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PRCI PR-151-123
- Cathodic Protection for Offshore Pipelines
- Report / Survey by Pipeline Research Council International, 02/01/1983
- Publisher: PRCI
$198.00$395.00
L51432e
Science Applications, Inc.
Need: A design methodology has been developed for cathodic protection systems on off-shore pipelines using galvanic anode bracelets. The methodology developed allows optimum spacing and sizing of anodes necessary for pipeline protection to be determined so as to satisfy minimum energy and weight criteria. It incorporates an electrical model of the pipeline that takes into account the effects of the non-linear polarization characteristics of the pipe steel and the galvanic anodes. The model allows design calculations to be made for a pipeline either completely in water or mud, and in addition, at the water-mud interface where current flow to the pipeline is governed by the characteristics of two different Media. Theoretical potential profiles can also be predicted for pipeline holidays and galvanic bracelet anodes. Profiles in the water surrounding the pipeline can be computed for both situations of the pipeline in water or under mud cover.
Result: The objective of this program was to develop mathematical equations which describe the potential and current profiles of offshore pipelines cathodically protected with galvanic bracelet anodes. Equations developed have been implemented into a computer program. The purpose of this work is to provide a technically sound basis for cathodic protection system design, and to resolve concerns regarding the interpretation and implementation of available pipe potential measurement techniques.
Benefit: Polarization data was taken at both near shore and offshore locations in the Gulf of Mexico. These data were used as input to the computer program so as to generate realistic design examples. Both sets of data exhibit a consistent initial current density threshold below which calcareous deposit development is not observed. The design procedure takes into account this factor. The modeling approach has been validated on a limited basis by near shore coupon tests. It is recommended that field validation of the design techniques developed be made by tests on an offshore pipeline. Examples presented should not be regarded as viable designs to be used indiscriminately regardless of particular circumstances.
Science Applications, Inc.
Need: A design methodology has been developed for cathodic protection systems on off-shore pipelines using galvanic anode bracelets. The methodology developed allows optimum spacing and sizing of anodes necessary for pipeline protection to be determined so as to satisfy minimum energy and weight criteria. It incorporates an electrical model of the pipeline that takes into account the effects of the non-linear polarization characteristics of the pipe steel and the galvanic anodes. The model allows design calculations to be made for a pipeline either completely in water or mud, and in addition, at the water-mud interface where current flow to the pipeline is governed by the characteristics of two different Media. Theoretical potential profiles can also be predicted for pipeline holidays and galvanic bracelet anodes. Profiles in the water surrounding the pipeline can be computed for both situations of the pipeline in water or under mud cover.
Result: The objective of this program was to develop mathematical equations which describe the potential and current profiles of offshore pipelines cathodically protected with galvanic bracelet anodes. Equations developed have been implemented into a computer program. The purpose of this work is to provide a technically sound basis for cathodic protection system design, and to resolve concerns regarding the interpretation and implementation of available pipe potential measurement techniques.
Benefit: Polarization data was taken at both near shore and offshore locations in the Gulf of Mexico. These data were used as input to the computer program so as to generate realistic design examples. Both sets of data exhibit a consistent initial current density threshold below which calcareous deposit development is not observed. The design procedure takes into account this factor. The modeling approach has been validated on a limited basis by near shore coupon tests. It is recommended that field validation of the design techniques developed be made by tests on an offshore pipeline. Examples presented should not be regarded as viable designs to be used indiscriminately regardless of particular circumstances.
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