Weld crack characterization on offshore structures using AC potential difference and ultrasonics

• Published in: NDT international Vol. 19; no. 4; pp. 243 - 247
• Main Authors: Dover, W.D., Bond, L.J.
• Format: Journal Article
• Language: English
• Published: Guildford Elsevier B.V 01.08.1986; Butterworth Scientific Limited
• Subjects: AC potential difference; Analysing. Testing. Standards; Applied sciences; Buildings. Public works; crack characterization; Exact sciences and technology; Industrial metrology. Testing; Joining, thermal cutting: metallurgical aspects; Mechanical engineering. Machine design; Metals. Metallurgy; Non-destructive testing: methods and equipments; Nondestructive testing; offshore structures; Structural analysis. Stresses; Testing for defects; ultrasonic testing; welded nodes; Welding; AC potential difference; offshore structures; welded nodes; ultrasonic testing; crack characterization; Fracture mechanics; Tube; Fatigue; Potential drop method; Derrick; Automatic inspection; Electrical testing; Weld; Welded joint; Drilling rig; Ultrasonic control; Ultrasonic testing; Automatic monitoring; Alternating current; Electrical test; Crack; Defect characterization; Nondestructive test; Offshore drilling platform; Defect detection; Fatigue crack
• ISSN: 0308-9126
• DOI: 10.1016/0308-9126(86)90069-6

To assure the integrity of offshore structures greater reliability and accuracy in the detection and sizing of surface-breaking defects in fatigue-affected welded nodes is being demanded. Accurate defect measurements can be used with fracture mechanics based models to assess fatigue crack growth rate and the remaining life of the joint. This paper describes the application of the AC potential difference method to the inspection of offshore structures and also discusses improved ultrasonic techniques developed for this inspection problem. A ‘library’ of tubular welded joints of typical geometries and containing fatigue damage is being collected at the new Underwater NDE Centre established at University College London. Initial trails using some of these specimens to assess detection and crack sizing capability are discussed.