scope:

Introduction

This standard describes the NACE International internal corrosion direct assessment (ICDA) process for multiphase flow pipeline systems. It is intended to serve as a guide for applying the MP-ICDA process on multiphase flow pipeline systems that meet the feasibility requirements described in Paragraph 3.3.

The three primary purposes of the MP-ICDA method are to assess the integrity of a pipeline because of internal corrosion in multiphase flow pipelines, to identify the locations where pipeline integrity may be compromised, and determine the frequency of pipeline integrity assessment.

The MP-ICDA method assesses how the internal corrosion severity is distributed along the subregion. The methodology includes methods of examination available to a pipeline operator/producer to determine the occurrence, extent, and severity of internal corrosion.

MP-ICDA also provides a framework for the use of multiphase flow modeling results (e.g., flow velocities, temperature and pressure profiles, liquid hold-up, and flow patterns) in understanding the hydrodynamics of the flow along this pipeline segment and aids in understanding how these variables can affect internal corrosion.

MP-ICDA was developed for onshore and offshore multiphase flow pipelines that transport a combination of gas, water, solids, and/or crude oil or hydrocarbon liquids as part of normal operations. MPICDA is applicable to pipelines that transport multiphase flows including, but not limited to: gathering, producing pipelines, well lines, and flow lines. The basis of MP-ICDA is for pipelines, and consists of following the four types of the direct assessment methodology: pre-assessment, indirect inspection, detailed examination of selected locations, and post assessment.

One benefit of the MP-ICDA approach is that an assessment can be performed on a pipe segment for which alternative methods (e.g., ILI, hydrostatic testing, etc.) may be impractical.

MP-ICDA does have limitations, and not all pipelines can be successfully assessed using this method. These limitations are dependent on the specifics of each pipeline system and shall be identified in the preassessment step.

The provisions of this standard shall be applied by or under the direction of verifiably competent persons who, by reason of knowledge of the physical sciences and the principles of engineering and mathematics, acquired by education or related practical experience, are qualified to engage in the practice of corrosion control and corrosion risk-based assessment on multiphase pipeline systems. Such persons may be registered professional engineers with verifiable experience in internal corrosion for pipelines, certified as corrosion specialists or internal corrosion specialists by organizations such as NACE International, or professionals (e.g., scientists, engineers, or technologists) with professional experience including detection/mitigation and evaluation of internal corrosion in pipelines.

For accurate and correct application of this standard, all four steps shall be performed. Using or referring only to specific paragraphs or sections may lead to misinterpretation or misapplication of this standard.

In the process of applying MP-ICDA, while performing the detailed examination, other pipeline integrity threats such as external corrosion, mechanical damage, stress corrosion cracking (SCC), etc. may also be detected. When such threats are detected, additional detailed examination or inspections must be performed to ensure that pipeline integrity is not compromised, regardless of mechanism. This may require an external corrosion direct assessment (ECDA) or a stress corrosion cracking direct assessment (SCCDA).

This standard does not address specific remedial actions to be taken when corrosion is found. Individual companies have pipeline operating and maintenance manuals (or equivalent), which should cover such repair practices in compliance with local jurisdictional regulations. The pipeline operator/producer should use appropriate methods to address threats other than internal corrosion, such as those described in ASME⁽¹⁾B31.8,⁴ ASME B31.8S⁵, ASME B31.4⁶, API⁽²⁾ 1160,⁷ ANSI⁽³⁾/API 579,⁸ CSA⁽⁴⁾Z-662,⁹ BS⁽⁵⁾ 7910,¹⁰ ASME B31G,¹¹ RSTRENG,¹² NACE standards, international standards, and other documents.

⁽¹⁾ American Society of Mechanical Engineers, Two Park Ave., New York, N.Y 10016-5900.

⁽²⁾ American Petroleum Institute (API), 1220 L St. NW, Washington, DC 20005-4070.

⁽³⁾  American National Standards Institute (ANSI), 1899 L Street, NW, 11th Floor, Washington, DC, 20036.

⁽⁴⁾ Canadian Standards Association (CSA), 5060 Spectrum Way, Suite 100, Mississauga, Ontario L4W 5N6, Canada.

⁽⁵⁾ British Standard Institute (BSI) 389 Chiswick High Road, London, W4 4AL, England