Above Ground Coating Integrity Assessment: Experience with SUMED Pipelines

Abstract

External corrosion protection of the buried pipelines is primarily achieved by coatings and supported by cathodic protection. The coating damage occurs during pipeline installation, or due to aggressive soil. Coating integrity assessment is aimed to improve the safety of pipeline operation regarding personnel and environment as well as economic security. Inspection practice is intended to identify coating defect location and estimate corrosion activity of the pipeline. The inspection program includes the following steps:

• pre-assessment: collect information on pipeline physical characteristics and operating history,

• indirect inspection: field measurements,

• direct examination: evaluation of pipeline coating performance,

• post-assessment: analysis of data collected, coating defect repair, mitigate corrosion protection faults including cathodic protection system.

The techniques and measuring equipment for above ground coating inspection are well established as for Close Interval Potential Survey (CIPS) and Direct Current Voltage Gradient (DCVG) methods. However, analysis of the gathered inspection data is rather uncertain. The accuracy determining coating defect location and assessment depends on the vast experience of the inspection team dealing with diverse pipelines conditions. The paper describes in details the inspection technique, the required equipment to perform the measurement, and the means of data analysis. A comprehensive example is given by the survey works carried out on SUMED transmission pipelines between Suez (Red Sea) and Alexandria (Mediterranean Sea).