Indirect Assessment Surveys


Pipeline indirect assessment (IA) procedures are cost-effective, non-destructive methods of evaluating the integrity of buried or submersed metallic pipelines and do not interrupt the normal operation of the facility. Each of the IA techniques can be performed individually depending on the information that is required, or in conjunction with others, whereby correlating various IA data sets. This results in an efficient risk management program that minimizes excavation and repair costs through increased predictability of where corrosion activity is probable.

E-MAC Corrosion Inc. indirect assessment survey information is collected in conjunction with spatial GPS coordinates, providing a seamless correlation between all data sets. Utilizing GPS technology for data collection also allows easy consolidation of IA survey data with direct assessment (DA) data (i.e. in-line inspection).

Summary of E-MAC Corrosion Inc. Services

  • Coating Evaluation Surveys (E-MAC: Electro-Magnetic Attenuated Current)
  • River Assessment Surveys (X-WRAP: X-WRAP: Crossings at Waterways & Rivers; Attenuations & Profiles)
  • Close Interval CP Surveys (CIS)
  • Depth-of-Cover (DOC) Surveys
  • Global-Positioning-System (GPS) Surveys
  • Pipeline Integrity Data Correlation & Consolidation (In-Line Inspection)

E-MAC Coating Evaluation Survey

The Electro-Magnetic Attenuated Current (E-MAC) evaluation system is used for carrying out electromagnetic/voltage gradient coating assessment surveys of pipelines. The survey system is comprised of fully computerized equipment that is uniquely operated using procedures that were developed by the proprietors of E-MAC Corrosion Inc. Knowledge of suspect damaged coating regions is beneficial in maintaining integrity throughout the operating life of the pipeline, and when properly performed, an E-MAC survey can accurately identify the following coating deficiencies:

  • decomposition or failure of the pipeline's external material
  • mechanical damage resulting from poor construction/installation practices, foreign objects, rocks, pipeline movement or third party activities
  • inadequately applied or non-existent coating
  • disbondment (in some cases)
  • physical contact with a foreign body (sleeve, casing, another buried service, etc.)

In addition to the above, the following outlines the applications and advantages to the E-MAC survey system:

  • Evaluation of existing buried pipelines in high consequence areas susceptible to external corrosion
  • Alternative evaluation option for pipelines of which inline inspection or pressure testing are not possible or economical
  • Normal operation of the pipeline remains uninterrupted throughout the survey
  • Condition confirmation on potential pipeline acquisitions
  • Verification of damages from third party activity
  • Collect relevant information where a pipeline runs under roadways, concrete or water
  • Potential method of leak detection

Additionally, every measurement obtained during the execution of an E-MAC survey is captured using Global-Positioning-System (GPS) technology. This results in consistent and accurate post-survey analysis and relocating capabilities. In the event that a coating anomaly identification stake is damaged or removed, the exact location can be easily navigated to and reclaimed utilizing the corresponding GPS coordinates.

River Assessment Survey (X-WRAP)

Dynamic logging software and procedure is used in conjunction with the coating evaluation/depth of cover hardware on water course or river crossings where water depth and speed will not permit depth of cover information to be collected statically using conventional pipe locating/depth equipment. Multiplexing the GPS coordinates, sonar, and coating/depth information allows the data sets to be correlated using precise GPS time. Geodetic position can then be assigned with all collected pipeline and river hydro-graphic data. Directionally independent coils are employed in the receiver portion of the survey logging apparatus, therefore accurate results can be achieved without having to pass the pipeline at an exact perpendicular orientation. As consecutive passes are made over the pipeline, the software records all relevant peripheral outputs. A visual display informs the operator as the equipment approaches and passes over the pipeline. The information from each pipeline pass is stored with the associated GPS coordinates. The majority of the data collected relates to the riverbed profile and can be utilized in constructing a 3D model of the region where the pipeline crosses. The pertinent data that is recorded the instant the instrumentation is directly over the pipeline is extracted and the relevant information is consolidated to create the pipeline's positions and cross-sectional profile.

Close-Interval CP Survey (CIS)

Close-Interval CP Survey (CIS) is a method by which cathodic protection pipe-to-soil (P/S) potentials are obtained at close-intervals (approx. 1m) along the entire length of the pipeline. The result is a thorough representation of the CP status of the pipeline displayed graphically as an "on/off" P/S potential versus distance profile. Annual CP adjustive surveys only require that P/S potentials are obtained at the extremities of the pipeline and at intermediate locations such as test stations, risers, etc.

A properly performed CIS can determine whether adequate levels of protection are being achieved at all points in-between, and can sometimes identify specific areas of coating deficiencies depending on the degree of the damage. CIS is a cost-effective technique that can also be used to validate or enhance indications from an E-MAC survey and minimize excavation & repair costs through increased predictability of where corrosion activity is probable.

Depth-of-Cover (DOC) Survey

The depth values are typically obtained in conjunction with the coating integrity survey using the same equipment and are tabulated along with GPS coordinate information. However if coating information is not relevant, depth values only can be more rapidly obtained using the same equipment and similar procedure. The locating equipment measures depths to the center of the pipeline and DOC values are subsequently determined by correcting the measured values by one radius of the pipe. Once the data has been collected and tabulated, a DOC profile can then be presented graphically.

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