GRP materials are now commonly used in piping applications for offshore platforms and 'Floating Production Storage & Offloading' (FPSO) vessels. GRP pipe-work is now used in safety critical system applications include: (1) Ballast water systems, (2) Seawater cooling, (3) Firewater deluge systems, (4) Bilge systems and (5) natural gas networks. Although not used for high pressure applications, GRP non the less is used in safety critical pipelines operating at up to 20 bar, with diameters typically ranging from 50 to 200 mm's. Having a high strength to weight ratio, as well as being corrosion resistant, FRPs have ensured a positive role for themselves in the off shore marine and other environments. The fibres strengthen the plastic, but result in an inhomogeneous medium that is difficult to examine with NDT. Due to the low cost, suitability and abundance of the raw material glass fibres (GRP) is used in the widest range of applications and is the subject of the Sure2GRiP project.

Unfortunately, flaws in the fibres and the matrix affect the structural integrity of GRP. These can be created in the form of build damage (BD) during the installation process (weak bonds in adhesive joints); in-service as accidental damage (AD), when impact with solid objects at high speed can create a particularly undesirable defect termed Barely Visible Impact Damage (BVID), for the reason that the signs of significant internal damage are barely visible at the surface; or through environmental degradation (ED) in service (e.g. UV exposure and salt water osmosis) where despite an inherent resistance to corrosion, extreme environment can cause the plastic and bonds to deteriorate. The combination of these damage mechanisms and the particular inhomogeneous material properties are specific to GRP and are accompanied by unique inspection requirements, especially given the unique access problems when inspecting offshore installations. The vast array of proven NDT inspection techniques that exists for defects in traditional engineering materials are not available for those that seek a competitive advantage through the use of GRP materials. Furthermore, the existing limited NDT techniques are applied manually, further diminishing their usefulness as operator subjectivity and fatigue drastically decreases the probability of defect detection.

• Cracks in pipe material due to impact damage or in the extrados of fittings (elbows) due to stress. Elbows are generally 2-3 times thicker than pipes
• Air bubbles/inclusions in adhesive joints and epoxy matrix
• Foreign bodies such as tapes and contamination etc
• Kissing bond (at mechanical joints), where there is no air gap and no adhesion
• Delaminations
• Insufficient cure
• Incorrect mixture
• Loss of wall thickness due to erosion or chemical attack. Pipes are often lined with glass in chopped strand mat form to protect against chemical attack. Once this is breached, degradation will occur quickly

The drive towards the use of GRP for process critical or Structurally Significant Items (SSI) has focussed attention on the NDT of large fracture critical components. This has posed some special concerns in relation to defect detection including the unique case of kissing bonds (KB's). Conventional NDT methods have been found to be lacking in detecting these types of defects. In fact, the most common methods that are currently used to determine structural integrity are (1) visual outer surface inspection and (2) hydrostatic pressure, Visual testing cannot determine defects that are sub-surface and Hydrostatic testing can lead to catastrophic failure during the test with consummately high levels of collateral damage. The use of NDE for defect detection is of primary concern to GRP pipe assemblers and operators, since the consequences can be fatal. The risk of further failures and potential for loss of life is set to increase with the introduction of larger/heavier constructions carrying more toxic fluids that would have catastrophic effects should there be a lack of containment due to a pipe or joint failure. The inability to carry out demonstrably effective NDT and inspection of GRP pipelines is seriously limiting its use as a material in more demanding pipeline applications, where it would otherwise be seen as having significant economic and environmental advantages. The above issues highlight an urgent need to develop NDT technologies as applied to the inspection of GRP pipes and pipe joints.