Ancor Pipeline Integrity

The main objective of this project was to align and perform a corrosion growth assessment based on 3 inspection data set, to perform a subsequent Fitness for Service assessment to evaluate the future integrity of the line, develop a future repair plan and determinate an optimum re-inspection interval based on the remaining life of uninvestigated corrosion defects.

Two main corrosion growth rate calculation methods were used: local growth rate and segment growth rate. The combination of these methods were used the corrosion growth rates from the matched local defects as input into the segment method.

The evaluation of the corrosion growth rate was applied by following the steps below:

✔ Step 1: Obtaining and review the ILI data of all inspections of 3 inspection data set.

✔ Step 2: Selection of the comparison technique.

✔ Step 3: Weld and defects alignment.

✔ Step 4: Determination of local corrosion growth rates from the obtained run comparison results.

✔ Step 5: Evaluation of data uncertainties through a probabilistic assessments of corrosion growth rates.

The results of the data alignment for the metal loss features, evidenced an active external corrosion process, essentially identified by two parameters indicated below:

There is evidence of an increase in the number of anomalies reported, considering all 3 inspection data sets.
In addition, the anomalies reported had presented a growth in their dimensions (depth, length and width), mostly in depth.

Based on the assessment, one (1) external corrosion anomaly was detected with safe operating pressure less than Maximum Allowable Operating Pressure (Psafe < MAOP) and this feature was considered to pose a threat to the pipeline integrity.

The probabilistic assessment of the corrosion growth rate was performed through Monte Carlo simulation, according to indicated by API 1160 with 80% confidence level.

This evaluation was developed using as input variables, the results of the local growth estimation and using Crystal Ball software, through which probability distributions of corrosion rates were constructed of Monte Carlo simulations of 3000 possible sceneries (trials) to forecast the likelihood of results possible for each of corrosion features. This assessment was performed for each external corrosion anomalies reported and for the pipeline segment. Normal Fitted Distribution of external corrosion growth rate:

Based on the probabilistic assessment, the estimated external CGR was used in the future integrity of the FFS assessment.

Based on the above findings, ANCOR recommended repair activities as it's indicated below:

Perform a Fitness-for-Service (FFS) to assess the immediate integrity of the line to the anomaly considered to pose a threat to the pipeline integrity, to provide possible repair activities.
Assess the future integrity of the pipeline using the external corrosion growth rate of the pipe, based on the estimated external CGR in this analysis and provide any schedule for future repair activities (If it is necessary).
Establish an ILI re-inspection interval, according to the results of the future integrity assessment.

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