NEW MATHEMATICAL MODELS FOR DESIGNING OFFSHORE SACRIFICIAL CATHODIC PROTECTION SYSTEMS

The trend to unattended maintenance-free cathodic protection systems for offshore structures will be accelerated if improvements in sacrificial designs become more cost effective. Reduced anode weight for a given life and current density show promise in satisfying this need. This paper explores the historical basis for present conservative cathodic protection design criteria and practice for fixed offshore structures and proposes new design methods. New survey data is presented as additional support for these new design methods. A mathematical model is developed that fits the historical and recent data pertaining to anode current output and life when structure polarization is considered. A 39% materials cost saving and 36% anode weight reduction can be realized when reduced driving potentials due to polarization are considered. Cost comparisons between sacrificial systems using the present and proposed methods of design are presented. Some extended life projections are drawn on offshore pipelines from reduced driving potentials due to pipe polarization. This paper also presents a mathematical model used for designing sacrificial cathodic protection systems on jack-up rigs. It is shown that loading improvement and cost savings are realized when current density and life requirements are tuned to fit the operation cycle time in the mud (high resistivity) and water (low resistivity) zones.

Media Info

  • Features: References;
  • Pagination: p. 27-38

Subject/Index Terms

Filing Info

  • Accession Number: 00329922
  • Record Type: Publication
  • Report/Paper Numbers: Volume 4 Proceeding
  • Files: TRIS
  • Created Date: Apr 15 1981 12:00AM