Flow Measurement Of Hydrogen Gas: Assisting the Energy Transition

Hydrogen is certain to be a key element in the process of decarbonization. The global energy transition will require a multitude of new installations, alongside the conversion of existing infrastructure. The crucial question today is - will it also work with hydrogen?

Fit for the First Element

As the technological leader in the field of clamp-on ultrasonic flow measurement, FLEXIM pioneered the process of transferring this non-invasive hydrogen flow measurement technology to gases two decades ago. Since then, FLUXUS G ultrasonic systems have accurately and reliably measured the flow of all gases, including hydrogen.

Ready for Change

The physical properties of hydrogen differ highly from those of other gases, in particular natural gas. Plant operators are therefore faced with major challenges due to the necessary adaptations that need to be made. FLEXIM’s non-invasive measuring technology is not only flexible by principle, it also comes with further advantages which perfectly fit hydrogen gas measurement applications, including:

  • FLUXUS hydrogen flowmeters measure from the safe side – the outside of the pipe. The installation does not require any opening of the pipeline and is usually carried out during ongoing operation. The measuring device is not subject to wear and tear and it does not pose any leakage risk.
  • The acoustic measuring method is characterized by its exceptional dynamics – independent of the flow direction (bidirectional). This makes it possible to record even the lowest flow velocities as well as the highest.
  • Explosion protection is no issue. Both certified transmitters and transducers cover the relevant explosion group IIC (ATEX / IECEx).
  • Sophisticated analytical functionalities allow for determination of hydrogen purity as well as the proportion of hydrogen in natural gas-hydrogen mixtures.

Hydrogen Flow from Production to the Consumer

The application range of FLEXIM’s FLUXUS G hydrogen measurement instruments covers the entire value chain of the hydrogen economy, regardless of its method of production. These are:

  1. Green Hydrogen: Pure hydrogen produced from renewable resources such as wind and solar and after electrolysis is completed, offshore or onshore.
  2. Blue Hydrogen: Hydrogen produced as a by-product from fossil fuel resources (steam reforming).
  3. Mixed with Fossil Fuel: Combination of blue or green hydrogen used to reduce current carbon emissions.


Operators worldwide are looking at, and implementing hydrogen blending into existing natural gas infrastructure to reduce carbon emissions.

The introduction of hydrogen into natural gas transportation and distribution networks changes the composition of the stream, therefore higher volumes of gas must be transported in order to achieve the same BTUs or calorific values provided by pure natural gas. As the percentages of hydrogen blending rise, the energy calorific value of the natural gas decreases. As a result, an increased amount of gas in terms of volume must be consumed to meet the required energy needs of appliances, vehicles, etc.

Furthermore, many regions intend to simply utilise existing infrastructure for a quick and economical transition. Hydrogen metering instrumentation will therefore need to be able to cope with constant compositional changes and avoid pressure drops across the network at all costs.

Accuracy is Approved

FLUXUS stands its ground both in the field and in the lab. As the only manufacturer of clamp-on ultrasonic measuring technology, FLEXIM was invited to participate in the Joint Industry Project (JIP) on “Suitability of natural gas flow meters for renewable gases” in 2021.

The test facility was the multiphase flow lab at DNV in Groningen, The Netherlands. On behalf of all major pipeline operators in the EU, the flow meters’ capabilities to handle natural gas mixtures with up to 30% hydrogen and up to 20% CO2 were tested, with FLEXIM proving to deliver excellent results. Over the entire test program, the FLUXUS G 721 successfully performed within its specified measurement uncertainty (±1…2%) and repeatability (0.15%).


Results of the accuracy tests with pure H2 at the DNV HyLoop facility Groningen

Hydrogen Grading and Blending

Power to Hydrogen

Ammonia as Hydrogen carrier