BVAA: Hydrogen Valve Standardisation - Enabling a Revolution
Hardly a month seems to pass without a major new energy project being announced involving hydrogen as the primary energy carrier. Europe is very much at the forefront of this activity aimed at providing low carbon energy as the world strives to find solutions to combat climate change.
The Hydrogen Technology Spectrum
A new colourful language has also developed alongside this hydrogen technology to describe the method of production. Grey hydrogen is the term used to describe the traditional process of producing hydrogen from natural gas and also producing carbon dioxide, whilst blue hydrogen involves capturing the CO2 to prevent it being released to the atmosphere. The lowest carbon solutions produce hydrogen by electrolysing water using zero carbon electricity; they are referred to as green hydrogen. Typically, green hydrogen makes use of wind power, pink hydrogen from nuclear energy and yellow hydrogen has solar power as the source.
Significant Energy Market Investment
Many of the new projects under development such as H2Teesside (blue H2), Hynet (green / blue H2) and Gigastack (green H2) in the UK along with NortH2 (green H2) in the Netherlands, to name but a few, involve significant investment from major oil and gas companies. It is clear that the next few decades will see a seismic shift away from the extraction of fossil fuel resources with “big oil” development capital being used to invest in renewable energy with hydrogen as the primary fluid. This change potentially represents a significant challenge to valve manufacturers as they look to develop products and technology to enable the new hydrogen market, but also replace the inevitable reduction in demand for their established products in the traditional oil and gas industry.
Valve Manufacturers Development Challenge
The H2 and CO2 gases produced across the various colours of the hydrogen energy spectrum will need to be safely, stored, compressed, transported and reduced in pressure before they can be used by the consumer to supply energy for power, heating and transportation. All these applications will need to make use of industrial valves to safely manage the supply of gas. This will involve the construction of new process plants and pipelines along with the upgrading, adaptation, and re-purposing of the existing natural gas transmission network, including new and re-purposed storage sites like depleted gas reservoirs and salt caverns. There will also be a requirement to transport hydrogen over long distances, potentially in liquified form by bulk tanker at temperatures of -253°C, to meet the demand of global economies without the resources for local production. The potential use of hydrogen as a fuel source for transport will also require new logistics solutions and infrastructure to safely deliver high pressure gas at pressures of up to 100MPa to the refuelling station network.
Whilst the opportunities to develop and supply industrial valves into the developing hydrogen economy look likely to be extensive, the operating conditions and challenges of these products will be quite different from those posed by the established oil and gas industries. The fluid is clean and homogeneous making the materials used unlikely to require the same high levels of corrosion resistance that is often needed for upstream oil and gas. However, opportunities are likely to exist for greater levels of valve product standardisation and commoditisation for hydrogen applications than was possible in the upstream oil and gas industry. This is likely to result in reduced valve product diversity and lower product costs.
Material Compatibility with Hydrogen
The technical challenge posed by valves operating on hydrogen is not insignificant, however. The potential hazards of hydrogen embrittlement and stress corrosion cracking in some high strength metallic materials are issues that cannot be ignored. The bulk gas transportation sector for vehicle fuel involves H2 pressures as high as 100 MPa which will undoubtedly require high strength steels to be used, making effective material selection vital to achieve reliable safe performance. Lower pressures of 10MPa and below will be used to supply hydrogen in the existing natural gas pipeline network. However, a significant challenge remains to ensure that potential hydrogen embrittlement issues, particularly those resulting from fabrication processes, are eliminated. Generally, the larger size of molecular hydrogen gas is not considered to be an issue as far as hydrogen embrittlement is concerned, however the potential for creating hydrogen ions from the formation of corrosion cells or through material manufacturing processes presents risks that will require robust management.
Research conducted by the US department of energy on permeation rates has shown that the small molecular size of H2 is an issue that can affect the integrity of steel pipelines. The permeation rates measured in various steels, including coated pipes and materials of different surface finish, has shown significant H2 leakage rates can occur. For example, using measured H2 gas permeation rates, a 1 mile long 36” diameter pipe (1/2” thick) at 5000psig (34.5MPa) in ambient 25°C air, would leak up to 24,000 SCF/day, if the H2 gas was at 170°C. So, it is likely that much tighter manufacturing controls on the quality of pressure envelope materials, particularly with regard to destructive and non-destructive testing, will be included in material specifications for hydrogen service.
