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Back ground

Corrosion protection of off-shore steel pipes by retrofitting felt-epoxy liners, a method qualification of Insituform ™. Back ground. Since start-up in 1986 less oil, more gas and more water are being produced at Gullfaks Less demand for oil storage capacity

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Back ground

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  1. Corrosion protection of off-shore steel pipes by retrofitting felt-epoxy liners, a method qualification of Insituform™

  2. Back ground • Since start-up in 1986 less oil, more gas and more water are being produced at Gullfaks • Less demand for oil storage capacity • Re-assign oil storage tanks to produced water settling tanks

  3. Challenges • Carbon steel piping from utility shaft to storage cells • Crude oil OK • Produced water corrosive • Piping cannot be replaced • Corrosion protection essential • One-sided access only • Long and intricate routing of pipes • Pipe failure or blockage → loss of storage cell

  4. Considerations • Internal painting ruled out • Surface preparation extremely difficult • Paint application • Inspection • Cathodic protection ruled out • Temperature, Oxygen, Chlorides and Sulfides • Uncharted territory • Liner most favoured solution

  5. Liner Requirements • Loose liner ruled out → rigid liner • Compliant during placement → thermoset based • Adhesion to pipe surface cannot be critical → structural liner • Be able to ensure position of liner end → non-stretch liner • Ample ‘pot-life’ → epoxy • ‘What if’ contingencies → ensure back-up solutions for relevant failures during installation

  6. Insituform™ from Olimb AS • Thermoset liner based on felt and epoxy • Felt thickness can be tailored to give appropriate structural capacity • Epoxy quality can be chosen to give temperature and chemical performance (NA) • Inserted (inverted) into pipe using compressed air • Cured using steam • Mature product in terms of renovating municipal piping • Less history on complex geometries • Ensure most demanding relining is well within the process window → do a test relining of replica of most challenging pipe on land

  7. Pipe replica • Length of chosen pipe approx 80 metres • Pipe diameter 16’’ • Starts off with 3 x 90º bends then 12 m straight up • Then 10 more bends

  8. In a quarry near Moss

  9. The liner principles • A tubular felt sheath clad with a layer of PU on the outside • Prior to placing the liner in the pipe, the felt is saturated with epoxy • Even distribution of epoxy using rollers • Curing can be delayed by placing in cold water

  10. The liner principles • Silicone ‘plug’ loosely glued to end of liner • Perforated to allow controlled escape of steam • Glue must allow pull-off by attached rope after curing

  11. Liner reeled • Lubricant applied to outer surface • Rope and liner reeled up inside pressure vessel

  12. Inverting the liner • Rope and liner reeled up inside pressure vessel • End of liner pulled back over spout • Tank pressurised to force liner into pipe

  13. A sketchy illustration... → o → Liner Pressure vessel Corroded pipe

  14. Results • Maximum recorded pressure 1.2 barg • Allowable 1.5 barg • Burst 2.5 barg • All bends negotiated first attempt • Curing temperature achieved at far end • Silicone ‘plug’ came off (no force measurements were done) • End of liner within tolerances • No contingency plans were put into action

  15. Results • Destructive inspection of pipe revealed • Wrinkles at the bends • Some lack of adhesion to the steel • Minor liner thickness variations • The method is deemed successfully qualified for this application

  16. Thank you Corrosion protection of off-shore steel pipes by retrofitting felt-epoxy liners, a method qualification of Insituform™ Gunnar Hognestad Principal Engineer guhog@statoil.com www.statoil.com

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