Lifetime testing | technical paper Statoil’s decommissioning of its Tordis fi eld presented a rare
opportunity to determine the real impact that 20 years of continuous operation places on the PP foam line pipe insulation system
Long term ageing of PP foam
Polypropylene foam has been used as a thermal insulation material for over 20 years and a good track record has been built up over that period. Statoil recent- ly decommissioned its Tordis fi eld after 20 years of operation and sections of line pipe and fi eld joints were retrieved for testing of corrosion attack on the steel pipe. Sections were also made available to Bredero Shaw for testing and analysis. This is the fi rst time that testing has been able to be performed on real samples after the full fi eld life and serves as an acid test for the validity of the assumptions made in the selection of materials and the design of the system. Both mechani- cal and chemical testing was performed on the retrieved coating samples and the results are reported in this paper. The Tordis fi eld was originally developed by Saga Petroleum and came on stream in 1994. The fi eld is in
Block 34/7 in the Tampen area of the Norwegian North Sea. The water depth was 200m and the design operating temperature was 70˚C. The insulation coating was applied to a 275 mm OD pipe, with a wall thickness of 15.9mm and the total system (all layers) was applied at a thickness of 50 mm. The design lifetime used for the Tordis project was 20 years. The insulation itself represents the fi rst generation
Table 1: Results of GPC analysis on exposed and unexposed PP samples Sample
Unexposed fi eld joint Exposed fi eld joint Unexposed foam Exposed foam
Mw Mn PDI 380000 73000 5,2 385000 75000 5,1 505000 81000 6,2 520000 80000 6,5
May 2013 | PIPELINE COATING 21
Decommission- ing of the
Tordis fi eld (main image) presented an opportunity to analyse long
term ageing of foamed PP insulation
PHOTO: STATOIL
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