Abstract — Inspect, assess and repair forms the integrity-management cycle for pipelines. Repair-and-reinforcement technique is a critical lever for both integrity and service-life extension. This article summarises and categorises the available methods and compares their strengths and weaknesses.
Three Families, Seven Sub-Techniques
Pipeline repair methods worldwide fall into three families:
- Welding — weld overlay, weld patch, sleeve
- Mechanical clamps — clamp, clamp with epoxy injection
- Fiber composite — glass fiber composite, carbon fiber composite
Each has merits, but on combined performance and outlook, carbon-fiber composite reinforcement leads.
Introduction
In-service pipelines inevitably accumulate defects from corrosion, fatigue and mechanical damage, lowering the maximum safe operating pressure and reliability. China currently operates more than 40 000 km of pipelines; maintaining their integrity and safe operation is a major challenge for the oil and gas industry.
Industry practice in China and abroad confirms that the inspect–assess–repair cycle is the effective workflow for integrity:
- Inspect — internal or external inspection to detect coating and wall defects and damage
- Assess — elasto-plastic, fracture and damage mechanics models, methods and software to estimate the residual strength of defective pipe and, combined with defect-growth kinematics, predict remaining life
- Repair — apply suitable methods to restore safe operating pressure at the defect
This article focuses on classifying and comparing the repair techniques, sketching their principles, as a reference for plant managers and field engineers.