Start Date
June 2015

Background
This project was officially established as a major pipeline participant-based project in 2015. It was based on initial work performed outside the CCQTA from 2009 to 2011 and then within the CCQTA Pipeline Corrosion project from 2014 to 2015. A project proposal was circulated to the membership in mid 2015 encouraging additional participation at reduced fees or under a Work-in-Kind agreement.

This project was initiated in response to the National Energy Board requirement for transmission pipelines to meet the CSA Z662 standard for Sour Service. The project focus is the evaluate the conditions required that would allow sulfide stress cracking to occur which will allow transmission pipeline operations to evaluate their systems and whether the conditions exist to promote SSC.

The project scope involved the collation of H₂S in crude test data, testing of available pipeline water samples, and the development of a Sulfide Stress Cracking (SSC) test protocol for transmission lines.

The project became a CCQTA funded project in June 2017.

Milestones as of September 2024

• Determined that under acidic conditions, oil contact with the SSC test solution prior to testing using NACE TM0177 significantly altered failure rates. Similar testing using a slightly basic brine (ASTM D1141) contacted with crude prior to TM0177 testing did not see significant variation from blank. 2017
  
• Project group presented to the NACE MR0175 maintenance panel in March 2016, March 2017, April 2018 and most recently in March 2019. The maintenance panel was engaged to make them aware of the work that was going on relating to differentiating transmission pipelines conditions from conventional gathering system conditions and how those conditions may affect SSC and to seek feedback.
  
• H2S partitioning testing determined that H₂S migration from oil to brine in the absence of a gas phase (no bubble point) results in significantly lower H₂S concentrations in water than those observed during a direct gas/brine exchange. Results were inconclusive regarding the effect of dissolved versus free H₂S on the SSC mechanism.
  
• Determined that pre-coating of coupons with both heavy and light oils, inhibited SSC failures in the ASTM D1141 solution - over the full 30-day test period.
  
• Enlisted the participation of NEB and AER in project work.
  
• The survey form for use with field experience data collection was finalized and sent to pipeline operators in November 2019.
  
• Available survey data was presented at the June 2020 project meeting.
  
• Ballot proposal presented to NACE MR0175/ISO 15156 maintenance panel in early October 2020.
  
• NACE MR0175/ISO15156 Maintenance Panel ballot passed in December 2020 and moved on to the TG299 Oversight Committee for review and ballot in 2021.
  
• A presentation was made to the TC299 OSC in January 2021 to provide context to the ballot. Presentation is available in the members area of the Sour Service project.
  
• NACE ballot has passed both the MR0175 Maintenance Panel and TG299 Oversight Committee. Next step will be to formally approve the revision in October 2021.
  
• A NACE technical bulletin (ISO_15156_3_2020_Cir_1_2021) was issued on 2021-12-09 including the new exclusion clause for transmission pipelines. The bulletin This bulletin has been added to the Sour Service director of the CCQTA website.
  
• Project was moved to “Project Maintenance Activities” as opposed to a stand-alone project
  
• Two ballots have been submitted to CSA for revision to Z662. These ballots are intended to harmonize the recent MR0175/ISO15156 revision with CSA Z662.
  
• The first ballot item is a revision to § 2.2 (Definitions) regarding “Pipeline System, Sales Quality Liquid Hydrocarbons” item b. The revised definition removes the ambiguous bubble point statement as well as the associated note.
  
• The § 2.2 revision also requests an update to the definitions of low vapor pressure (LVP) and high vapor pressure (HVP) to replace ASTM D323 with ASTM D6377.
  
• The second ballot item is a revision to §16.1.2 a) to remove the dissolved H₂S criteria from the exclusion requirements.
  
• The public review of the revisions to CSA Z662, closed on March 5, 2022. The CSA ballot will take place in late summer/early fall 2022. Ballot comments are then dispositioned, and changes are finalized at the Feb 2023 Technical Committee meeting, at which point they would be considered final and included in the 2023 edition.
  

• A new revision to ISO 15156 is currently in review.
  
• AMPP editors of MR0175/ISO15156 have agreed to maintain the transmission pipeline exclusion as approved and published in ISO_15156_3_2020_Cir_1_2021.
  
• The abstract for a technical paper titled “SYMP-ANNUAL-2025: Research, Experience Survey and Ballot that Justifies Exclusion of Gas-Phase Free, Low-Water Stabilized Crude Pipelines from NACE/ISO Sour Service Cracking Requirements” has been accepted for the AMPP Conference in April 2025 (Nashville, TN).
  
• The paper, which is a summary of the CCQTA’s work, will document the technical basis for the MR0175/ISO15156 exclusion.