An Approach to Establishing Manufacturing Process and Vintage of Line Pipe Using In-Situ Nondestructive Examination and Historical Manufacturing Data

Abstract

The October 2019 revisions to US federal rules governing natural gas pipelines require Operators to establish vintage and manufacturing process for line-pipe assets with incomplete records. Vintage and manufacturing process are considerations when establishing populations of pipe for maximum allowable operating pressure (MAOP) reconfirmation, materials verification, and integrity management programs. Additionally, the rule changes establish an allowance to utilize in-situ nondestructive examination (NDE) technologies to verify line-pipe material properties including strength, composition, microstructure, and hardness. Economic and market demands have driven changes in steelmaking technologies and pipe-forming approaches. Knowledge of the relationships between processing, microstructure and mechanical properties have been fundamental to the evolution of steel line pipe manufacturing. Product specifications and standards for the manufacture and testing of pipe and tube have crystallized this evolution as performance expectations increased. The resulting manufacturing process changes have left a variety of “fingerprints” observable from in-situ materials verification NDE data, when analyzed holistically. The purpose of this work is to enable operators to begin leveraging these fingerprints to illuminate the vintage and manufacturing process of their line pipe assets using the NDE data. A method is proposed to re-establish line-pipe asset manufacturing and vintage records using historical line pipe manufacturing practices and NDE materials verification data.

Accurate Estimation of Yield Strength and Ultimate Tensile Strength through Instrumented Indentation Testing and Chemical Composition Testing

“…Equation (1) applies only for low-carbon ferrite-pearlite steels, and the reported accuracy of Equation (1) was ±31 MPa (4.5 ksi). Both manganese and carbon increase UTS, as observed by the following relationship developed by the same authors, because carbon makes up 0.77 wt.% of the microstructural constituent, pearlite, where pearlite represents the percent pearlite observed via metallographic evaluation [19]: UTS(MPa) = 294 + 28Mn + 83Si + 3.85(pearlite) + 7.7d − 1 2 (2) Recent findings [23] have shown that, over the past 100 years, manganese content and the content of microalloying elements such as vanadium, titanium, niobium, chromium, and molybdenum in line pipe steels has tended to increase, while carbon content has tended to decrease. Therefore, these long-accepted empirical relationships in Equations ( 1) and (2) may not hold for some contemporary line pipe steels.…”