Offshore Technology Research Center

 

Abstract ID# :

NDEWS

Report Title:

Non-Destructive Evaluation (NDE) Methods for Inspecting the Integrity of Composite Structures Used in the Offshore Oil Industry

Authors:

Ozden Ochoa, Texas A&M University and Jerry Williams, Petroleum Composites

Report Date:

November, 2002

The advantages of using light-weight, corrosion resistant composite materials and structures for deepwater developments have become increasingly important in recent years and many composite components are being used or developed for use in the exploration and production of oil and gas.  Early composite applications have been lightly-loaded, i.e., pipes and gratings which are primarily constructed of glass fiber and epoxy resin.   Most qualification and in-service re-qualification to date have been based on test data and visual inspection.  Advanced composite applications are now emerging for critical, primary structural components, such as drilling and production risers, drill pipe, spoolable high-pressure pipe, subsea pipelines, tendons, and synthetic fiber mooring ropes.  These components are much more highly-loaded and therefore structurally demanding, and their remoteness from the surface introduces inspection and monitoring challenges.  Alternative carbon, polyester, and other fibers as well as advanced resins are being proposed for applications.  One of the main issues which has been identified as a technology deficiency inhibiting the deployment of composite components offshore is the effect of damage to components and the associated issue of how to find and determine the extent of damage.   At issue is “Are there reliable, affordable Non Destructive Evaluation (NDE) methods which could be used to ascertain the fitness for service of components following manufacture and during service?”  Reliable NDE methods that can economically monitor the performance and continuing integrity of composite component in critical structural applications could provide better understanding and confidence and lead to the development of rationale and realistic inspection strategies. 

Composite manufacturing defects such as delamination and voids as well as damage experienced in service can lead to premature failure of the component.  It is important that Non-Destructive Examination (NDE) methods be available to examine composite structure components to determine their state of fitness-for-service following manufacture as well as at scheduled and special times during the service life.  Some of the NDE methods used for metals such as x-ray are also applicable to composites, but for the most part a completely different set of NDE tools must be used.  There has been considerable research in recent years to develop NDE methods for the inspection of composite aerospace and automotive components.  With a small amount of adaptation, some of these methods can be applied to composite structures used offshore.  Methods such as ultrasonic, radiography, thermography and acoustic emission are well established, but require skilled technician interpretation.  Other promising methods such as fiber optic sensors, trip metal strain sensors and embedded sensors are just emerging.  In addition, considerable research results are emerging from NDE applications in other industries.  Interferometry methods such as shearography are being used to inspect large aerospace structures and may have merit for oil industry components.  The lack of familiarity with the unique problems and challenges of the oil industry by NDE experts and similar unfamiliarity by the oil industry of the advancements that have been made in NDE technology currently inhibit the utilization of NDE methods.   

The primary barriers to applying NDE technology in the oil industry are thus both technical and inadequate communications including:  (1) lack of opportunity to develop experience-base inspection strategies based on actual in-situ performance of these new components, (2) need for advancements in applying NDE methods to the specific needs of the oil industry and (3) lack of information to assess the potential benefits, costs and limitations in applying NDE methods.  The workshop on “Non-Destructive Evaluation Methods for Inspecting Offshore Composite Components” sponsored by the Texas A&M University Offshore Technology Research Center and the Minerals Management Service held on November 21, 2002 was designed to address these issues.   The long-term benefit is expected to be to sort out what is needed, what is available, what can be developed, and to serve as a catalyst for development efforts to make available the technology to inspect composite components used in the offshore oil industry.  The availability of reliable NDE inspection methods is important not only to the operators, but also for regulatory authorities to gain the both experience and confidence in the safe application of critical composite components being introduced offshore.  

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