The performance of existing sealing technology is an area likely to cause some challenges during the process of converting existing infrastructure. Hydrogen has a much smaller molecular size than natural gas so commonly used sealing materials and technologies may no longer be suitable for use. The correct selection of polymeric sealing materials will represent a particular challenge with a requirement for a temperature range of -40°C to 85°C being typical for gas applications, let alone the need for service at -253°C in liquid hydrogen applications. Blistering and rapid gas decompression are also potential seal performance issues associated with gases of small molecular size such as hydrogen. The high pressure gas is able to permeate into the seal material and then destructively expand as the system pressure reduces.
Ensuring Safety through Standardisation
Safety is paramount in any modern industry. The safety record of today’s gas industry has been particularly good featuring strong regulation controls and widespread adoption of standardisation rules. However, the introduction of hydrogen gas will bring its own challenges in the area of safety. This is partly because it is colourless and odourless making leaks difficult to detect without some form of additive being used. It has a similar lower flammability limit to natural gas, but the upper limit extends to concentrations of 75% by volume compared to only around 15% for natural gas. This makes hydrogen a significantly greater explosion hazard than natural gas, however the low mass of the gas does at least mean that it is easily dispersed into the atmosphere in outdoor environments. Nevertheless, reliable, low leakage rate sealing performance in hydrogen applications will be vital to ensure effective safety levels. This will make the development of effective valve application standards essential to ensuring a good safety and reliability record in the developing hydrogen gas industry.
The European Commission has recognised the need to support the rapid development of the new hydrogen industry in Europe and they have requested both CEN and CENELEC to draft new European standards to reduce the technical barriers associated with the rapid, safe adoption of the technology. This has resulted in a high level of activity in developing new and adapted standards addressing areas such as electrolysers and storage and use of hydrogen in the gas infrastructure. The CEN technical committees, TC 234 and TC 235, are responsible for both developing new standards and revising existing ones for gas infrastructure, pressure regulators and safety devices. This work will cover the introduction of H2 into the existing gas grid at various quantities and also the requirements for the transmission and use of 100% hydrogen.
New and Existing Valve Performance Standards for Hydrogen
Some ISO standards that cover key aspects of hydrogen valves are already in place such as the ISO 19880 family of standards. These standards relate to the gaseous hydrogen vehicle fuel dispensing sector with ISO 19880-3 covering the design and type approval testing of valves for these applications. Another area of standardisation also already in place and relevant to hydrogen valves is the ISO 15848 family of standards covering testing of fugitive emissions from valves. These standards already specify laboratory and workshop emissions testing for valves, using helium gas. Because the atomic radius of helium is smaller, than that of either elemental hydrogen or a hydrogen gas molecule, the use of helium as a test medium is considered applicable to hydrogen applications. The ISO 15848 standards family is currently being expanded to include a third part covering the specific type approval testing of stem or shaft seals using helium. ISO 15848-3 will allow seal manufacturers to type test their products to an international standard without the need to make the seal type approval specific to a particular valve manufacturer’s product range. This will enable seal manufacturers to demonstrate the suitability of their products for use with the specified leakage rates on hydrogen applications. Importantly, it will also provide some assurance to valve manufacturers, who will still be required to complete type approval testing for their products, that the selected stem seals are capable of providing the required level of sealing under static and dynamic conditions.
There is still a need for broader standardisation relating to hydrogen valves across the various segments where they will be used to ensure that the required levels of performance and safety are achieved. To this end standardisation efforts have also started within CEN/TC69, the technical committee dealing with industrial valve standardisation, with the formation of a new working group CEN/TC69 WG17. This group covers valves for hydrogen applications and networks, and it is proposed that they will be responsible for the creation of two new valve application standards: the first covering valves for use on gaseous hydrogen and the second focussing on liquid hydrogen valves. The BVAA has also formed a technical expert group (TEG) to allow members to discuss and offer their views and experience towards the development of these standards. The work is very much in the early stages of consideration, but it is hoped that it will result in requirements to support the safe consistent use of industrial valves in the various hydrogen applications currently being developed. As such these standards are likely to be valuable tools for valve specifiers and manufacturers alike to include in new valve specifications covering this developing hydrogen technology.
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