Corrosion Simulation Newsletter
Dr Andres Peratta presented some recent conceptual work on the application of simulation modelling to predict the corrosion related potentials and electric and magnetic fields on and surrounding naval vessels at the International Conference On Marine Electromagnetics (MARELEC) in Philadelphia, USA. Modelling is used to predict the corrosion related potentials on the vessel itself, and the electric and magnetic fields surrounding the vessel. For naval vessels, modelling can be exploited to not only assess the performance of cathodic protection systems on the vessel (ICCP and sacrificial) but also the corrosion related magnetic fields as they make a significant contribution to the vessel signature.
The paper evaluated the magnetic field caused by return-path current flowing in the hull of a vessel, and compared the electromagnetic fields calculated using different assumptions regarding how the cathodic protection currents flow. The cases assessed included flow along an equivalent horizontal wire, and flow through the vessel skin to selected collection points at which cables return current to the power supply. The effects of different layouts of collection points were investigated to determine the sensitivity of the magnetic field to the layout.
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BEASY attended the NACE Corrosion Conference in Dallas this March where we were active at the exhibition as well as presenting and participating in the technical sessions and exchange groups.
It was great to meet many friends at the conference and discuss how modelling can be used to improve and optimize CP systems as well as providing further confidence in their performance as part of "due diligence" activities.
In addition to the activities by BEASY staff there were papers presented at NACE incorporating BEASY modelling, including Application Of Linear Anodes To Protect Isolated And Unisolated Piping In A Petrochemical Plant by Mobeen Hassan, Sharjah, United Arab Emirates & Stephen Wroe Corrosion Technology Services LLC Sharjah, United Arab Emirates.
The paper describes an application of cathodic protection using linear anodes in a congested petrochemical plant in the Middle East. The initial design of the cathodic protection is discussed along with the problems found due to faulty isolating flanges and loss of current to other structures. Computer modelling of a typical electrically continuous cathode including steel in concrete and earth rods is included to demonstrate the need to consider all components of complex structures. Lessons learnt from this case study are applicable for the application of cathodic protection in plant using distributed anodes.
The results shown below illustrate the effect of adding continuous reinforced concrete paving into the circuit. The dramatic effect is that the pipe potentials are hardly shifted from the natural potential even with the anode operating at 100mA/m.
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An interesting article was published in a recent issue of the NACE Materials Performance magazine.
Researchers used modelling tools to design effective cathodic protection systems that address challenging seawater conditions and coating damage from ice abrasion.
According to researchers Min-Jeong Lee, senior engineer, and Chae-Seon Lim, principal research engineer, both in the Material & Coating Research Department at Samsung Heavy Industries, Co., Ltd, South Korea, the performance of a CP system for a ship's external hull is dependent on several factors, including the geometry of the ship's hull, the resistivity of the surrounding seawater, the chemicals in the seawater, and the degree of coating damage. The ICCP design for many commercial vessels is often based on current density (CD) calculations and the designers' experience rather than an analytical method. For an icebreaker travelling in Arctic conditions, the researchers note, this traditional approach to CP design may not result in an adequate amount of corrosion protection for the hull in this environment.
To determine the optimum ICCP design for the external hull of an icebreaker, the researchers explored a modelling approach using computational analysis based on the boundary element method (BEM). Lee comments that modelling tools are often used to design ICCP for stationary offshore structures such as oil and gas production platforms; floating production, storage, and offloading (FPSO) units; and semi-submersibles.
Using computational analysis and modelling was successful in determining that an ICCP system design is effective for a vessel exposed to Arctic seawater conditions. Going forward, Lee expects more use of CP modelling when designing ICCP systems for ship hulls, particularly those headed for the Arctic.
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BEASY will once again be attending the annual NACE Corrosion Conference, which this year is being held in Dallas, Texas, between 16th and 19th March.
We will be active in both the conference program and exhibit hall showing our corrosion modelling services and software.
