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Cathodic Protection Systems and the NEC

Jun 1, 2008 12:00 PM, By Whitt L. Trimble and Eddie Guidry, Fluor Enterprises, Inc.

The second solution activity is to determine if the facility can be cathodically protected as a whole. With few exceptions, this is generally the case. Again, ASTs will still have to be constructed on solid slabs or with dielectric liners; however, steel reinforcement of concrete foundations can be cathodically protected. Sometimes, unusual facility instrumentation requirements or locations with extremely high soil resistance require limited area CP systems. When the facility is suitable for total CP, several remote or deep anode beds can generally be installed to provide suitable total current and current distribution. Sometimes, supplemental limited local distributed anodes will have to be installed in congested areas or in areas of corrosion “hot spots.”

When the above “strategic” solutions are not possible, targeted solutions must be employed. These will involve a combination of the use of non-copper grounding materials, specialized isolation equipment, separate grounding systems, nonmetallic materials for a variety of purposes, combinations of local and area CP systems, and possibly the use of automatically controlled rectifiers. This type of facility treatment will require complex structure-to-soil potential and/or voltage gradient surveys to determine the existence or mitigation of “stray current” situations. Personnel safety and mechanical integrity can both be accomplished, but the methods may be non-traditional — and engineering and procedures may need to be site specific.

Providing CP to “all” of a facility will initially appear to be the most expensive of the strategic solutions. However, when the “lifetime” monitoring and maintenance costs of targeted facility CP systems are considered, applying CP to “only what we need or have to have to meet regulatory requirements” is often the most expensive course of action.

Trimble is a NACE International Certified Cathodic Protection Specialist, an instructor for the NACE CP1 and CP2 courses, and a member of numerous NACE technical committees. He is also a member of the ASME B31.4 Committee “Pipeline Transportation Systems for Transportation Systems for Liquid Hydrocarbons and Other Liquids.” He can be reached at Whitt.Trimble@fluor.com. Guidry is a senior electrical design supervisor at Fluor, Sugar Land, Texas. He is a licensed master electrician in Texas and a certified ICC/IAEI electrical inspector. An active member of Code Panel 11 since 1999, he is also a member of the International Association of Electrical Inspectors and the NFPA. He can be reached at Eddie.Guidry@Fluor.com.

Based on “The Conflicts and Solutions to Complying with the Grounding Revisions of the 2005 National Electrical Code for Cathodically Protected Facilities” by Whitt L. Trimble and Eddie Guidry, which appeared in the IEEE 2007 PCIC Record of Conference Papers. © 2007 IEEE.

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