Following the recent global launch of the platform-deployed Cathodic Protection (CP) Retrofit solutions for the extension of CP life of jackets, VTA and Galvo-String, IEV is introducing Galvo-Array, in conjunction with its technology partner, Galvotec Corrosion Services LLC, to address the needs for subsea pipeline CP Retrofit.
Challenges
Ageing infrastructure in the oil & gas industry, particularly subsea pipelines are subject to high possibilities of severe external corrosion issues due to stress, coating disbondment or poor electrical isolation. Corrosion control of subsea pipelines are generally achieved through the application of a high quality coating, supplemented by bracelet-type anodes designed to protect any exposed portions of the pipeline for up to a design life of typically 20 to 30 years.
Over time, these initial anodes will deplete and the installation of a second generation of anodes may be required. However, a one-for-one replacement is not practical due to several new design factors that must be considered.
Firstly, there may now be more exposed surface areas on the pipeline due to general degradation or external damage to the coating. Secondly, the re-attachment of bracelet anodes in situ on their original spacing is impractical due to the high labor cost associated with removing and replacing each one along the entirety of the pipeline, as well as the need to weld or braze a connecting bond wire from each bracelet half to the pipeline.
For these reasons, there is a need for a subsea retrofit anode system that is able to provide greater CP current in a way that is also practical and economical to install. The Galvo-Array CP retrofit system is designed to meet these requirements in several ways.
Diver/ROV deployed CP Retrofit System
The Galvo-Array CP retrofit system is comprised of, one or more, series of anodes each that lay adjacent to the pipeline, with a single mechanical bonding clamp used to establish and maintain electrical continuity. Since multiple anodes can be attached to the pipeline via a single bonding clamp, installation time is greatly reduced. Altogether, this results in a retrofit solution where a high number of anodes can be added to the pipeline in the fewest number of installations, generating sufficient cathodic protection current to provide a life extension for as long as is desired. Diver-installed or ROV compatible clamps are available, which means that this system can be applied at any water depth.
DNV-RP-F103 and DNV-RP-B401 are used to determine the number of anodes required to meet the present CP current requirement and the total anodic mass requirement for the desired life extension. Attenuation studies are then done to determine the number of anodes comprising each individual Galvo-Array and the appropriate spacing between installations, with an average of 1,000 meter spacing being typical. In shallower water depths where the Galvo-Array can be installed by divers, a simple clamp with a contact bolt would be recommended. For deeper environments where ROV installation is required, a hydraulically-activated clamp is normally used; this alternate clamp has small “teeth” that makes electrical contact through the coating as it is tightened onto the pipeline.