What are the material and welding considerations for piping and pipelines in hydrogen gas transport according to ASME B31.12?

Introduction

ASME B31.12 provides guidelines for the design and maintenance of piping and pipelines used in gaseous and liquid hydrogen service. It covers various aspects, including material selection, welding practices, and maintenance routines.

Answer

ASME B31.12 specifies material criteria and Charpy impact testing requirements for low-temperature service. It recommends the use of carbon steels with low hardness for service at the operating conditions. The code also addresses the risks associated with carbon steel and stainless steel in high-temperature service. Nickel-based alloys are generally recommended to be avoided. Welding practices, such as gas tungsten arc welding (GTAW), flux-cored arc welding (FCAW), gas metal arc welding (GMAW), and shielded metal arc welding (SMAW), are regulated, and welds need to be qualified by an approved inspector. Preheat treatment is required for all carbon steel welds, and non-destructive examination (NDE) testing, such as full radiography or ultrasound, is more comprehensive than in other standards. It is important to adhere to approved procedures for replacement and repair, while maintaining access to joints and fittings for inspection.