What are the considerations for maintaining the surface condition of valve components in hydrogen pipeline systems according to EIGA Doc 121/14?

Introduction

EIGA Doc 121/14 provides guidance on maintaining the surface condition of valve components in hydrogen pipeline systems. It emphasizes the importance of appropriate heat treatment and surface treatment to ensure the integrity of the components.

Answer

According to EIGA Doc 121/14, it is generally accepted that valve components for hydrogen service should undergo a normalized heat treatment. This treatment assures the presence of fine-grained homogenous microstructures in the components. It is crucial to pay special attention to the surface condition of alloy mill forms during and after treatment. The normalizing heat treatment condition is widely available for valve components. Additionally, the guideline suggests considering newer melting processes that reduce sulfur and phosphorus for severe applications. Maintaining the lowest possible tensile strength consistent with the application is recommended for all alloy selections. It is worth noting that substituting a higher strength material in hydrogen environments does not improve corrosion resistance. For pressures above 50 bar, the guideline highly recommends considering toughness requirements for specific steel mill forms used in hydrogen pipeline applications, as specified in Pipeline Design and Construction.