Please come and visit us at booth 21096, or if you would like to set up a meeting to discuss any aspect of BEASY's modelling and software services, please contact us
An article in December 2014's MP magazine looked at the effect of grounding on the cathodic protection (CP) potential distribution at an oil station, which had been studied using BEASY's corrosion and cathodic protection simulation software.
Influences from four factors were analysed: grounding system material, relative position between the grounding conductor and the pipeline, and length and buried depth of the grounding conductors. CP designs with and without grounding were compared.
Corrosion Modeling Solutions Showcased at NACE 2014
BEASY participated in a very busy NACE Corrosion Conference in San Antonio last month. We were active in the conference program and exhibition hall, highlighting corrosion modeling services and software. It was good to see many friends and interested engineers visiting us at our booth. There were a number of papers presented during the Technical Program which featured some engineering projects carried out by the BEASY engineering services team and by customers.
Improved Effectiveness Of Direct Assessment Field Surveys Through The Application Of Boundary Element Analysis (BEA) To Simulate Electrical Field Interference Between Collocated Pipelines. Katurah Hansen, Angel R. Kowalski, Shane Finneran, Jason Land. Det Norske Veritas (USA), Inc.
Direct Assessment above ground surveys are often time consuming, laborious, expensive and require operational knowledge of NACE Standard TM0109-2009. The use of boundary element analysis (BEA) software allows for a more comprehensive re-creation of different possible conditions and can provide additional analysis to validate survey results when conditions, such as buried metallic structures adjacent to the pipeline being assessed limit the sensitivity of the survey tools. This combined use approach offers the benefit that a simulation model can be developed that fits well to the actual conditions of the pipeline, with minimal assumptions.
To evaluate the effectiveness of the designed CP System, a boundary element analysis (BEA) was performed to analyze the predicted potential distribution and current density for the natural gas pipeline collocation. The interfering current makes it difficult to accurately calculate these distributions by other methods. Results from the BEA allow for current shielding, over potential hot spots, and other critical areas where the CP is least effective, to be identified.
ICCP System Design on the Hull of an Ice Breaker by Computational Analysis. Min-Jung Lee, Chae-Seon Lim. Samsung Heavy Industries Co., Ltd
Impressed current cathodic protection (ICCP) systems have been employed with coatings to prevent corrosion on the hulls of ice breakers. Many ICCP systems used for commercial vessels are designed based on the designer's experiences rather than by analytical method. The purpose of this paper is to simulate the performance of ICCP systems on hulls under Arctic conditions by a computational analysis based on boundary element methods (BEM) and to deduce an optimized design. For this purpose, an Arctic shuttle tanker that will travel across the Barents Sea was investigated. The coating breakdown factors at the end of the design life were assumed to range from 1% to 5% depending on the ice strengthening areas of the hull. The design optimization process consisted of a series of calculations of the structure potential with several cases of ICCP system arrangements and reference cell target potentials. The effects of these factors were studied under Arctic conditions.
The model predicted the potential distributions on the hull and the results were used to determine the optimized design of the ICCP systems under the service conditions.
Image: Coating damage on the hull of an Arctic vessel after 2.5 years under Arctic Sea
The Application Of Computer Modeling To Improve The Integrity Of Ballast Tanks. Robert Adey, Guy Bishop, John Baynham, CM BEASY Ltd
Generally additional cathodic protection (CP) systems are installed in ballast tanks to provide protection to the areas that may become unprotected by degraded coatings. Because of the complex geometry of the tanks and the presence of pipework, equipment and in some cases ladders and walkways the correct placement of both sacrificial & ICCP anodes is essential to get a good potential distribution that ensures no areas are either under or over protected.
Computer modeling has become widely used in the maritime corrosion industry to predict the performance of CP designs and to ensure adequate protection is provided to the structure over its life. In this paper a case study is presented where computer modeling is used to verify and optimize the design of the corrosion control system of a ballast tank and to predict how it will perform over the service life of the tank. Case studies are presented for both a sacrificial CP system and ICCP design.
Image: Optimized anode layout showing initial consumption rates