PACIFIC GAS & ELECTRIC CO — Integrity Assurance Notification

MAOP RECONFIRMATION METHOD 6This utility procedure describes the steps Pacific Gas and Electric Company (Company or PG&E) personnel must perform to validate the maximum allowable operating pressure (MAOP) of gas transmission systems in accordance with the requirements of Code of Federal Regulations (CFR} Title 49, Transportation, Part 192-Transportation of Natural and other Gas by Pipeline: Minimum Federal Safety Standards, the California Public Utilities Commission (CPUC) Decision 11-06-017 issued June 9, 2011 and General Order (GO) 112-F. Pacific Gas and Electric Company (PG&E) has performed a comprehensive evaluation of all station features at its Madrone Ave Regulator Station (Madrone Ave Station) to reconfirm the Maximum Allowable Operating Pressure (MAOP).1 This station is in Cotati, California and provides regulated gas supplies to District Reg Station R-390 and Cotati Reg Station. 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. One (1) joint at Madrone Ave Station was identified as having a non-TVC record of a pressure test2 in this review. The joint considered in this evaluation is located in a High Consequence Area (HCA) and is 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 Madrone Ave Station, records were non-TVC for materials properties of the one joint. PG&E utilized nondestructive examination (NDE), satisfying the requirements of §192.607, to verify the materials properties of this joint. A combination of NDE to establish material strength, chemical composition, hardness, microstructure, wall thickness, and long seam was deployed. This joint’s 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 the vintage and operating temperature. PG&E utilized NDE-based ECA methodologies for reconfirming MAOP at Madrone Ave Station, satisfying the requirements of §§192.624(c)(3) and 192.632. Flaw detection-NDE was performed on the Madrone Ave Station joint 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 joint at the station. PFP calculations used the API 579 level 2 model. Computations established that the PFP of the joint, for all theoretical flaws, is above 1.5 times the corresponding MAOP (1.5 x 275 psig = 412.5 psig). Fatigue analysis was performed using relevant operational pressure history data. Fatigue life (remaining life) simulations produced a remaining life of over 500 years.#