Introduction

This standard covers the NACE internal corrosion direct assessment (ICDA) process for normally dry natural gas pipeline systems. This standard is interned to serve as a guide for applying the NACE DG-ICDA process on natural gas pipeline systems that meet the feasibility requirements of Paragraph 3.3 of this standard.

The primary purposes of the DG-ICDA method are (1) to enhance the assessment of internal corrosion in natural gas pipelines, and (2) to ensure pipeline integrity.

DG-ICDA was developed for natural gas pipelines that normally carry dry gas, but may suffer from infrequent short-term upsets of water. Because of this DG-ICDA is not applicable to wet gathering and producing pipelines.

One benefit of the DG-ICDA approach is that an assessment can be performed on a pipe segment for which alternative methods (e.g., in-line inspection (ILI), hydrostatic testing, etc.) may not be practical.

This basis of DG-ICDA for gas lines is a detailed examination of locations along a pipeline where water or other electrolyte first accumulates, allowing inferences to be made about the integrity of the remaining downstream length of pipe.

If the locations along a length of pipe that are most likely to accumulate water have not corroded, other locations less likely to accumulate water are unlikely to have suffered corrosion when operating under the same conditions.

Identifying areas in which internal corrosion (or the potential for future internal corrosion) exists, and conversely, where internal corrosion is unlikely, may also be incorporated into corrosion integrity and risk management plans.

In the process of applying DG-ICDA, other pipeline integrity threats, such as external corrosion, mechanical damage, stress corrosion cracking (SCC), etc., may be detected. When such threats are detected, additional assessments or inspections must be performed. The pipeline operator should utilize appropriate methods to address risks other than internal corrosion, such as those described in NACE standards, ASME⁽¹⁾ B31.8,⁴ API⁽²⁾ 1160,⁵ ANSI⁽³⁾/API 579,⁶ and BS⁽⁴⁾ 7910,⁷ International Standards, and other documents.

The DG-ICDA methodology assesses the likelihood of internal corrosion and includes existing methods of examination available to a pipeline operator to determine whether internal corrosion is actually present, or may occur.

DG-ICDA uses flow modeling results and provides a framework to utilize those methods

DG-ICDA has limitations, and not all pipelines can be successfully assessed with DG-ICDA. These limitations are identified in the pre-assessment step. For accurate and correct application of this standard, it shall be used in its entirely. Using or referring to only specific paragraphs or sections can lead to misinterpretation or misapplication of the recommendations and practices contained herein.

This standard does not designate practices for every specific situation because of the complexity of internal conditions that may be present in various pipeline systems.

This standard does not address specific remedial actions that may be taken when corrosion is found; however, the reader is referred to ASME B31.84 and other relevant documents for guidance.

The previsions of this standard shall be applied by or under the direction of competent persons who, by reason of knowledge of the physical sciences and the principles of engineering and mathematics, acquired by education and related practical experience, are qualified to engage in the practice of corrosion control and risk assessment on pipeline systems. Such persons may be (1) registered professional engineers, (2) recognized as corrosion specialists by organizations such as NACE, or (3) professionals (i.e., engineers or technicians) with professional experience including detection/mitigation of internal corrosion and evaluation of internal corrosion on pipelines.

⁽¹⁾ ASME International (ASME), Three Park Ave., New York, NY, 10016-5990.

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

⁽³⁾ American National Standards Institute (ANSI), 11 W. 42nd St., New York, NY 10036.

⁽⁴⁾ British Standards Institute (BSI), British Standards House, 389 Chiswick High Rd., London W4 4AL, United Kingdom.

Customers who purchased NACE SP0206
also purchased

• ASME B31.8 INTERPRETATIONS : Code for Pressure Piping-Includes Interpretations 1-15: September 1981 Through September 2009
• API STD 1104 : Welding of Pipelines and Related Facilities-Twentieth Edition; Incorporates Errata/Addendum: July 2007, Errata 2: December 2008
• ASME B31G : Manual for Determining the Remaining Strength of Corroded Pipelines

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