What are the existing valve design standards and leak testing methods for hydrogen gas transport?

Introduction

This FAQ provides information on the valve design standards and leak testing methods specifically relevant to hydrogen gas transport. It highlights the standards used for evaluating valve performance and leakage rates in hydrogen service.

Answer

In the context of hydrogen gas transport, the commonly used valve design standards include BS EN 12266-1, BS EN 12266-2, and API Spec 6D. However, it is important to note that these standards do not include specific tests for hydrogen leakage. Instead, references are made to the leak rates provided in ISO 5208, which are applicable to various fluids without specifying those recommended for testing. For hydrogen leak testing, the ISO 19880-3 standard offers limited recommendations. Notably, hydrogen molecules are smaller than methane, which can potentially lead to increased leaks through seals. Trials conducted by the National Grid Future Grid and other teams confirm that valves leaking natural gas will also leak hydrogen, with hydrogen leaks occurring at a greater rate than natural gas. Tests comparing hydrogen and methane leak rates indicate that volumetric hydrogen leaks are 2.20-2.70 times higher than methane leaks, based on pressure ranges of 2–67 barg. These findings align with theoretical calculations, suggesting that volumetric hydrogen flow rates can be 2.80-2.82 times higher than methane under turbulent flow and 1.20-1.29 times higher for laminar flow. The study assumes a conservative ratio of hydrogen leaks being 3 times higher than methane leaks, accounting for various flow conditions and permeation contributions.