This paper concentrates on the development of procedures for the inspection of adhesive bonds in GRP pipelines. Firstly, attention is paid to the origin and type of defects. Secondly, the experimental results for a number of NDT methods are presented and discussed.

The most important defects in adhesive joints in GRP pipelines are voids, lack of adhesion, lack of cohesion and misalignment. Voids, lack of adhesion and lack of cohesion are all responsible for 30% of the failures. Misalignment is responsible for only 10% of the failures. It should be noted that most of the failures occur during the hydrostatic test of the GRP pipeline. Only a fraction of the failures occur in service.

The literature study and experimental evaluations have shown that for the detection and sizing of voids both ultrasonic methods and the X-ray projection method can be used. The X-ray projection method can also be used for the detection of misalignment. For lack of cohesion use is made of differential scanning calorimetry (DSC) to determine the glass transition point of the adhesive. At present no NDT method is available for the detection of lack of adhesion in adhesive joints between GRP pipes.

Results obtained on artificial defects with the ultrasonic reflection, ultrasonic two-way transmission method and the X-ray projection method will be shown. Advantages and disadvantages of the different methods will be discussed.