Based on Federal laws, pipeline operators in USA were required to develop a proactive Pipeline Integrity Management Plan to manage risk and protect public areas near pipelines. NACE initially published RP0502-02 for ECDA (External Corrosion Direct Assessment), and standard practices for other methodologies followed. Since many techniques used for ECDA rely on electrochemical tools, soil contact is an important consideration from an applicability standpoint. Contact resistance can cause increase in signal-to-noise ratio and the concern is how this may bias the recorded data or mask anomalies. DA was recently applied to pipelines of various design & operating conditions that traverse desert conditions like arid soil, and "Sabkha" (salt flat). This was an ideal opportunity to determine the effectiveness of the methods in extremely arid and high saline conditions with consideration of electrical and geological shielding. Results are presented and a comparison is made between predicted & actual findings.
Inline inspection (ILI) was the preferred methodology to inspect pipelines, and hydrostatic testing was the alternative, but based on federal laws signed in 2001, the Interstate Gas Association of America, together with the Gas Technology Institute, assembled an expert team to develop an alternate inspection methodology, called Direct Assessment (DA), which made use of a combination of proven techniques.
NACE International, as the industry representative initially published RP0502 for ECDA in 2002, and standard practices for the other methodologies followed. As living documents, these standard practices are subjected to peer review every 4-6 years and improvement are made based on experience in use.
ECDA is a structured methodology to enhance safety of pipelines by assessing and managing external corrosion defects. This is achieved by identifying the external corrosion locations, then prioritizing remedial action that prevents them from growing to a size that affects the structural integrity of the inspected pipeline section. ECDA is a proactive and continuous process by which if applied successively the pipeline operator would be able to have a better outlook not only where the corrosion has happened but on where it would happen in future. Based on the ECDA results the operator would be abler to streamline maintenance works in a cost effective and timely manner.1
