1. For buried or submerged pipelines, the occurrence of coating damage is normally monitored by cathodic protection measurements (refer to DEP 30.10.73.31-Gen.).
2. If the pipeline is made of corrosion resistant material (e.g. duplex, GRP, cladsteel), there is normally no need to monitor for internal corrosion.
3. For carbon steel pipelines, the control of internal corrosion is normally by applying a tight control on the process parameters (e.g. water dewpoint in gas transmission systems, injection of corrosion inhibitor).
4. Corrosion probes and corrosion coupons cannot be relied upon to provide a definite assessment of the pipeline condition, nor to demonstrate that internal corrosion is not occurring.
5. Some indication of internal corrosion in the pipeline may be given by an analysis of debris recovered following a pigging operation; this technique is qualitative and is not able to provide any estimate of corrosion rates.
6. When corrosive conditions which may lead to significant corrosion damage are present, either internally or externally, a complete inspection of the pipeline should be carried out using intelligent pigging.
7. Intelligent pigging should also be used when the criticality of the pipeline is such that proof of continued integrity is required.