Multi-layer polypropylene (MLPP) insulation coating is used for thermal insulation of subsea pipelines. However in recent years - with higher wellhead operating temperatures - high temperature (HT) Fusion Bonded Epoxies have been used. This paper describes the author's experience with the MLPP systems over the last 20 years.
The alloys (used in chem/process industries) are usually in the solution annealed condition & must be fast cooled from the annealing temperature to prevent the precipitation of third phases such as sigma chi nitrides & alpha prime. This paper describes a reactivation test to detect alpha prime - used with 22%Cr and 25% Cr alloys. Case studies.