The development and qualification of welding procedures for hydrogen service presents a number of technical challenges, which need to be explored as pipelines are increasingly used as a method to transport hydrogen. At the 2023 APGA Convention, Dr Robin Gordon discussed these challenges on behalf of CRC Evans.
On behalf of CRC Evans, Gordon presented on the development and qualification of welding procedures for hydrogen service, covering welding procedures for hydrogen pipelines and hydrogen gas transport modules.
CRC Evans is actively engaged in the API 1104 Hydrogen Task Group to develop Girth Weld Requirements for Hydrogen Pipelines.
Gordon explained that the main challenge with hydrogen pipelines is girth weld procedure qualification and in particular the measurement of toughness in a hydrogen environment.
There are currently two test procedures to measuring hydrogen fracture toughness:
- ASME B31.12 – 2019 ‘Hydrogen Piping and Pipelines’.
- ANSI/CSA CHMC 1-2014 ‘Test methods for Evaluating Material Compatibility in Compressed Hydrogen Applications – Metals’.
In his presentation, Gordon compared the two current test methods, highlighted their limitations and proposed a best practice guide for fracture toughness testing of pipeline girth welds. He explained that ASME B31.8 procedures are well suited for heavy wall pressure vessel applications but not well suited for thinner wall pipeline applications. ANSI/CSA CHMC 1-2014, on the other hand, is much closer to best practice.
Hydrogen gas transport modules
Gordon outlined that, unlike hydrogen pipelines where fatigue is generally not a major concern, hydrogen gas transport modules can experience very high fatigue demand requiring the optimisation of welding procedures to provide high fatigue resistance.
But Gordon also stated that the evaluation of a weld design suitability for service is often minimised to be a discussion about mechanical properties and weld quality – whereas this shouldn’t be the case.
“Mature industries governed with well-established design and construction standards simplify the path for ensuring a weld suitability for service and often weld design is simply a selection from a variety of well-developed pre-existing welding procedures,” he said.
“In cases where new design considerations and subsequent performance requirements are introduced, defaulting to existing weld design requirements from other design standards may misrepresent a weld design suitability for service.”
The increasing trend of blended and pure hydrogen service introduces many design and material selection considerations that will directly influence joint design and weld procedure development to ensure suitability for service.
“With what appears to be a varying amount of design approaches for hydrogen service, the suitability of any one given welding procedure or technology is difficult to identify, and it is becoming clear that weld engineering will need to be ready to meet the charge when designs approaches mature in development,” Gordon said.
The CRC Evans approach
Gordon explained that CRC Evans’ experience was that consideration for fatigue is becoming one criterion that is an important consideration for hydrogen service.
He then outlined one of CRC Evans’ approaches at weld design for a specific hydrogen service application where construction limitations and fatigue performance introduced a need for unique weld design.
This approach used mechanised welding technologies – the CRC Evans M500 Welding Bug – as a solution to create a weld design suitable for the applicable design intentions of a specific application, which was found to be suitable for the intended service. This approach included very careful process selection, joint design, parameter optimisation and equipment development.
To learn more about CRC Evans’ approach to hydrogen service welding, contact Brett Trembath at email@example.com or call 07 3344 1066.