Theoretical validation of the physical scale modelling of the electrical potential characteristics of marine impressed current cathodic protection

1995 ◽  
Vol 25 (1) ◽  
Author(s):  
R.W. Ditchfield ◽  
J.N. McGrath ◽  
D.J. Tighe-Ford
Keyword(s):  
Cathodic Protection ◽  
Electrical Potential ◽  
Physical Scale ◽  
Scale Modelling ◽  
Impressed Current ◽  
Impressed Current Cathodic Protection

Evaluation of the Effect of Paint Degradation on Shipboard Impressed Current Cathodic Protection Performance: A Physical Scale Modeling Approach

2009 ◽  
Author(s):  
Yueping Wang ◽  
Ken J. KarisAllen
Keyword(s):  
Numerical Modeling ◽  
Cathodic Protection ◽  
Polarization Resistance ◽  
Current Control ◽  
Aluminum Bronze ◽  
Scale Modeling ◽  
Physical Scale ◽  
Discrete Area ◽  
Impressed Current ◽  
Impressed Current Cathodic Protection

Physical scale modeling (PSM) has been used to evaluate and design shipboard impressed current cathodic protection (ICCP) systems in several NATO countries. With the application of numerical modeling techniques for the evaluation of shipboard ICCP performance, efforts to validate numerical modeling results using PSM data have been gaining increasing importance. As part of the efforts, a discrete area current control (DACC) technique was developed in previous studies to simulate the polarization resistance behavior of multiple cathodes including nickel aluminum bronze propellers and paint damage areas under a variety of conditions. The application of the DACC technique facilitated the use of identical polarization resistance data as boundary conditions for both PSM and numerical modeling analyses in the validation studies. In the current work, the DACC technique was extended to simulating polarization resistance behavior of various paint degradation scenarios (with polarization resistances varying from 1×107 Ωcm2 to 2×105 Ωcm2) to study the effect of paint degradation on the performance of a shipboard ICCP system. The results indicated that overall paint degradation does not significantly affect the hull potential profile until the magnitude of the polarization resistance of the paint coating decreases below 1×107 Ωcm2. The PSM profiles were also compared with numerical modeling data acquired using a boundary element code resulting in a good agreement between the two techniques. The discrepancies observed between the PSM and numerical modeling profiles have also been discussed.

Cathodic Protection Design Consideration for an Offshore Flexible Riser Connected to an Impressed Current System

2021 ◽  
Author(s):  
Thierry Dequin ◽  
Clark Weldon ◽  
Matthew Hense
Keyword(s):  
Cathodic Protection ◽  
Sacrificial Anode ◽  
Flexible Riser ◽  
Flexible Pipe ◽  
Linear Resistance ◽  
Flexible Pipes ◽  
Flexible Risers ◽  
Impressed Current ◽  
Host Structure ◽  
Impressed Current Cathodic Protection

Abstract Flexible risers are regularly used to produce oil and gas in subsea production systems and by nature interconnect the subsea production system to the floating or fixed host facilities. Unbonded flexible pipes are made of a combination of metallic and non-metallic layers, each layer being individually terminated at each extremity by complex end fittings. Mostly submerged in seawater, the metallic parts require careful material selection and cathodic protection (CP) to survive the expected service life. Design engineers must determine whether the flexible pipe risers should be electrically connected to the host in order to receive cathodic protection current or be electrically isolated. If the host structure is equipped with a sacrificial anode system, then electrical continuity between the riser and the host structure is generally preferred. The exception is often when the riser and host structure are operated by separate organizations, in which case electrical isolation may be preferred simply to provide delineation of ownership between the two CP systems. The paper discusses these interface issues between hull and subsea where the hull is equipped with an impressed current cathodic protection (ICCP) system, and provides guidance for addressing them during flexible pipe CP design, operation, and monitoring. Specifically, CP design philosophies for flexible risers will be addressed with respect to manufacturing, installation and interface with the host structure’s Impressed Current Cathodic Protection (ICCP) system. The discussion will emphasize the importance of early coordination between the host structure ICCP system designers and the subsea SACP system designers, and will include recommendations for CP system computer modeling, CP system design operation and CP system monitoring. One of the challenges is to understand what to consider for the exposed surfaces in the flexible pipes and its multiple layers, and also the evaluation of the linear resistance of each riser segment. The linear resistance of the riser is a major determinant with respect to potential attenuation, which in turn largely determines the extent of current drain between the subsea sacrificial anode system and the hull ICCP system. To model the flexible riser CP system behavior for self-protection, linear resistance may be maximized, however the use of a realistic linear resistance is recommended for evaluation of the interaction between the host structure and subsea system. Realistic flexible linear resistance would also reduce conservatism in the CP design, potentially save time during the offshore campaign by reducing anode quantities, and also providing correct evaluation of drain current and stray currents.

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