical element in the field development of the Norne and Åsgard fields. At a later stage this also included the Kristin field. The high temperature leads to the selection of PVDF as the liner (pressure sheath) material. Due to numerous leaks from pressure sheath sliding in the end fittings of risers with three layer PVDF liners in the middle of 90’s, it was necessary to requalify the end fitting design. An extensive test 10 year program was initiated where mid-scale riser samples were cycled between the minimum and maximum operating temperatures. In the 10 year long test program were some test pipes were subjected to more than 1000 cycles without pressure sheath sliding or a failure. The modified end fittings were qualified for service.

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