ABSTRACT

In the past 5 years, Conventional Non-Destructive Examination (NDE) for High-Temperature Hydrogen Attack (HTHA) has been improved with remarkable success. This technology, combined with emerging Fitness-for-Service (FFS) methodologies, has been used in the evaluation of equipment in HTHA service with a higher level of confidence. Some of these evaluations have led to a systematic approach to continued operation, limited service, or retirement decisions not possible just 5 years ago. This paper will highlight some of the ongoing advances of the HTHA Joint Industry Project (JIP) to date and provide a preview into upcoming developments in the NDE and FFS codes. Some case studies will be presented along with recent advances in laboratory methods for HTHA prediction.

INTRODUCTION

In 2012, a Joint Industry Project (JIP) was launched consisting of support from eight refining and petrochemical companies (ranging from multi-national integrated oil companies to single-site refineries) and managed by The Equity Engineering Group, Inc. (E2G). There was a multi-prong approach for this project. The results of the round robin testing of the commercial NDE service provider were poor and have been previously presented [1, 2]. Since that time, the results of the erroneous NDE calls have been reviewed by a third party NDE SME. A large amount of ex-service HTHA material was analyzed, and methods for both detection and sizing have been developed. This NDE Path, along with a new approach to HTHA assessment similar to that in API 579 methodology, are being formulated into a FFS technology. This paper will summarize some aspects of the JIP.

IMPROVED NDE NEEDED FOR FFS TECHNOLOGIES

There was a need for finding more reliable NDE methods for HTHA in the refining and petrochemical industries. The primary purpose of NDE is Detection, Characterization and Sizing (surface breaking vs. sub-surface, length, height, depth, crack orientation, singular flaw vs. colonies of cracking). Of secondary importance those involving productivity: screening (as measured in scan rates of feet per minute) and surface preparation (scale or paint removal, weld protuberances, pitting) and accessibility (insulation removal, and for metal temperatures). The only methodologies considered practical for field use and commercially available, although proprietary methods were allowed. As in the case of the JIP Part 1 NDE Round Robin, all NDT indications were validated by metallography. A summary of the modalities tried is provided in Table 1. A further subset of Ultrasonic Methods will be discussed and are found in Table 2.

Time of Flight Diffraction and Phased Array Ultrasonic show best Results

Time of Flight Diffraction (ToFD) originated in the late 70s as a reliable ultrasonic detection and sizing methodology. During the 80s, several industrial trials validated ToFD to be one of the most reliable ultrasonic defect detection mediums available. Since then ToFD have been the backbone of most AUT pipeline girth-weld inspection and has been used extensively in the power generation industry, nuclear and fossil fuel, to detect and precisely size defects in pressure vessels, high-pressure pipelines and weldments.

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