External corrosion damage assessment

As an example, a tank farm that is to be cathodically protected by this method is shown schematically in Fig. 11-4. As can be seen in the figure, injection of the protection current occurs with two current circuits of a total of about 9 A, via 16 vertically installed high-silicon iron anodes embedded in coke. These are distributed over several locations in the tank farm to achieve an approximately uniform potential drop. The details of the transformer-rectifier as well as the individual anode currents are included in Fig. 11-4. Anodes 4, 5 and 6 have been placed at areas where corrosion damage previously occurred. Since off potentials for 7/ -free potential measurements cannot be used, external measuring probes should be installed for accurate assessment (see Section 3.3.3.2 and Chapter 12). 

One company s pipeline team, comprised of a first-level supervisor and other personnel responsible for operating and maintaining the pipeline system, established an objective of developing a more effective approach to serious-incident prevention based on the eight-element process model. The team s assessment of risks included evaluating causes of past U.S. pipeline accidents. Department of Transportation (DOT) data (Fig. 18.5) identify third-party damage as the most frequent cause of pipeline incidents, followed by defective equipment or repair, external corrosion, internal corrosion, and operator error. The team s thorough evaluation of potential risks has helped ensure that the appropriate tasks and safe... 

Flexible risers are key components in transportation of hydrocarbons from the seabed up to the offshore floating production units. The time-varying chemical composition of the internal flow and the diffusion of some aggressive components through the various layers of the flexible pipe also implies a strong variation of the corrosive environment between the layers. This implies that assessment of the fatigue damage which is induced by the external loads and dynamic response of the flexible pipes must take these variable conditions into account. 

---