Managing Stress Corrosion Cracking Williams Gas Pipeline Transco – Ron Scrivner Northwest Pipeline – Dave Katz

Transco’s Experience In-Service SCC Ruptures – 1967 & 1968 In-Service SCC Ruptures – 1967 & 1968 Transco Reacted Transco Reacted –Hydrostatic tested to ensure integrity –Tested the first crack detection tool in 1972 –Performed random digs to determine the extent of the cracking –Participated in research to understand SCC

Results Hydrostatic testing in 1968 & 1969 removed 34 SCC colonies Hydrostatic testing in 1968 & 1969 removed 34 SCC colonies In-Line inspection tool proved unreliable In-Line inspection tool proved unreliable Random dig program found: Random dig program found: –SCC was predominately in the first valve section down stream compressor stations on Line “A” –No SCC was found on line “B”

Understanding SCC Research has developed an understanding of SCC (High Ph) Research has developed an understanding of SCC (High Ph) Conditions necessary for SCC Conditions necessary for SCC –Potent Environment –Stress –Susceptible material

Experience Continued In-Service SCC Rupture in 1972 In-Service SCC Rupture in 1972 Contracted Battelle to review Hydrostatic testing procedures Contracted Battelle to review Hydrostatic testing procedures –Recommend testing to 110% of Yield –Recommended testing on a 3/6 year cycle

Experience Continued Transco followed Battelle’s recommendations Transco followed Battelle’s recommendations Implemented an SCC integrity program Implemented an SCC integrity program –Continued random digs & Hydrostatic testing Has not had an In-Service SCC failure since 1972 Has not had an In-Service SCC failure since 1972 Has not had any failure (leak or rupture) since 1989 Has not had any failure (leak or rupture) since 1989

Minimizing the Potential for SCC Control Gas Temperature Control Gas Temperature –Install Gas Cooling Minimize Susceptible Environment Minimize Susceptible Environment –Maintain CP System Improved Coating Systems Improved Coating Systems –Blast Cleaning –Fusion Bonded Epoxy

In Conclusion (Transco) Transco continues to hydrostatically test pipeline segments where there is a threat of SCC. Transco continues to hydrostatically test pipeline segments where there is a threat of SCC. Transco continues to inspect for SCC threats Transco continues to inspect for SCC threats No new threats have been identified since 1976 No new threats have been identified since 1976 –Any line segment that experience a SCC rupture is considered to be at risk