FEA Approach to Problem Solving is Not New for
CC Technologies

04/21/03

For more than a decade, CC Technologies has been using Finite Element Analysis (FEA) to solve many types of problems related to structural integrity, corrosion, and heat transfer. Perhaps the greatest advantage to FEA is the ability to simulate various conditions without constructing numerous laboratory experiments. This is particularly useful when trying to duplicate a cathodic protection system on a buried structure such as a pipeline, for example. While the input parameters may be known, the interaction between the parameters may be unknown, or there may be innumerable conditions to which the structure may be subjected. Thus, FEA models are often used to predict behavior in hypothetical cases, or where the collection of field data is not practical.

The modeling process may contain many steps, depending on the complexity of the problem and the number of iterations required. Ideally, the modeling process begins with the collection of field data. Field data are collected for a particular condition. These data serve as both input and validation for the model. For most problems, the next step is to generate the FEA model. The model incorporates geometry and any applicable parameters such as loading, electrochemical, and heat transfer, depending on the specific problem. The model is analyzed and the output is carefully studied to verify the reasonableness of the results. When possible, the results are compared with other analytical models. During model development and verification, the FEA model is often adjusted to make the geometry more detailed to fit the exact application. The model is most often intended to simulate actual field conditions and the field data is used to verify the model results. The philosophy is to generate a model detailed enough to produce accurate results, while maintaining a reasonable size to minimize analysis time and file size. An analysis of the finished model should produce results that are comparable with the data collected in the field. The validation process lends credibility to the model and allows the model to be used to predict behavior for many conditions at a higher confidence level. A matrix of various conditions is often analyzed to understand the influence of the input parameters.

Input for the models depends on the type of problem being solved. Although many types of problems can be solved using FEA, CC Technologies has utilized FEA modeling for solving electrochemical (primarily cathodic protection), heat transfer, and structural analysis problems. Cathodic protection models involve specifying electrochemical potentials, anode voltages and current output, and resistivity. Structural problems can involve numerous applied loads (including time dependent) and material properties (including temperature dependent). Whatever the problem type, the properties and loadings of the real world can be simulated.

CC Technologies has provided FEA solutions to a variety of problems, including the following:

• Area of pipe sampled during ground-level pipe-to-soil potential measurements.
• Cathodic protection (CP) of multiple pipes in the same right-of-way.
• Coupon placement near a pipe for CP monitoring.
• CP current distribution of a buried pipe in a rock ditch.
• CP current distribution beneath a concrete river weight.
• Heat transfer from a hot oil pipeline in frozen ground.
• CP design for multiple pipe river crossing involving (1) pipes going through soils of greatly differing resistivities, (2) pipes of differing coating quality, (3) pipes of greatly differing sizes, and (4) Time dependent development of the thaw bulb around the pipes.
• Structural analysis of full-encirclement steel repair sleeves.
• Structural analysis of power transmission poles with various degrees of corrosion.
• Structural analysis of pipe containing combined dent and corrosion defects.
• Structural analysis and fatigue crack growth in corroded sections of aging aircraft.
• Potential and current distribution in galvanic cells caused by dissimilar fireproofing materials.

Clifford Maier
Staff Engineer
2/10/03

This figure shows a model used to simulate a dent in a pipe. The color contours represent a stress concentration factor (stress magnification) in the pipe wall. The results of the model were used to characterize the stress field and the effects of metal loss due to corrosion of the pipe.

This figure shows a cross section of a buried pipe and anode. The color contours represent electrochemical potentials. The results of this model were used to evaluate current distribution around cathodically-protected pipe based on various anode spacing.

This figure shows a model intended to simulate a hole in a power transmission pole. The color contours represent the Von Mises stress. The results of this model were used to evaluate the integrity of the pole for various wind and weight loadings and various degrees of metal loss due to corrosion.

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