Patent ID: 7768270

Claim:
A method of inspecting an internal coating along a length of a pipe using a tether-free pigable inspection device, the method comprising the steps of: (a) determining measurements of a thickness of the internal coating along the length of the pipe using one or more probes, the probes having a support mechanism which allows for constant contact with a surface of the internal coating so that the measurements are responsive to changes in the thickness of the internal coating; (b) modifying a voltage of a holiday detector responsive to the measurements of the changes in the thickness of the internal coating along the length of the pipe, the voltage being modified such that the holiday detector will only trigger when holidays are present within the internal coating without causing damage to the internal coating; and (c) detecting the presence of holidays within the internal coating along the length of the pipe, the detecting comprising the steps of: injecting a conductive fluid into the pipe behind the holiday detector, the conductive fluid being in contact with a grounding point and being prevented from contacting the holiday detector by a sealing mechanism; and applying the voltage to the surface of the internal coating using the holiday detector, the voltage being conducted to a wall of the pipe and back to the holiday detector via the conductive fluid in the presence of the holidays, the conductive fluid thereby acting as an electrical coupling creating a closed circuit when the presence of the holidays is detected.