PR-610-183867-R01 Fracture Toughness via In-ditch Non-destructive Testing – Validation

A challenge for many pipeline operators is missing or incomplete records for sections of their transmission pipeline networks, especially regarding fracture toughness properties. These toughness values are necessary for performing fitness for service calculations and engineering critical assessment. New regulations for gas transmission pipelines stipulate conservative default values for applicable assets when traceable, verifiable, and complete (TVC) records are not available. The new rules allow for the use of nondestructive techniques within material verification programs to measure the actual steel properties in lieu of conventional destructive cut-outs. However, the nondestructive technique must be validated, and the measurement must account for error and uncertainty of the nondestructive process. The aim of this research program is to assess the capabilities and limitations of the Nondestructive Toughness Tester (NDTT) to meet the requirements of a material verification process for measuring fracture toughness properties. The NDTT is a new approach for measuring the toughness of steel pipelines through the application of a contact mechanics technique known as frictional sliding. This project consists of testing on 41 vintage steel pipe joints to compare the NDTT measurement of the tensile fracture response in a superficial volume of surface material with conventional laboratory measurements of toughness on the same sample. The outcomes include the development and assessment of nondestructive prediction models for the initiation fracture toughness from compact tension (CT) testing and the upper shelf Charpy V-Notch (CVN) impact energy. This report summarizes the testing procedures and analysis methodologies used, and the prediction performance of models based on NDTT measurements.