Corrosion effects on structural integrity and life of oil rig drill pipes

Abstract

Corrosion effects on structural integrity and life of oil rig welded pipes are analysed by experimental, analytical, and numerical methods. Experiments were performed using standard tensile specimens and CT specimens for static loading, Charpy specimens for impact loading, and 3 Point Bending specimens for fatigue crack growth with amplitude loading. In each case new and old pipes were used to evaluate corrosion effects. Results indicated negligible corrosion effects in the case of tensile properties and impact toughness, and strong effects in the case of fracture toughness and especially fatigue crack growth rates, increasing the risk of static failure and reducing significantly structural life. Analytical expressions are used for oil rig pipe structural integrity and life assessment to quantify these effects. Recently introduced risk-based approach is applied to analyse oil rig drill pipe with a corrosion defect treated as a surface crack.

Keywords

• risk-based assessment
• failure analysis diagram
• fatigue
• risk matrix