Inspection of engineered composite repairs applied to oil and gas pipework and piping to support life extension


This paper describes work carried out on behalf of the HOIS joint industry project* over the past two years. It is primarily concerned with assessing the most appropriate in-service inspection techniques for engineered composite repairs applied to pipework and piping. This repair method has been used extensively in the UK North Sea and elsewhere for several years to allow aging assets, particularly offshore platforms, to continue safe operations. This type of repair represents an attractive technical and financial proposition compared to an unplanned pipe or spool replacement. Engineered composite repairs are designed, manufactured and installed to have a defined life based on the repair risk classification (representing likelihood and consequences of failure) and is defined in current ISO and ASME standards.    

A blind trial inspection programme, using a combination of donated ex-service and manufactured components is described. Capabilities and limitations of existing NDT and inspection techniques are presented together with guidelines for assessing the condition of the substrate, the adhesive bond and the composite repair laminate. Trials have been done using in-service radiography using iridium gamma sources and digital detector arrays (DDAs), also by using pulsed eddy current (PEC) equipment from several vendors and a novel resonance technique from Sonomatic Ltd called dynamic response spectroscopy (DRS).

The work is expected to deliver results in the form of a guidance document which will support long term application of repairs by defining the significance and criticality of defects, methods of inspection and improving understanding of the long-term performance and possible extension of defined life repairs.