NACE SP0204

Abstract

Introduction <br> This standard covers the NACE SCCDA process for buried steel pipeline systems. It is intended to serve as a guide for applying the NACE SCCDA process on typical petroleum (natural gas, crude oil, and refined products) pipeline systems. Background information can be obtained from NACE Publication 35103. <br> SCCDA as described in this standard is specifically intended to address buried onshore petroleum (natural gas, crude oil, and refined products) pipelines constructed from line-pipe steel. <br> This procedure is designed to be applied to both forms of external SCC (near-neutral-pH SCC and high-pH SCC) on these pipelines. <br> SCCDA requires the integration of data from historical records, indirect surveys, field examinations, and pipe surface evaluations (i.e., direct examination) combined with the physical characteristics and operating history of the pipeline. <br> This standard was written as a flexible guideline for an operator to tailor the SCCDA process to specific pipeline situations. Nothing in this standard is intended to preclude modifications that tailor the SCCDA process to specific pipeline situations and operators. <br> SCCDA is a continuous improvement process. Through successive applications, SCCDA should identify and address locations where SCC has occurred, is occurring, or might occur. <br> SCCDA provides the advantage and benefit of indicating areas where SCC might occur in the future rather than only areas where SCC is known to exist. <br> Comparing the results of successive SCCDA applications is one method of evaluating SCCDA effectiveness and demonstrating that confidence in the integrity of the pipeline is continuously improving. <br> SCCDA was developed as a process for improving pipeline safety. Its primary purpose is to reduce the threat of external SCC on pipeline integrity by means of condition monitoring, mitigation, documentation, and reporting. <br> This standard assumes SCC is a threat to be evaluated. It can be used to establish a baseline from which future SCC can be assessed for pipelines on which SCC is not currently a significant threat. <br> SCCDA is complementary with other inspection methods such as in-line inspection (ILI) or hydrostatic testing and is not necessarily an alternative or replacement for these methods in all instances. SCCDA also is complementary with other direct assessment procedures such as those given in the proposed NACE standard recommended practice on internal corrosion direct assessment (ICDA) methodology. <br> ILI or hydrostatic testing might not be warranted if the initial SCCDA assessment indicates that "significant" and extensive cracking is not present on a pipeline system. <br> SCCDA can be used to prioritize a pipeline system for ILI or hydrostatic testing if significant and extensive SCC is found. <br> SCCDA may detect other pipeline integrity threats, such as mechanical damage, external corrosion, etc. When such threats are detected, additional assessments and/or inspections shall be performed. The pipeline operator shall utilize appropriate methods such as ASME B31.8S, ASME B31.4, ASME B31.8, API(Footnote 2) 1160, NACE standards, international standards, and other documents to address risks other than external SCC. <br> SCCDA can be applied to most onshore petroleum pipelines, regardless of the coating system. Precautions should be taken when applying these techniques just as with other assessment methods. <br> Given the diversity of pipelines and their operation, this standard recognizes that SCCDA may be inappropriate for some situations because of the complexity of conditions to which buried pipeline systems are exposed. <br> The provisions of this standard shall be applied under the direction of competent persons who, by reason of knowledge of the physical sciences and the principles of engineering, geosciences, and mathematics, acquired by education and related practical experience, are qualified to engage in the practice of corrosion control, integrity management, and risk assessment on buried steel pipeline systems. <br> Footnote 2 - American Petroleum Institute (API), 1220 L St. NW, Washington, DC 20005.