Damage Control: High-Temperature Hydrogen Attack Mitigation

Editor’s Note: This regular column offers practical insights into various damage mechanisms affecting equipment in the O&G, petrochemical, chemical, power generation, and related industries. Readers are encouraged to send us suggestions for future topics, comments on the current article, and raise issues of concern. All submissions will be reviewed and used to pick topics and guide the direction of this column. We will treat all submissions as strictly confidential. Only Inspectioneering and the author will know the names and identities of those who submit. Please send your inputs to the author at damagecontrol@inspectioneering.com.

Introduction

The previous two installments of Damage Control outlined the fundamental chemical reaction and damage characteristics associated with high-temperature hydrogen attack (HTHA) in carbon and low-alloy steel pressure retaining equipment. Specifically, Part 1 of this three-part series on HTHA offered perspective on the typical damage morphology of HTHA in welded pressure vessel and piping components in addition to the challenges associated with accurately detecting and characterizing HTHA damage using non-destructive examination (NDE) techniques. Part 2 of this series provided an overview of the evolution of material testing efforts in high-temperature hydrogen environments, HTHA damage prediction methods, and remaining life estimation approaches (including volumetric damage/void formation and the propagation of crack-like flaws). While HTHA-related research and joint industry projects have become more prevalent in recent years, particularly since the fatal 2010 HTHA failure of a heat exchanger at a U.S. oil refinery, HTHA remains a complex and often confounding damage mechanisms that continues to afflict aging infrastructure in plants around the world [1]. Pragmatic and carefully tuned inspection approaches coupled with technically based engineering and fitness-for-service assessment methods can be leveraged to better understand the likelihood of HTHA-driven failures.

This Damage Control article concludes this three-part series on HTHA and focuses on HTHA damage mitigation strategies and good engineering mechanical and process design concepts that can maximize the useful operating life of equipment in high-temperature hydrogen environments. Additionally, an investigation into the deleterious effects of HTHA-driven decarburization on steel material properties is offered in this final installment. Furthermore, the importance of establishing integrity operating windows (IOWs) for critical pressure equipment to mitigate extensive HTHA damage progression is highlighted herein. Commentary on the beneficial effects of stainless-steel cladding is given in this article, and a high-level summary of recently proposed time-dependent HTHA resistance curves, intended for eventual inclusion in API 941 (pending committee review and approval), is also provided [2]. A concerted special emphasis mechanical integrity (SEMI) program aimed at managing the risks associated with HTHA (e.g., through rational HTHA screening and risk categorization) in conjunction with favorable pressure equipment engineering design, material selection, welding, and heat treatment practices can minimize costly equipment downtime and repairs and augment long-term safety and reliability.