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Mears Hosts Workshop On ECDA For Cased Pipelines
Other issues PHMSA will address are conditions to justify that the threat of external corrosion has been mitigated sufficiently as to not require full re-assessment and determine how to address casings filled prior to the IM rule.
ECDA employs engineering processes to proactively assess locations for the likelihood of corrosion, and to focus remediation where the corrosion exists. Pre-assessment requires the operator to organize the testing, analysis and remediation methods used by categorizing cased crossings into like-similar regions.
The Mears workshop addressed prompters for external corrosion of cased pipelines, including metallic contact, electrolytic contact and atmospheric corrosion. Attendees were given live demonstrations on various testing methods on both coated and uncoated casings including:
- PCM current attenuation across casing, which measures the magnetic field caused by AC current flow. This method can be limited by overhead AC power lines, parallel structures and points of inflection.
- PCM with A-Frame which measures voltage gradient and its direction. This is one of the most reliable indicators of electrolytic contacts. Its limitations are position-sensitive relative to the end of the casing and possible masking by coating flaws on the outside of the pipe.
- P/S and C/S On Potentials where current is applied and potentials are measured to a common reference electrode.
- P/S and & C/S Shift which is a good indicator of metallic shorts.
- Internal Resistance where current is applied between pipe and casing and uses Ohm’s law to calculate resistance, which can possibly locate contact.
All these tools are complementary and look for the same potential corrosive conditions in different manners. All have strengths and limitations depending on conditions.
The 2.75-acre Mears test facility can simulate all types of corrosion conditions from coating holidays to electrolytic contact. Testing results and results reported by customers in the field have allowed Mears to compile a large data base on the effectiveness of all ECDA methods.