Malaysia
Pipe Details
- 305-mm (12-inch) diameter riser with back-to-back bends
- 40 bar (580 psi) operating pressure
- 35° C (95° F) operating temperature
Summary
- Extensive external corrosion of a riser on an offshore energy asset
- Corrosion extent 60%
- Trained local installers carried out repairs, installing SnapWrap, followed by Contour to restore structural integrity to the riser
- Production was not interrupted while the repair was carried out
- The repair will allow the riser to operate in this environment for 20 years
Offshore asset owners closely monitor offshore assets for structural integrity to prevent safety concerns caused by corrosion. Seawater expedites corrosion, and offshore structures often develop pits, which in addition to weakening the metal structure, can have an equally negative effect on joints and welds. Over time, stress caused by pits lead to structural weaknesses and if left unaddressed, eventually cause fractures.
In examining the risers on an offshore production facility, an operator offshore Malaysia identified extensive pitting in a 305-mm (12-inch) riser with back-to-back bends. In some portions of the pipe, pitting had resulted in 60% wall loss. The company addressed this problem with a composite repair.
A team of CSNRI specially trained local experts cleaned the riser, grit-blasting it an SA 2.5 surface preparation, removing rust, coating, and mill scale to produce a near-white surface prior to the application of the CSNRI repair. The defects were identified and marked so they could be appropriately treated. The defects, which were concentrated at the bends, were first repaired with 76-mm (3-inch) wide SnapWrap strips along a 1.8-m (6-foot) length of pipe.
In cases like this, where SnapWrap applied around pipe bends is placed with spacing that exceeds 13 mm (0.5 in), the repair is overlaid by a CSNRI Contour system.
In this application, Contour overwrapped the entire 5-m (16.4-foot) length of the repair to create a solid covering. This hybrid system of prefabricated sleeves and in-the-field cured composite repair merges a robust structural laminate with a flexible protective outer composite jacket. The repair is designed to last for two decades.
The CSNRI Contour repair was performed in a day and a half of on-site work without taking the riser out of service.