Det Norske Veritas - Germanischer Lloyd

DNVGL  CATHODIC PROTECTION OF SUBMARINE PIPELINES BY GALVANIC ANODES
 N DNV-RP-F103

Annotation

This Recommended Practice (RP) has been prepared to facilitate the execution of detailed CP design and the specification of galvanic anode manufacturing and installation. While the requirements and recommendations are general, the document contains advice on how amendments can be made to include project specific requirements. The document can also easily be amended to include requirements/guidelines by a regulating authority, or to reflect the pipeline operator's general philosophy on pipeline corrosion control.

Guidance note:

It is recommended that any additional conservatism is introduced by use of a "design factor" rather than modification of one or more of the many design parameters used for CP calculations. For example, it may be specified that the design life shall be based on the maximum estimated lifetime of the pipeline multiplied with some constant larger than 1 (one).

The document covers the detailed design of CP for submarine pipeline systems (see 1.3.1) using galvanic anodes, either Al - or Zn -based, and the manufacturing and installation of such anodes. For CP of subsea manifold templates, riser bases and other subsea structures where components of a pipeline system are electrically connected to major surfaces of structural C-steel, use of DNV-RP-B401 is recommended for CP design (see 1.5.3). For conceptual CP design, Sec.5 is applicable to preliminary calculations of the anode net mass and anode distribution. This RP is based on the sections in ISO 15589-2 that are applicable (see 1.3.1). For compliance with the general philosophy in DNV-OS-F101, primarily with respect to procedures for quality control, or for the purpose of clarification and guidance, some amendments are given. This RP further contains some formula for calculation of CP protective range from adjacent structures and minimum distance between pipeline anodes that are not included in the ISO standard. Default values for galvanic anode performance and design current densities that do not require any special qualification or field testing are also recommended.