The primary risk factors for crude-oil pipeline operation are third-party damage and coating-failure corrosion. For mechanically damaged or corroded pipe, the leading repair options are welding, replacement, clamps and fiber composite repair.
Method Comparison
- Welding is dangerous — weld-induced incidents are common
- Replacement carries heavy economic and social cost, severely constrained in dense areas
- Clamps wrap a metal sleeve over the defect to restore pressure capacity. Useful for leaks but expensive and hard to install on non-leaking pipe
Composite Repair
Composite repair is the efficient modern alternative — already common in oil-and-gas maintenance and overhaul. Hot-work-free, simple to install, modulus close to steel, high tensile strength with excellent creep resistance, thin section, conformable wrap, broad defect scope.
Field Case: Western Pipeline Wulan
A routine inspection found mechanical damage on the Wulan crude line: OD 559 mm, nominal wall 10 mm; surface dent 15 mm deep, outer diameter ~ 200 mm; wall thinning of ~ 2 mm.
Plan: level the dent with repair resin, then wrap with high-strength carbon-fiber composite.
FEA:
- Defect-free pipe at 3 MPa: hoop stress 83.85 MPa
- Without repair: peak hoop stress at the dent edge 322 MPa — close to steel yield
- With 6 plies of carbon-fiber composite: peak drops to 164 MPa — within the elastic range
Workflow:
- Strip the coating
- Power-tool clean to St3
- Solvent wipe and dry
- Apply filler resin until flush
- After tack-cure, wrap 6 plies of high-strength carbon-fiber composite over the defect
- Recoat and back-fill
Post-repair the line returned to normal operating pressure.