PACIFIC GAS & ELECTRIC CO — Integrity Assurance Notification

MAOP RECONFIRMATION METHOD 6Pacific Gas and Electric Company (PG&E) has performed a comprehensive evaluation of all station features at its Tarpey Regulator Station (Tarpey Station) to reconfirm Maximum Allowable Operating Pressure (MAOP).1 This station is in Fresno, California and meters, regulates, and supplies gas through lines 1202-14 and 1202-12 to the Fresno 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. Seven (7) joints at Tarpey Station were identified as having non-TVC records of a pressure test in this review. The joints considered in this evaluation are located in a moderate consequence area (MCA) 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 3.2 At Tarpey Station, records were TVC for materials properties of three of the seven joints. PG&E’s station records identified all material properties including joint length, outside diameter, nominal wall thickness, and pipe grade for these three joints. For the other four joints, materials verification was determined through manufacturer markings. Charpy V-notch toughness and material fracture toughness were calculated based on vintage and operating temperature. PG&E utilized NDE-based ECA methodologies for reconfirming MAOP at Tarpey Station, satisfying the requirements of §§192.624(c)(3) and 192.632. Flaw detection-NDE was performed on these joints to detect external (outer diameter), internal (inner diameter), and mid wall indications. For three joints, the Predicted Failure Pressure (PFP) was calculated for hypothetical maximum remaining flaws. PFP calculations used the API 579 level 2 model. Computations established that the PFP of these joints, for all hypothetical flaws, is above 1.5 times the corresponding MAOP (1.5 x 650 psig = 975 psig). Fatigue analysis was performed using relevant operational pressure history data. Fatigue life (remaining life) simulations produced a remaining life of over 500 years. The remaining four joints were continuously scanned to confirm the absence of manufacturing, construction, and any other defects that would cause failure of a pressure test at 1.5 times MAOP (1.5 x 650 psig = 975 psig). As there were no found cracks or crack-like defects, no flaws exist that will grow in service due to fatigue.#