4.1 General

The calibration methods summarised below are to be used as a guideline. A detailed description of these calibration methods is also given in ISO 7278-2:1988. National regulations should specify that pipe provers are to be calibrated when they are installed, and that they should be re-calibrated periodically at an interval fixed by these regulations. Pipe provers should also be re-calibrated when they have been repaired or modified (e.g. change of detectors, recoating, dismantling and/or re-installation).