PACIFIC GAS & ELECTRIC CO — Integrity Assurance Notification

MAOP RECONFIRMATION OTHER ECA TECHNOLOGYPacific Gas and Electric Company (PG&E) has performed a comprehensive evaluation of all station features at its Coffee & Claratina Regulator Station (Coffee & Claratina Station) to reconfirm the Maximum Allowable Operating Pressure (MAOP).1 This station is in Modesto, California and provides regulated gas supplies to the Modesto, Riverbank, Escalon, and Oakdale area. PG&E’s initial phase of this project identified all traceable, verifiable, and complete (TVC) records to reconfirm MAOP based on design and pressure test records. Six (6) joints at Coffee & Claratina Station were identified as having non-TVC records of a pressure test2 in this review. The joints considered in this evaluation are located in a high consequence area and are located in a Class 3 location. PG&E proposes to establish a TVC MAOP record via 49 Code of Federal Regulations (CFR) §192.624(c)(3), Method 3.3. At the Coffee & Claratina Station, records were non-TVC for material properties of six joints. PG&E utilized nondestructive examination (NDE), satisfying the requirements of §192.607, to verify the materials properties of these joints. A combination of NDE to establish material strength, chemical composition, hardness, microstructure, wall thickness, and long seam was deployed. These joints’ grade and nominal wall thickness were determined using a combination of materials verification-NDE data and engineering analysis. Charpy V-notch toughness and material fracture toughness were calculated based on vintage and operating temperatures. PG&E utilized NDE-based ECA methodologies for reconfirming MAOP at Coffee & Claratina Station that satisfies the requirements of §192.624(c)(3) and §192.632. Flaw detection-NDE was performed to detect external (outer diameter), internal (inner diameter), and mid wall indications. The Predicted Failure Pressure (PFP) was calculated for theoretical maximum remaining flaw sizes, based on NDE detection and sizing thresholds, as no actual flaws were discovered on the joints at the station. PFP calculations used the PRCI MAT-8 and API 579 level 2 model. Computations established that the PFP of these joints, for all theoretical flaws, is above 1.5 times the corresponding MAOP (1.5 x 408 psig = 612 psig). Fatigue analysis was performed using relevant operational pressure history data. Fatigue life (remaining life) simulations produced a remaining life over 500 years.#