Hydrogen is the most abundant element in the universe, and it consists of one electron and one proton. It is a colourless, odourless and highly inflammable gas.
Now, why is hydrogen important?
First, it’s one of the cleanest available sources of energy. For example, when hydrogen is used as fuel, the byproduct is water vapour, i.e., no carbon emissions. Hydrogen is also a vital gas in manufacturing, chemicals, and even space exploration industries (NASA uses hydrogen).
The advantages and uses of hydrogen are numerous and cannot be overemphasised. However, the problem now comes in the extraction and piping of this gas. Since it’s highly inflammable, strict measures must be put in place for the use of this gas. This is why the American Society of Mechanical Engineers (ASME) developed the “B31.12 Hydrogen Piping and Pipelines Code” to address these safety concerns.
ASME B31.12
The ASME B31.12 Hydrogen Piping and Pipelines Code provides detailed guidelines for the design, construction and maintenance of hydrogen piping and pipeline systems. The code is divided into three major parts:
- Part GR (General Requirements): This section, as the name implies, highlights universal hydrogen safety requirements, definitions, heat treatment, etc.
- Part IP (Industrial Piping): This part focuses on industrial applications, standards for fabrication, assembly, erection, etc, of piping systems.
- Part PL (Pipelines): This section includes requirements, materials, components, installation and testing protocols for hydrogen pipelines.
Scope and Applicability
The ASME B31.12 applies to all high-pressure liquid and gaseous hydrogen piping systems. It is designed for stationary hydrogen systems like facilities for production, storage, distribution and utilisation. The code also applies to a wide range of system components like pipes, fittings, valves, pressure vessels and other related equipment.
Design Consideration
The code provides detailed design considerations to ensure the safety of hydrogen piping systems. It stipulates the maximum operating conditions for design pressure and temperature. The code also emphasises careful material selection to prevent hydrogen permeation and embrittlement. It also provides the guidelines for calculating the required wall thickness with consideration of external pressures, temperature fluctuations and corrosion allowances.
Material Selection
One of the biggest challenges of hydrogen piping is hydrogen embrittlement. Hydrogen embrittlement is where hydrogen seeps into certain metals and makes them brittle or prone to cracking.
To avoid this, ASME B31.12 sets clear guidelines to ensure the materials used are safe and long-lasting. It specifically recommends using materials like austenitic stainless steels (like 316/316L) and some nickel-based alloys because they can resist the effect of hydrogen better than others.
ASME B31.12 also requires strict testing to ensure these materials can handle hydrogen safely. This includes running tensile, impact, and hardness tests to see how the material behaves under pressure. Plus, there’s a big focus on documentation and traceability, ensuring every piece used in the system can be traced back to its source.
Construction Fabrications
The ASME B31.12 sets strict standards for the construction and fabrication of any hydrogen pipe. The code provides detailed guidelines on welding techniques that ensure that the piping systems maintain strength and do not leak. This part of the code is very important because hydrogen has a small molecular size and can easily leak. This means that the slightest mistake in piping construction can be very costly.
The part of the code places a lot of emphasis on “joint design.” The code stipulates that extra care and attention should be paid to avoid leaks. It also provides for strict quality control measures and encourages non-destructive testing methods like radiographic and ultrasonic examinations.
Inspection and Testing
ASME B31.12 sets strict inspection and testing requirements to ensure hydrogen piping systems remain safe and reliable throughout their lifespan. One of the first steps is regular visual inspections. These help spot surface defects, corrosion, or any signs of leaks before they become serious issues.
In addition to visual inspections, as earlier mentioned, the code enforces non-destructive testing methods like radiographic and ultrasonic examinations. The code mandates either hydrostatic or pneumatic pressure testing to make sure that the system can handle the expected operating pressures without leaking or failing. It also requires hydrogen-specific leak detection sensors to catch even the smallest leaks quickly.
Safety Considerations
The ASME hydrogen piping code stresses the need for robust emergency shutdown procedures. It suggests using automated shutdown systems that can react instantly in case of a problem.
The automated shutdown should also be used with manual override options so operators can take control when necessary. Additionally, the code encourages the installation of safety devices like pressure relief valves to manage pressure fluctuations and prevent potential accidents.
Regulatory Compliance and Code Enforcement
ASME B31.12 is widely recognised as the standard for hydrogen piping systems, and compliance with this code is often a legal necessity enforced by regulatory bodies. Government agencies and regulatory authorities carry out regular inspections to ensure companies stick to these rules.
These inspections check if systems are built and maintained according to ASME B31.12 standards.
Conclusion
Hydrogen may be a safe and clean source of energy; however, challenges like high diffusivity and the potential to cause embrittlement make it dangerous for use. This is why the ASME B31.12 has been set up to address these challenges. With these guidelines, organisations and industries can confidently develop hydrogen infrastructure that meets the highest safety and reliability standards.
With the ASME B31.12 code, pipelines can now be built and operated with up to 100% hydrogen. Hence, one thing is clear: adherence to ASME B31.12 standards ensures the safe handling and transport of hydrogen.
Also Read: Stainless Steel Press Fit for High-Pressure Applications
