Optimization of Cathodic Protection Systems of Tank Bottoms Using Boundary Elements, Inverse Analysis, and Genetic Algorithm

CORROSION ◽  
10.5006/3641 ◽  
2020 ◽  
Vol 76 (12) ◽  
Author(s):  
W.J. Santos ◽  
S.L.D.C. Brasil ◽  
J.A.F. Santiago ◽  
J.C.F. Telles ◽  
J.P.K. Gervasio
Keyword(s):  
Genetic Algorithm ◽  
Boundary Element ◽  
Polarization Curve ◽  
Cathodic Protection ◽  
Inverse Analysis ◽  
Nonlinear Boundary Conditions ◽  
Concrete Layer ◽  
Protection Systems ◽  
Impressed Current

The required current to efficiently protect the external bottom of aboveground storage tanks by means of impressed current cathodic protection was evaluated and optimized for anode number and positioning. The study introduced a numerical polarization curve obtained by inverse analysis, using a genetic algorithm, based on potential values measured in a real tank. An inverse boundary element-based genetic algorithm was developed to find the expected polarization curve from potential values measured in situ. To the problem optimization, an axisymmetric boundary element with a Newton-Raphson solution algorithm was used to accommodate the nonlinear boundary conditions. The system consisted of a tank directly over soil or a slender conductive concrete support layer. Impressed current anodes were positioned between the base and a secondary liner containment installed below the tank to prevent environmental damages in case of leakage. An alternative technique was adopted to analyze the two-region problem. Here a single soil region, with a calculated modified polarization curve was chosen, avoiding the two subregion analysis needed to represent the concrete layer and soil.

Evaluation of Designs of Shipboard Cathodic Protection Systems Using Boundary Element Modelling Technique

2011 ◽  
Author(s):  
Yueping Wang
Keyword(s):  
Boundary Element ◽  
Cathodic Protection ◽  
Modelling Technique ◽  
Hull Form ◽  
Corrosion Failure ◽  
Element Modelling ◽  
Protection Systems ◽  
Uniform Current ◽  
Impressed Current ◽  
Cathodic Protection System

Boundary element modelling technique was used to evaluate the performance of the underwater hull impressed current cathodic protection (ICCP) system of a steel-hulled vessel, as part of an investigation of the corrosion failure of the steel hull near the ICCP anodes. The same technique was also used to evaluate the designs of an alternate sacrificial anode cathodic protection system. The modelling results indicated that the existing ICCP system was capable of providing adequate cathodic protection to the underwater hull and appendages if the current demand is less than 2.4 A. Small anode size was found to have a profound effect on the potentials immediately adjacent to the anode, stressing the need for an effective, intact anode shield. Application of paint coating on the bronze propellers could substantially reduce the current demand from the anodes, resulting in less negative potentials adjacent to the anodes. The modelling results also showed that the anode design adopted from a vessel of similar size (<5% difference in all dimensions), which consists of 8 hull mounted aluminum anodes and 4 rudder zinc anodes, would provide adequate cathodic protection for the underwater hull structures of the existing vessel for more than 3 years. The performance of a modified anode placement was also studied in comparison with that of the original anode placement. The results indicated that the anodes in the modified anode placement would not only contribute more uniform current than the anodes in the original anode placement, but also result in the potential profiles that have less variations along the hull form. This modified anode placement would potentially result in a longer service life of the anodes.

Modeling of Impressed Current Cathodic Protection Anode Arrangements for Storage Tank Bottoms

2011 ◽  
Author(s):  
Robert Adey ◽  
John Baynham ◽  
Cristina Peratta
Keyword(s):  
Cathodic Protection ◽  
Economic Consequences ◽  
Design Concepts ◽  
Modeling Methodology ◽  
Protection Systems ◽  
Gas Products ◽  
Impressed Current ◽  
Protection Potential ◽  
The Cost ◽  
Impressed Current Cathodic Protection

Above ground tanks are frequently used for the storage of Oil & Gas products and they can present a challenge to design an optimum corrosion control system. The base of the tank lies on or near the surface of the ground and is in contact with the material used to support the tank and therefore presents a corrosion challenge. One method of protecting the bottom of a tank is by use of an impressed current cathodic protection (ICCP) system. There are a number of types of Cathodic Protection systems which are designed to protect the tank base in these circumstances. The details of the design of such a system are very important for optimal performance and also the cost, if a number of such systems are to be installed The consequence of a poor design can be uneven distribution of protection potential on the tank base or in the worst cases regions where corrosion of the tank base can take place. An over designed system on the other hand can have significant economic consequences both in terms of installation cost and running costs. Computer modeling is now widely used to optimize CP Designs and verify that the design of the cathodic protection (CP) system meets the design requirements. In this paper a modeling tool is presented which enables corrosion engineers to evaluate the performance of tank base CP systems by predicting the protection provided to the tank for a given CP design. The paper describes and discusses all aspects of the modeling methodology, which it then applies to several different design concepts.

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