Unique Long Term Simulated Service Testing of Selected Deep Water Wet Insulation Coating Systems

The oil and gas industry is moving to deeper water developments and thermal insulation of pipelines at 2–3000 meter water depths is required. Wet thermal insulation systems are exposed directly to the seawater and large hydrostatic water pressure in combination with high fluid temperatures challenge the integrity of the insulation systems. The thermal insulation properties of the insulation system can be gradually decreased by thermal and physical strains and challenge the flow assurance if not taken into account in the design. Wet thermal insulation systems have traditionally been qualified for long term use by a combination of long-term small scale aging tests and shorter term full scale simulated service tests (typically 7–28 days). To evaluate the long performance, simulated service tests have been run for one full year at high water pressure and internal pipe temperatures. A selection of commercially available wet insulation systems have been tested together with system specific field joint coatings under the maximum internal pipe temperature specified for the individual coating systems. The test has been run in natural seawater at 300 barg pressure and temperature of 2–4 °C. The coating thicknesses have been selected to give U-values of 3–4 W/(m2K). Before the simulated service testing all test pipes were run through a simulated reel installation to impose realistic strains on the coating systems before testing. All tested coatings performed according to expectations during the simulated service test. The syntactic systems (PP and PU based) gave gradual decrease in thermal insulation efficiency with time but the reduction was close to linear and can be accounted for in the design. The coating systems based on solid polymer materials did not show the same reduction of thermal insulation properties with time. Tests of natural cool-down performance of the insulated test pipes showed that the cool down times were maintained during the one year simulated service tests. Post-test investigations of the insulation materials did not reveal significant degradation of the materials as result of the tests but coating systems application related defects were identified which had developed over the test period. None of the pre-existing defects developed to such an extent as to affect the overall U-value of the coating system.