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| Home >> Services >> External Corrosion Direct Assessment |
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| External Corrosion Direct Assessment (ECDA) is a structured process used to evaluate buried onshore ferrous pipeline integrity. The ECDA goal is to enhance safety by managing the risk of pipeline corrosion failures while minimizing the cost required for excavations and repairs. ECDA may also be used when more established methods such as in-line inspection (ILI) and pressure testing are not possible or not practical. NACE Standard Recommended Practice on Pipeline External Corrosion Direct Assessment Methodology (RP0502-2002) describes the ECDA process as allowing “...the prediction of susceptible areas where corrosion activity has occurred, is occurring or may occur.” |
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| Although ECDA field assessment techniques are well established, specialized field equipment and staff experienced in the collection, recording, and analysis of data are necessary to obtain reliable and meaningful results. Corrosion Service quickly embraced the new ECDA techniques and both our field and professional staff are well versed in their application. We are equipped with state-of-the-art equipment for surveys and the collection of data which is then analyzed by professional engineers with many years of pipeline corrosion prevention experience. |
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| This four step process consists of: 1) Pre-Assessment; 2) Indirect Inspection; 3) Direct Examination; and 4) Post Assessment, which can be summarized as follows: |
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- The “Pre-Assessment” step involves the collection and evaluation of historical data and pipeline characteristics. Based on this information, the feasibility of an ECDA application is determined and once affirmed, the pipeline is divided into regions with similar exposure and areas where the same indirect inspection tools may be used.
- The “Indirect Inspection” step uses a combination of 2 or more above ground survey techniques such as close interval potential survey (CIPS), alternating current voltage gradient (ACVG), direct current voltage gradient (DCVG), AC attenuation for the identification of areas with corrosion activities or coating faults. The data is evaluated via systematic analysis and high-risk areas are identified for excavation.
- The “Direct Examination” step covers the selection of sites to be excavated and the physical identification of defects requiring repair or replacement.
- The “Post Assessment” step evaluates the previous 3 steps of the ECDA process and establishes a future assessment schedule.
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| Corrosion Service has developed an integrated indirect inspection technique merging both the CIPS and DCVG measurements. This integrated technique allows data acquisition of both CIPS and DCVG simultaneously. Higher efficiency and lower survey costs are achieved by merging both techniques. |
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21 Lines (In progress)
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Author : S.M Segall, R.A. Gummow and R. Reid
Date : Mar-06
Notes : NACE Corrosion 2006, Paper No.06193, San Diego, CA |
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| The paper describes the theoretical and practical aspects of merging two indirect inspection tools (i.e. Close Interval Potential Survey and DC Voltage Gradient) in one integrated survey, as used in 2004 during an ECDA project covering more than 21 km of gas pipelines in Southern Ontario.A method was developed and verified in the field to calculate the %IR at coating defects using the recorded data, with no need to interrupt the survey or to return to the defect location in order to measure the total gradient to remote earth.The data processing was improved by deriving the longitudinal gradient profile from the Close Interval Potential Survey data. This enhancement will be used in future surveys to validate indications, in conjunction with the measured lateral gradient data. |
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Author : R. Reid / S. Segall
Date : Apr-05
Notes : NACE Corrosion 2005, Paper No.05184, Houston, TX |
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| Under an Integrity Management Program (IMP) for natural gas transmission lines, the ECDA concept was analyzed and the process was validated from 2002 to 2004. A plan was developed and implemented in 2004 on one 17 km pipeline and segments of two other pipelines. This paper covers the Request for Proposal (RFP) methodology, the selection of a service provider, the execution plan and the results obtained. |
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