Nace CP 1, Course Manual

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Monitoring Cathodic Protection Effectiveness and Recordkeeping 7:2
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
07/01/04
Monitoring Requirements
Although regulatory agencies have adopted standards set forth by NACE,
International Standards Organization (ISO), Det Norske Veritas (DNV),
etc. regarding corrosion control, many have gone a step further by
specifying specific measurements and time intervals in which these
measurements must by taken. The measurements not only include structure-
to-electrolyte potentials, but other indirect methods of monitoring
protection on a system in between potential surveys. Also, in the United
States pipeline industry, efforts are being
made by the U.S. Department of
Transportation (DOT) to enact “Operator Pipeline Qualification” standards
that will govern the required qualifications of personnel who are
monitoring cathodic protection.
In the United States, a majority of facilities containing hazardous materials
are regulated by agencies enforcing the Code of Federal Regulations
(CFR). Corrosion control requirements can be found in these parts of the
code:
•
Natural Gas Pipelines – 49 CFR, Part 192, Subpart I
•
Liquefied Natural Gas 49 CFR, Part 193, Subpart G Hazardous Liquids
49 CFR, Part 195, Subpart D
•
Underground Storage Tanks 40 CFR, Part 280
Monitoring Cathodic Protection
To determine that a cathodic protection system is operating properly and
protecting a structure from corrosion, the following data are recorded on a
routine basis:
•
Structure-to-electrolyte potential.
•
Rectifier voltage and current outputs.
•
Current output of galvanic anodes.
•
Magnitude and direction of current through mitigation bonds.
•
Resistance of groundbeds.
•
Integrity of rectifiers, isolating joints, electrical bonds, and other
physical features associated with the corrosion control system.
Measurement of structure-to-electrolyte potentials is the only method of
determining when adequate cathodic protection is achieved. After a