External corrosion threat

Definition of hazard
• A characteristic or group Of characteristics that provides the potential for a loss.
• Examples: Internal and external corrosion, stress corrosion crack, material defects, third-party damage and environment including toxicity, flammability, exposed pipes, lack of signage, etc. Pipeline Corrosion Control
• Coating is the main corrosion control technique.
• But dependence on one source for protection is not a very wise approach - No coating is perfect.
 • To protect coating flaws, cathodic protection (CP) is applied.
• Coatings and CP are successful combination for corrosion control. External corrosion on a pipeline could be microbiologically induced corrosion (MIC), or from galvanic action or elec- trochemical reaction, where the steel pipe becomes an anode in an electrochemical cell. This is a tinl&dependent hazard,and occurs after some time iri service.

To address these threats, collection of data is carried out, and based on the analysis of those data, a risk assessment plan is prepared. This is an important step. The data collection process is a painstaking and detailed activity. In the beginning, the collected data may be  verwhelming and intimidating, but a good risk assessment program is data dependent. In fact, most of these data are already in the computers of the pipeline op erators but they keep sitting as dead data. In the world ofcomputers, it is easy to share, download, and transfer most of these valuable data and put them to better use. "Better use" IS the availability of the data for analysis that helps manage the risk. Periodically this collection ofdata can be refreshed and updated. There is no limit to the available data and its possible use. However, the basic data that needs to be collected in this context is listed below:

a. Pipeline year of installation
b. Pipe grade (ASTM A 106 Grade B, API 5L Grade B, X42, X65, X70, etc.)
c. Pipe diameter and wall thickness
d. Maximum operating pressure (MAOP) (or design pressure) and temperature e.
seamless, double submerged arc welding (DSAW)
f. Pipe seam type, e.g., electric resistance welding (ERW), Coating type, e.g., coaltar enamel, fusion bonded epoxy (FBE), three-layer polyethylene (3LPE)
g. Coating condition at the time of lxst inspection (updated periodically)

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