Voids, blisters, and delaminations

This chapter presents a number of phenomena related to local material failure in plastic and composite pipes. These phenomena may be caused by the processing of the material or may be caused by the handling and service conditions. Voids are macro and micro-cavities, which may exist in the material or be caused by the production procedure, service conditions, and chemicals. Voids are empty spaces inside the pipe wall. Voids may sometimes be filled with gases other than the air. Blisters are visible voids near the pipe internal and external surface. In some cases, blisters are in the form of large bulging of some layers of a laminated pipe. Delamination is debonding of the layers of composite pipes or detachment of a pipe liner from the host pipe. This chapter elucidates these concepts along with an assessment of damages and investigation of failure cases. It closes with an account on the preventive measures against voids, blisters, and delaminations.