External Corrosion Direct Assessment (ECDA)

The purpose of the “External Corrosion Direct Assessment” is to proactively prevent corrosion defects from growing to a size that would adversely impact a pipeline’s structural integrity. The ECDA is a four-step process:

1. Pre-assessment

In the pre-assessment phase, a detailed right-of-way (ROW) inspection is conducted and all pipeline operating data is collected. The data is analysed to give an indication on the current condition of the pipeline and estimate the overall effectiveness of the existing corrosion protection measures.

2. Indirect inspection

The indirect testing phase includes two or more of the following testing methods:

• Close interval surveys (CIS)
• Direct and alternating current voltage gradient surveys (DCVG/ACVG)
• Pipeline current mapping (PCM)

3. Direct examination

The results of the indirect assessment surveys determine the critical points along the pipeline where there is a high likelihood of corrosion. These locations are selected for further examination. The following are inspected during the Direct Examination stage:

• Pipeline coating condition
• Cathodic protection system condition
• Pipeline defects
• Pipeline corrosion damage
• Soil characteristics such as resistivity and pH at pipeline depth

4. Post assessment

The final step of the ECDA process is to determine the following :

• Re-assessment interval
• Corrosion rate estimation
• Remaining life analysis
• Remaining strength analysis
• All recommendations necessary for pipeline corrosion protection

Internal Corrosion Direct Assessment(ICDA)

1.Pre-assessment

This step involves analysis of the current pipeline condition and determination of feasibility of the direct assessment.

• Detailed right-of-way (ROW) inspection.
• All pipeline operating data collectection.
• Pipeline Corrosion and Inspection History.
• Fluid chemical composition.
• Pipeline Metallurgical History.

2.Indirect inspection

The indirect testing phase includes two or more of the following testing methods:

• Pipeline Elevation Profile Survey
• Fluid Flow Modelling
• Internal Corrosion Process Modelling
• Laboratory Analysis of Gas, Liquids and Solids
• Microbiologically Influences Corrosion(MIC) Testing, Studies and Evaluations.

3. Direct examination

After the data from the indirect assessment methods are analysed and reviewed, locations for direct examination are targeted for review and inspection of:

• Pipeline defects Identification
• Pipeline corrosion damage measurement and assessment
• NDT (Non-Destructive Testing, In-line Inspection,Ultrasonic)
• Corrosion Monitoring / Coupons / Probes

4.Post assessment

Upon completion of the direct examinations, a post assessment report provides:

• Re assessment Interval
• Remaining Life Analysis
• All recommendations necessary for pipeline corrosion protection